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As differences in seed dormancy between Actinidia species have not been reported previously, in this study we characterized the variation in the dormancy of seeds in 13 kiwifruit species that originated from different regions of China and Taiwan, and for which mature plants are now growing in New Zealand orchards. Dormancy-breaking treatments, including cold-moist stratification, seed coat scarification and soaking in water and gibberellic acid (GA3), were tested for their efficacy in alleviating dormancy and improving final germination and germination rates. In addition, we assessed seed viability using RNA integrity analysis to distinguish dead seeds from dormant seeds. This study identified that dormancy type in Actinidia seeds is species-specific and can be morphological, morphophysiological or a combination of physiological and physical, and that seed RNA integrity is a useful metric to incorporate into seed dormancy studies. Our results also suggest that species originating from colder climates that experience large differences between winter minimum and summer maximum temperatures exhibit physiological dormancy and require cold-moist stratification, contrasting with species originating in milder climates. Interestingly, although not all seeds from all the species were dormant, the proportion of dormant seeds in each species did not correlate to the climatic data of the region from which they originated. These findings provide new insights into mechanisms of seed dormancy in kiwifruit. [ABSTRACT FROM AUTHOR]

As differences in seed dormancy between Actinidia species have not been reported previously, in this study we characterized the variation in the dormancy of seeds in 13 kiwifruit species that originated from different regions of China and Taiwan, and for which mature plants are now growing in New Zealand orchards. Dormancy-breaking treatments, including cold-moist stratification, seed coat scarification and soaking in water and gibberellic acid (GA3), were tested for their efficacy in alleviating dormancy and improving final germination and germination rates. In addition, we assessed seed viability using RNA integrity analysis to distinguish dead seeds from dormant seeds. This study identified that dormancy type in Actinidia seeds is species-specific and can be morphological, morphophysiological or a combination of physiological and physical, and that seed RNA integrity is a useful metric to incorporate into seed dormancy studies. Our results also suggest that species originating from colder climates that experience large differences between winter minimum and summer maximum temperatures exhibit physiological dormancy and require cold-moist stratification, contrasting with species originating in milder climates. Interestingly, although not all seeds from all the species were dormant, the proportion of dormant seeds in each species did not correlate to the climatic data of the region from which they originated. These findings provide new insights into mechanisms of seed dormancy in kiwifruit.

Abstract Background The silver wattle Acacia dealbata is a fast-growing tree from Australia that has become naturalised in different regions of the world, attaining invasive status in most of them. In Chile, A. dealbata reaches large abundances along banks and floodplains of invaded fluvial systems, suggesting that rivers may act as a vector for seed dispersal. As hydrochory has not been documented previously in this species, the aim of this study is to evaluate the potential for water dispersal of seeds of this invasive tree along rivers. Methods Seed samples from rivers were collected at three sites along two A. dealbata-invaded rivers within the Cachapoal basin, central Chile. Number of seeds collected was contrasted versus hydraulic and local conditions with RDA. Seed buoyancy and sedimentation velocity were determined and compared between sites with an ANCOVA. Finally, the probability of seed germination after long periods of immersion in water was assessed, simulating transport conditions in the flow. Germination results were tested with a GLM. Results Results indicate that increasing abundance of A. dealbata seeds in the flow is related to the level of turbulence of the flow. Seeds display high floatability but their sedimentation velocity is high when they do sink. Finally, silver wattle seeds can germinate after long periods (many weeks) of immersion in water; however, their probability of germination depends to a large extent on whether seeds are scarified or not. Conclusions Based on the evidence collected, we suggest that the seeds of A. dealbata have the necessary traits to be dispersed by rivers, this being the first research testing this hypothesis. The success of hydrochory of A. dealbata would depend on river flow turbulence, and whether there are natural mechanisms for scarifying the seeds either before or during transport. The proposed methodology can be used to assess river hydrochory for any tree species.

Saskatoon berry has become as important as a commercial fruit crop. One main goal is to release new plant cultivars well adapted to different climatic and soil conditions. Dormant seeds obtained from breeding are serious problems delaying the program. The seeds were directly extracted from fruits after harvest (unstored) or after storage at −18 °C for 6 months (stored) and subjected to modified stratification (3 °C) with KNO3, H2O2, NO, smoke-water (SW) or scarification using sandpaper or H2SO4 for 10, 20, 30, 40 min or treatments with pulsed radio frequency (PRF) or red light. The seeds were also subjected to warm–cool stratification (20/3 °C). Unstored seeds germinated in a higher percentage and with better uniformity (T75–T25) than stored seeds. Stored seeds positively affected the onset of seed germination (T1) and mean germination time (MGT). Dormancy breakage was promoted by stratification with KNO3, SW or scarification with sandpaper, H2SO4 or treatments with PRF. The recommended method for the breeding program of breaking seeds dormancy is when unstored seeds are subjected to stratification in KNO3 (0.2%) or SW (1:100). Depending on the applied methods, the percentage of seeds' germination increased to 87% compared to untreated (64%) control seeds. The positive effects of the selected methods persisted during seedling development by stimulating their growth and enhancing the chlorophyll content index (SPAD) and effective quantum yield of PSII of chlorophyll in leaves (ΦPSII). [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect of inoculation with the biofertilizer IHPLUS®BF on seed germination of Leucaena leucocephala (Lam) de Witt cv. Cunningham. Materials and Methods: The study was carried out at the Pastures and Forages Research Station Indio Hatuey, located in the Perico municipality, Matanzas province, Cuba. To study the germination response of seeds of L. leucocephala cv. Cunningham, an experiment was carried out with a completely randomized design with a 3 x 4 factorial arrangement. The treatments were formed by the combination of two factors: a) imbibition time and b) dilutions of IHPLUS®BF. Three different times (8, 10 and 28 h) were combined with four dilutions (2,5; 5; 10; 15 mL L-1), and a control: seeds with thermal scarification treatment (water at 80 °C for two minutes). Results: Germination kinetics maintained a similar performance in all treatments. The best response was obtained with the combination of the thermal scarification method, with 28 hours of imbibition at 10 days and 96 % germination. Germination potential, speed index, average germination time and time to reach maximum germination performed best when the bioproduct was used with doses of 2,5, 5, 10 and 15 %, imbibed for 28 hours. These doses did not show significant differences among themselves and had higher germination efficiency and a minimum of six days to reach maximum germination. Conclusions: The effectiveness of IHPLUS®BF during the germination process of L. leucocephala cv. Cunningham seeds was proven, being the best combination the use at 5 % for 28 hours with higher germination efficiency. [ABSTRACT FROM AUTHOR]

Astragalus sikokianus is a rare Japanese perennial of the seashore that was reported to be extinct in the wild. The small seed size and deep dormancy of A. sikokianus make it difficult for direct seeding restoration in aspects of seed handling, transport, planting, and seedling establishment. For the large-scale economic restoration of dormant small-seeded species, seed pelleting combined with the breaking of dormancy was studied. Physiological (prechilling and plant hormones) and physical (hot water, hydrochloric acid, and sulfuric acid) seed dormancy break treatments were evaluated. The dormant broken seeds were used for pelleting. The effects of the substrate, pellet sizes, and their interactions on germination were measured. The scarification of five rubs of seeds placed between sandpapers completely broke the physical dormancy of A. sikokianus. Seed coat impermeability inhibited germination. Pelleted seeds ranging from 2.0 to 4.0 mm in diameter showed more than 90% germination on filter paper. The germination of the pelleted seeds was measured in commercial, field, and sand soil conditions. The highest germination was shown in sand (70–74% GP), regardless of the pellet size, whereas unpelleted scarified seeds germinated only 48%. These results suggest that small-seeded species with physical dormancy can be used for seed-based restoration after seed pelleting. [ABSTRACT FROM AUTHOR]

Accelerated global warming is leading to the loss of plant species diversity, and ex situ preservation of seeds is becoming an increasingly important aspect of species conservation. However, information on dormancy and germination is lacking in many endangered species. Amsonia elliptica (Apocynaceae) is the only Amsonia species native to Korea, and the South Korean Ministry of Environment has designated it Class II endangered wildlife. Nevertheless, the dormancy class and the dormancy breaking method for seeds of this species for germination are not precisely known. We identified the structure of A. elliptica seeds and the causes of dormancy, which inhibits germination. In addition, we tried to develop an effective germination promotion method by testing the wet stratified condition, which breaks dormancy, and the form of gibberellin that can replace it. Fresh seeds of A. elliptica imbibe water, but the covering layers (endosperm and seed coat) inhibit germination by mechanically restricting the embryo. Initial germination tests confirmed low embryo growth potential and physiological dormancy (PD). Restriction due to the covering layer was eliminated by seed scarification, and abnormal germination was observed. After 12 weeks of cold moist stratification at 4°C, only 12% of seeds germinated. However, 68.8% of seeds subjected to 8 weeks of warm moist stratification followed by 12 weeks of cold stratification germinated, indicating that warm stratification pretreatment before cold stratification is effective in breaking dormancy. A. elliptica seeds exhibited intermediate PD. Furthermore, 61.3% of seeds soaked in 500 mg/L GA4+7 for 14 days and incubated at 25/15°C germinated. Therefore, GA4+7 rapidly broke the dormancy of A. elliptica seeds compared with warm plus cold stratification treatment, thus providing an efficient method for seedling production. [ABSTRACT FROM AUTHOR]

Background: The silver wattle Acacia dealbata is a fast-growing tree from Australia that has become naturalised in different regions of the world, attaining invasive status in most of them. In Chile, A. dealbata reaches large abundances along banks and floodplains of invaded fluvial systems, suggesting that rivers may act as a vector for seed dispersal. As hydrochory has not been documented previously in this species, the aim of this study is to evaluate the potential for water dispersal of seeds of this invasive tree along rivers. Methods: Seed samples from rivers were collected at three sites along two A. dealbata-invaded rivers within the Cachapoal basin, central Chile. Number of seeds collected was contrasted versus hydraulic and local conditions with RDA. Seed buoyancy and sedimentation velocity were determined and compared between sites with an ANCOVA. Finally, the probability of seed germination after long periods of immersion in water was assessed, simulating transport conditions in the flow. Germination results were tested with a GLM. Results: Results indicate that increasing abundance of A. dealbata seeds in the flow is related to the level of turbulence of the flow. Seeds display high floatability but their sedimentation velocity is high when they do sink. Finally, silver wattle seeds can germinate after long periods (many weeks) of immersion in water; however, their probability of germination depends to a large extent on whether seeds are scarified or not. Conclusions: Based on the evidence collected, we suggest that the seeds of A. dealbata have the necessary traits to be dispersed by rivers, this being the first research testing this hypothesis. The success of hydrochory of A. dealbata would depend on river flow turbulence, and whether there are natural mechanisms for scarifying the seeds either before or during transport. The proposed methodology can be used to assess river hydrochory for any tree species. [ABSTRACT FROM AUTHOR]

Saskatoon berry has become as important as a commercial fruit crop. One main goal is to release new plant cultivars well adapted to different climatic and soil conditions. Dormant seeds obtained from breeding are serious problems delaying the program. The seeds were directly extracted from fruits after harvest (unstored) or after storage at −18 °C for 6 months (stored) and subjected to modified stratification (3 °C) with KNO3, H2O2, NO, smoke-water (SW) or scarification using sandpaper or H2SO4 for 10, 20, 30, 40 min or treatments with pulsed radio frequency (PRF) or red light. The seeds were also subjected to warm–cool stratification (20/3 °C). Unstored seeds germinated in a higher percentage and with better uniformity (T75–T25) than stored seeds. Stored seeds positively affected the onset of seed germination (T1) and mean germination time (MGT). Dormancy breakage was promoted by stratification with KNO3, SW or scarification with sandpaper, H2SO4 or treatments with PRF. The recommended method for the breeding program of breaking seeds dormancy is when unstored seeds are subjected to stratification in KNO3 (0.2%) or SW (1:100). Depending on the applied methods, the percentage of seeds’ germination increased to 87% compared to untreated (64%) control seeds. The positive effects of the selected methods persisted during seedling development by stimulating their growth and enhancing the chlorophyll content index (SPAD) and effective quantum yield of PSII of chlorophyll in leaves (ΦPSII).

Astragalus sikokianus is a rare Japanese perennial of the seashore that was reported to be extinct in the wild. The small seed size and deep dormancy of A. sikokianus make it difficult for direct seeding restoration in aspects of seed handling, transport, planting, and seedling establishment. For the large-scale economic restoration of dormant small-seeded species, seed pelleting combined with the breaking of dormancy was studied. Physiological (prechilling and plant hormones) and physical (hot water, hydrochloric acid, and sulfuric acid) seed dormancy break treatments were evaluated. The dormant broken seeds were used for pelleting. The effects of the substrate, pellet sizes, and their interactions on germination were measured. The scarification of five rubs of seeds placed between sandpapers completely broke the physical dormancy of A. sikokianus. Seed coat impermeability inhibited germination. Pelleted seeds ranging from 2.0 to 4.0 mm in diameter showed more than 90% germination on filter paper. The germination of the pelleted seeds was measured in commercial, field, and sand soil conditions. The highest germination was shown in sand (70–74% GP), regardless of the pellet size, whereas unpelleted scarified seeds germinated only 48%. These results suggest that small-seeded species with physical dormancy can be used for seed-based restoration after seed pelleting.

Restoration programs face several challenges in degraded drylands and desert environments, such as high temperatures, soil salinity, water scarcity, loose soils with low water-holding capacity, and poor fertility. Seed-enhancement technologies (SETs) are proposed to improve soil physical and chemical properties, improve seed germination and seedling recruitment, and promote plant growth. SETs improve seed, seedling, and adult plant growth through three main approaches: adding materials to seed coats (seed coating), removing barriers of seed coats (seed scarification), and physiologically altering metabolites through priming (seed priming). These three main approaches (categories) are further divided into several other subcategories. This review aims to define the general categorization of SETs, adopt the proper SETs for arid lands, and indicate the benefits of SETs to overcome the biotic and abiotic barriers in agricultural systems and the ecological restoration of degraded dryland ecosystems. In general, integrating different seed-enhancement technologies (SETs) for rehabilitating degraded lands with a mixture of seeds from various species is recommended, especially since some technologies tend to be species-specific.

The paper presents development of a high-performance process for extracting oil from quinoa seeds (Chenopodium quinoa Willd.) by supercritical CO2 extraction. The pre-treatment of seeds involving mechanical scarification was applied. The abrasive material gradation and time of abrasion were optimized. Optimum scarification conditions were obtained using the abrasive gradation P40 at scarification time of 50-100 min. Under these conditions, a seed coat was obtained in an amount of 10% of the seed weight and it contained 20 g oil/100 g seed. The oil was separated from the seed coats by supercritical fluid extraction. Approximately 61% of oil recovery was obtained under extraction conditions: pressure 25 MPa, temperature 40° C and extraction time 120 min. From seeds containing 5.6 g oil/100 g seed, after scarification and extraction with supercritical carbon dioxide, approx. 1.2 g oil/100 g seed was obtained from the seed coat. [ABSTRACT FROM AUTHOR]

Dodonaea viscosa (Sapindaceae) is widespread in the mountainous highlands of the southwestern part of Kingdom of Saudi Arabia, where it is a medicinally important species for the people in Saudi Arabia. Seeds of this species were collected from Mount Atharb in Al-Baha region, at an altitude of 2100 m. The aims of this study were to determine if the seeds of D. viscosa have physical dormancy (i.e. a water-impermeable seed coat) and, if so, what treatments would break dormancy, and what conditions promote germination after dormancy has been broken. The dormancy-breaking treatments included: soaking of seeds in concentrated sulfuric acid (H 2 SO 4) for 10 min, immersion in boiling water for 10 min and exposure to 50 °C for 1 min. After seeds had been pre-treated with H 2 SO 4 , to break dormancy, they were incubated at constant temperatures from 5 to 35 °C, under 12-h photoperiods or in continuous darkness, and germination recorded. Salinity tolerance was investigated by incubating acid-scarified seeds in different concentrations of mM NaCl in the light at 25 °C. Untreated seeds had low final germination 30%. Seeds that had been acid-scarified, immersed in boiling water or exposed to 50 °C all achieved 91% subsequently when incubated at 25 °C. Thus, seeds of this species in Saudi Arabia have physical dormancy, which can be broken by all three treatments designed to increase the permeability of the testa. After pre-treatment, there was a broad optimum constant temperature for germination that ranged between 5 and 25 °C but germination was inhibited by higher temperatures (30 and 35 °C). Light had little effect on this germination response. Scarified seeds were also sensitive to salinity, with the highest germination in distilled water and complete inhibition in 400 mM NaCl. Seeds that failed to germinate in saline treatments were mostly able to germinate on transfer to distilled water, suggesting osmotic inhibition. [ABSTRACT FROM AUTHOR]

Chrysophyllum albidum is an important fruit tree species with peculiar hard seed coat and slow growth. This study investigated effectiveness of mechanical scarification on seed germination and fertilizer types on sustainable growth of C. albidum seedlings. Five batches of 50 seeds each were subjected to 5 mechanical scarification treatments. Uniform seedlings were subjected to NPK 15:15:15 and organo-mineral fertilizer treatments. The experiment was laid out in completely randomized design with 4 treatments replicated 3 times; T1 = Organo-mineral fertilizer, T2 = NPK 15:15:15, T3 = Organic fertilizer and T4 = Control. There were significant differences among the treatments on the germination (p<0.05). On the growth assessment, T3 gave the highest Shoot height (35.80cm) and leaf production (15). Highest collar diameter (0.87cm) and leaf area (13.40cm²) were recorded for T1. Mechanical scarification and growth media amendment with the use of organic and inorganic fertilizers catalyzed the growth of the species sustainably. [ABSTRACT FROM AUTHOR]

In 2014, this research was conducted at the Research Institute of Horticulture in Skierniewice, Poland. It was based on different red raspberry seed treatments with sulfuric acid during the scarification process. The seeds were obtained from crosses among ten parental forms, producing 55 hybrid families. During scarification, the seeds were subjected to concentrated sulfuric acid for 20, 30 and 40 minutes. Assessment of the germinated seeds, performed 2.5 months after the sowing, revealed different effects of the seed origin/pedigree and the applied scarification treatments. The best seed germination was recorded for the hybrid families where 'Radziejowa' (56.5% of germinated seeds), 'Laszka' (63.9%) and 'Sokolica' (73.5%) were the maternal forms, and the poorest one - where 'Polana' (6.2% of germinated seeds), 'Glen Ample' (32.5%) and 'Canby' (33.1%) were used as the maternal cultivars. The highest germination, on average for all the hybrid families, was obtained for seeds treated with H2SO4 for 30 min (45.3% of germinated seeds), and the lowest when the seeds were treated with H2SO4 for 40 min (35.6%).

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Abstract: Many invasive plant species have fleshy fruits that are eaten by native frugivorous birds which disperse their seeds and may facilitate their germination, playing an important role in plant invasion success. The fleshy‐fruited shrub Cotoneaster franchetii (Rosaceae) is an important invasive alien in the mountainous regions of central Argentina. To determine the role of avian frugivorous in fruit removal of this species, we conducted a frugivore exclusion experiment including bagged and unbagged branches in 75 plants of C. franchetii. At the end of the dispersal period, we compared the percentage of missing fruits (removed by birds + naturally dropped) in unbagged branches with the percentage of naturally dropped fruits in bagged branches. To assess whether any mechanism acting on seeds during their passage through bird guts (de‐inhibition by pulp removal and/or seed scarification) affects seed germination of this species, we compared percentage and speed of germination among seeds obtained from faeces of the native frugivorous Turdus chiguanco, from manually de‐pulped fruits, and from intact fruits. The percentage of missing fruits per shrub in unbagged branches was significantly higher than the percentage of naturally dropped fruits in bagged branches, suggesting that frugivorous birds play an important role in fruit removal of C. franchetii in the study area. Seeds from bird faeces and from manually de‐pulped fruits germinated in higher percentage and faster than seeds from intact fruits. Germination percentage and speed of seeds from manually de‐pulped fruits were significantly higher than those of gut‐passed seeds. These results indicate that T. chiguanco increases and accelerates seed germination of C. franchetii through pulp removal, but not through seed scarification. Overall, our findings indicate that native frugivorous birds facilitate the dispersal and germination success of C. franchetii, likely playing an important role in its invasion throughout the mountainous region of central Argentina. [ABSTRACT FROM AUTHOR]

Scarification involves the partial removal of the seed coat on the side of the hilum, opposite the radicle, to speed up germination in acorns. The aim of this study was to determine the influence of scarification on the germination capacity of pedunculate oak acorns, selected and prepared for sowing. The diameter, length and mass of acorns were measured before and after scarification in four batches of acorns harvested from uneven-aged trees (76, 91, 131 and 161 years). The measured parameters were used to determine the correlations between acorn dimensions and mass, and to calculate the dimensional scarification index and the mass scarification index in acorns. Individual complete and scarified acorns from every batch were germinated on sand and peat substrate for 28 days. The analyzed acorns were characterized by average size and mass. Scarification decreased acorn mass by around 22% and acorn length by around 31% on average. Scarification and the elimination of infected acorns increased germination capacity from around 64% to around 81% on average. Acorns can be divided into size groups before scarification to obtain seed material with varied germination capacity. Larger acorns with higher germination capacity can be used for sowing in container nurseries, whereas smaller acorns with lower germination capacity can be sown in open-field nurseries. [ABSTRACT FROM AUTHOR]

Aim of study: The purpose was to determine the type of dormancy and the optimal germination conditions of Phillyrea angustifolia (Oleaceae) seeds. Area of study: Germination requirements of P. angustifolia seeds collected from wild plants growing in the province of Ávila (Central Spain) were studied. Materials and methods: Seed water uptake was measured. Seeds with and without an endocarp were germinated at different temperatures, and several treatments were tested. Main results: The lignified endocarp interferes mechanically with the emergence of the radicle, and the treatments that achieved the highest germination percentages were the total removal of the endocarp with pliers (84%) or the immersion in liquid nitrogen for 1 min (97%). Scarification with concentrated sulphuric acid did not significantly increase germination compared to the control seeds, and treatments with dry heat or wet heat were detrimental to seed germination. The optimum temperature for germination was 15 ºC. A pre-sowing treatment of soaking in distilled water for 24 h slightly increased germination speed. Neither cold stratification at 5 ºC nor soaking in a gibberellic acid solution improved seed germination. Research highlights: Phillyrea angustifolia seeds have physiological dormancy – that is, the embryo does not have enough growth potential to overcome the mechanical restriction of the lignified endocarp. The seeds do not exhibit physical dormancy, given their water-permeable lignified endocarp. Our results suggest that the optimum germination protocol for P. angustifolia would be the total removal of the endocarp or immersion in liquid nitrogen for 1 min, followed by immersion in distilled water for 24 h and then seed incubation at 15 ºC in light or darkness.

Background: Mycoheterotrophic plants are one of the most difficult plant groups to conserve because they are entirely dependent on symbiotic fungi. Establishment of viable culture systems would greatly aid their conservation. We describe a simple culture system for the mycoheterotrophic orchid, Gastrodia pubilabiata, that does not require laboratory facilities. The orchid is symbiotic with leaf-litter-decomposing fungi. Results: Gastrodia pubilabiata seeds were incubated in plastic boxes or glass bottles filled with leaf litter collected from the natural habitat of the species. Seed germination was observed after 35 days and seedling development followed. Fungal isolates from seedlings were identified as Mycenaceae (Basidiomycota), a leaf-litter-decomposing mycorrhizal fungus of Gastrodia species. Conclusion: Our method can be used to conserve endangered mycoheterotrophic plants associated with leaf litter-decomposing fungi efficiently, and can also serve as a model system for physiological and molecular studies of such plants. [ABSTRACT FROM AUTHOR]

Background: Dimorphic seeds from Suaeda aralocaspica exhibit different germination behaviors that are thought to be a bet-hedging strategy advantageous in harsh and unpredictable environments. To understand the molecular mechanisms of Suaeda aralocaspica dimorphic seed germination, we applied RNA sequencing and small RNA sequencing for samples collected at three germination stages. Results: A total of 79,414 transcripts were assembled using Trinity, of which 57.67% were functionally annotated. KEGG enrichment unveiled that photosynthesis and flavonol biosynthesis pathways were activated earlier in brown seed compared with black seed. Gene expression analysis revealed that nine candidate unigenes in gibberellic acid and abscisic acid signal transduction and 23 unigenes in circadian rhythm-plant pathway showed distinct expression profiles to promote dimorphic seed germination. 194 conserved miRNAs comprising 40 families and 21 novel miRNAs belonging to 20 families in Suaeda aralocaspica were identified using miRDeep-P and Mfold. The expression of miRNAs in black seed was suppressed at imbibition stage. Among the identified miRNAs, 59 conserved and 13 novel miRNAs differentially expressed during seed germination. Of which, 43 conserved and nine novel miRNAs showed distinct expression patterns between black and brown seed. Using TAPIR, 208 unigenes were predicted as putative targets of 35 conserved miRNA families and 17 novel miRNA families. Among functionally annotated targets, genes participated in transcription regulation constituted the dominant category, followed by genes involved in signaling and stress response. Seven of the predicted targets were validated using 5'rapid amplification of cDNA ends or real-time quantitative reverse transcription-PCR. Conclusions: Our results indicate that specific genes and miRNAs are regulated differently between black and brown seed during germination, which may contribute to the different germination behaviors of Suaeda aralocaspica dimorphic seeds in unpredictable variable environments. Our results lay a solid foundation for further studying the roles of candidate genes and miRNAs in Suaeda aralocaspica dimorphic seed germination. [ABSTRACT FROM AUTHOR]

In 2014, this research was conducted at the Research Institute of Horticulture in Skierniewice, Poland. It was based on different red raspberry seed treatments with sulfuric acid during the scarification process. The seeds were obtained from crosses among ten parental forms, producing 55 hybrid families. During scarification, the seeds were subjected to concentrated sulfuric acid for 20, 30 and 40 minutes. Assessment of the germinated seeds, performed 2.5 months after the sowing, revealed different effects of the seed origin/pedigree and the applied scarification treatments. The best seed germination was recorded for the hybrid families where 'Radziejowa' (56.5% of germinated seeds), 'Laszka' (63.9%) and 'Sokolica' (73.5%) were the maternal forms, and the poorest one - where 'Polana' (6.2% of germinated seeds), 'Glen Ample' (32.5%) and 'Canby' (33.1%) were used as the maternal cultivars. The highest germination, on average for all the hybrid families, was obtained for seeds treated with H2SO4 for 30 min (45.3% of germinated seeds), and the lowest when the seeds were treated with H2SO4 for 40 min (35.6%). [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) inhibits seed germination and the regulation of ABA biosynthesis has a role in maintenance of seed dormancy. The key rate-limiting step in ABA biosynthesis is catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). Two hydroxamic acid inhibitors of carotenoid cleavage dioxygenase (CCD), D4 and D7, previously found to inhibit CCD and NCED in vitro, are shown to have the novel property of decreasing mean germination time of tomato (SolanumlycopersicumL.) seeds constitutively overexpressing LeNCED1. Post-germination, D4 exhibited no negative effects on tomato seedling growth in terms of height, dry weight, and fresh weight. Tobacco (Nicotiana tabacum L.) seeds containing a tetracycline-inducible LeNCED1 transgene were used to show that germination could be negatively and positively controlled through the chemical induction of gene expression and the chemical inhibition of the NCED protein: application of tetracycline increased mean germination time and delayed hypocotyl emergence in a similar manner to that observed when exogenous ABA was applied and this was reversed by D4 when NCED expression was induced at intermediate levels. D4 also improved germination in lettuce (Lactuca sativa L.) seeds under thermoinhibitory temperatures and in tomato seeds imbibed in high osmolarity solutions of polyethylene glycol. D4 reduced ABA and dihydrophaseic acid accumulation in tomato seeds overexpressing LeNCED1 and reduced ABA accumulation in wild type tomato seeds imbibed on polyethylene glycol. The evidence supports amode of action of D4 through NCED inhibition, and thismolecule provides a lead compound for the design of NCED inhibitors with greater specificity and potency. [ABSTRACT FROM AUTHOR]

Two of the most troublesome weeds in soybean, cotton, and corn in cropping systems of mid-south United States (US) are Senna obtusifolia and Xanthium strumarium. Understanding their population dynamics, particularly weed seedling emergence patterns, is important for the timely implementation and the success of weed management strategies. Identifying the sources of variation of emergence patterns could greatly improve our ability to predict emergence timing. A three-years field study was conducted to determine the effect of environmental conditions on S. obtusifolia and X. strumarium seedling emergence and seedbank potential. The experiment was conducted with two seed sources; X. strumarium burs and S. obtusifolia seeds from a single maternal plant source, and X. strumarium burs and S. obtusifolia seeds from multiple maternal plant sources, both being exposed either to 5 cm burial depth (buried) or left on the soil surface (soil surface) in the fallow or planted in spring after their storage under chilled (chill) or room temperature (no chill) conditions. X. strumarium and S. obtusifolia seedling emergence was lower from burs and seeds that were planted in the soil in September as compared with the chill and/or no chill seeds/burs stored for six months. X. strumarium seedling emergence was reduced from 37 to 1% when burs were left on the soil surface when compared to buried burs. S. obtusifolia seedling emergence was reduced from 47 to 13% when seeds were left on the soil surface as compared to buried. At the end of the experimental period, the soil seedbank of X. strumarium had been significantly depleted, whereas the remaining seeds of S. obtusifolia were viable.

The effects of temperature and relative humidity (RH) on germination of Fusarium graminearum ascospores, and of dry periods (DP) of different lengths and of temperature and RH during DP on ascospore survival were studied both in vitro and in planta. Optimal temperatures for ascospore germination at 100% RH were 20 and 25°C; germination was <5% when ascospores were incubated at 20°C and RH < 93.5%. Viable ascospores were found at all tested combinations of DP duration (0 to 48 h) x temperature (5 to 40°C) or RH (32.5 to 100% RH). Germination declined as DP duration and temperature increased. Germination was lower for ascospores kept at 65.5% RH during the DP than at 76.0, 32.5, or 93.5% RH. Equations were developed describing the relationships between ascospore germination, DP duration and temperature or RH during DP. Durum wheat spikes were inoculated with ascospores and kept dry for 0 to 48 h at approximately 15°C and 65% RH; plants were then kept in saturated atmosphere for 48 h tofavor infection. Fungal biomass, measured as F. graminearum DNA by quantitative polymerase chain reaction. declined as DP increased to 24 and 48 h at 3 and 9 days postinfection but not in spikes at maturity. [ABSTRACT FROM AUTHOR]

The soil seed bank has a limited role in the seasonal dry tropical forest regeneration process, but seed removal and germination can also be limiting factors during the early forest recovery. In central Veracruz, Mexico, the soil seed bank was determined en five fallows and two forests. Seed bank decreased from fallow to forest (1303 to 101 seeds m-2); herbs and grasses predominated thus the similarity between species composition of seed bank and vegetation was low. Seed removal and germination were evaluated for Acacia cochliacantha, Caesalpinia cacalaco, Ipomoea wolcottiana and Senna atomaria in contrasting habitats represented by pasture, fallow and forest. Seed removal was determined under treatments of total access, rodent exclosure, and insect exclosure. Caesalpinia (largest seeds) displayed the lowest seed removal (5%), whereas Senna (63%) and Ipomoea (29%) displayed the highest. Rodent exclosure reduced seed removal for Ipomoea (medium-sized seeds); and insect exclosure reduced removal for Senna and Acacia (small seeds). With the exception of Senna (18% germination), the scarified seeds displayed the highest germination percentage (53-99%). For all species, germination was higher in forest than in open habitats, only Senna seeds displayed the lowest germination percentage in the forest habitat. Results suggested that in the dry forest of Veracruz, seed removal may not limit forest regeneration; however seeds must be scarified for use in restoration activities.

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the last decades a new goal for agriculture is to develop environmentally friendly innovative technologies. One of the interest solutions, in perspective, is the treatment of plants with low power microwave irradiation in order to obtain a higher and healthier production. This approach could also contribute to mitigation of harmful effects produced by excessive use of chemical products in treatment of seeds and also field culture phytoprotection. Investigating effects of microwave irradiation, on the germination of common bean (Phaseolus vulgaris L. cv. Ardeleana) seeds, and on the growth and development of bean plantules, in specific experimental conditions. The trial was developed within Laboratories of the Advanced Research Centre for Environmental Protection and Assessment of Life Quality from USAMV Cluj-Napoca. The growing experiment of 10 - 8 days (with 49 individuals each) was developed until the seeds have grown up to 15 cm height, in conditions of microwave irradiated and no irradiated conditions. The studied parameters were: length of stems, length of roots, and seedling vigour index. Data were statistically processed with STATISTICA v 6.0 Office. The studied parameters were quantified by biometric approach (length of stems and roots). The use of low power microwave irradiation in germination of common bean in laboratory conditions may be taken into consideration for large scale cultivation. Further research is needed in order to establish appropriate practices for the success of this innovative technique. [ABSTRACT FROM AUTHOR]

The aim of this study was to optimize nursery production of Retama sphaerocarpa (Fabaceae), an important shrub species characterized by a seed coat dormancy hindering germination, and used in the restoration of degraded arid and semi-arid areas. To assess the influence of scarification agents and mother plant effect on germination rate and seedling vigor, a germination test with fresh seed was performed in a germination chamber using a factorial design with two fixed factors (mother plant effect and scarification agent). Fresh seeds were scarified by sulphuric acid (96% concentration, 60 min) and hot water (80 °C, 30 sec) and their germination compared with untreated control seeds. Scarification of seeds using sulphuric acid has proven the best method to enhance germination of this species, achieving the highest germination rate (>79%) and the best vigor index. Differences between seed lots from different mother plants were statistically significant and could influence seed germination success. We suggest that effectiveness of hot water scarification method may be improved by additional time of seed immersion. Owing to its potential for use in land restoration, bioenergy production and ornamental purposes, increment of commercial demand of this species is expected in the near future. [ABSTRACT FROM AUTHOR]

Astragalus gines-lopezii Talavera, Podlech, Devesa & F.M.Vázquez (Fabaceae) is a threatened endemic species with a distribution restricted to a very small area in Badajoz Province (Extremadura Region, SW Spain) and only 2 populations are known. This species was catalogued in the "Endangered" category in the 2008 Red List and the 2010 Threatened Spanish Vascular Flora List. Despite its status as an endangered species, at present very little is known about the distribution, census, and reproductive biology of this species. In this study we have carried out an exhaustive census of A. gines-lopezii, and we have evaluated the production of flowers, fruits, and seeds and the existence or not of intra- and interpopulation variability in seed germination. Results have highlighted the high reproductive capacity of this species on the basis of a high production of flowers, fruits, and seeds. Mechanical scarification of seeds was effective for increasing germination. Thus, initial germination (22%-60%) was increased to 97%-99% when seeds were rubbed with sandpapers. A high intra- and interpopulation variability in seed germination was found in this species. A. gines-lopezii produces seeds with different degrees of physical dormancy, varying this grade among different individuals within a population. [ABSTRACT FROM AUTHOR]

In vitro and in vivo A. ligtu hybrid seed germination tests were conducted at different treatments: soaking in gibberellic acid (GA3) or salicylic acid (SA) (0, 100, 200 and 400 mg.l-1) and Potassium nitrate (KNO3) (0.1, 0.2, 0.4 and 0.8%) with and without stratification in 5±1 °C. Stratification had a significant effect on seed germination (p < 0.05). Maximum germination (86.67%, 96.50% after 16.44, 15.05 days under in vivo and in vitro conditions, respectively) was found in 100 mg.l-1 GA3 + 21 days of stratification and was followed by 0.8% KNO3 and 100 mg.l-1 SA along with 21 days of stratification. Mean germination time (MGT) decreased with duration of stratification and GA3, SA and KNO3 application, respectively. The present results indicated that, GA3, SA and KNO3 stimulated various growth aspects of Alstroemeria seedlings growth in both under in vitro and in vivo, but seeds treated in 100 mg.l-1 GA3 soulation was more effective. Seeds treated with SA and KNO3 without stratification and control had no germination. A.ligtu hybrid species probably exhibits a combination of physiological dormancy. Stratification at 5±1 °C for 21 days or GA3 + 21 days of stratification overcame seed dormancy and increased the germination percentage of A.ligtu hybrid seeds. Seedlings growth in vivo conditions was higher as compared with in vitro conditions. [ABSTRACT FROM AUTHOR]

Accelerated global warming is leading to the loss of plant species diversity, and ex situ preservation of seeds is becoming an increasingly important aspect of species conservation. However, information on dormancy and germination is lacking in many endangered species. Amsonia elliptica (Apocynaceae) is the only Amsonia species native to Korea, and the South Korean Ministry of Environment has designated it Class II endangered wildlife. Nevertheless, the dormancy class and the dormancy breaking method for seeds of this species for germination are not precisely known. We identified the structure of A. elliptica seeds and the causes of dormancy, which inhibits germination. In addition, we tried to develop an effective germination promotion method by testing the wet stratified condition, which breaks dormancy, and the form of gibberellin that can replace it. Fresh seeds of A. elliptica imbibe water, but the covering layers (endosperm and seed coat) inhibit germination by mechanically restricting the embryo. Initial germination tests confirmed low embryo growth potential and physiological dormancy (PD). Restriction due to the covering layer was eliminated by seed scarification, and abnormal germination was observed. After 12 weeks of cold moist stratification at 4°C, only 12% of seeds germinated. However, 68.8% of seeds subjected to 8 weeks of warm moist stratification followed by 12 weeks of cold stratification germinated, indicating that warm stratification pretreatment before cold stratification is effective in breaking dormancy. A. elliptica seeds exhibited intermediate PD. Furthermore, 61.3% of seeds soaked in 500 mg/L GA 4+7 for 14 days and incubated at 25/15°C germinated. Therefore, GA 4+7 rapidly broke the dormancy of A. elliptica seeds compared with warm plus cold stratification treatment, thus providing an efficient method for seedling production., Competing Interests: Author SL is employed by The Kiban co. Ltd., The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lee, Park, Jang, Ji, Lee, Baskin and Cho.)

Seed reserves play an essential role during germination and seedling establishment and are particularly important for species that grow in seasonal ecosystems with a short growing season. In this study, we examined (a) how and when the seedlings change their dependence from seed resources to external resources, (b) the lipid, nitrogen, and non-structural carbohydrate reserve translocation from seeds to seedlings over time, and (c) whether reserve translocation may be correlated to cotyledon and leaf lifespan of seedlings for eight tree species in a tropical deciduous forest in north-western Mexico. Our results showed that the cotyledon lifespan was not related to the cotyledon type (photosynthetic or reserve) and that the cotyledon biomass did not decrease significantly until germination. In six of the eight studied species, biomass allocation to the leaves was favored; lipids were the first reserve exhausted before the first leaves were totally expanded in seven of the eight study species. Species with the highest N concentration had expanded leaves and lost their cotyledons faster than species with a low N concentration. Our results suggest that tropical deciduous forest species employ different strategies to survive the dry season and re-sprout in the next growing season mediated by seed reserve concentrations, translocation patterns and subsequent biomass allocation. [ABSTRACT FROM AUTHOR]

Piocho (Melia azedarach L.) seeds were scarified with H2SO4 at 30, 45, 60, 90, 120 min. and a control group, to evaluate germination days (%) and seedling/seed and purity (%). Two hundred seeds/treatment (four replications) were used. Emergency was similar (p> 0.05) among treatments: 42.90±3.40%. Purity and seeds/berry, averaged 74.30% and 3.47+0.92, respectively. Days to emergency were only different (p<0.05) at 0 (30.0+0.9 days) and 120 min. (23.0 +2.4 days). After 60 min., there was a reduction from 2.18 +0.1 berry seedlings emergency to 1.75 min. We conclude that immersion times affected the number and purity of seedlings. [ABSTRACT FROM AUTHOR]

The emergence and growth of Hibiscus elatus seedlings under nursery conditions was studied, in seeds subject to acid scarification treatments in combination --or not- with partial hydration treatments in water. The seeds were collected in four forest provenances of the Sierra del Rosario Biosphere Reserve (two seasonal evergreen mature forests and two secondary forests) and were subject to different irrigation frequencies (daily, alternate days and once a week) during their permanence in nursery. The pregerminative treatments were adequate to increase seedling emergence and growth with regards to the control (untreated seeds), for all provenances, although the positive effect depended on the irrigation rate of the substratum. The water stress significantly affected seedling vigor, independently from the treatment used; nevertheless, under these planting conditions, the water treatment was the most favorable to improve plant functioning in the seeds collected in the mature forest; while those from the secondary forest had a better ability to respond to water stress with scarification treatment, combined with partial hydration in water. The use of hardening treatments in the seeds was proven to decrease the damaging effect caused by the insufficient soil moisture on seedling establishment, independently from the collection site. [ABSTRACT FROM AUTHOR]

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An evaluation was made of the germinative response of 20 legume accessions from different storage times, under inadequate humidity and temperature conditions, and subject to thermal and acid scarification treatments before seeding, with different temperatures of the substratum. Independently from the storage time, the moisture content of the seeds was lower than 15%. The seeds from the accessions with more than 12 years showed germination percentages lower than 10% for all the essayed planting treatments, except in Centrosema pubescens cv. CIAT 438, Crotalaria sp. cv. Derecha, Crotalaria spectabilis, Crotalaria brownii cv. 687, Macroptilium atropurpureum, Stylosanthes guianensis cv. CIAT 136 and Mimosa invisa. The other accessions showed different degrees of viability loss. The best germinative response occurred in Crotalaria sp. cv. Derecha, M. invisa and Indigofera sp., because they reached final germination percentages higher than 70% for, at least, one of the studied seeding thermoperiods. [ABSTRACT FROM AUTHOR]

Scorpiurus subvillosus L., wide spread in pastures of Mediterranean basin, is disappearing in the native pastures of the Hyblean plateau (Sicily, southern Italy), because of overgrazing and intensive management techniques. Moreover, it exhibits seed coat dormancy, which delays and reduces germination preventing its diffusion. This paper represents a first attempt in order to investigate changing in germination determined by storage time and temperature on seeds of two populations of S. subvillosus. Germination of S.␣subvillosus seeds was tested in relation to four storage time (30, 130, 200 and 360 days after harvest (DAH)), eight constant temperatures (5, 10, 15, 20, 25, 30, 35 and 40°C) and two populations of different provenience (30 and 600 m above mean sea level). The experiments were conducted either on scarified and unscarified seeds. In S. subvillosus the failure of germination under favourable conditions must be attributed␣only to seed coat, since seed scarification enhanced germination percentage with values up to 100% at almost all tested temperatures. In both treatments, but with a grater incidence in unscarified, seed germination increased gradually as temperature raised, peaking at 20–25°C, then declined with further increases of temperatures. At 40°C no germination occurred. Storage time induced a softening effect, which is somewhat limited by the natural ageing of seeds occurring from about 6 months after harvest. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dormancy in the hard seed coats of Mediterranean species is considered a strategy that enables persistent seed banks to be formed in the soil. An important factor related to seed coat fracture and dormancy breakage in Mediterranean ecosystems is heat. Nevertheless, the effect of factors other than heat on dormancy breakage in these species has hardly been studied. To investigate the different ecological factors involved in germination, in the laboratory we applied several scarification treatments to seeds with chromatic polymorphism. We evaluated the effect of soil seed depth during experimental burns by sowing seeds at −1, −3 and −5 cm in the soil profile, and we also studied the effect of seed origin on the posterior germination of seeds from 4 and 10 year-old shrubs as well as from the soil seed bank. U. parviflorus shows clear chromatic polymorphism: its brown seeds present higher dormancy levels than its yellow seeds. The different techniques of dormancy breakage result in different degrees of germination; the highest degree of germination is generated by the mechanical treatment, followed by the acid and the heat treatments, in that order. The depth of the seeds in the soil determines the temperature thresholds and the residence times of these temperatures and whether they stimulate a massive germination at the −1 cm soil profile or only a slight germination at the −5 cm depth. Seeds recently produced by the plant show higher dormancy levels than seeds extracted from soil seed banks. Dormancy levels also depend on the shrubland age used for extracting the soil samples (3>9 years old). In effect, from the point of view of dormancy, the germination behaviour of U. parviflorus seeds seems to follow a multiresponse strategy based on different seed populations and involving both biological and abiotic processes to break dormancy. [ABSTRACT FROM AUTHOR]

Seed predation and desiccation present major limitations to the use of direct seeding as an efficient forest restoration technique. The study was designed based on the premise that scarifying seeds before sowing them in fields cleared of weeds would shorten seed dormancy to decrease the time available for seed predation to occur and that burial conceals seeds from potential predators. Therefore, the effects of four treatments (scarification, burial, application of mulch and scarification with burial) were tested on seed germination of four native forest tree species, sown in abandoned agricultural land in an upper watershed in Doi Suthep-Pui National Park, northern Thailand. The four tree species studied were Sapindus rarak, Lithocarpus elegans, Spondias axillaris and Erythrina subumbrans. Field tests showed that instead of rodents, ants were the seed predators. Scarification without burial did not accelerate seed germination in the field due to desiccation and severe predation by ants. Burial helped protect the seeds from predation as well as blocked direct sunlight and increased moisture retention, thus preventing desiccation of seeds. Seeds that benefit from scarification but which are susceptible to seed predation and desiccation should be scarified and buried to a depth twice the diameter of the seed (3-5 cm). For certain suitable species, this technique could offer an effective, cost-efficient alternative to outplanting nurseryraised seedlings for forest restoration projects, particularly in montane areas. [ABSTRACT FROM AUTHOR]

In the present paper we studied the life history traits related to seed germination of Stipa tenacissima, a key species in semiarid environments of western Mediterranean areas. S. tenacissima is a perennial tussock grass, which has traditionally been considered to expand mainly by vegetative propagation with little or no sexual reproduction. We analysed seed longevity as well as the type of seed dormancy and the role of the seed covers from seeds collected from different populations in SE Spain. We also studied the variation in seed germinability among populations, individuals, and years and the ability of seeds of S. tenacissima to form soil seed banks. There was significant variation in seed germination among individuals, populations and years. Lemma and palea were the main factor controlling these differences since their removal promoted higher and faster germination and eliminated the differences in germination parameters among populations. However, the control of dormancy by lemma and palea was independent of their weight, suggesting that their chemical nature plays a more important role than does size in controlling seed germination. Mechanical scarification treatments (via abrasion with sand) did not affect seed germination. The decay in seed germinability two years after seed collection and the low density of viable seeds in soils one year after seed dispersal indicated that S. tenacissima forms transient soil seed banks. [ABSTRACT FROM AUTHOR]

The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the demand of stabilization of drift sand will increase. The non-invasive alien grass species Ammophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized and indigenous sand-binding species would be preferred. The germination requirements of the native Arctotheca populifolia, Ipomoea pes-caprae, Myrica cordifolia and Scaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments broke the dormancy of I. pes-caprae, M. cordifolia and S.plumieri, whereas the seeds of A.populifolia were not dormant. Seeds of I. pes-caprae and M.cordifolia had induced an innate dormancy, respectively, whereas the type of dormancy in seeds of S. plumieri dormancy processes remained unknown. [ABSTRACT FROM AUTHOR]

The potential allelopathic role of Artemisia herba-alba has been evaluated in order to explain the community pattern of the gypsum semiarid environments of central Spain. This pattern shows a sharp ecotone between a gypsophile sparse shrubby community dominated by Helianthemum squamatum, which grows on slopes with gypsum surface crusts, and a nitrohalophilous community on the gypsum alluvial soils of piedmont dominated by Artemisia herba-alba. In order to explain this pattern, resource limitation was discarded because no significant differences in several soil parametrers, but fine earth fraction and organic matter content, had been detected in a previous study. Results confirm the inhibitory effect of aqueous extracts on the final germination percentage of scarified seeds of Helianthemum squamatum and also on the shape of the germination curves, which indicate delay of germination for the aqueous extracts. Assays with soil of the Artemisiacommunity (three types) showed that germination was strongly inhibited in soils obtained below the canopy of mature plants (litter maintained) and retarded in the other treatments. We suggest that the spatial community pattern detected in this gypsum environment and characterised by a sharp ecotone could be at least partially controlled by interference through allelopathy. This determines the excliusion of Helianthemum squamatum plants from alluvial soils. [ABSTRACT FROM AUTHOR]