Proportion Of Seeds Research Articles

МЕХАНИЧЕСКИЙ СОСТАВ ГРОЗДЕЙ У ТЕМНОЯГОДНЫХ ТЕХНИЧЕСКИХ СОРТОВ ВИНОГРАДА СЕЛЕКЦИИ ВНИИВиВ ИМ. Я.И. ПОТАПЕНКО И СКФНЦСВВ

The results of studying the mechanical composition of bunches and berries of a young vineyard of dark-berry technical grape varieties Vecherniy, Dmitriy and Kurchanskiy are presented. The research was carried out in a standard own-root vineyard located in the first department of the Kuban educational farm of KubSAU. Data on the average mass of a bunch and berry, as well as the mass of their constituent structural elements are given: the proportion of berries and stems in the bunch weight, the proportion of skin, seeds and pulp with juice in the berry weight, the structure index of the bunch and the berry index are calculated. It was revealed that the smallest bunch weight was obtained from the Vecherniy variety, and the largest from the Kurchanskiy variety. In both years, the smallest average berry weight was observed in the Dmitriy variety, and the largest in the Vecherniy variety. The proportion of berries from the bunch weight in the studied varieties turned out to be approximately the same and amounted to 96.1–97.7 %, which was within the normal range. In both years, the structure index had the highest values in the Kurchanskiy variety, and the lowest in the Vecherniy variety. The highest values of the berry index were observed in the Dmitriy variety, which has the smallest berries, and the lowest values in the Vecherniy variety, which has the largest berries. The proportion of skin in four out of six cases was significantly higher than the standard values. The proportion of seeds from the bunch weight between varieties ranged from 5.0-9.8 %, which exceeded the norm by 1.0-3.8 %. The proportion of pulp with juice in five out of six cases was 58.2-71.7 %, which was significantly less than the standard values (75-80 %). The share of structural indicators of berries depended not only on varietal characteristics, but also on the conditions of the year.

The role of bushpigs (Potamochoerus larvatus) as seed dispersers in indigenous forests in the Soutpansberg Mountain range, South Africa

Abstract Seed dispersal influences the survival and distribution of plant species and is an important mechanism for maintaining floristic diversity. Bushpigs (Potamochoerus larvatus) are large mammals of indigenous forests and well-wooded areas of eastern and southern Africa and may play an important role as seed dispersers. However, the diversity of fruits consumed and the effect of digestion on seeds remains poorly understood. This study was conducted from October 2018 to January 2019 and gives first insights into seed dispersal by bushpigs in the Soutpansberg Mountain range, South Africa. Here, we collected bushpig faeces and assessed the number of seeds and seed species found. Furthermore, germination experiments with digested and nondigested seeds and fruits were conducted. Our results show that bushpigs are omnivorous, consuming fruits and seeds of 126 different plant species. The proportion of seeds per plant species found in faeces was unhomogeneously distributed with a few hyperabundant species, in particular Searsia chirindensis (55%). The germination experiments showed that gut passage did, overall, not influence germination or seedling growth rates. However, seeds remaining within fruits showed reduced growth, pointing to a high importance of fruit consumption for seed fate. Our results suggest that bushpigs are major seed dispersers of a large variety of fruiting plant species in wooded areas of Africa.

Inter-specific competition between seeds and seedlings of two confamilial tropical trees

Inter-specific competition among species in a mixed species plantation is inevitable, and the degree of competition for available resources determines the success of species co-existence. Different species compete and interact for resources at different physiological and developmental stages. However, most research has investigated inter-specific competition at the mature stage. We examined seed germination and seedling growth of two confamilial species, Albizia saman and Albizia lebbeck, and explored inter-specific competition at their early life stages, grown in a mixture of different proportions of seeds and seedlings through a series of replacement experiment. The experiment included germination and height growth tests for each species on its own, as well as three mixtures of species with ratios of 25:75, 50:50 and 75:25. We found that the germination speed and percentage, the probability of seedling emergence, and the seedling height were significantly higher in A. saman than in A. lebbeck. Moreover, in mixtures, we observed that A. saman exhibits higher germination speed and percentages compared to A. lebbeck. The increase in seedling height did not vary significantly among treatments when the seedlings of the studied species were mixed in different proportions. However, both species showed an apparent benefit when growing together, which was significantly influenced by A. saman in terms of inter-specific competition indexes. The knowledge of the early growth performance of these species and their inter-specific competition presented in this study may influence recruitment success and will be useful in understanding the population dynamics in the case of a mixed species plantation. Furthermore, our study suggests that there could be an impact of species mixture on the regeneration or recruitment process, even when the species are confamilial. Therefore, this information could be useful for selecting suitable species mixtures in any afforestation and reforestation activities.

Omnivore diet composition alters parasite resistance and host condition.

Diet composition modulates animals' ability to resist parasites and recover from stress. Broader diet breadths enable omnivores to mount dynamic responses to parasite attack, but little is known about how plant/prey mixing might influence responses to infection. Using omnivorous deer mice (Peromyscus maniculatus) as a model, we examine how varying plant and prey concentrations in blended diets influence resistance and body condition following infestation by Rocky Mountain wood ticks (Dermacentor andersoni). In two repeated experiments, deer mice fed for 4 weeks on controlled diets that varied in proportions of seeds and insects were then challenged with 50 tick larvae in two sequential infestations. The numbers of ticks successfully feeding on mice declined by 25% and 66% after the first infestation (in the first and second experiments, respectively), reflecting a pattern of acquired resistance, and resistance was strongest when plant/prey ratios were more equally balanced in mouse diets, relative to seed-dominated diets. Diet also dramatically impacted the capacity of mice to cope with tick infestations. Mice fed insect-rich diets lost 15% of their body weight when parasitized by ticks, while mice fed seed-rich diets lost no weight at all. While mounting/maintaining an immune response may be energetically demanding, mice may compensate for parasitism with fat and carbohydrate-rich diets. Altogether, these results suggest that a diverse nutritional landscape may be key in enabling omnivores' resistance and resilience to infection and immune stressors in their environments.

Germination Pattern and Seed Longevity of Echinochloa colona (L.) Link in Eastern Australia

Knowledge of the germination pattern and seed longevity of Echinochloa colona under field conditions could play a crucial role in effective weed management. Germination patterns of four populations (B17/12, B17/13, B17/7, and B17/25) of E. colona collected from eastern Australia were studied under field conditions for two years. Each population had multiple cohorts, and peak germination occurred in December 2018. Population B17/12 had a lower dormancy level compared with other populations, as 87% of the seeds germinated in the first cohort. Regression analysis revealed that populations B17/12, B17/13, B17/7, and B17/25 required 2130, 3110, 4320, and 6040 cumulative growing degree days (GDD), respectively, for 80% germination. The last cohorts of each population (100% germination) were observed in February 2020. This suggests that the populations of E. colona had innate dormancy, and a proportion of seeds can germinate in the next season. For the seed persistence study, seed bags of three populations (B17/4, B17/26, and B17/35) were exhumed at different intervals at two locations (Gatton and St George) over 30 months to evaluate decay components. Averaged over locations, burial duration, and burial depth, populations behaved similarly for the seed decay component. After 30 months of seed placement at Gatton, viable seeds at 1, 5, and 15 cm burial depths were 8, 26, and 15%, respectively. However, during the same time period at St George, viable seeds at 1, 5, and 15 cm burial depths were 0, 4, and 3%, respectively. These results implied that E. colona seeds persisted for a longer period (>2 years) in the light-textured soil (Gatton), particularly at the 5 cm burial depth. After 30 months of seed placement at Gatton, seeds decayed faster at 1 cm compared with the 5 cm burial depth. The studies demonstrated that seed persistence and germination patterns of E. colona may vary with different soil and agro-climatic conditions. The results suggest that management strategies should be followed to enable early control of E. colona over a three year period and that restricting reinfestation of weed seeds through seed rains could lead to almost complete control of E. colona in the field.

Interactions between large-scale and local factors influence seed predation rates and seed loss.

Herbivores often have highly variable impacts on plant fecundity. The relative contribution of different environmental factors operating at varying spatial scales in affecting this variability is often unclear. We examined how density-dependent seed predation at local scales and regional differences in primary productivity are associated with variation in the magnitude of pre-dispersal seed predation on Monarda fistulosa (Lamiaceae). Within M. fistulosa populations growing in a low-productivity region (LPR), Montana, USA, and a high-productivity region (HPR), Wisconsin, USA, we quantified the magnitude of pre-dispersal seed predation among individual plants differing in seed head densities. Out of a total of 303 M. fistulosa plants that were surveyed, we found half as many herbivores in seed heads in the LPR (n = 133 herbivores) compared to the HPR (n = 316). In the LPR, 30% of the seed heads were damaged in plants with low seed head density, while 61% of seed heads were damaged in plants with high seed head density. Seed head damage was consistently high in the HPR (about 49% across the range of seed head density) compared to the LPR (45% across a range of seed head density). However, the proportion of seeds per seed head that were destroyed by herbivores was nearly two times higher (~38% loss) in the LPR compared to HPR (22% loss). Considering the combined effects of probability of damage and seed loss per seed head, the proportion seed loss per plant was consistently higher in the HPR regardless of seed head density. Nevertheless, because of greater seed head production, the total number of viable seeds produced per plant was higher in HPR and high-density plants, despite being exposed to greater herbivore pressure. These findings show how large-scale factors can interact with local-scale factors to influence how strongly herbivores suppress plant fecundity.

Multiple intrinsic and extrinsic drivers influence the quantity and quality components of seed dispersal effectiveness in the rare shrub Lindera subcoriacea.

Information about seed dispersal effectiveness (SDE) for plant species of conservation concern is rarely available to inform management strategies and actions. For Lindera subcoriacea (bog spicebush, Lauraceae), a rare endemic dioecious shrub of the southeastern United States, we examined the influence of two intrinsic and five extrinsic drivers on the number and proportion of seeds either dispersed, or predated pre- and post-dispersal. The number of seeds dispersed characterizes the quantitative component of SDE, while pre- and post-dispersal seed predation can affect the qualitative component of SDE. Using fruit counts, seed traps, and seed removal depots over multiple years, we estimated that approximately 28% of L. subcoriacea seeds are lost to pre-dispersal predation, 69% of seeds are dispersed, 3% of seeds fail to disperse, and 65% of dispersed seeds are predated post-dispersal. We observed substantial variation in these three processes among individuals. We also found that both intrinsic (plant height, crop size) and extrinsic (understory cover, time since last fire, conspecific fruiting neighborhood, substrate) drivers differentially influenced the three processes. We identified four generalist, seasonally frugivorous, avian visitors at fruiting individuals that likely act as variably effective dispersers, while the Northern Cardinal (Cardinalis cardinalis L.) is a seed predator. Rodent granivores were important pre- and post-dispersal seed predators. The magnitude of our pre-dispersal and post-dispersal seed predation estimates suggest that, given the low fecundity of L. subcoriacea, conservation strategies should emphasize facilitating dispersal and reducing the effects of seed predation.

Germination physiology of Cochlospermum fraseri (Bixaceae), a deciduous tree from Northern Australia with physical seed dormancy.

Cochlospermum fraseri ('Kapok', Bixaceae) is a deciduous tree widely distributed throughout semi-arid and monsoon tropical northern Australia, and an important species for ecological restoration in the region. We aimed to better understand the seed biology and ecology of C. fraseri to determine the mechanisms by which seed dormancy might be alleviated, and the conditions that support germination to inform the use of this species in restoration. Dormancy breaking treatments (wet heat, dry heat, scarification) commonly applied to species with physical seed dormancy (PY) were tested along with stratification at 5-35°C (nine treatments). Following dormancy alleviation, seeds were germinated at nine temperatures (5 to 40°C) and five water potentials (0 to -0.8MPa) to understand environmental thresholds that regulate germination physiology in non-dormant seeds. A proportion of seeds (<0.3) lose dormancy naturally in response to warm (25 to 35°C) moist conditions, which dislodges the hypostase plug that prevents water uptake, whilst neither dry (≥100°C) nor wet (~100°C) heat were effective. Dormancy loss was also achieved by exposing seeds to concentrated (95-98% v/v) sulphuric acid for 3-7hours, after which high proportions (>0.75) of germination were observed. Cochlospermum fraseri seeds possess PY, which is alleviated by seasonal temperatures that occur when soil moisture is high, allowing seeds to employ a risk-adverse strategy and maximize establishment success in episodic environments with stochastic rainfall events. The understanding of dormancy alleviation requirements gained here adds to our knowledge of PY worldwide and recruitment dynamics in the Australian monsoonal tropics and will aid land managers and restoration practitioners by informing both seeding sites and optimal time for in situ sowing as well as the potential capacity of this species to form a persistent soil seed bank.

Жыңғыл құмтышқанының (Meriones tamariscinus Pallas,1773) қоректенуінің Қазақстанның оңтүстік бөлігіндегі аймақтық ерекшеліктері

In the article, the features of the feeding of the tamarisk gerbil inhabiting some regions of Kazakhstan (floodplain tugai of the lower course of Ile River, the Aral Sea sands, Moyinkum, and Southern Balkhash) are considered. During the research, the following methods were used: basic-trap-site and indirect – analysis of the habits of birds of prey. As a result of the study of the digestive tract of the tamarisk gerbil in the floodplain tugai of the lower reaches of the Ile River, it was found that the proportion of seeds occupies an average of 63%, the green part-27%, other parts of plants-10% of the studied stomachs. In the Aral Sea sands, the tamarisk gerbil feeds on seeds (on average, 68%), and green parts (32%) of plants. In early spring, 24 stomachs of this gerbil were examined in the Moyinkum sands and it was found that the proportion of seeds in the digestive tracts of males and females was very high, due to the small abundance of the green part of the plant at this time of year. In the Southern Balkhash region, in summer and autumn, the tamarisk gerbil feeds on mixed feeds (40%), green parts (10%), and seeds (50%). It was found that seasonal changes occur in the composition of feed: in the spring during the breeding season or with a lack of moisture in the body, these rodents also consume insects. In the spring-summer period, the proportion of the green part of the plant increased in the diet, with a shortage of green feeds, the gerbil diligently consumes the underground parts of plants. In such cases, mixed feeds are found in the digestive tract of many rodents. It was found that the composition of the feed of the tamarisk gerbil differs depending on the seasons and habitats. It was found out that from the west to the east of the republic, the frequency of occurrence of the green part of the plant increases in the composition of feeds, the frequency of occurrence of seeds decreases on the contrary, and nutrition with mixed feeds increases from spring to autumn. The results of this work can be used as a basis for further study of the feeding of the tamarisk gerbil in various regions of Kazakhstan.

Complex adaptive landscape for a "Simple" structure: The role of trade-offs in the evolutionary dynamics of mandibular shape in ground squirrels.

Trade‐offs are inherent features of many biomechanical systems and are often seen as evolutionary constraints. Structural decoupling may provide a way to escape those limits in some systems but not for structures that transmit large forces, such as mammalian mandibles. For such structures to evolve in multiple directions on a complex adaptive landscape, different regions must change shape while maintaining structural integrity. We evaluated the complexity of the adaptive landscape for mandibular shape in Marmotini, a lineage of ground squirrels that varies in the proportions of seeds and foliage in their diets, by comparing the fit of models based on traits that predict changes in mandibular loading. The adaptive landscape was more complex than predicted by a two‐peak model with a single dietary shift. The large number of adaptive peaks reflects a high diversity of directions of shape evolution. The number of adaptive peaks also reflects a multiplicity of functional trade‐offs posed by the conflicting demands of processing foods with various combinations of material properties. The ability to balance trade‐offs for diets with different proportions of the same foods may account for diversification and disparity of lineages in heterogeneous environments. Rather than constraints, trade‐offs may be the impetus of evolutionary change.

Experimental Warming Hastens Physical Dormancy Break and Germination in Tropical Fabaceae.

Climate warming may threaten the germination strategies of many plants that are uniquely adapted to today’s climate. For instance, species that employ physical dormancy (PY) – the production of seeds that are impermeable to water until high temperatures break them, consequently synchronizing germination with favorable growing conditions – may find that their seeds germinate during unfavorable or potentially fatal periods if threshold temperatures are reached earlier in the year. To explore this, we subjected the seeds of five species with physical dormancy (from the genera Abrus, Bauhinia, Cassia, Albizia, and Acacia) to “mild” (+2°C) and “extreme” (+4°C) future warming scenarios and documented their germination over 2 years relative to a control treatment. Under current climatic conditions, a proportion of seeds from all five species remained dormant in the soil for 2 years. A mild warming of 2°C had little to no effect on the germination of four of the five study species. Contrastingly, an extreme warming of 4°C dramatically increased germination in all five species within the first year, indicating a reduction in their ability to persist in the soil long-term. Cassia fistula was particularly susceptible to warming, exhibiting a similar increase in germination under both mild and extreme warming relative to control. Our findings suggest that climate warming in the tropics may cause the seeds of species that rely on physical dormancy to stagger the risk of unsuccessful germination across years to leave soil seed banks prematurely – the long-term implications of which remain unknown.

Симбиотические свойства люцерны хмелевидной сорта Мира

The first Russian variety of black medic of the Mira was created and included in the State Register of Breeding Achievements. The study of the symbiotic properties of this variety showed that the most promising strains for pre-sowing inoculation were LX1 and 412b, the first increased the collection of dry matter and seeds by 96 and 115%, and the second – by 81 and 73%, respectively. Both strains can be used when cultivating this variety for feed and seeds. Inoculation with the LX6 strain increased seed productivity by 84%. Strains LX2, LX5 and LX6 increase the adaptive ability of varieties of the Mira, shifting the metabolism of the alfalfa-rhizobial system towards increasing seed productivity. The proportion of seeds in plants inoculated with the above-mentioned strains increases to 24–31% of the total plant weight, and in other symbiotic systems this indicator was 19–22%. Strain LX1 was isolated from nodules of plants belonging to the same population on the basis of which the Mira variety was created and it is the most genetically complementary to this variety. The yield of black medic of the Mira variety without inoculation for two years of use was 3.3 t/ha of dry matter, 0.67 t/ha of seeds. Pre-sowing inoculation of seeds with the LX1 strain increased the yield of this variety to 6.48 t/ha (+96%) of dry matter and seeds – to 1.44 t/ha (+115%). In the vegetation experiment, inoculation with the rhizobium strain LX1 significantly increased the height of plants by 4.2 cm, the leaf area by 0.69 cm2 (+49%), productivity by 176%. The total nitrogen content in the aboveground part of the plants reached 3.63%, the roots 3.31%, the control indicators were 3.02 and 2.77%, respectively.

Long-term population dynamics of Aphelenchoides besseyi on Oryza sativa in a paddy field, and changes in the pathological and ecological traits of the two populations

Summary An Oryza sativa cultivar inoculated with the white tip nematode, Aphelenchoides besseyi, was cultivated over 18 years to investigate the population dynamics of the nematode and the change in the virulence of nematodes and tolerance/resistance of plants. The mean number of living nematodes per seed (S) showed two peaks, each of which was followed by a 3-year decrease in the S value, during the initial 10 years. The annual reproduction curve between in year and in year t had a peak in a range of of &lt;1.1. The incidence of white tip disease increased with increasing mean number of living nematodes seed−1 in the previous year, whereas the proportion of seeds with living nematodes increased with increasing mean number of living nematodes seed−1 in the current year. Inoculation tests of the nematode cohorts on the seedling cohorts derived from seeds harvested in the same or different years indicated that the initial 6-year interaction between the rice and nematode populations caused the nematodes to increase the incidence of white tip disease and to decrease the degree of seed swelling and the proportion of heavy seeds. On the other hand, the interaction caused the rice plants to prevent the incidence of disease from increasing and the degree of seed swelling and the proportion of heavy seeds from decreasing.

Seedbank persistence and emergence pattern of Argemone mexicana, Rapistrum rugosum and Sonchus oleraceus in the eastern grain region of Australia

A thorough understanding of the emergence pattern and persistence of weed seeds is a prerequisite in framing appropriate weed management options for noxious weeds. In a study conducted at the University of Queensland, Australia, the emergence and seed persistence behavior of three major weeds Sonchus oleraceous, Rapistrum rugosum, and Argemone mexicana were explored with seeds collected from Gatton and St George, Queensland, Australia, with an average annual rainfall of 760 and 470 mm, respectively. Seed persistence was evaluated by placing seeds at the surface layer (0 cm) or buried at 2 and 10 cm depths enclosed in nylon mesh bags and examined their viability for 42 months. In another study, the emergence pattern of four populations, each from these two locations, was evaluated under a rainfed environment in trays. In the mesh-bag study, rapid depletion of seed viability of S. oleraceous from the surface layer (within 18 months) and lack of seed persistence beyond two years from 2 and 10 cm depths were observed. In trays, S. oleraceous germinated 3 months after seeding in response to summer rains and there was progressive germination throughout the winter season reaching cumulative germination ranging from 22 to 29% for all the populations. In the mesh-bag study, it took about 30 months for the viability of seeds of R. rugosum to deplete at the surface layer and a proportion of seeds (5 to 13%) remained viable at 2 and 10 cm depths even at 42 months. Although fresh seeds of R. rugosum exhibit dormancy imposed due to the hard seed coat, a proportion of seeds germinated during the summer months in response to summer rains. Rapid loss of seed viability was observed for A. mexicana from the surface layer; however, more than 30% of the seeds were persistent at 2 and 10 cm depths at 42 months. Notably, poor emergence was observed for A. mexicana in trays and that was mostly confined to the winter season.

The impact of fire on the quality of drooping sheoak (Allocasuarina verticillata) cones for the endangered Kangaroo Island glossy black-cockatoo (Calyptorhynchus lathami halmaturinus)

The Kangaroo Island glossy black-cockatoo (Calyptorhynchus lathami halmaturinus) is an endangered subspecies that feeds almost entirely on the kernels of drooping sheoak (Allocasuarina verticillata). Hence, it is highly susceptible to changes in the quantity or quality of A. verticillata. Fire has the potential to severely impact glossy black-cockatoo feeding habitat on the island, but since A. verticillata is serotinous, it is partially reliant on fire for regeneration. Here, we quantified the effects of time-since-fire (over a 60-year period) on cone quality for C. lathami halmaturinus. Cone quality in A. verticillata woodlands with a range of fire histories was examined using three measures of cone profitability: the ratio of seed-to-cone mass (Clout’s Index), the ratio of kernel-to-cone mass (Kernel Ratio) and the proportion of seeds containing kernels (Seed Fill). We then mapped the fire history of A. verticillata woodlands on Kangaroo Island before and after the 2019/20 bushfire season. We found that time-since-fire had a significant negative impact on Clout’s Index, as well as a negative but non-significant impact on Seed Fill and Kernel Ratio. This suggests that trees that have not experienced fire in over 60 years may have cones that are of lesser value to C. lathami halmaturinus. This is concerning, because up to 94% of A. verticillata woodlands not impacted by the 2019/20 bushfires are likely of a similar age class, having had no fire in over 60 years. Our findings highlight the need for ongoing assessment and management of critical habitat for this endangered subspecies.

The pollination of Habenaria rhodocheila (Orchidaceae) in South China: When butterflies take sides.

Habenaria is one of the largest terrestrial genera in the family Orchidaceae. Most field studies on Habenaria species with greenish–white and nocturnal scented flowers are pollinated by nocturnal hawkmoths and settling moths. However, H. rhodocheila presents reddish flowers lacking a detectable scent and fails to fit the moth pollination syndrome. We investigated the pollinators, breeding system, and functional traits of H. rhodocheila in South China and found that two diurnal swallowtail butterflies Papilio helenus and Papilio nephelus (Papilionidae) were the effective pollinators. When butterflies foraged for nectar in the spur, the pollinia became attached between the palpi. A triangular projected median rostellar lobe was found at the entrance (sinus) of the spur of H. rhodocheila. This lobe divided the spur opening into two entrances forcing butterflies to enter their proboscides through the left or right side. When the projection of median rostellar lobe was removed, the site of pollinium attachment changed to the eyes of the butterflies, leading to a higher rate of pollinium removal but lower rate of pollinium deposition. Our quartz glass cylinder choice experiment suggested that visual rather than olfactory cues provided the major stimuli for butterflies to locate these flowers. Hand pollination experiments suggested this species was self‐compatible but pollinator‐dependent. However, the proportion of seeds with large embryos produced in self‐pollinated fruits was significantly lower than in cross‐pollinated fruits, indicating a significant inbreeding depression. Unlike many other orchid species, fruit set was higher than rates of pollinium removal, indicating a high level of pollination efficiency in a species with friable pollinia. Shifts from moth to butterfly pollination in the genus Habenaria parallel other orchid lineages providing insights into the potential for pollinator‐mediated floral trait selection.

Post-dispersion humidity condition alters the surface of the testa and the proportion of seeds with physical dormancy in Erythrina speciosa

AbstractSeeds of Papilionoideae (Leguminosae) species lose water after dispersal, increasing the proportion of water-impermeable seeds (physical dormancy, PY). However, changes in testa structure during this process remain unknown. The present study investigated how variation in relative humidity (RH) during the post-dispersion period affects the proportion of seeds of Erythrina speciosa with PY. Seeds from two populations were stored in drier (40% RH) and wetter (80% RH) environments and periodically subjected to physiological analysis (seed water content, imbibition and germination) and structural analysis of the testa (light and scanning electron microscopy). Drier storage resulted in seed dehydration, increasing the proportion of water-impermeable seeds and closure of cracks in the mucilaginous stratum. In contrast, wetter storage led to an increase in seed water content, a decrease in the proportion of seeds with PY, and the formation of cracks. As a result of variation in environmental humidity, we conclude that changes occur in the mucilaginous stratum of seeds, altering water loss and, consequently, the proportion of seeds with PY. Environments with low humidity cause a decrease in seed water content, the closing of cracks in the mucilaginous stratum, and, consequently, an increase in the proportion of water-impermeable seeds. On the other hand, a high RH environment increases the seed water content and the formation of superficial cracks, through which water enters during imbibition, causing a decrease in the proportion of seeds with PY.

Seed fates of four rainforest tree species in the fragmented forests of Anamalais in the southern Western Ghats, India

Seed predation is one of the key ecosystem processes governing the plant population and community structure in forests. Forest fragmentation and habitat loss have been shown to affect seed predation, leading to altered tree recruitment. However, the effects of fragmentation and habitat loss on seed predation are highly variable and context-specific, with limited information from South Asia. For four rainforest tree species in a production landscape of tea and coffee, we examined the influence of forest type (benchmark, N = 3, and fragmented, N = 5, forests) and seed size on the proportion of seeds, 1) predated by vertebrate seed predators, 2) predated by invertebrate seed predators, and 3) removed by vertebrate seed predators. The seed fates were tracked by placing the seeds in four 1 × 1 m plots under the canopy of the tree (N ≥ 11 individuals per tree species and 48 trees overall), and camera traps were placed under a subset of trees (N = 29, trap-nights = 712). Overall, we recorded nine species of seed predators, and that the seed predator species composition differed among the four tree species. However, there was no significant difference in either seed predator species composition or their visitations across the forest types. The seeds were more likely to be predated (on average 6% higher predation) by vertebrate seed predators in the fragments than in the benchmark forests. Medium-seeded species were more likely to be predated by vertebrate seed predators than large-seeded species (on average 41% higher predation). Invertebrate seed predation and seed removal by vertebrate seed predators had a weak relationship with forest type, with higher invertebrate seed predation in the fragments and higher seed removal in the benchmark forests. With altered seed dispersal patterns resulting from habitat fragmentation and habitat loss, differential seed predation can alter regeneration patterns, thereby influencing adult tree communities in fragmented forests.

Abiotic factors controlling germination of the multipurpose invasive Prosopis pallida: towards afforestation of salt-affected lands in the subtropical arid Arabian desert

Prosopis pallida is an exotic invasive tree recently recorded in the hot arid subtropical deserts of the UAE and has the potential for afforestation of degraded arid lands. Little information is available about the effects of abiotic stresses on the germination of this species. Here, we aimed to assess the response of drought (as simulated by polyethylene glycol, PEG) and salinity (NaCl) stresses to light and temperature of seed incubation. Seeds treated with four salinities (0–600 mM NaCl) and seven PEG (0 to – 1.8 MPa) levels were incubated at three temperatures and two light regimes. The results showed that the response of seed germination to NaCl depended on temperature, but on both light and temperatures in PEG. In both NaCl and PEG solutions, germination did not differ significantly between the three temperatures at higher osmotic potentials. Still, it was reduced significantly in the lower potentials when seeds incubated at higher temperatures. Additionally, germination in light and dark did not differ at higher osmotic potentials of PEG, but germination in the dark was significantly higher at lower osmotic potentials. A considerable proportion of seeds that failed to germinate in PEG recovered their germination when transferred to distilled water (62%), but few seeds were able to recover from NaCl (4.2%). The higher tolerance to NaCl indicates that seeds might use sodium and chloride ions as osmoregulators to alleviate the osmotic inhibitory effects. Future research should monitor seedling establishment and growth to explain plant persistence in salt-affected lands in arid environments.

Inferring trait‐based mechanisms and variance consequences of abiotic secondary dispersal from the spatio‐temporal distribution of a desert soil seed bank

AbstractQuestionsQuantifying the combined effects of seed traits, microsite types, and abiotic dispersal agents on the mean and variance of seed bank density and composition will help understand vegetation dynamics in deserts. In a site with NE slope and mainly southerly winds, we asked whether large and oblong seeds were more likely to be transported and deposited in water obstructions and underneath the northern part of shrub understories. We also asked whether seed standing crop was less variable in water obstructions than in other microsites less affected by seed deposition.LocationA sand field in San Juan province, Argentina.MethodsWe sampled the soil seed banks of four microsite types: water obstructions where debris/litter accumulates, southern and northern shrub understories, and open spaces among shrubs. Sampling was carried out in 11 plots and replicated at six moments between 2010 and 2012.ResultsDebris microsites showed the highest levels of seed density, species richness and standing crop; seed density and standing crop were also least variable in these microsites. Debris microsites also contained high seed abundance of stress‐intolerant, shrub‐dependent species. Seed density, species richness, seed standing crop, and the proportions of both large and oblong seeds were all higher in northern than in southern understories. The relationship between seed mass and the proportion of seeds that were apparently retained (i.e., not washed away and deposited in water obstructions) was more strongly negative in southern than in northern understories.ConclusionsNorthern and southern understories appeared to act as water run‐on (i.e., seed recipients) and run‐off zones (i.e., seed donors), respectively. Seed accumulation under the shelter provided by shrubs may promote seed predation in these microsites. Abiotic dispersal would therefore contribute to the maintenance of vegetation patches when seed arrival underneath shrub canopies saturates granivore consumption.