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• 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]

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]

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]

• 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]

Success artificial pollination with viable pollen is crucial process in the production chain of date palms. This study evaluated the impact of pollen storage temperature and duration, pollination time following spathe cracking, and the hour of daytime on pollen viability, germinability, fruit set and yield of 'Deglet Nour' date palm cultivar. In in vitro tests, fresh pollen showed the maximum viability (96.3%) and germination (85%) but it decreased thereafter upon the storage temperature (28, 4 and −30 °C) and duration (3, 6, 9 and 12 months). In this respect, pollen stored at −30 °C retained highest viability and germinability followed by those stored at 4 and then at 28 °C. In filed experiments, fruit set was 85, 75, 65, and 45% with pollination using fresh pollen, or pollen stored at −30, 4 and 28 °C, respectively. Fruit set was 95%, 75%, and less than 50%, for pollination performed on the same day of spathe cracking, 6 and 12 days later, respectively. The highest fruit set percentage and yield/bunch were obtained with pollination performed between 12.0 pm and 15.0 pm in contrast to 8.0–11.0 am or 16.0–17.0. [ABSTRACT FROM AUTHOR]

• The androgynous and staminate catkins showed similar pollen viability frequency. • Cultivars 'Morioase' and 'Tamatsukuri' showed the highest percentage of viability, but lower amounts of pollen per anther and per flower. • The cultivars showed differences for in vitro pollen germination. Chestnuts have staminate (male) and androgynous (hermaphrodite) flowers in the same individual. The male flowers are grouped into unisexual catkins, while the female flowers are located at the base of male inflorescences. There is divergence in the functionality of pollen grains among chestnut species. As this species requires cross-pollination, germination tests are essential in breeding programs. The objective of this study was to comparatively evaluate pollen viability as a function of the type of flower using colorimetric assays, to develop a culture medium protocol for in vitro pollen germination and characterize the floral morphology of the Japanese chestnut (C. crenata). Eleven Japanese chestnut cultivars were evaluated for characterization and description of the floral morphology, pollen viability by staining, and in vitro germination with determination of the percentage of viability regarding the type of inflorescence (staminate x androgynous). In addition, a culture medium was established to induce germination of chestnut pollen and determination of the percentage of in vitro pollen germination, as well as quantification of the number of anthers per flower and pollen grains per anther and per flower for all cultivars. There was no difference in pollen viability between androgynous and staminate catkins. The culture medium containing 6 g L−1 of agar, 46.5 g L−1 of sucrose, and 460.23 mg L−1 of boric acid in the absence of calcium nitrate, pH 5.25, promoted the best conditions for in vitro pollen germination. Cultivars with the highest percentage of viability recorded the lowest amounts of pollen per anther and per flower. This characteristic may influence the number of flowers necessary for extraction of anthers in crosses and the success of hybridization in the field. [ABSTRACT FROM AUTHOR]

Temperature is a primary factor affecting the rate of plant development. Warmer temperatures expected with climate change and the potential for more extreme temperature events will impact plant productivity. Pollination is one of the most sensitive phenological stages to temperature extremes and in this study an in vitro pollen germination technique is used to screen coconut genotypes tolerant to high temperature. The pollen of twelve coconut genotypes comprising five talls (CCNT, FMST, LCT, PHOT and WCT), five dwarfs (CGD, COD, CRD, GBGD and MYD) and two hybrids (COD X WCT and MYD X WCT) were screened at different temperature levels from 10 to 50 °C at an interval of 2.5 °C. Cultivar variation existed for cardinal temperatures (T min , T opt and T max ) of pollen germination percentage and pollen tube growth. Mean cardinal temperatures calculated from the bilinear model for the 12 genotypes ranged from 23.5 °C to 29.5 °C, 9.7 °C to 16.5 °C and 40.1 °C to 43.9 °C for T opt , T min and T max , respectively. In general tall, cultivars FMST, LCT, WCT, dwarf cultivar COD and hybrids showed better adaptability to high temperature while dwarf MYD was the least adaptable. At the metabolic level, high temperatures induced about 20% reduction in soluble protein content compared to optimal temperature in all the studied genotypes. There was an inverse relationship between superoxide dismutase activity and pollen germination percentage. Overall, there was wide variation in coconut cultivars for cardinal temperatures (T min , T opt and T max ) of pollen germination percentage and pollen tube growth. The genotypes with higher T max for pollen germination and tube growth may be more tolerant to high temperature stress during flowering. Further studies are required to validate the results under in vivo condition; and also to understand the mechanism and factors that lead to pollen sterility in coconut. [ABSTRACT FROM AUTHOR]

Most Passiflora species present self-incompatibility and thus depend on cross-pollination for fruit production. Therefore, the objective of this work was to evaluate the floral and reproductive biology of 17 Passiflora species, through pollen viability, stigma receptivity, fruit and seed set formation, as well as the pollen-pistil interaction in three floral development stages (pre-anthesis, anthesis and post-anthesis), seeking to maximize the efficiency of controlled pollinations. Pollen viability was estimated by in vitro pollen germination, fluorochromatic reaction and Alexander’s solution, as well as fruiting and pollen-pistil interaction. The stigma receptivity was determined in alpha-naphthyl acetate. The highest percentages of pollen viability, stigma receptivity, fruit and seed set were observed during floral anthesis for all Passiflora species studied, while the lowest values were observed in pre-anthesis. The species P. rubra L. presented the highest percentages of in vitro pollen germination, viability with FDA, stigma receptivity, pollen/pistil compatibility, and high fruit set in anthesis. In contrast, the lowest values of these traits were observed in P. galbana L. The results obtained can support the selection of genetic material and allow inferences about the best pollen collection moment and the peak stigma receptivity to maximize the chances of pollen germination and consequently increase the efficiency of controlled pollinations for both agronomic and ornamental purposes. [ABSTRACT FROM AUTHOR]

Asynchronous maturation of male and female flowers in date palm trees is frequently occurs, making pollen storage operation necessary to ensure pollination. The aim of this study was to investigate the effect of pollen storage temperatures on pollen viability, fruit set and fruit quality of six date palm male cultivars. Pollen grains of six date palm cultivars namely ‘Bouhlesse’, ‘Deglat Beida’, ‘Deglet Nour’, ‘Ghars’, ‘Halwaya’ and ‘Moch Deglat’ were stored at room temperature (24 ± 2 °C), 4 °C or −20 °C. In vitro pollen germination and pollen tube growth were examined after 0, 1, 3 and 13 months of storage. Influence of pollen storage on fruit set and fruit quality were also analyzed. Storage temperature, storage duration, cultivar and interaction between all variables had highly significant effect on pollen viability and pollen tube length (p < 0.0001). High values of pollen germination (up to 87%) and pollen tube length were recorded in fresh pollen (at 0 months of storage). For all cultivars, pollen stored at room temperature lost the most of their viability between the 2 or 3 months of storage. However, pollen viability was extended over time when pollen was stored under low temperature, with a storage temperature of −20 °C preferable to 4 °C. Fruit and pulp weight decreased slightly but significantly in most cultivars as a result of pollen storage temperature, although fruit set was not affected. The pollen of ‘Deglet Nour’ showed high pollen viability after 1 year of storage at −20 °C (∼89%) and may be used as good cultivar for storage. [ABSTRACT FROM AUTHOR]

Artificial pollination is key in the commercial production of the sugar apple ( Annona squamosa ). The influence of the marked climatic seasonality typical of the semi-arid regions, characterized by two seasons (dry and rainy) where this crop is grown on pollen grain development and performance and, consequently, productivity is unclear. To assess whether pre- and post-pollination events are sensitive to seasonal variations, the anther structure, the pollen grain ultrastructure and germination, the in vitro growth of the pollen tube and the fruit set of the species were investigated in the dry and rainy seasons in central Brazil. Floral bud development time and thermal requirement were, 22 days and 360.8 degree-days in the dry season and 34 days and 622.2 degree-days in the rainy season, respectively. Anther development was slower in the rainy season, but the anatomy was not affected. Pollen grains showed greater mucilage content, reserve accumulation, in vitro germination and pollen tube length in the rainy season. Although seasonality did not influence the efficiency of artificial pollination, its effects on microsporogenesis and microgametogenesis, promote higher fruit quality in the rainy season. [ABSTRACT FROM AUTHOR]

Cryopreservation of pollen is an additional way to conserve many species. In particular, it can be used as an alternative strategy to preserve the genetic variation of the genus Ananas. The aim of this study was to cryopreserve pollen from wild pineapple accessions to conserve a gene pool of the genus Ananas , as well as to minimize problems of asynchronous flowering among accessions preserved in a germplasm bank. Accessions of all botanical varieties were used to investigate different protocols for freezing pollen, as well as to determine their viability in vitro/in vivo during the investigation and after freezing in liquid nitrogen. Anthers with pollen of the different accessions were dehydrated and then immersed in liquid nitrogen for periods of 24 h, 60 days and 120 days. After freezing, the viability percentage and pollen tube length were determined. In vivo viability tests were performed through 24 pollinations involving different accessions. The results showed that the cryopreservation of pollen was efficient, attaining in vitro germination rates ranging from 8.24% to 94.25%, with average of 62.67% achieved 120 days after cryopreservation and pollen tube lengths longer than 0.23 mm after this same period. In the in vivo pollinations with cryopreserved grains, the seed formation rate was 70.83% for the different combinations. It was possible to cryopreserve pollen from all the pineapple accessions investigated after dehydration for 6 h on silica gel, with significant in vitro germination percentages and production of viable seeds. [ABSTRACT FROM AUTHOR]

Pollination remains crucial to achieve valuable fruit yield in European pear ( Pyrus communis ) orchards. An innovative approach to improve pollen transfer involves the use of pollen dispensers at the hive entrance. Due to its commercial availability, Nashi ( Pyrus pyrifolia ) pollen is proposed in pollen dispensers fitted in bumblebee hives for European pear tree pollination. Our objectives were (1) to investigate whether Nashi pollen is suitable for pollination of European pear and (2) to assess the efficiency of pollen dispenser in bumblebee hives. To test the compatibility between both species, Nashi pollen were used in hand-pollination of two European pear tree cultivars ‘Conférence’ and ‘Doyenné du Comice’. The impact of Nashi pollen on the bumblebee behaviour was investigated at the hive exit. Nashi pollen was suitable for pollination of ‘Conférence’ and ‘Doyenné du Comice’. ‘Conférence’ fruits resulting from pollination with Nashi were smaller (53 ± 1.5 mm) than those pollinated with ‘Doyenné du Comice’ (60 ± 1.1 mm) while fruit diameter of ‘Doyenné du Comice’ did not vary with the pollen origin (71 ± 1.3 vs. 69 ± 1.2 mm). Pollen deposit at the hive entrance did not modify bumblebee behaviour. All insects leaving the hive were covered with pollen even if their pollen charge decreased by 53% 24 h after pollen deposit. All together our results suggest that Nashi pollen could be used in pollen dispenser for pollination of the European pear cultivars ‘Conférence’ and ‘Doyenné du Comice’ if pollen dispenser is refilled at least once a day. [ABSTRACT FROM AUTHOR]

Nymphoides fallax Ornduff (Menyanthaceae) is an aquatic distylous plant endemic to the Mexican and Guatemalan highlands. Although vegetative reproduction is frequently reported for Nymphoides species, evidence suggests a high prevalence of sexual reproduction in N. fallax. This study aimed: (i) to test homomorphic self-incompatibility, (ii) to describe aspects of floral phenology, estimate the pollen/ovule ratio and the viability of pollen grains, (iii) to evaluate floral morph proportion in natural populations, and (iv) to identify the assemblage of floral visitors, estimating their frequency and capacity to transport N. fallax pollen. The studied populations were located in Central Mexico. We carried out a controlled pollination experiment with eight treatments (n = 80), and we also estimated pollen/ovule ratio and observed floral phenology aspects. We counted the proportion of floral morphs in seven natural populations and observed the presence of visitors to 891 flowers in three natural populations. We observed pollen on the insects using scanning electron microscopy. Our findings showed that N. fallax has diurnal flowers with one-day anthesis, high stigma receptivity, high pollen viability, and intramorph self-incompatibility. The average pollen/ovule ratio (5.1 × 103) was consistent with xenogamy. Five natural populations were found to have both morphs in approximately equal proportions, and two populations consisted only of the long-style morph. An assemblage of 28 floral visitor taxa was observed in 944 visits. The most frequent visitors were exotic bees (Apis mellifera : 43.5 %) and native dipterans (Ephydridae family: 33.3 %; Stratiomyidae and Syrphidae: 7.2 %). Pollen grains were observed attached to the bodies of the most frequent visitors, suggesting that they are potentially effective pollinators. This research expands the knowledge of heterostylous syndrome and sexual reproduction in N. fallax. • Nymphoides fallax has diurnal one-day flowers, high stigma receptivity, and high pollen viability. • We observed high intermorph compatibility and high intramorph self-incompatibility. • The average pollen/ovule ratio (5.1 × 103) is consistent with xenogamy. • Morph ratios approach equal proportions in a majority of populations. • Dipterans were the most frequent native visitors and had N. fallax pollen adhered on their bodies. [ABSTRACT FROM AUTHOR]

• Liquid medium without Ca+2 at 32 °C was optimal for onion pollen germination in vitro. • Pollen should be dehydrated before storage at low temperatures (−80 1 1 Add °C after -80 in the second highlight and −20 °C). • The viability of pollen stored at −80 °C was higher than that stored at −20 °C. • Pollen stored at −80 and −20 °C for two years was successfully used to produce seeds. The preservation of viable pollen is essential to overcome the problems related to the asynchronous flowering of the parental lines in onion hybrid breeding programs. The aim of this study was to establish a simple, inexpensive, and easily reproducible protocol for medium-term onion pollen storage. First, the conditions for assessing the in vitro pollen germination were optimized. The liquid medium favored the counting of germination of pollen grains in comparison to the solid medium. The addition of 75 mg/l Ca(NO 3) 2. 4H 2 O to the medium did not improve pollen germination, while that of 150 mg/l Ca(NO 3) 2. 4H 2 O inhibited pollen germination. The highest germination percentage was achieved by incubation at 30–35 °C in the dark. Second, fresh or dehydrated pollen (maintained in a desiccator with silica gel at 25 °C for 18 h) was stored at 4, –20, and –80 °C for two years to study pollen preservation. In addition, the viability and germination capacity of stored pollen were periodically evaluated at 0, 15 and 30 days; 2 and 6 months; and 1 and 2 years. Pollen viability was best retained at low relative humidity and temperatures below zero. Dehydration was essential for pollen preservation at –20 and –80 °C. The results showed that dehydrated pollen stored at –20 °C could be used, with guarantees, for pollination throughout the flowering season. However, the highest viability and in vitro germination percentages after two years of storage (29 and 32%, respectively) were achieved with dehydrated pollen stored at –80 °C. Finally, the capacity of stored pollen to produce seeds was confirmed in crosses with male sterile lines. In this way, dehydrated pollen stored at –80 °C for two years produced an average of 47.9 seeds/100 flowers, representing 43% of the seed in the control crosses. This is the first report in onion research of seed production after pollination with preserved pollen at –80 °C for two years. [Display omitted] [ABSTRACT FROM AUTHOR]

• The study describes a method for creating novel germplasm combining the rich flower color of tropical water lilies with the cold resistance of hardy cultivars. • The use of stigmatic secretion culture is an efficient method to measure the pollen viability of water lilies. • The optimal time for pollination was in the cup phase with extension for one-day of the flat period, shown by optimal stigma morphology, stigma receptivity, and stigmatic secretion. • Serious pre-fertilization barriers were found in the crosses between hardy and tropical water lilies, and overcoming the pre-fertilization barrier is an important way to improve the cross efficiency of these water lily cultivars. An improved germplasm combining the advantageous traits of tropical and hardy water lilies was assembled by cross-breeding. The pollen viability, stigma receptivity, and pollen tube behavior were assessed to avoid potential developmental problems resulting from cross-breeding. This is the investigation using the measurement of water lily pollen viability by culturing stigmatic secretions in vitro. Germination rates measured by this method were consistent with those found using 2,3,5 triphenyl-tetrazolium chloride staining. Pollen growth in vitro was the same on both the stigma and the style. Stigma morphology, stigma receptivity, and stigmatic secretions showed that the optimal time for pollination was in the cup phase with extension for one-day of the flat period. Three crosses in tropical water lilies all resulted in seeds (73.33%, 86.67%, and 100%) with the pollen tube growing normally in the style. Two out of three hardy water lily crosses produced seeds (16.67% and 65.38%); the third cross produced no seeds and little pollen germination, and it was found that the pollen tube was bent and the pollen was not able to enter the ovule smoothly. There were serious pre-fertilization barriers in the crosses between hardy and tropical water lilies, including low pollen germination, abnormal growth of the pollen tube in the style, showing bending at the apex or expansion in the middle, or the production of a callose, preventing the pollen tube from entering the ovule effectively. Overcoming the pre-fertilization barrier is an important way to improve the cross efficiency of tropical and hardy water lilies. [ABSTRACT FROM AUTHOR]

• Salvia majdae , contrary to most Salvia species, has four exposed stamens and lacks the lever mechanism. • Flower of S. majdae is visited by diverse insects, but not effective pollinators. Pollen grains are transferred ventrally. • S. majdae suffers from extreme habitat conditions. Population size is limited by selfing and weak seedling establishment. Salvia (Lamiaceae), one of the largest plant genera, was not monophyletic as originally circumscribed. To recognize Salvia as a monophyletic genus, five small genera have been placed within Salvia s.l. including the monotypic genus Zhumeria. Little is known about the floral biology of Salvia majdae (syn. Z. majdae), an aromatic medicinal shrub species endemic to dry montane areas in the Hormozgan Province in southern Iran. Floral and ecological features of the species are provided as a basis for more detailed discussion about its taxonomic treatment and conservation. S. majdae produces flowers in the axils of the uppermost leaves as racemes. Unlike most Salvia species, flowers are weakly monosymmetric and lack the typical upper lip that usually hides the pollen-sacs. Each flower has four protruding stamens, the abaxial pair is always fertile, and the adaxial one is mostly sterile. Anthers are bithecate and immobile, the connective is slightly widened but not separating the thecae from each other as in most Salvia species. A staminal lever mechanism is lacking and, contrary to most Salvia flowers, pollen is ventrally transferred. Floral longevity is about three days. Flowers are protandrous on the first day and present both pollen and receptive stigmas on the second day. Controlled pollination experiments confirm self-compatibility of the species. Butterflies, bees and flies visited flowers and were likely attracted by scent and the conspicuous, dark violet color of the flowers. Medium-sized bees (Anthophora spp.) are probably the main pollinators, but pollen transfer by bee flies and occasionally by butterflies cannot be excluded. A moderate pollen/ovule ratio (∼2600:1), high pollen viability (∼90%), relatively high fruit set (75%), and moderate seed set (51%) indicate that the species successfully reproduces sexually. Herbivores strongly contributed to reduced seed set as they destroyed parts of the reproductive organs. The presence of only few seedlings and young plants in the field suggests that environmental pressures are acting on the species demography. To protect the species, we recommend harvest reduction by local people, propagating the plant in nurseries for medicinal purposes, and restocking their natural habitat with young plants. Flower morphology of S. majdae differs considerably from those of its closest Salvia relatives. The species represents a number of plesiomorphic characters which may either represent the ancestral stage or a reversal evolved from a more derived Salvia flower. We discuss these alternatives pointing to the problems linked with the present taxonomic treatment of Salvia s.l. [ABSTRACT FROM AUTHOR]

Abstract: We studied reversible anther opening in a dichogamous aquatic plant Butomus umbellatus L. (Butomaceae) to assess its consequence on male fitness. Light microscope observations indicated that stomium breakage was simultaneous in all the anthers within an opening flower; however, detachment of the epidermis and outward bending of the anther wall were asynchronous. SEM observations showed that epidermis cells alternated between orbicular and crinkly shapes in response to absorption and loss of water. This generated centripetal and centrifugal forces which were significant enough to cause inward and outward bending of the anther wall, thus causing opened anthers to close and closed anthers to re-open respectively, depending on relative humidity of the environment. Behaviour of in vitro and in situ anthers from different whorls within a flower was recorded under four regimes of relative humidity or under a water-spraying treatment. The three stages of anther opening namely stomium breakage, epidermis detachment and outward bending of the anther wall were affected differently by moisture levels. Outward bending of anther wall which was responsible for reversible anther opening was mainly dependent on environmental relative humidity levels. Notably, on sunny days, anther re-opening was inhibited at high relative humidity for in vitro anthers, but not for anthers in situ. Reabsorption, rather than evaporation was responsible for reversible anther opening for this aquatic plant. Water-spraying treatment indicated that flowers with re-closed anthers attracted fewer pollinators. Results using pollen stainability and germinability of pollen on stigmas for pollen grains from different treatments also showed the mechanism of reversible anther opening significantly prolonged pollen longevity by maintaining high viability in a simulated rainy. Discontinuous pollen presentation due to reversible anther opening avoided unfavorable pollination environment and pollen loss. [Copyright &y& Elsevier]

Abstract: Acacia mearnsii (black wattle) is a commercially important forestry species in South Africa, grown for its timber as well as its bark. It is, however, also considered to be an alien invader of indigenous vegetation and for this reason the production of a sterile variety would be highly desirable for commercial forestry in South Africa. Previous research on crosses between diploid and tetraploid parent plants to produce triploid progeny has resulted in poor seed set. One possible barrier preventing seed set could be the viability of the pollen used in the cross pollination operations. Thus a study was conducted to test the pollen viability. In vitro agar media germination tests (ACIAR and Brewbaker and Kwack media) were optimised on Acacia podalyriifolia pollen and then used together with vital stain tests (Sigma® DAB peroxidase and p-phenylendiamine) to test pollen germination and viability of A. mearnsii pollen. These were then compared to in vivo pollen germination on the stigma, and were conducted on both diploid and tetraploid pollen mixes. Results showed that the vital stain tests gave significantly (p <0.05) higher pollen viability than the agar germination tests and were more in agreement with the results from the pollen germination rate on the stigma. For both the diploid and tetraploid pollen mixes tested, there were no significant differences (p >0.05) between the two agar media germination tests and between the two vital stain tests. [Copyright &y& Elsevier]

Abstract: Previous studies have examined the rate of viability loss in pollen grains based on surface conditions but some pollen grains are lifted throughout the atmospheric boundary layer to heights where temperature and moisture differ markedly from near the surface. This transport may affect pollen viability in maize pollen which has been linked to its moisture content. The objective of this study was to examine how predictions of pollen viability may differ when considering the effects of boundary layer transport rather than only considering the conditions at the pollen source. We used Large-Eddy Simulation to simulate pollen dispersion and predict pollen viability upon deposition. We compared the predicted viability that was diagnosed using the atmospheric conditions at the pollen source when a pollen grain was released to viability diagnosed using the atmospheric conditions following the pollen grain''s trajectory as it moved through the atmospheric boundary layer. Using surface values provided a reasonable prediction of viability for pollen grains that traveled less than a kilometer from the source field, but underpredicted pollen viability by as much as 20% for pollen that traveled several kilometers. The difference is attributed to the tendency for longer range transport to require lofting of pollen grains into the upper part of the atmospheric boundary layer, where cooler temperature and higher relative humidity are conducive to increased viability. Our results suggest that pollen grains traveling many kilometers are more likely to pollinate a receptive silk than would be expected based on the atmospheric conditions at the pollen source. [Copyright &y& Elsevier]

Abstract: An improved in vitro pollen germination assay was developed to assess the viability of stored Hedychium pollen. The effect of polyethylene glycol (PEG) (10, 15, and 20%, w/v) on pollen germination and tube growth was evaluated for Hedychium longicornutum and two commercial Hedychium cultivars, ‘Orange Brush’ and ‘Filigree’. Overall, the inclusion of PEG 4000 in the medium improved both pollen germination and tube growth for the three different genotypes tested and the results varied depending on genotype. In vitro germination was used to assess the viability of Hedychium pollen stored up to two months. Pollen nucleus status was determined for four Hedychium cultivars, ‘Orange Brush’, ‘Anne Bishop’, ‘Filigree’, and ‘Daniel Weeks’. Pollens of ‘Orange Brush’, ‘Anne Bishop’, and ‘Daniel Weeks’ were found to be binucleate but ‘Filigree’ was shown to possess both binucleate and trinucleate pollens. High pollen:ovule ratio values were obtained in several Hedychium taxa. The results obtained on the nuclear pollen status and pollen:ovule ratios will further our understanding of the pollination biology and help clarify the taxonomy and phylogeny of Hedychium species. [Copyright &y& Elsevier]

Abstract: Magnolia denudata is an excellent ornamental and ecologically important tree that exhibits low fecundity because of seed abortion. To better understand the cause of this low sexual reproduction, pistil receptivity, and pollen quality were investigated using culture medium and histochemical staining, with emphasis on pollen viability at different flowering stages. Cross-pollination, geitonogamy, and self-pollination were undertaken on flowers of sample trees. We found that flowers produce a large number of pollen grains available for effective pollination. Pollen viability varied at different stages, but was highest during stage 3, in which the stamens detach from the axis, the anthers dehisce, and the gynoecium stigma starts to fade. The duration of pistil receptivity was approximately 5h. These results indicate that poor fertilisation may occur if the optimum period for pollination is missed or the stigma receives poor-quality pollen grains from stages other than stage 3. Although dichogamy avoids selfing, it has led to considerable geitonogamy. Our anatomical analysis of ovule and seed development further revealed that fertilisation occurred in samples with geitonogamy, but that the embryo degenerated in the torpedo stage, demonstrating that aborted seeds were produced by fertilisation, rather than by pseudogamy. Our results provide new insights into the mechanism of reduced seed set under natural conditions. [Copyright &y& Elsevier]

Abstract: ‘Success’ or ‘Red Splendor’ plants propagated by shoot tip culture or embryogenesis had higher pollen germination than those propagated by cutting. All clones of ‘Pepride’, ‘Peter Star’ and ‘Nobel Star’ propagated by cutting or by embryogenesis or shoot tip culture did not have viable pollen. ‘Peter Star’ mutants through mutagenesis could recover pollen viability. When both parents were propagated by tissue culture, fruit set increased compared to when one or both parents were propagated by cuttings. Furthermore, the number of the harvested seeds doubled per pollination set, when the tissue culture parents were used instead of cutting-propagation plants. [Copyright &y& Elsevier]

The ability of maize pollen to remain viable during exposure in the atmosphere can potentially have an overriding effect on outcrossing distances in maize. The survival of maize pollen was determined for various lengths of exposure to atmospheric conditions outdoors. Maize pollen was freshly collected from dehiscing anthers of maize plants and immediately exposed to direct sunlight and to the air. Pollen viability was assessed using in vitro germination tests. The length of exposure time required for pollen germination to be reduced by 50% ranged from 60 to 240 min, depending on environmental conditions. Pollen viability was found to be relatively insensitive to solar radiation and was affected most by loss of moisture, which depended on the energy input from the sun and on the vapor pressure deficit of the ambient air. Maize pollen germination was described well for a wide range of environmental conditions by the integral over time of the vapor pressure deficit of the air. These findings were combined with previously determined values for the water vapor conductance of pollen walls and with a relationship for pollen germination as a function of pollen relative water content to arrive at an equation for predicting the dynamics of pollen survival as a function of exposure to the environment. This model successfully predicted germination percentage over at least a two-decade range for maize pollen freshly collected from anthers. [Copyright &y& Elsevier]

Maize (Zea mays L.) is one of the world’s most important crops. Until recent times, improvement in maize resulted from the manipulation and exchange of genetic information within the genus Zea. With the advent of genetic engineering, genetic information from other species is routinely incorporated into the maize genome. Since maize is a wind-pollinated outcrossing species, questions arise concerning the flow of genetic information between genetically modified (GM) and non-GM maize. Because of the rapidly accelerating introduction of GM corn into agricultural production, improved aerobiological models to predict how far and to what extent maize pollen can be transported in the atmosphere are needed today. Models should provide quantitative understanding of both short- and long-range pollen dispersal, thereby offering a means to evaluate deposition of viable maize pollen in seed production fields as well as on neighboring farms. Central to pollen dispersal is the rich interplay between physics and biology and between space and time. We present an aerobiological framework for assessing corn pollen movement in the atmosphere that could also be applied to other crops and to uncultivated species. An important aim of this paper is to spark interest in the scientific community to generate a more complete framework of corn pollen dispersal. As such this manuscript presents a multidisciplinary albeit incomplete perspective to an emerging applied problem. [Copyright &y& Elsevier]

• Adaptability of floral characteristics of N. hybrid to pollinators was investigated. • Breeding system was gauged via P/O ratio, outcrossing index, and field experiments. • N. hybrid stigma receptivity was the highest on the 1st day of floral anthesis. • Pollen viability was the highest before noon on the 2nd day of floral anthesis. • Reproductive biology favored outcrossing and bee pollinators in N. hybrid. Nymphaea hybrid is a precious aquatic plant of the family Nymphaeaceae that has esthetic, economic, medicinal, and ecological values. Owing to its spectrum of color, especially that of the rare blue strain of the genus Nymphaea , it has gained importance in the breeding of water lilies. However, the lack of research on its flowering characteristics and reproductive biology has severely hindered the reproduction and breeding of superior water lily varieties. In this study, the flowering phenology, floral characteristics, and flower-visiting insects of N. hybrid were assessed. The microstructures of stigmata and pollen grains were observed and the stigma receptivity was determined. Pollen viability was measured by an in vitro germination experiment. We also evaluated the breeding system by measuring the pollen/ovule (P/O) ratio, determining the outcrossing index (OCI), and performing field pollination experiments. The N. hybrid population flowered from late May to mid-November, with a flowering period of approximately 160 days. The florescence of a single flower ranged for 3‒5 days from June‒August and for 5‒10 days from September‒November. Inverse herkogamy and protogyny were exhibited by N. hybrid flowers. Stigmata were wet with papillae distributed on their surface, and the pollen grains were oblate with granular ornamentation of different sizes on their surface. The pollen germination rate was highest when they were deposited in a medium containing 5% sucrose, 0.001% boric acid, 1% agar, and 20 mg/L calcium chloride and cultured at 30 °C. Stigma receptivity was the strongest on the 1st day of floral anthesis, and pollen viability was the highest between 9:30 a.m. and 11:30 a.m. on the 2nd day of floral anthesis. The P/O ratio suggests that xenogamy is the main reproductive system. Artificial pollination results indicated that N. hybrid favored outcrossing and required the participation of pollinators, such as Bombus lucorum L. and Xylocopa s.str. valga Gerstaecker, both of which are effective bee pollinators. These results can aid in formulation and implementation of strategies for N. hybrid hybridization programs, and can also improve the controlled pollination efficiency for agronomic and ornamental purposes. [Display omitted] [ABSTRACT FROM AUTHOR]

• Halophyte Elaeagnus angustifolia can't bear fruits in non-saline soils. • Pollen viability and stigma receptivity were also high in non-saline soils. • No pollen tubes presented in styles after nature pollination in non-saline soils. • Pollen tubes formed in styles after hand pollination in non-saline soils. • No fruits in non-saline soils due to expressional level changes of related genes. Anther development affects the reproduction of flowering plants. Halophyte Elaeagnus angustifolia can bear fruits when grown in saline soils. However, no fruits are born in non-saline soils. The possible reasons and differences in E. angustifolia under two growing conditions were elucidated. We examined features including pollen viability and germination, in situ pollen germination after natural and hand pollination, anthers after pollen release, and the transcriptome in anthers. No significant difference was observed in pollen viability or stigma receptivity in E. angustifolia in non-saline vs. saline habitats. However, no pollen tubes were present in styles, and pollen grains were abundant in E. angustifolia anthers under non-saline conditions. Notably, many pollen tubes formed in styles of E. angustifolia after hand pollination in the non-saline habitat. The differentially expressed genes in anthers from saline vs. non-saline habitats were mainly related to phytohormone, cell wall secondary thickening, transcription factors and ion transport. E. angustifolia fail to form fruits in non-saline habitats due to poor anther pollen release. The induction and coordinated upregulation of genes related to anther cell wall formation and JA biosynthesis likely contribute to anther dehiscence in E. angustifolia in saline habitats, whereas anther dehiscence is blocked in plants grown in non-saline habitats. [ABSTRACT FROM AUTHOR]

• We examined the reproductive biology of Physalis angulata , known popularly as "camapu". • The flowers are hermaphrodite and the anthesis occurs between 06:00 -0:800 h (am). • Apis mellifera was identified as main floral visitor of P. angulata. • Acetocarmine and 2,3,5-triphenyltetrazolium chloride exhibited high viability above 80% and there was no in vitro pollen germination. • The pollen/ovule ratio and in vivo pollination, will help better understand the reproductive system of P. angulata. Physalis angulata L., a member of the family Solanaceae, known popularly in Brazil as "camapu", is widely used in folk medicine. Its leaves have various pharmacological activities and fruits can also be used as human food. Considering the species' potential economic importance, further knowledge is necessary of its reproductive biology for germplasm conservation and to obtain new hybrid combinations in breeding programs. Therefore, the objective of this study was to elucidate aspects of the reproductive biology of P. angulata. We investigated the floral morphology, anthesis, nectaries and pollinator-attraction structures, identified floral visitors, and estimated pollen viability by the colorimetric method with acetocarmine and 2,3,5-triphenyltetrazolium chloride (TTC) at different collection times. In addition, we evaluated the reproductive systems by measuring the pollen/ovule ratio (P/O), as well as by observing pollen-pistil interaction and seed germination after pollination. The P. angulata plants presented hermaphrodite flowers, and the floral opening occurred between 06:00 h and 08:00 h. Anthers and pollen were the main attractive structures to pollinating insects, especially Apis mellifera , the floral visitor found in greatest abundance, followed by nectar, which was analyzed by neutral red solution. Regarding pollen viability, in the first three collection hours it was greater than 90 % according to both staining methods evaluated, and no in vitro pollen germination was observed. According to the P/O ratio, P. angulata was classified as facultative autogamous. Controlled pollination under field conditions indicated the species is self-compatible with a mixed reproductive system. With respect to fruit production and seed formation, the plants originating from natural self-pollination had the best results, with a fruiting rate of 86 % and production of 156 seeds per fruit. The results obtained from studies of the reproductive biology can aid in planning of crosses and establishment of Physalis breeding programs, and also increase the efficiency of controlled pollinations for agronomic purposes. [ABSTRACT FROM AUTHOR]

Pear trees require insect pollination among compatible cultivars to set fruit. However, pollen transfer limitation is the main cause of poor yields in this species, due to low visitation rates and few pollen transfer among compatible cultivars. Assisted pollination using "pollen dispensers" containing precollected compatible pollen fitted into the opening of a beehive could increase yield. We investigated whether stored pollen collected from flowers or bee visitors is suitable for pollinating two European pear (Pyrus communis) cultivars, 'Conférence' and 'Doyenné du Comice'. Pollen collected directly from flowers and indirectly from insects was stored for up to 1 year at 4 °C and −20 °C. Pollen stored at −20 °C showed high viability for both cultivars (60–72%). Consequently, fruit set and fruit diameter using this pollen for pollination was similar to that of fresh pollen. However, the viability of pollen that had been stored at 4 °C was low (6%–14%) and fruit diameter was 6.5% lower when flowers were pollinated with pollen stored at 4 °C compared to fresh pollen. The viability of bee-collected pollen was up to 62% lower than that of pollen collected from flowers. The use of bee-collected pollen as a pollen source resulted in a 48% lower fruit set and 95% lower seed set in 'Conférence' compared to fresh pollen, whereas it did not affect 'Doyenné du Comice' fruit and seed sets. The fruit diameter was smaller when flowers were pollinated with bee-collected pollen than with fresh pollen in both 'Conférence' (54.7 vs. 60.6 mm) and 'Doyenné du Comice' (62.5 vs. 70.0 mm). Therefore, pear pollen collected from flowers and stored at −20 °C could successfully be used for alternative pollination without affecting fruit production. • Stored floral pollen and bee-collected pollen were used in pear pollination trials. • Storage at −20 °C did not affect pear pollen viability, fruit set and quality. • Storage at 4 °C decreased pear pollen viability and fruit quality. • Bee-collected pollen had low pollen viability and reduced fruit set and quality. • Floral pollen stored at −20 °C could be used for alternative pollination. [ABSTRACT FROM AUTHOR]

• Eleven floral developmental stages of Tagetes minuta L. (Wild Marigold) were identified each having distinct characteristic feature. • The floral biology of wild marigold suggests often cross pollinated breeding behaviour. • Significant variations in essential oil composition at each floral development stages were recorded. The (Z)-β-ocimene content was highest in inflorescence, while dihydrotagetone content was highest in foliage. • Study of pollination behavior of wild marigold is critical to decide the breeding strategies required for its improvement. Wild marigold (Tagetes minuta L.) is being commercially cultivated due to high demand of its essential oil in flavor and perfumery industry. Present study investigates pollination behavior, mechanism of pollination and floral developmental of wild marigold in to 11 stages each having distinct characteristic feature as observed by visual and light microscopy. Pollen production starts from stage-2, shape of pollen is spherical tricolpate and size varies from 0.025 - 0.031 mm. However, highest pollen availability and viability is observed at stage-6. Bilobed stigma protrude from the flowers at stage-7 indicating protandry. High bee activity is evident under open field conditions suggesting entomophilous mechanism of pollination. Based on viable seed formation and per cent germination, open field conditions are most suitable for good seed set as these conditions favor cross pollination. Despite poor seed set in self-pollinated condition germination percentage was not affected significantly. Floral biology of wild marigold suggests often cross pollinated breeding behaviour. Gas Chromatography - Mass spectrometry results showed significant variation in essential oil composition at foliage and inflorescence. The (Z)-β-ocimene (52.01 %) content was highest in inflorescence while dihydrotagetone (84.85 %) content was highest in foliage. Knowledge of pollination behavior of wild marigold is critical to decide the breeding strategies required for its improvement. [ABSTRACT FROM AUTHOR]

• Myrcianthes coquimbensis can produce seeds by outcrossing and selfing. • Some plants produced seeds via autonomous agamospermy. • The highest rate of fruit abortion resulted from selfing and agamospermy. • Flowers exhibited incomplete protandry. Many plants can produce seeds via multiple reproductive modes, such as selfing and outcrossing. Having multiple reproductive modes can be advantageous if it assures seed production when outcrossing fails, which is important for species inhabiting environments where pollinators are scarce or variable. However, it can also be disadvantageous due to the fitness costs associated to selfing. Consequently, plants have mechanisms to reduce the incidence of selfing. Here we examined the breeding system of Myrcianthes coquimbensis ; this threatened Atacama Desert shrub is the last species to bloom in the community and exhibits low visitation rates per flower because pollinators are less abundant. Our aim was to determine whether this plant can produce fruits by modes other than outcrossing, and whether it possesses floral traits to prevent sexual interference. We conducted experimental flower treatments in two localities to determine whether fruits were produced by outcrossing, selfing, autonomous selfing and agamospermy. We also evaluated stigma receptivity and pollen viability during a flower's lifespan. M. coquimbensis developed fruits and seeds by all the reproductive modes assessed, including selfing and agamospermy. Flowers presented partial segregation of sexual functions, with the peak of pollen viability occurring before the peak of stigma receptivity. Selfing is unavoidable in M. coquimbensis and likely interferes with outcrossing. Coupled with possible early inbreeding depression, it probably results in a cost for seed production. Our results suggest that this species may be vulnerable in scenarios where pollinators are scarce; however, agamospermy may provide an alternative route of seed production in these scenarios. [ABSTRACT FROM AUTHOR]