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East African diploid cooking bananas, commonly called Mchare, are a staple crop for millions of subsistence farmers in Tanzania, particularly in the Pangani region in northern Tanzania. Several pathogens constrain Mchare production significantly and threaten food security. Sources of resistance to these pathogens have been identified; however, partial male and female sterility impedes successful resistance introgression, complicating the breeding process. Mchare cultivars are also the only known surviving representatives of a diploid banana subgroup that contributed unreduced gametes to many of the most widely grown and successful triploid dessert bananas (‘Cavendish’, ‘Gros-Michel’, ‘Silk’, and ‘Prata’). As such, they represent an essential intermediate step in the conventional improvement of bananas worldwide. We assess the amount and viability of pollen among Mchare and wild genotypes to identify the most fertile Mchare cultivars that can be used in conventional banana improvement. Pollen was collected from 14 banana genotypes for quantification and viability testing over 7 months, and the optimal time for pollen collection was determined to be 0800 HR. Significant variation among banana genotypes in terms of both overall pollen production and percentage of pollen viability was observed. The wild-type bananas ‘Calcutta 4’ (International Musa Germplasm Transit Center (ITC) 0249] and ‘Borneo’ (ITC0253) had the greatest overall pollen production (> 31,000 pollen grains/anther) and viability (~74%), whereas ‘Ijihu Inkundu’ (ITC1460; Mchare genotype) was the least productive (almost completely sterile), with an average pollen production of a few hundred grains per anther and a viability of 7%. There were significant differences among months in terms of pollen viability, with the greatest average viability observed in May, April, and February (> 51%), and the lowest average pollen viability in July (41%). Significant differences were observed among the Mchare genotypes, with ‘Huti-White’, ‘Huti green bell’ (ITC1559), and ‘Mchare Laini’ consistently producing more substantial amounts of total pollen and an overall more significant proportion of viable pollen. This information is vital to improve Mchare bananas and the global breeding of dessert bananas. The choice of Mchare banana used in improvement programs could affect fertility and the likelihood of breeding success. [ABSTRACT FROM AUTHOR]

Fig types such as "Smyrna" and "San Pedro" require pollination (called caprification in fig cultivation) to produce a commercial crop, based on the crop and pollination characteristics of figs. Caprification is the process of hanging caprifig (male fig) fruits on female fig trees to ensure the transfer of pollen from the female fig to the caprifig by a wasp (Blastophaga psenes) that lives within the caprifig. It is necessary to extend the caprification period by using caprifig genotypes that ripen at different times, as female fig fruits ripen gradually. However, as caprifigs may not be continuously available for pollinating female figs, storing suitable caprifigs is necessary. The aim of this study was to assess changes in Blastophaga psenes, the duration of Blastophaga's exit, and the viability of pollen from caprifigs of different genotypes (16 08 05, 16 08 09, 16 08 10, 16 09 10, and 16 ZF 08) stored for caprification. These stored caprifig genotypes were subsequently used for pollination three times at 8-day intervals, after which their impact on the set and quality of the edible fig fruits was evaluated. According to the average data, at the end of storage, the least B. psenes loss was obtained from the 16 08 05 (61.03%) genotype, and the highest was obtained from the 16 09 10 (67.00%) genotype. Pollen germination tended to increase with the storage of caprifig fruits, but this increase was not linear. After storage, the 16 08 09 and 16 09 10 genotypes exhibited greater pollen germination. The highest fruit set and quality were obtained when the 16 08 09 and 16 09 10 genotypes were used as pollen sources. Furthermore, since the 16 08 10 genotype is the latest ripening caprifig genotype, it has been determined that it can pollinate late-ripening "Bursa Siyahı" fruits. Principal component and path analysis demonstrated that pollen viability and germination rate were crucial in selecting caprifig genotypes for fruit set and quality. [ABSTRACT FROM AUTHOR]

Flowers of most Piperales do not reward pollinators. However, a few mutualistic pollination relationships have been proposed among the perianth-bearing species. To test the hypothesis of a mutualistic relationship between Prosopanche and beetle pollinators, we studied the pollination biology of three species (P. americana , P. bonacinae , P. panguanensis). For all three species, we recorded flower visitors and flower volatile organic compounds (VOCSs). In addition, for P. americana we investigated flower phases, thermogenesis, visitors' behaviour, and viability of transported pollen. Using a behavioural experiment, we identified the role of flower heat and fragrance in pollinator attraction. We recorded Neopocadius nitiduloides and Lasiodactylus sp. sap beetles (Nitidulidae) as main pollinators and Hydnorobius hydnorae and H. helleri weevils (Belidae) as occasional pollinators. Thermogenic female flowers heat up to 8°C above the ambient temperature. Flowers only trap the small-sized sap beetles. Methyl-3-methyl-2-butenoate dominated the VOC profile. This was a powerful attractant for sap beetles in controlled bioassays. We conclude that pollination in Prosopanche is mutualistic. This was observed through a pollinator-size-based access limit to the stigmatic chamber and a strong olfactory attractant. Mutualism in Prosopanche therefore contrasts with that of most perianth-bearing Piperales, suggesting it is a novel pollination relationship in early-diverging angiosperms. [ABSTRACT FROM AUTHOR]

The production of melons (Cucumis melo L.) in greenhouses relies on pollination. Extreme temperature and insufficient light reduce not only flower visitation by pollinators but also pollen viability, resulting in inefficient pollination. In this study, we investigated the effects of forchlorfenuron [(N-(2-chloro-4-pyridyl)-N0-phenylurea (CPPU)] on the fruit setting and growth of oriental melons (C. melo L. var. makuwa Makino). The primary objective was to devise a new strategy for the management of oriental melons. Treatment with 5 mg·L21 CPPU a day before flowering (T1), on the day of flowering (T2), and a day after flowering (T3) increased the fruit setting rate (by 20.1% to 30%) in melons subjected to artificial pollination (AP) or no pollination (NP) compared with the rate in those subjected to only artificial pollination without CPPU (CK). CPPU treatment induced unfertilized seeds; in addition, a tendency toward parthenocarpy was noted. The highest fruit setting rate (~95%) was noted in plants subjected to the following treatments: AP+T1 and NP+T3. The rates of abnormal fruit formation decreased from 45.2% of CK group to 9.4% in plants subjected to AP+T1 and to 19.4% in those subjected to NP+T3. Elevated exogenous concentrations of CPPU markedly increased fruit weight. Plants subjected to NP+10 mg·L21 CPPU bore the heaviest fruits (541.0 g), which were heavier than those borne by plants subjected to AP+10 mg·L21 CPPU. CPPU treatment reduced the fruit cavity ratio in a concentration-dependent manner from 47.3% to 33.6% and increased the pulp thickness from 1.5 to 2.5 cm. Notably, supplementary CPPU treatment exerted no significant effects on fruit traits. Regarding taste, inconsistent results were obtained for sugar accumulation. Although the content of cucurbitacin B increased immediately after the initial CPPU treatment, it markedly decreased after 15 days of CPPU treatment. Therefore, mature melons did not have a bitter taste. [ABSTRACT FROM AUTHOR]

Brinjal hybrid seed production primarily utilizes the seed-to-seed method. Optimal results require synchronized stigma receptivity and pollen viability, timing of emasculation and pollination along with the appropriate quantity of pollen on the female parent's stigma. With this perspective, the research was carried out, employing the parents of the GJBH 4 brinjal hybrid. The study involved 18 experiments, considering two emasculation options namely emasculation on same day as flower opening, emasculation on a day prior to flower opening, three pollination times namely 8-9 am, 9-10 am and 10-11 am and three cross-pollination ratios namely two female flowers per male flower, four female flowers per male flower, six female flowers per male flower. The results revealed that for better hybrid seed yield, emasculation on the day prior to flower opening, pollination between 9-10 am and using one male flower to pollinate four female flowers could be adopted. [ABSTRACT FROM AUTHOR]

Reproductive barriers are the single largest impediment in breeding of Solanum aethiopicum (Shum and Gilo cultivars). Knowledge of these barriers is important for prudent germplasm utilization and genetic improvement of the species. This study investigated compatibility barriers between S. aethiopicum and its relatives. A randomized complete block design and a full diallel mating method were used to evaluate crossability and floral traits of six genotypes of four different species (S. aethiopicum, S. macrocarpon, S. anguivi and S. incanum) across two seasons. Parameters assessed were petal opening time, stigma receptivity, anther dehiscence, pollen quantity, pollen viability and crossing success. Most flowers for all parental genotypes were opened by 08:00 am. Mean number of open flowers was higher (12 ± 6) for S. aethiopicum Shum (N11) and lowest (n = 3 ± 1) for S. macrocarpon (E12; (p < 0.001), with other genotypes being intermediate. Stigma receptivity differed (p < 0.001) among genotypes and seasons and was highest for N11 at 3.31 ± 1.32 and lowest for S. incanum (In1) at 2.24 ± 1.27; other genotypes were intermediate. All genotypes possessed high pollen viability (µ > 80%) though species differed (p < 0.01). All genotypes exhibited self-compatibility to varying degrees with N11 showing the highest fruit success (67.9 ± 15.6%), seeds per fruit (82 ± 51), and F1 germination rate (79 ± 18%). Interspecific crosses using S. macrocarpon, S. anguivi and S. incanum as females showed poor or no fruit and seed. N11 (S. aethiopicum Shum) was the top performer as a female; crosses with S. macrocarpon (N11xE12) showed highest fruit success (65.9 ± 26.5), with S. anguivi (N11xA1) showing the highest seed set (n = 56 ± 34) and S. incanum (N11xIN1) showing the highest F1 germination (64 ± 19). The F1 intraspecific cross between S. aethiopicum Shum (N4) and S. aethiopicum Gilo (G4) did not germinate. Female parent functioning may be a key feature for the failure of interspecific crosses where S. aethiopicum is a donor as observed by the unilateral incompatibility. [ABSTRACT FROM AUTHOR]

Occurrence of male and bisexual flowers (andromonoecy) in a species is thought to be an adaptation to enhance reproductive success through increasing male function or by diverting resources otherwise used for the formation of pistils. Commelina diffusa Burm. f. is a pantropical, herbaceous, and andromonoecious species from the family Commelinaceae. A typical inflorescence comprises male and bisexual flowers enclosed within a spathe. Morphology of the different floral types, floral phenology, pollen viability, pollen production, and mating system were studied in this annual, bearing small fruits. Being nectarless, pollen is the only reward for the pollinators in this species. The number of fruits developing was found to influence the gender of the subsequent flowers within the spathe. The floral visitors, including members of Diptera and Hymenoptera, facilitate outcrossing and may mediate geitonogamous selfing as well. Delayed selfing takes place when floral organs intertwine as the flower fades. Andromonoecy in itself does not promote outcrossing, but it may be advantageous to present pollen in more flowers, thereby attracting and feeding more insects and potentially increase male function. [ABSTRACT FROM AUTHOR]

Exacum bicolor (Roxb.) is an herbaceous perennial endemic to peninsular India and enlisted as an endangered plant species. Since a thorough insight into the reproductive biology of a species is necessary to aid conservation and crop improvement, the present study was formulated to assess the floral biology and reproductive behaviour of the plant. It was found that the bisexual flowers of this plant possess pollen grains that remain viable for nine days after anthesis exhibiting maximum viability on the first day of anthesis (84.61%) and 84.18 per cent viability on the previous day of anthesis. Stigma was found to be receptive upto four days after anthesis. Maximum seed weight per capsule (17.21 mg) was realised from flowers pollinated on the third day of flower opening. There was 100 per cent fruit set in flowers that were open pollinated as well as in the flowers which were either controlled out-crossed or self-pollinated under control. Fruit set was not observed on bagging the flowers to avoid natural out-crossing, and on open pollination. Hence, it became evident that Exacum bicolor (Roxb.) is primarily a cross-pollinated species, although no self-incompatibility mechanism operates in the species. Also, natural self-pollination is not favoured for procreation; reproduction via apomixis is absent in the species. [ABSTRACT FROM AUTHOR]

Interspecific hybridization has long been used to produce Phalaenopsis hybrids with superior traits such as flower size, color, lip morphology, heavy pigmentation spots, spike number, plant height, floret number and size, inflorescence angle, and branching. For a successful breeding program, superior parents with desirable horticultural traits must be selected for hybridization based on market preferences. However, many existing hybrids produce triploids or aneuploids and are almost completely sterile. A database of the cytogenetic backgrou nds of species and cultivars is essential for formulating systematic breeding programs. However, this information is limited to the Phalaenopsis cultivars. Therefore, chromosome composition, pollen viability, and meiotic abnormality of two Phalaenopsis yellow cultivars, namely Phalaenopsis ‘Fuller’s Sunset’ and Phalaenopsis ‘Geumgongju,’ were analyzed in this study. Cytogenetic analyses revealed that both cultivars had hypotetraploid and asymmetrical chromosomes. Assessment of pollen viability using the 2,3,5-triphenyl tetrazolium chloride (TTC) staining test and in vitro pollen germination in five flower developmental stages demonstrated that P. ‘Fuller’s Sunset’ pollinia were viable because it were stained in all stages with pollen tube growth. In contrast, unstained pollinia and the absence of pollen tubes were observed in P. ‘Geumgongju.’ Sporad stage analysis showed that P. ‘Geumgongju’ contained predominantly abnormal sporads with micronuclei compared to those of P. ‘Fuller’s Sunset.’ The results of this study provide vital information for breeding programs for Phalaenopsis cultivars and emphasize the importance of selecting appropriate parents for hybridization. [ABSTRACT FROM AUTHOR]

In vitro pollen germination is considered the most efficient method to assess pollen viability. The pollen germination frequency and pollen tube length, which are key indicators of pollen viability, should be accurately measured during in vitro culture. In this study, a Mask R-CNN model trained using microscopic images of tree peony (Paeonia suffruticosa) pollen has been proposed to rapidly detect the pollen germination rate and pollen tube length. To reduce the workload during image acquisition, images of synthesized crossed pollen tubes were added to the training dataset, significantly improving the model accuracy in recognizing crossed pollen tubes. At an Intersection over Union threshold of 50%, a mean average precision of 0.949 was achieved. The performance of the model was verified using 120 testing images. The R 2 value of the linear regression model using detected pollen germination frequency against the ground truth was 0.909 and that using average pollen tube length was 0.958. Further, the model was successfully applied to two other plant species, indicating a good generalizability and potential to be applied widely. [ABSTRACT FROM AUTHOR]

• Comprehensive phenology from the onset of the primordial bud to the senescence phase, is documented for Macrotyloma uniflorum. • Floral organs exhibits ultrastructural variation in Macrotyloma uniflorum. • Macrotyloma uniflorum accessions from Republic of Benin are non-echinate; other accessions exhibit spinuliferous pollen. • There is a positive correlation between days to flowering and most floral traits. • Pollens of Macrotyloma uniflorum are viable during the day. The absence of information on the reproductive biology of some nutritive legumes has been an obstacle to their genetic improvement. Gathering information on reproductive biology contributes significantly to the interest of breeders to have adequate tools for initiating the improvement program through crosses among high performing genotypes. To contribute to this, we examined the flowering phenology, pollen biology, stigma receptiveness at bud dehiscence and anthesis phases, and the in-vitro germination of the pollens in horsegram (Macrotyloma uniflorum). Pollens of horsegram were found to be either tricolporate or triporate, echinates in all accessions except in the collections from Benin. Ovaries in horsegram showed great variation in the number of ovules and activities of peroxidase indicated the receptiveness of stigma at bud dehiscence phase and during anthesis. A high number of ovules per ovary was found in accessions from Australia (Leichardt 1 and 2), Mali (LeichardtMali) and India (CPI22679). Pollen viability analysis implies the possibility of better results when pollinating during the day and immediately after the flower opens. The study provides information on the reproductive biology of horsegram for future hybridization program in order to enhance the performance of the crop and increase production. It also reveals differences in accessions from Benin compared with all other accessions from Mali, India or Australia. [ABSTRACT FROM AUTHOR]

Pollen hydration on dry stigmas is strictly regulated by pollen–stigma interactions in Brassicaceae. Although several related molecular events have been described, the molecular mechanism underlying pollen hydration remains elusive. Multiple B‐class pollen coat proteins (PCP‐Bs) are involved in pollen hydration. Here, by analyzing the interactions of two PCP‐Bs with three Arabidopsis thaliana stigmas strongly expressing S‐domain receptor kinase (SD‐RLK), we determined that SD‐RLK28 directly interacts with PCP‐Bβ. We investigated pollen hydration, pollen germination, pollen tube growth, and stigma receptivity in the sd‐rlk28 and pcp‐bβ mutants. PCP‐Bβ acts in the pollen to regulate pollen hydration on stigmas. Loss of SD‐RLK28 had no effect on pollen viability, and sd‐rlk28 plants had normal life cycles without obvious defects. However, pollen hydration on sd‐rlk28 stigmas was impaired and pollen tube growth in sd‐rlk28 pistils was delayed. The defect in pollen hydration on sd‐rlk28 stigmas was independent of changes in reactive oxygen species levels in stigmas. These results indicate that SD‐RLK28 functions in the stigma as a PCP‐Bβ receptor to positively regulate pollen hydration on dry stigmas. [ABSTRACT FROM AUTHOR]

Cannabis sativa is a widely studied species and is currently accepted worldwide due to its medicinal properties, especially those conferred to the CBD phytocannabinoid, which is synthesized mainly in the globular trichomes of female flowers. Males are undesirable and rare in commercial plantations; however, they are necessary for breeding programs. This research aimed to evaluate sexual reversion methods in female cannabis plants as a preliminary stage of a plant breeding program. A completely randomized design with eight treatments and four repetitions was used. The treatments consisted of protocols for the sexual reversion of female plants through drip application and foliar spraying of Silver Thiosulfate (STS), Aminoethoxy-vinyl-glycine (AVG), 1-Methylcyclopropene (1-MCP), and Gibberellic acid (AG3), plus a control treatment without application. Male flower production was evaluated in female cannabis plants, and pollen viability in male flowers was determined. The AVG treatments applied to the apex by dripping, and the AG3 applied to the foliage in the form of a spray influenced the sexual reversion of female plants and produced a total of 132 and 32 male flowers, respectively, without difference between them (P=0.08383). For AVG dripping, only male flowers were observed at the apex, where the application was made directly. Moreover, STS and 1-MCP did not induce the production of male flowers. The pollen from male plants treated with AG3 in spray, and AVG dripping showed high viability (>50%), contrary to the low viability observed in plants treated with AGC applied in spray. The plants treated with AG3 (spray) were higher due to the elongation of the internodes. The AVG and AG3 compounds are effective in the sexual reversion of female cannabis and generate male flowers with viable pollen. [ABSTRACT FROM AUTHOR]

Bdallophytum americanum (Cytinaceae) is an endoparasitic plant species, meaning only the flowers emerge from the host during the reproductive season. Reports on the pollination biology of this species state that its primary pollinators are carrion flies attracted by the smell of the flowers and nectar as a reward. However, the functional role of one of the most outstanding attributes of B. americanum has been neglected. These are the staminal appendages formed by the apical overgrowth of connective tissue during anther development. To determine whether these staminal appendages play a role in pollination, we monitored a nectarless population of B. americanum. We described the inflorescence emergence, floral movements, and pollination and performed field experiments to test whether the absence of the staminal connective appendages affected the visitation frequency. Male inflorescences emerge early, and both male and female flowers open during the day and do not close. Hoverflies are the most frequent visitors to both floral sexes and carry the most pollen. Moreover, the movement of staminal appendages matching the pollen viability changes is reported for the first time. The staminal appendages are the structures where pollinators land before foraging. The field experiments showed that the visitation frequency decreased sharply without staminal appendages. As a landing platform, the staminal connective appendages in B. americanum are crucial for pollinator positioning and collecting viable pollen. [ABSTRACT FROM AUTHOR]

Background: Sweetpotato is an important vegetable and food crop that is bred through sexual crosses and systematic selection. The use of in vitro germination of sweetpotato pollen to test its viability has important theoretical and practical implications for improving the efficiency of sweetpotato crossbreeding by controlling pollination and conducting research on sweetpotato pollen biology. Results: In this study, we observed the morphological structure of sweetpotato pollen under a scanning electron microscope (SEM), developed an effective method for the in vitro germination of sweetpotato pollen, and examined the viability of sweetpotato pollen after treating plants at different temperatures before blossoming. Sweetpotato pollen grains are spherical, with an average diameter of 87.07 ± 3.27 μm (excluding spines), with multiple germination pores and reticulate pollen surface sculpture. We applied numerous media to sweetpotato pollen germination in vitro to screen the initial medium and optimised the medium components through single-factor design. The most effective liquid medium for in vitro sweetpotato pollen germination contained 50 g/L Sucrose, 50 g/L Polyethylene glycol 4000 (PEG4000), 100 mg/L Boric acid and 300 mg/L Calcium nitrate, with a pH = 6.0. The optimum growth temperature for pollen development in sweetpotato was from 25 to 30 °C. Neither staining nor in situ germination could accurately determine the viability of sweetpotato pollen. Conclusions: In vitro germination can be used to effectively determine sweetpotato pollen viability. The best liquid medium for in vitro germination of sweetpotato pollen contained 50 g/L Sucrose, 50 g/L Polyethylene glycol 4000 (PEG4000), 100 mg/L Boric acid and 300 mg/L Calcium nitrate, with the pH adjusted to 6.0. This study provides a reliable medium for the detection of sweetpotato pollen viability, which can provide a theoretical reference for sweetpotato genetics and breeding. [ABSTRACT FROM AUTHOR]

Prunus cerasoides have a high value in phytochemistry and pharmacology. It was classified as the Least Concern globally based on the IUCN red list due to its widespread distribution in eastern Asia. This research aims to evaluate the reproductive biology of P. cerasoides through the study of pollen morphology, pollen viability, stigma receptivity, and pollination in the Cibodas Botanical Garden, located in the Cibodas subdistrict of West Java, Indonesia. The pollen morphology was observed using SEM. Moreover, the pollen viability test was followed by the staining method (aceto-orcein 2%, I2KI 1%, TTC 1%) and in vitro pollen germination with thirteen treatments (aquadest [control]; 5-30% sucrose; and 5-30% sucrose + 5 ppm boric acid). Stigma receptivity was observed daily, from 7 days before anthesis until the anthesis stage. Furthermore, several types of pollination were evaluated, including open pollination, autogamy, geitonogamy, and allogamy. The results showed that the best staining method on P. cerasoides was aceto-orcein 2%, with pollen viability at 87.87%. The sucrose concentration of 25% at 72 hours of observation gave the highest pollen viability results, 52.48%. Stigma receptivity was optimal in the two days before anthesis until anthesis. The highest pollination efficiency was cross-pollination at 53.33%, with an average percentage of the total fruit set of 24.17%. [ABSTRACT FROM AUTHOR]

An experiment is conducted in bitter gourd cropping system at Coimbatore district in India, to study bitter gourd floral character, the foraging ecology of native pollinators and their modes of pollination. Bitter gourd is a monoecious plant bears separate male and female flowers. Male flower blooms early followed by female flowers. Stigma receptivity of pistillate flowers was confirmed on 4th day old flower showed yellowish-green stigma with shining stigmatic exudation. The stigma receptivity lasts up to 24 hours after anthesis. Pollen viability test done with 2 per cent acetocarmine solution indicated that pollen collected during morning hours (06:00 h) were more viable and were deeply stained, whereas pollens collected at evening hours (17:00 h) remained unstained and considered as nonviable. The foraging activities of Apis cerana indica Fabricius and Tetragonula iridipennis begin at 06:00 h and 06:30 h respectively and ceased by evening 17:00 h. T. iridipennis foragers spent more time in pollen collection (31.1 seconds/flower) and nectar collection (26.14 seconds/flower) whereas, A. cerana indica spent less time in pollen collection (8.62 seconds/flowers) and nectar collection (3.56 seconds/flower) respectively. A total of 17 pollinator species belongs to four orders viz., Hymenoptera, Diptera, Lepidoptera and Coleoptera have been documented and grouped based on their mode of foraging in bitter gourd flowers. [ABSTRACT FROM AUTHOR]

Context: Metrosideros bartlettii is one of the most threatened trees in New Zealand and with less than 14 individuals spread across three populations, the species is at high risk of extinction. Despite reproductive failure being identified as one of the factors contributing to population decline, little is known about its pollination biology. Aim: The current study aimed to gain knowledge of the reproductive biology of M. bartlettii by using trees in cultivation of which origin is known. Methods: We tested the effect of self-pollination, cross-pollination and hybridisation treatments on reproductive output. In addition, the viability of fresh pollen was determined for each tree and the impact of desiccation and storage temperature (5°C, −18°C and −196°C) on pollen viability assessed. Key results: Metrosideros bartlettii was found to be highly self-incompatible with seed formed via autonomous self-pollination having low viability. Hybridisation with Metrosideros excelsa , another native species commonly found in cultivation, produced viable seeds, but seedlings failed to survive. Pollen viability differed significantly among trees, and pollen stored at −18°C and −196°C retained viability after 6 months. Conclusion: Metrosideros bartlettii is self-incompatible and cross-pollination is required to increase seed production and supplement wild populations. Implications: Trees in cultivation provide a valuable tool for the conservation of M. bartlettii. However, cross-pollination is essential to prevent hybridisation and ensure genetically robust seed. Long-term storage of pollen at the temperatures determined here will help to overcome challenges in cross-pollination of trees that are spatially and geographically isolated. Metrosideros bartlettii is a critically endangered tree represented by less than 14 individuals in the wild. Due to its self-incompatible breeding system, pollen from an individual from a different population is required to produce viable seed. Short- and long-term pollen storage helps to overcome challenges in cross-pollination both in the wild and in ex situ collections. [ABSTRACT FROM AUTHOR]

Ardisia humilis is an excellent wild ornamental plant. For the purpose of fully utilization of this elite germplasm, the flowering biology and breeding system of this plant had been explored in this study. We conducted field investigation in the flowering phenology, flower-visiting insect and their visiting behaviors on A. humilis individuals introduced in homogeneous garden. Furthermore, pollen viability and stigma receptivity were detected by pollen germination in vitro and benzidine-hydrogen peroxide method, respectively. Combined with artificial pollination,the self-compatibility and the self-pollination of A. humilis were also analyzed in this study. The results were as follows: (1) The florescence of A. humilis was from mid-late May to early June, and the full flowering period was at the end of May. The flowering period of the population, single plant and single flower were approximately 25 d, 17-20 d and 1 d, respectively. (2) A. humilis developed protogynic bisexual flowers, the pistil ripened first with partial overlaps on mature stage of pistil and that of stamen, while stigma remained receptivity until 1 d after stamens fall. (3) With the out-crossing index (OCI) value of 4 and pollen / ovule value of 5.61×103, the breeding system of A. humilis was considered to be outcrossing with partial self-compatibility, and the pollinator insects were essential. (4) The seed set of natural pollination ranked the highest level (average 52.96%), followed by that of autogamy (52.29%) and of artificial-cross pollination (50.33%), with no significant differences among the three (P>0.05), but significantly higher than that of artificial geitonogamy (28.67%) (P<0.05). This study indicated that, beside of being excellent flowering plant, A. humilis was also a potentially important ornamental fruit plant due to the generalized pollination system and the strongly autogamy ability which enhancing the high success of fruits development from blossoms. (5) Lasioglossum sp. 1, Lasioglossum sp. 2 and Halictus sp. were the most observed floral visitors on Ardisia humilis. This study provides an important theoretical reference for the resource utilization and germplasm innovation of A. humilis. [ABSTRACT FROM AUTHOR]

Triticum aestivum is a self-pollinated species with a high proportion of cleistogamous flowers constituting a blockade for out-crossing. Therefore, male parent characteristics are the main goal in the production of hybrid wheat seeds. In a two-year study conducted in Lublin (Poland), the features of flowering biology that can be relevant for the cross-pollination ability of the pollen donor were investigated in winter wheat genotypes. In particular, the anther extrusion capacity, pollen production at the anther and spike levels, and pollen biological value were examined. The pollen production in the anthers was established using an electronic particle counter. The pollen biological value was assessed based on viability (acetocarmine staining) and in vitro pollen germination (raffinose medium) assays. The inter-genotype effect for anther extrusion was significantly correlated to the post-anthesis filament length. The anther extrusion for the individual genotypes fluctuated significantly between the years of the study; however, the interaction with meteorological factors was not assessed. The considerable inter-genotype variability in the pollen donor capability for cross-pollination was highly significantly correlated with the proportion of extruded anthers rather than pollen production, indicating that anther extrusion plays a more important role in the contribution to the final amount of pollen available for cross pollination. The pollen viability determined by staining was high (between 97.5% and 100%), while the in vitro pollen germination varied substantially among the genotypes (between 17.3% and 87.8%). The pollen dispersal ability for cross-pollination in wheat can be improved mainly by increasing the proportion of extruded anthers; however, the pollen production and pollen germination potential cannot be ignored if complete characterization of the ideal male idiotype is to be achieved. [Display omitted] • Proportion of extruded anthers plays substantial role for cross-pollination in wheat. • Anther extrusion is mainly related to the post-anthesis filament length. • Pollen production and pollen germination are important for the ideal male idiotype. [ABSTRACT FROM AUTHOR]

Reproductive-stage heat stress (RSHS) poses a major constraint to cereal crop production by damaging main plant reproductive structures and hampering reproductive processes, including pollen and stigma viability, pollination, fertilization, grain setting and grain filling. Despite this well-recognized fact, research on crop heat stress (HS) is relatively recent compared to other abiotic stresses, such as drought and salinity, and in particular, RSHS studies in cereals are considerably few in comparison with seedling-stage and vegetative-stage-centered studies. Meanwhile, climate change-exacerbated HS, independently or synergistically with drought, will have huge implications on crop performance and future global food security. Fortunately, due to their sedentary nature, crop plants have evolved complex and diverse transient and long-term mechanisms to perceive, transduce, respond and adapt to HS at the molecular, cell, physiological and whole plant levels. Therefore, uncovering the molecular and physiological mechanisms governing plant response and tolerance to RSHS facilitates the designing of effective strategies to improve HS tolerance in cereal crops. In this review, we update our understanding of several aspects of RSHS in cereals, particularly impacts on physiological processes and yield; HS signal perception and transduction; and transcriptional regulation by heat shock factors and heat stress-responsive genes. We also discuss the epigenetic, post-translational modification and HS memory mechanisms modulating plant HS tolerance. Moreover, we offer a critical set of strategies (encompassing genomics and plant breeding, transgenesis, omics and agronomy) that could accelerate the development of RSHS-resilient cereal crop cultivars. We underline that a judicious combination of all of these strategies offers the best foot forward in RSHS tolerance improvement in cereals. Further, we highlight critical shortcomings to RSHS tolerance investigations in cereals and propositions for their circumvention, as well as some knowledge gaps, which should guide future research priorities. Overall, our review furthers our understanding of HS tolerance in plants and supports the rational designing of RSHS-tolerant cereal crop cultivars for the warming climate. [ABSTRACT FROM AUTHOR]

• Zygotic quiescence prolongation is the main reason for the long reproductive cycle of Berchemia. sinica. • The young fruits of Berchemia. sinica entered dormancy in the form of "overwintering complex", and it is the result of convergent evolution. • Androdioecy in Berchemia is reported for the first time. More than two-thirds of the species in Berchemia exhibit remarkable reproductive phenology, characterized by prolonged fruit ripening and the occurrence of overlapping fruit ripening and flowering. However, the underlying reasons for these phenomena remain unknown. Therefore, this study employed routine paraffin section technology, histochemical technique and scanning electron microscopy to investigate embryo sac development, differences between male and hermaphroditic flowers, as well as the overwintering strategy in Berchemia sinica. The findings of this study revealed a significant reduction in pollen viability and the number of pollen grains per flower in hermaphroditic compared to male flowers. Following fertilization, the ovary of hermaphroditic flowers does not undergo significant enlargement but gradually enters the state of zygotic quiescence. Zygotic quiescence prolongation is the main reason for the long reproductive cycle of B. sinica , and it takes approximately 14 months for the entire cycle from flower bud differentiation to fruit ripening to complete. Long reproductive cycle and complex overwintering mechanism exhibited by B. sinica resemble those seen in species belonging to Betulaceae, Fagaceae, Tapisciaceae, and Theaceae, suggesting convergent evolution during Earth's glacial period resulted in similar adaptive structures among these groups delayed fruit ripening leads to overlap between current year's flowers with previous year's fruits. The trade-off between flower and fruit for reproductive resources may have driven evolutionary transition from ancestral hermaphroditism towards androdioecy in Berchemia. [ABSTRACT FROM AUTHOR]

Pollen pistil interaction studies were carried out in six sunnhemp genotypes. Pollen viability percentage of the six genotypes ranged from 0.0 to 93.5% and pollen germination ranged from 0.0 to 84.0% at four different floral stages starting from bud to opening of a flower. The viable pollen grains were present at the later three stages of flower for globose type anthers, while the pollen grains were viable at the later two floral stages for heart shaped anthers. Stigma receptivity was high to very high during S3 and S4 stages. Artificial self-pollination and sib pollination with a mixture of pollen grains were carried out and in vivo pollen tube growth in the style was investigated using fluorescence microscopy. In self-pollinated pistils, eight hours after pollination, callose wall development was seen around the nucellus cell. However, under sib pollinated pistil, eight hours after pollination, pollen tube penetrated into embryo sac of an ovule. The formation of callose in self-fertilized pistil prevented fertilization and seed set. But sib pollinated flowers were fertilized normally and a seed set could be observed. The investigation proved the existence of selfincompatibility. [ABSTRACT FROM AUTHOR]

Roses are one of the most highly produced and purchased ornamental plants worldwide. Procurement and preservation of pollen is essential for the production of diverse rose varieties. In this study, we analyzed pollen management conditions, such as the pollen collection stage, drying time, and storage temperature, to determine optimal conditions for rose pollen management. Pollens were stored under different conditions and the pollen vitality and germination rate were investigated through an optical microscope. The vitality of pollen was an essential factor for rose breeding and depended on the storage conditions. Collecting pollen in the seventh flowering stage resulted in a relatively higher pollen yield. Drying the flower for 5 h after the anther opened improved pollen germination. The germination rate of freshly collected pollen was similar to that of pollen stored at temperatures between −20 °C and −72 °C for up to 30 days, indicating the efficacy of pollen storage at sub-zero temperatures. Since the rate of fruiting increases when pollination is performed three times, considering the time and cost of breeding, it is appropriate to pollinate three times to increase the number of seeds. This study provides an efficient pollen management method to collect and store pollen for breeding. [ABSTRACT FROM AUTHOR]

A key step in the pre-breeding stage of plant breeding is the selection of cultivars with desirable characteristics for use as parents to develop new crop varieties. With the development of technology, numerous laboratory techniques have emerged as key tools for breeding programs to save time and resources. For these reasons, the aim of this review was to describe techniques based on cytological and cytogenetic studies that are feasible for the selection of parents during the pre-breeding stage. Among the cytological techniques addressed in this review are: pollen viability and quality, stigmatic receptivity to know how long the stigma is receptive, and pollen tube growth to study incompatibility events. Another key step in pre-breeding is to determine the chromosomal number of the parents, which is possible by different techniques of classical cytogenetics (studies during mitosis and meiosis) and molecular cytogenetics (flow cytometry, Fluorescent in situ Hybridization and Genomic in situ Hybridization) that are discussed in this review. [ABSTRACT FROM AUTHOR]

[ Objective] The presnet paper aimed to understand flowering habits and pollen fenility of Pueraria lobata, and provide reference for improving the success rate of P. lobata cross pollination. [ Method] In Longzhou county, Guangxi, the bud development process of P. lobata inflorescences were observed every day after it was formed, marked the inflorescences that were about to open in the full bloom period, continuously observed the blooming process of the flowers and recorded the blooming time and weather conditions of the day. Triphenyl tetrazolium chloride (TIC) staining and 12 -KI staining were used to detect pollen activity of P. lobata at different bud stages ( half stretch period, presentation period, half period and blooming period), and the pollen with the strongest pollen viability was selected to carry out the pollen germination test according to the pollen viability measurement results. [ Result] In Longzhou county, Guangxi, P. lobata began to flower on October 16, reached the flowering stage on October 20, and the last flowering stage was from November 2 to November 5. The flowering time of P. lobata was mainly from 15: 10 to 15 :40 every day, and the flowering powder was affected by the weather conditions. Flowering was early when the weather was clear and the temperatute was high, while flowering was delayed when the temperature was low and cloudy and rainy. The pollen activity of P. lobata in different bud stages ( half stretch period, presentation period, half period and blooming period) detected by 12 -KI staining method were 82. l %,95. 3%,93. 5% and 92. 7%,respectively, which were significantly higher than TIC staining method ( P <0. 05, the same as below), and it was more suitable for the detection of the pollen activity of P. lobata. Most of the anthers of the P. lobata flower have already loosened their powder at the beginning of the presentation period, and the stigma was wrapped with large amount. The pollen vitality in the presentation period detected by 12-KI staining was the highest, reaching 95. 3%, which was significantly higher than the other three stages. The pollen quantity and pollen vitality remained at a high level from half stretch period to blooming period. In the medium containing 15 % sucrose, the germination rate of P. lobata pollen was the highest( 36. 23 % ), which was significantly higher than that of the other three sucrose concentrations. [ Conclusion]The 12 -KI staining method can quickly detect the pollen viability of P. lobata. The pollen viability of P. lobata was maintained at a high level from half period to blooming period, and the germination rate was the highest in the medium containing 15% sucrose in sunny weather. 12 -Kl staining method can be used to detect pueraria pollen viability rapidly. Pollen viability of P. lobata remained at a high level from bud opening stage to blooming stage, and pollen at a suitable period could be selected for cross-pollination according to weather conditions to improve the success rate of cross-pollination. [ABSTRACT FROM AUTHOR]

While no significant differences in initial ovule number were found among oilseed rape Brassica napus genotypes, there was a large variation in effective ovule number (EON), which determines the final seeds per silique (SPS), a critical component of yield. In this study, we selected 18 oilseed rape Brassica napus genotypes with contrasting nitrogen utilization efficiency (NUtE) to unravel the main factors responsible for different EON and determine the critical period of EON formation under both a field and a pot experiments from 2016–2018. The high NUtE genotypes displayed significantly higher NUtE by 14.3%, along with greater yield per plant (29.4%) and SPS (21.1%) than the low NUtE genotypes. The greater productivity of the high NUtE genotypes was associated with 44.1% higher pollen grain number, 23.5% greater pollen viability, and 39.3% lower ovule abortion rate, compared to the low NUtE genotypes. In addition, the heart stage was the critical ovule development period for delineating the variability of EON among contrasting NUtE oilseed rape Brassica napus genotypes, when the high NUtE genotypes displayed higher silique net photosynthetic rate, surface area, biomass, and RNA expression levels. Taken together, this study indicated the pollen grain number, pollen viability and ovule abortion rate contributed to the final variation in EON and the heart stage was the critical period of determining the EON differences among contrasting NUtE genotypes. Increasing pollen grain number and pollen viability, and decreasing ovule abortion rate before heart stage should be the prerequisite for breeders to improve yield and NUtE of oilseed rape Brassica napus genotypes. [ABSTRACT FROM AUTHOR]

Genus Garcinia shows high diversity of sexual systems; most of them are dioecious in nature. The other reported sexual systems of Garcinia include gynodioecious, androdioecious, monoecious, and andromonoecious. Garcinia indica (Thouars) Choisy was reported as facultative apomictic polygamodioecious species. There is a large diversity in floral types. Hence, a detailed study of various floral types found on different types of plants of G. indica and to correlate its functionality with sexual reproduction was undertaken. The study at Kokum Plot, BSSKVV, Dapoli, revealed that the male plants could be categorized into four types – androecious, functional males, andromonoecious, and hermaphrodites. The female plants displayed large variation in number and viability of stamens/staminodes. Each category showed significant difference in phenology, floral morphology and pollen types. In December, the percentage of staminate flowers (79.13 ± 2.93%) in androecious trees was significantly higher than functional males (58.61 ± 8.60%) or andromonoecious trees (56.36 ± 2.77%) (p ≤.01). As female plants started flowering, all male morphotypes bore significantly higher numbers of staminate flowers and carpellate flowers were significantly reduced. Pollen viability was highest in androecious flowers at 90.11 ± 1.10% and lowest at 64.70 ± 2.09% in hermaphrodite trees. Earlier studies reported female flowers bore well-developed female gametophyte, but the embryo development was not observed. Thus, the fruit formation might be apomictic, but in present embryological investigation; more than 60% of female and andromonoecious flowers, a well-developed embryo was formed between 8 and 24 h after anthesis. Thus, the embryo formation might be sexual or apomictic. Floral types favoring sexual reproduction are essential for conservation of highly endemic species. [ABSTRACT FROM AUTHOR]

To test for pollination syndrome and to complement records of foraging visitors of an associate mangrove, Barringtonia racemosa (L.) Spreng., aspects of its floral biology were investigated. Phenology and floral rewards (pollen viability, pollen histochemistry and nectar sugar concentration) were focused on owing to their role in plant-pollinator interaction. During the floral opening at 19:00, pollen viability, lipid presence and nectar sugar concentration were highest at 88.05 ± 0.98%, 80.69 ± 10.51%, and 68.98 ± 1.09% mg flower--1, respectively. Starch presence in pollen was rather low (mean 24.95 ± 14.58%), due to hydrolysis of starch occurring during anthesis. These floral characteristics, which reflected the highest reproductive activity, coincided with nocturnal foraging of previously recorded moth visitors. Although bats were rarely observed in previous studies, nocturnal anthesis complemented with the recorded large amount of sugar in nectar (68.98 ± 1.09% mg flower--1 = 1158 J) might be sufficient to provide the average needs of nocturnally foraging bats. Investigation of floral characteristics to complement observation of floral visitors is highly recommended to give a better understanding of the pollination system. Moreover, this study supports the pollination syndrome concept, emphasizing the need for investigation of the role of floral rewards in plant-pollinator relationships. [ABSTRACT FROM AUTHOR]

Programmed cell death (PCD) is an important factor to reduces the viability of plant germplasm after cryopreservation. However, the pathways by which PCD occurs is not fully understood. To investigate whether there is a mitochondrial pathway for pollen PCD after cryopreservation, the pollen of Paeonia lactiflora two cultivars with different PCD levels after cryopreservation was used as test material and the changes of mitochondrial calcium ions (Ca2+), structure, function and their relationship with PCD were compared. The results showed that compared with fresh pollen, the PCD of 'Feng Huang Nie Pan' was significantly reduced after cryopreservation. Their mitochondrial Ca2+ content decreased by 74.27%, mitochondrial permeability transition pore (MPTP) opening reduced by 25.41%, mitochondrial membrane potential slightly decreased by 5.02%, cardiolipin oxidation decreased by 65.31%, and oxygen consumption remained stable, with a slightly ATP production increase. On the contrary, compared with fresh pollen, 'Zi Feng Chao Yang' showed severe PCD after cryopreservation. The decline in mitochondrial Ca2+-ATPase activity led to an accumulation of excessive Ca2+ within mitochondria, triggering widespread opening of MPTP, significantly affecting mitochondrial respiration and energy synthesis. These results suggest the mitochondrial pathway of PCD exists in pollen cryopreservation. • After cryopreservation, the imbalance of mitochondrial homeostasis leads to the occurrence of PCD. • The opening of MPTP plays an indispensable role in the occurrence of PCD during pollen cryopreservation. • Mitochondrial Ca2+ signaling is a pivotal regulatory factor in PCD occurrence. • For the first time established the measurement method for respiratory metabolism (OCR and ECAR) of pollen. [ABSTRACT FROM AUTHOR]

Cassava breeding is hampered by high flower abortion rates that prevent efficient recombination among promising clones. To better understand the factors causing flower abortion and propose strategies to overcome them, we 1) analyzed the reproductive barriers to intraspecific crossing, 2) evaluated pollen-pistil interactions to maximize hand pollination efficiency, and 3) identified the population structure of elite parental clones. From 2016 to 2018, the abortion and fertilization rates of 5,748 hand crossings involving 91 parents and 157 progenies were estimated. We used 16,300 single nucleotide polymorphism markers to study the parents' population structure via discriminant analysis of principal components, and three clusters were identified. To test for male and female effects, we used a mixed model in which the environment (month and year) was fixed, while female and male (nested to female) were random effects. Regardless of the population structure, significant parental effects were identified for abortion and fertilization rates, suggesting the existence of reproductive barriers among certain cassava clones. Matching ability between cassava parents was significant for pollen grains that adhered to the stigma surface, germinated pollen grains, and the number of fertilized ovules. Non-additive genetic effects were important to the inheritance of these traits. Pollen viability and pollen-pistil interactions in cross- and self-pollination were also investigated to characterize pollen-stigma compatibility. Various events related to pollen tube growth dynamics indicated fertilization abnormalities. These abnormalities included the reticulated deposition of callose in the pollen tube, pollen tube growth cessation in a specific region of the stylet, and low pollen grain germination rate. Generally, pollen viability and stigma receptivity varied depending on the clone and flowering stage and were lost during flowering. This study provides novel insights into cassava reproduction that can assist in practical crossing and maximize the recombination of contrasting clones. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the flowering biological characteristics, floral organ characteristics, and pollen morphology of Camellia weiningensis Y.K. Li. These features of adult C. weiningensis plants were observed via light microscopy and scanning electron microscopy (SEM). Pollen viability and stigma receptivity were detected We investigated the possibility of either exogenous ethylene or endogenous ethylene production having an association with the increase in shoot number when nodal explants of Gentiana spp. 'Little Pinkie' were cultured in an in vitro medium supplemented with ethephon (10 mg.L-1). For the first time within an in vitro system, we report the application of laser ethylene detector technology, and optimization of the methodology to quantify concentrations of ethylene (in the part-per-billion range) released from ethephon decomposition within the atmosphere of gas-exchangeable culture vessels including nodal explants. Compared with continuous (continuous measurements on the same replicate of vessels) and repeated (sampling same replicate of vessels every 48 hours) sampling methodologies, the nonrepeated (sampling fresh replicate of vessels every 48 hours) method of measurement of ethylene concentration was more representative of the actual condition within vessels. Although no prior published data exist showing the positive or negative effect of gaseous ethylene in the headspace of culture vessels on bud outgrowth in gentian, our study shows gaseous ethylene in the headspace of culture vessels was not effective in increasing shoot formation in gentian explants cultured in vitro, whereas ethephon supplementation in agar was effective. Plant material in culture vessels did not have a significant effect on ethylene production regardless of the presence or absence of ethephon. Therefore, although ethephon supplementation in the medium produced gaseous ethylene in the headspace, it was unlikely to cause endogenous ethylene production in explants, but it did trigger shoot formation in 'Little Pinkie', perhaps through decomposition to ethylene within the explant tissue, enhancing the internal ethylene level possibly at a locally high concentration. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the flowering biological characteristics, floral organ characteristics, and pollen morphology of Camellia weiningensis Y.K. Li. These features of adult C. weiningensis plants were observed via light microscopy and scanning electron microscopy (SEM). Pollen viability and stigma receptivity were detected using 2,3,5-triphenyltetrazole chloride (TTC) staining and the benzidine-hydrogen peroxide reaction method. C. weiningensis is monoecious, with alternate leaves and glabrous branchlets. Its flowering period lasts 2 to 4 months, and the flowering time of individual plants lasts =50 days, with the peak flowering period from the end of February to the middle of March. It is a "centralized flowering" plant that attracts a large number of pollinators. Individual flowers are open for 12 to 13 days, mostly between 1230 and 1630 HR, and include four to six sepals, six to eight petals, =106 stamens, an outer ring of =24.6-mm-long stamens, an inner ring of =13.4-mm-long stamens, one pistil, and nine to 12 ovules. The flowers are light pink. The style is two- to three-lobed and 16.6 mm long, showing a curly "Y" shape. The contact surface of the style is covered with papillary cells and displays abundant secretory fluid and a full shape, facilitating pollen adhesion. The pollen is rhombohedral cone-shaped, and there are germ pores (tremoids). The groove of the germ pore is slender and extends to the two poles (nearly reaching the two poles). The pollen is spherical in equatorial view and trilobate in polar view. The pollen vitality was highest at the full flowering stage, and the stigma receptivity was greatest on days 2 to 3 of flowering. The best concentration of sucrose medium for pollen germination was 100 g/L. The number of pollen grains per anther was =2173, and the pollen-to-ovule ratio was 23,034:1. C. weiningensis is cross-pollinated. Seventy-two hours after cross-pollination, the pollen tube reached the base, and a small part entered the ovary. The time when the pollen tube reached the base after pollination was later than that in commonly grown Camellia oleifera. The results of this study might lay an important foundation for the flowering management, pollination time selection, and cross-breeding of C. weiningensis. [ABSTRACT FROM AUTHOR]

Artificial hybridization in Phaseolus lunatus L. is still little used in genetic improvement programs in Brazil due to the low establishment percentages. This work aimed to evaluate pollen viability and stigma receptivity in different Lima bean genotypes throughout the day. Accessions 'Roxinha -MT' and 'Cana Longa-PB' were used in the experiment. Five flower buds were collected from each genotype at 6:00 a.m., 10:00 a.m., 2:00 p.m., and 6:00 p.m. The stigma receptivity was determined using 3% hydrogen peroxide, whereas pollen viability was determined with 2% acetocarmine colouration. The genotype and time factors acted independently on the percentage of viable and non-viable pollen grains and stigma receptivity. The genotype 'Roxinha' presented 88.54% viable pollen grains, a value 84.27% higher than that of the 'Cana Longa' genotype. This percentage varied as a function of time, with the highest means observed at 6:00 a.m. Stigma receptivity was influenced only by the time of the day, undergoing a great reduction in receptivity, from 88% in the early morning to slightly more than 40% around noon. These results indicate that 6:00 a.m. is the most suitable time to perform artificial crosses in Lima bean plants. [ABSTRACT FROM AUTHOR]

Background and aims: Paspalum lilloi (Poaceae) is a diploid species, endemic of Iguazú Waterfalls and nearby areas. The reproductive biology and current geographical distribution of this species are poorly known. The aims of this work were to determine the genetic system and to delimit the endemism area and conservation status of the species. M&M: The genetic system was determined by cytoembryological analysis of ovules, viability and in vivo germination of pollen grains, pollen-pistils compatibility, fertility and flow cytometry of single seeds. Herbarium specimens and our collection sites delimited the geographical distribution. Results: Meiotic embryo sacs of Polygonum type were observed in all analyzed ovules. No evidence of apomixis was detected. The mean pollen viability and in vivo pollen germination was 95.2% and 41.8%, respectively. The pollen tube growth in the selfed stigmas was 59.2 ± 6.39 µm / 3h. Seed set in self-pollination was 93.6 % and decreased to 52.7 % when there was heterospecific pollen available. Seeds analyzed by flow cytometric seed screen showed an embryo: endosperm ratio 2:3 indicated a sexual origin. Paspalum lilloi is a reophile and rupicolous species, specialized in fast-moving waters of waterfalls and it is a critically endangered endemism of Iguazu Waterfalls, in South America. Conclusions: P. lilloi is sexual, self-compatible and self-fertile species. Has a highly specialized habitat, which conservation will be a key step to avoid its extinction. [ABSTRACT FROM AUTHOR]

Objective: To explore the influence of biological characteristics on the yield of Amomum villosum Lour. and Amomum longiligulare T. L. Wu, to find an effective pollen viability evaluation method and storage method to solve the problem of the low yield of Amomum plants. Methods: Five germplasm of Amomum plants were used to investigate the effects of the phenological phase, pollen viability, and stigma receptivity on natural and artificial fruit set. Results: Amomum longiligulare T. L. Wu showed late flowering, and its natural pollination rate is higher than that of Amomum villosum Lour. In all germplasm, the artificial pollination rate and fruit setting rate are more than 3 times higher than that under natural conditions. Fruits begin to drop seven days after successful pollination, and the fruit drop is basically stable after one month. The hybridization verification showed that TTC method was simpler and more accurate than in vitro germination method. Optimal storage conditions for pollen are 4°C and high humidity. After 36 h of storage, pollen can still be used for artificial cross-pollination or as hybrid parents. Conclusion: The special biological characteristics are the fundamental reason for the low natural pollination rate of Amomum plants. The accurate measurement method of Amomum plants pollen is the TTC method, and storage at 4°C and high humidity can increase the yield, which was six times that of the natural yield. [ABSTRACT FROM AUTHOR]

Tephrosia purpurea and T. villosa display vegetative growth and sexual reproduction throughout the year. T. purpurea produces resupinate and non-resupinate flowers with an explosive pollination mechanism, while T. villosa produces exclusively non-resupinate flowers with a valvular pollination mechanism. Flower-tripping is essential for the function of pollination mechanism and occurrence of self- or cross-pollination; tripping is effected by wind, rain, temperature, thrips, bees and wasps. Both species are facultatively xenogamous. Empty pods, ill-formed seeds and variation in the number of produced seeds has been attributed to the internal regulation by plants, in order to allow cross-pollinated flowers to produce more seeds and abort selectively the genetically inferior pollen resulting from self-pollination. The low fruit and seed set rates recorded in open-pollinated flowers of both Tephrosia species have been attributed to the presence of untripped flowers, extent of cross-pollination rate, short tenure of pollen viability, number of foraging visits made by pollinating insects, flower closure by the end of the day of anthesis, and availability of energy resources. Both species are autochorous, with short-range seed dispersal. Seeds germinate if the soil has moisture and nutrients but their continued growth and development is largely related to their efficiency in utilizing the available nutrients over other co-occurring seedlings or plants growing simultaneously with them. The plants also sprout from the perennial root stock, usually during rainy season. Therefore, the dual modes of propagation ensure these species' recolonizing of the same habitat and invading new habitats. [ABSTRACT FROM AUTHOR]

[Objective] In order to provide theoretical basis for pollen viability identification, artificial pollination and cross breeding of large- fruited yellow passion fruit, the effects of different culture medium in vitro and storage conditions on pollen germination were analyzed. [ Method] Pollens were collected from newly blooming flowers of large-fruited yellow passion fruit The suitable concentrations of sucrose, boric acid, calcium nitrate and suitable pH for pollen in vitro culture were screened by Li, (5 4) onhogonal design. The effects of sampling time of flowers, storage humidity and temperature on pollen viability were studied by using the most suitable pollen culture medium. The suitable storage condition for pollen of large-fruited yellow passion fruit was determined. [Result] The results of onhogonal test showed that the order of influencing factors on pollen germination rate of large-fruited yellow passion fruit was calcium nitrate > sucrose > boric acid > pH. The optimum medium for pollen germination in vitro was 100. 00 g/L sucrose + 0. 02 g/L boric acid + 0. 40 g/L calcium nitrate, and the medium pH was 5. 0. The pollen germination rate in the optimum medium was 85. 55 % . The pollen germination rate of large-fruited yellow passion fruit was more than 80. 00% when the sampling time was from 11 :30 to 17 :30. The pollen viability was the highest in the third hour ( 16: 30) after flowering, which was significantly higher than the germination rate of pol- lens collected at other times except 13 : 30 and 15 : 30 (P <0. 05, the same as below). The results of storage test showed that, the pollen germination rate of natural air drying on sulfur paper treatment for 3 - 48 hours was significantly higher than that of sealed centrifugation tube storage at room temperature and storage in desiccator on sulfur paper for the same time, and the pollen germination rate of 48 h storage was still 34. 28%. The pollen germination rate was 61. 49% after natural air drying for 5 hours and sealed in centrifugal tube at 4 °C for 24 hours, which was significantly higher than that (55. 22%) after natural air drying for 5 hours and sealed in centrifuge tube at - 20 °C for 24 hours. [Conclusion] The optimum medium for pollen germination in vitro of large-fruited yellow passion fruit is 100. 00 g/L sucrose+ 0. 02 g/L boric acid+ 0. 40 g/L calcium nitrate, and pH is 5. 0. The best storage condition is that the pollens collected on the day are dried naturally for 5 hours and sealed in centrifuge tube at 4 °C [ABSTRACT FROM AUTHOR]

To study the effect of boron deficiency and toxicity on the reproductive development and pollen-stigma interaction in sunflower (Helianthus annuus var. Sungold), plants were raised in sand culture under glass house condition till maturity at 0.033 (deficient), 0.33 (sufficient) and 3.3 (toxic) mg B L−1 supply. The effect of deficiency and toxicity of boron on the number, size and weight of inflorescence, anther size, pollen producing capacity (PPC) of an anther and pollen viability were determined. Enzymes peroxidase, acid phosphatase and esterase and protein were cytochemically localized on the stigmatic surface of disk floret. As compared to control plants (0.33 mg B L−1 supply) development of inflorescence was not only delayed but also poor under boron deficiency and toxicity. Pollen grains produced under boron deficiency and toxicity had reduced size with low viability. Histochemical localization of proteins showed marked decrease in concentration on the stigmatic surface of plants receiving deficient and toxic boron supply. Cytochemical localization of peroxidase enzymes on the stigmatic surface showed increased activity whereas a decrease in acid phosphatase and esterase activity was observed suggesting poor pollen stigma interaction under boron stress condition which might be the cause of poor fertilization. [ABSTRACT FROM AUTHOR]

Cross-pollination in cultivated rice (Oryza sativa L.) is rarely reported to exceed 2%. This low crosspollination frequency (CPF) is conducive to successfully maintaining the purity of rice landraces for many generations. We were therefore surprised to notice a dramatic loss of genetic purity in some of the pure line landraces in many farmers' fields. Having ruled out the possibility of mixing of seeds from different varieties, we surmised this rapid loss of genetic purity to be due to a somewhat higher degree of crosspollination, and conducted a carefully designed experiment with suitably chosen pairs of landraces. We report here an unusually high (>81%) CPF seen in a pair of landraces whose flower opening times (FOTs) were coincident. Our control experiment on a pair of landraces with non-overlapping FOTs failed to detect any cross-pollination. This preliminary report suggests that the crucial importance of FOT diversity in landraces in determining CPF has not been recognized in designs of previous reports of crossing experiments, resulting in a severe underestimation of CPF in cultivated rice under natural conditions. [ABSTRACT FROM AUTHOR]

China is one of the five major distribution regions of Impatiens in the world, with more than 270 species distributed all over the country, especially in limestone areas such as Yunnan, Guizhou and Guangxi. In order to explore pollination ecology of Impatiens uliginosa, we conducted the following experiments: observing the floral traits and floral phenology, measuring the nectar volume and sugar concentration, counting pollen viability, deposition and removal, carrying out pollination treatments and recording floral visitors and their behavior. Results show that the average life span of a single flower is 3.23±0.68 d. The male and female phase lasted for 1.70±0.06 d and 1.53±0.63 d. The amount of nectar per flower is 6.97±0.47 ul and sugar concentration of nectar is 36.58±0.82%, respectively. Stigma is receptive on the first day of anthesis. Pollen viability is strongest on the second day of anthesis. The pollen-ovule ratio (P/O) is 3974.28±105.07. We investigated the contributions of different floral visitors. Bombus sp., Apis dorsata, Lobocla proxima, Ant sp. and Ephydra sp. are diurnal visitors. However, Bombus sp. is the most effective pollinator of I. uliginosa. Pollination treatments indicated that I. uliginosa is self-compatible but completely relies on pollinators for pollination. There is no restriction on pollination in the field and I. uliginosa can avoid inbreeding depression. This study is of great significance to enrich the biological data of pollination and protect the biodiversity of Impatiens. [ABSTRACT FROM AUTHOR]

Background: In order to reveal the pollination biological characteristics of Lespedeza davurica, wild L.davurica from eight regions of Shanxi Province was used as test materials to study their floral dynamic, pollen storage and other aspects. Methods: During 2019, the flowering dynamics of wild L. davurica collected from eight regions of Shanxi Province were observed by selecting the better-grown L.davurica. Freshly bloomed flowers were picked, and their pollen was set up for two treatments, dry and undried, for pollen storage experiments. Pollen viability was determined by the TTC (expand for first instance) and MTT (expand for first instance) methods and stigma receptivity was determined by the hydrogen peroxide-benzidine method. Result: The results showed us the following points: the flowers of L. davurica were pale yellow, large and fragrant; it usually opens from the base to the top with distinctly asymmetrical petals; it opens during the day and closes at night; the number of flowers reached its peak between 12:00 and 14:00. After measuring the pollen viability of L. davurica, we found that dry storage at -20ï,°C was the most effective treatment. And with the increase of temperature and decrease of humidity, the pollen viability and stigma receptivity of L. davurica increased continuously and the highest viability value occurs between 12:00 and 14:00. [ABSTRACT FROM AUTHOR]

Apomixis, the asexual formation of embryos and seeds, occurs in approximately 18% of angiosperm families. Melastomataceae exhibits a remarkable number of apomictic species, distributed among different tribes. This mode of reproduction has been elucidated in Miconieae, but remains unclarified for other groups, such as Microlicieae. Although apomixis has been previously described for Microlicieae species, the cytological basis for this phenomenon is entirely unknown in this group. Thus, populations of Microlicia fasciculata and M. polystemma were used in order to (a) investigate the presence of autonomous apomixis; (b) verify if this mode of reproduction leads to polyembryony; and (c) investigate whether apomixis may occur in parallel with the sexual process. We tested these species for autonomous fruit set and polyembryony, and pollen viability, and analyzed pollen tube growth. Anatomical techniques were used to elucidate the micro‐ and megasporogenesis and gametogenesis. The species showed autonomous fruit and seed formation and exhibited polyembryony. Apospory and adventitious embryony were the developmental mechanisms of apomixis in M. fasciculata and M. polystemma, respectively. Both species exhibited low pollen viability. However, some viable pollen, reduced embryo sac formation, natural pollination and pollen tube growth enable sexual reproduction and characterize these species as facultative apomicts. The independence of pollinators for fruit set, uniparental reproduction and the possibility of sexual reproduction, confer reproductive assurance and flexibility, bringing together advantages of sexual and asexual reproduction. In this sense, apomixis may have played an important role in the evolution and diversification of Microlicia, a widely distributed genus in the Brazilian Cerrado. [ABSTRACT FROM AUTHOR]

In red clover seed production, low seed yield is limiting the commercial exploitation of tetraploid red clover. To explore if pollination is the limiting factor for the seed yield in tetraploid red clover, we investigated pollinator behaviour and plant reproductive success in diploid (2x) cultivar 'Rajah' and tetraploid (4x) cultivar 'Amos' using honey bee and hand pollination approaches. We measured the seed set at the flower head level with the increasing visitation rate of honey bees (one bee, two bees and open pollination) and pollen diversity (one and two pollen donors) of hand pollination. We found no difference in honey bee pollination behaviour (visitation rate) between the diploid and tetraploid red clover. Surprisingly, the seed set in two bees was significantly lower than that of one bee in 'Rajah'. We suggest that honey bees prefer to visit already tripped florets or to visit fewer florets due to scent marks left by the previous honey bees. In open pollination, seed number per flower head in 'Amos' (on average 11) was half of 'Rajah' (on average 20). Seed set in 'Amos' was lower than 50% of 'Rajah' in honey bee (one bee treatment) and hand pollination (one and two pollen donors treatments). There were no differences in stigma receptivity whereas pollen viability in 'Amos' was lower than 'Rajah' after the peak pollen viability was reached (six days after the onset of flowering). We suggest that the fertility problems such as low pollen viability may be the reason for the low seed set in tetraploid red clover. This conclusion should be verified by investigating other fertility traits during the ovary, embryo and seed development with a broader range of diploid and tetraploid cultivars. [ABSTRACT FROM AUTHOR]

Parmentiera cereifera Seem. is an endangered species in the family Bignoniaceae. Related to the conservation effort, information about the reproductive biology of this species is very limited. Based on that, the objectives of this study were to provide knowledge about the reproductive properties such as floral biology and breeding system of P. cereifera. The research was conducted at Purwodadi Botanic Garden, from October 2019 to February 2021. Several important aspects of reproductive biology, including flower biology, pollen viability and stigma receptivity, pollen morphology and breeding system were investigated. The viability was tested with TTC (2, 3, 5-triphenly tetrazolium chloride) and stigma reseptivity was tested with hydrogen peroxide. The breeding system was determined based on outcrossing index (OCI) using Cruden's method. The results showed that P. cereifera flower was monoecious, had morphological character that supported nocturnal pollination. Stigma and anthers spatially separated, but there was no temporal separation of stigma receptivity and anther dehiscence. Based on the flower biology, the pollen ornamentation (reticulate type), and the Out-Crossing Index (OCI=4), the breeding system was outcrossing but partially self-compatible, required pollinators (zoophily). [ABSTRACT FROM AUTHOR]

Primula Hance(Gesneriaceae)is a group that has attracted much attention in recent years. Its intricate species diversity and its endemic distribution among species have aroused great interest among taxonomists and botany researchers. Except for a few species, like Primulina eburnea (Hance)Y. Z. Wang, most species have a very narrow distribution range, which belong to narrow distribution species or endemic species. In order to reveal the effects of the pollination biology and breeding system of P. eburnea on its reproductive process and colonization ability, we systematically studied the flowering phenology, the pollen and stigma viability, the species and visiting behavior of flower visiting insects, the pollen ovule ratio, the OCI index and the seed setting rate of manipulated pollination of P. eburnea. Besides, we explored whether its reproductive processes such as pollination had a positive effect on the spread of P. eburnea. The results showed that the natural flowering stage of P. eburnea was from March to May, and the entire flowering stage was about 45 d. Its full flowering stage was about 20 d, and the single flower flowering stage was 6-8 d. Pollens had the strongest viability 1-2 d after flowering, stigma did not have receptivity before flowering. The pollen ovule ratio was 537, and the hybridization index was 5. Bagged and emasculation could not bear fruit, indicating that this species did not have apomixis. Compared with natural pollination, the seed setting rate of hand self-pollination was slightly lower, and the seed setting rate of hand xenogamy was slightly higher, indicating self-compatibility. The main pollinators of P. eburnea were Anthophora florea and Bombus sp. Therefore, higher nectar volume, larger pollen amount and stronger pollen viability of P. eburnea were obviously beneficial for it to complete the entire process of pollination and reproduction. This result was obviously conducive to the colonization of P. eburnea and then widely spread in the karst areas of South China to Southwest China. [ABSTRACT FROM AUTHOR]

Cryopreservation of pollen is a complementary conservation strategy and can be used for conserve the diversity in the genus Psidium. The present study aims to cryopreserve the pollen of Psidium species to overcome asynchronous flowering. The pollen of different Psidium species were germinated in vitro in an optimized medium of germination. In vitro / in vivo pollen viability assessment and SEM analysis were carried out to determine the changes after cryopreservation. The in vitro pollen viability was determined at monthly intervals starting from fresh pollen until six months of cryopreservation. The in vivo fertility tests were carried out by pollination using both fresh and cryopreserved pollen. The cryopreserved pollen showed in vitro germination ranging from 1.78% (in P. molle) to 81.67% (in "H 12–5") compared to fresh pollen (2.16% in P. molle to 86.08% in P. guineense). In vivo fertility was tested by controlled pollination using six-month-old cryopreserved pollen and it resulted in fruit setting ranged between 3.33% (P. cattleianum var. cattleianum) and 27.66% (P. chinensis) as compared to fresh pollen between 4.0% (P. cattleianum var. cattleianum) and 30.66% (P. chinensis). Seed set and germination was also recorded in all the crosses attempted using cryopreserved pollen. These in vitro and in vivo results indicated that cryopreservation is an effective technique for breeding and conserving the haploid gene pool in cryo genebank. Scanning Electron Microscopic studies of pollen revealed no significant variation in shape and size after cryopreservation when compared to fresh pollen. • Method of collection and optimum pollen germination media for different Psidium species were standardized. • Cryopreservation of pollen of wild Psidium species were carried to overcome asynchronous flowering and used for wide hybridization resulted in fruit and seed set. • Pollen morphology assessment of fresh and cryopreserved pollen in guava genotypes and wild Psidium species using SEM. • A pollen cryobank established for Psidium genotypes. [ABSTRACT FROM AUTHOR]

The reproductive traits in Gagea are affected by both abiotic and biotic environmental factors. However, further intrinsic drivers, like the ploidy level, could also have a significant influence on the sexual efficiency of these geophytes. Here, we present a comparative study involving the reproductive biology of five species of Gagea occurring in southern Italy, and representing different ploidy levels. The experimental investigations included flower phenology, pollen quality (i.e., morphology, viability, and germination), and stigma receptivity. Such data were then combined with information on seed-set available from previous work. All the studied species showed a gradual pollen presentation, and an early and durable stigma receptivity. Such traits represent effective functional adaptations to prevent pollen limitation under the unpredictable weather dynamics typical of the early blooming season of these plants. The use of a diluted substrate favoured the rate of pollen germination in vitro and, likely, it represents a further adaptation versus adverse environmental conditions (i.e., rain damage on exposed pollen). However, the rates of pollen viability and germination were generally low and appeared related to the ploidy level. Data inherent pollen quality (i.e. morphology, viability and germination) and seedset indicated the hexaploid G. lutea as the most fertile species, while the heptaploid G. fragifera had the lowest scores for all the considered traits. Finally, by considering the isolation and reduced size of the studied population, the unexpected low fertility found in the diploid G. minima was possibly due to inbreeding depression related to the relict status of this species in southern Italy. [ABSTRACT FROM AUTHOR]