Germination Success Research Articles

The Role of Skill in Successful Germination of Melia Volkensii Seeds

Melia volkensii (Melia), locally known as Mukau in Kenya, is an important indigenous dryland forestry species. The species is propagated primarily through seeds, with germination percentage ranging from 40- 90%. Successful germination of seeds of forestry species requires skillful application of appropriate pre-sowing treatments. Studies that document and quantify the effect of skill/experience on the germination outcomes for tree seeds are rare. This study sought to fill this gap by documenting the results from a capacity building exercise on testing M. volkensii seeds. Seeds were collected from the KEFRI Kibwezi seed orchard, pretreated and sown by seven participants with different skill levels based on years of experience. The seeds were sown in glasshouse and nursery conditions. There were significant differences (p < 0.001) in germination capacity, mean germination time, T 50, mean germination rate, mean daily germination (MDG) and peak value (PV) depending on the skill level of the participants. The results also varied between germination environment (p < 0.001) for all germination traits except MGD and T50. The highest germination outcomes were recorded for participants with the longest experience in testing of M. volkensii seed germination. These findings therefore signify the importance of skill/experience in germination of M. volkensiiseeds, an outcome that may have implications for other forestry seeds with special pre-sowing requirements.

From seed dispersal service to reproductive collapse: density‐dependent outcome of a palm–mammal interaction

Interspecific ecological interactions are inherently context‐dependent. They may vary in both magnitude and sign depending on the biotic and abiotic conditions, depicting a mutualism–antagonism continuum. However, how population abundances and the activity of interacting species modulate these interactions remains underexplored. Here, we chose the interaction between the Mediterranean palm Chamaerops humilis and the feral goat Capra hircus in Mallorca (Balearic Islands, Spain). We selected three study plots with low, intermediate and high intensities of goat activity where we characterized palm distribution, seed rain, seed predation and early palm recruitment during two consecutive years. Since goats can cause both costs (e.g. florivory) and benefits (e.g. seed dispersal) to C. humilis performance, we investigated the following three questions: 1) does the spatial distribution of adult palms vary depending on the intensity of goat activity? 2) Does the intensity of goat activity influence seed rain and its potential spatial association with adult palms? 3) To what extent does the intensity of goat activity determine post‐dispersal events such as seed predation and seedling emergence? We found that adult palms showed a more clumped and complex distribution (double‐cluster process) in plots with low and intermediate goat activity compared to that with high goat activity (simple‐cluster process). In the low goat activity plot, dispersed seeds were spatially aggregated around adult palms, showing twice as much insect‐seed predation and nearly three times lower seed germination success than those in the intermediate goat activity plot. Palm seed dispersal and recruitment were almost nil in the high goat activity plot due to heavy consumption of palm inflorescences and developing fruits by goats. Our findings demonstrate how the net outcome of plant–animal interactions can change from mutualism to antagonism, from reproductive service to reproductive collapse, depending on the abundance and the activity of the interacting species.

Optimization of iron-ZIF-8 catalysts for degradation of tartrazine in water by Fenton-like reaction

Optimization of iron zeolitic imidazole framework-8 (FeZIF-8) nanoparticles, as heterogeneous catalysts, were synthesized and evaluated by the Fenton-like reaction for to degrade tartrazine (Tar) in aqueous environment. To achieve this, ZIF-8 nanoparticles were modified with different iron species (Fe2+ or Fe3O4), and subsequently assessed through the Fenton-like oxidation. The effect of different parameters such as the concentration of hydrogen peroxide, the mass of catalyst and the contact time of reaction on the degradation of Tar by Fenton-like oxidation was studied by using the Box-Behnken design (BBD). The BBD model indicated that the optimum catalytic conditions for Fenton-like reaction with an initial pollutant concentration of 30 ppm at pH 3.0 were T = 40 °C and 12 mM of H2O2, 2 g/L of catalyst and 4 h of reaction. The maximum Tar conversion value achieved with the best catalyst, Fe1ZIF-8, was 66.5% with high mineralization (in terms of decrease of total organic carbon – TOC), 44.2%. To assess phytotoxicity, the germination success of corn kernels was used as an indicator in the laboratory. The results show that the catalytic oxidation by Fenton-like reaction using heterogeneous iron ZIF-8 catalysts is a viable alternative for treating contaminated effluents with organic pollutants and highlighted the importance of the validation of the optimized experimental conditions by mathematical models.

Using the Aqueous Phase Produced from Hydrothermal Carbonization Process of Brown Seaweed to Improve the Growth of Phaseolus vulgaris.

Seaweeds are considered a biomass for third-generation biofuel, and hydrothermal carbonization (HTC) is a valuable process for efficiently disposing of the excess of macroalgae biomass for conversion into multiple value-added products. However, the HTC process produces a liquid phase to be disposed of. The present study aims to investigate the effects of seed-priming treatment with three HTC-discarded liquid phases (namely AHL180, AHL240, and AHL300), obtained from different experimental procedures, on seed germination and plant growth and productivity of Phaseolus vulgaris L. To disentangle the osmotic effects from the use of AHL, isotonic solutions of polyethylene glycol (PEG) 6000 have also been tested. Seed germination was not affected by AHL seed-priming treatment. In contrast, PEG-treated samples showed significantly lower seed germination success. AHL-treated samples showed changes in plant biomass: higher shoot biomass was recorded especially in AHL180 samples. Conversely, AHL240 and AHL300 samples showed higher root biomass. The higher plant biomass values recorded in AHL-treated samples were the consequence of higher values of photosynthesis rate and water use efficiency, which, in turn, were related to higher stomatal density. Recorded data strongly support the hypothesis of the AHL solution reuse in agriculture in the framework of resource management and circular green economy.

Conflicting selection pressures on seed size and germination caused by carnivorous seed dispersers.

Plants produce nutritious, fleshy fruits that attract various animals to facilitate seed dispersal and recruitment dynamic. Species-specific differential selection of seed size by multiple frugivorous disperser assemblages may affect the subsequent germination of the ingested seeds. However, there is little empirical evidence supporting this association. In the present study, we documented conflicting selection pressures exerted on seed size and germination by five frugivorous carnivores on a mammal-dispersed pioneer tree, the date-plum persimmon (Diospyros lotus), in a subtropical forest. Fecal analyses revealed that these carnivores acted as primary seed dispersers of D. lotus. We also observed that seed sizes were selected based on body mass and were species-specific, confirming the "gape limitation" hypothesis; three small carnivores (the masked palm civet Paguma larvata, yellow-throated marten Martes flavigula, and Chinese ferret-badger Melogale moschata) significantly preferred to disperse smaller seeds in comparison with control seeds obtained directly from wild plants whereas the largest Asiatic black bears (Ursus thibetanus) ingested larger seeds. Seeds dispersed by medium-sized hog badgers (Arctonyx albogularis) were not significantly different from control seeds. However, regarding the influence of gut passage on seed germination, three arboreal dispersal agents (martens, civets, and bears) enhanced germination success whereas terrestrial species (ferret-badgers and hog badgers) inhibited the germination process compared with undigested control seeds. These conflicting selection pressures on seed size and germination may enhance the heterogeneity of germination dynamics and thus increase species fitness through diversification of the regeneration niche. Our results advance our understanding of seed dispersal mechanisms and have important implications for forest recruitment and ecosystem dynamics.

Effect of Seed Processing by Flying Foxes and the Patas Monkey on the Germination Success of the African Ebony (Diospyros mespiliformis)

Abstract Animals deliver an important ecosystem service by dispersing plant seeds. Seed dispersers have different effects on the germination success of seeds. This study aimed at examining the effect of seed processing by the patas monkey (Erythrocebus patas) and two flying foxes (Micropteropus pusillus and Epomophorus gambianus) on the germination success of African ebony (Diospyros mespiliformis). Flying foxes and patas monkeys were kept in cages and fed ad libitum with African ebony fruits. Seeds processed were collected, measured, and germinated. Seeds processed by monkeys and flying foxes were compared to control seeds which were removed by hand from fruits. Our results showed that the patas monkey and flying foxes preferably processed smaller seeds. Flying foxes improved the germination success from 6.67 to 72.5%. They also reduced the mean germination time up to 5 days. The patas monkey also improved the germination success from 6.67 to 52.5% and reduced the mean germination time up to 4 days. The effect of flying foxes and the patas monkey on the seed germination and its implication for the African ebony plantation dynamic should be explained to communities for their conservation.

High Temperature Tolerance in a Novel, High-Quality Phaseolus vulgaris Breeding Line Is Due to Maintenance of Pollen Viability and Successful Germination on the Stigma.

The common bean (Phaseolus vulgaris L.) is an important nutritional source globally but is sensitive to high temperatures and thus particularly vulnerable to climate change. Derived from a breeding program at CIAT (Colombia), a heat-tolerant breeding line, named heat-tolerant Andean-type 4 (HTA4), was developed by a series of crosses of parents with a small-bean tepary genotype (Phaseolus acutifolius L.) in their pedigree, which might be the donor of heat stress (HS) tolerance. Importantly, in HTA4, the large, commercially desirable Andean-type beans was restored. To assess underlying tolerance mechanisms, HTA4, together with a heat-sensitive Colombian variety (Calima), was exposed to HS (31 °C/24 °C HS vs. 26 °C/19 °C day/night) under controlled environment conditions. Vegetative growth and photosynthetic performance were not negatively impacted by HS in either genotype, although senescence was delayed in Calima. HS during the reproductive stage caused an increase in pod number in Calima but with few fully developed seeds and many pods aborted and/or abscised. In contrast, HTA4 maintained a similar filled pod number under HS and a higher seed weight per plant. Pollen showed high sterility in Calima, with many non-viable pollen grains (24.9% viability compared to 98.4% in control) with a thicker exine and fewer starch granules under HS. Calima pollen failed to adhere to the stigma and germinate under HS. In HTA4, pollen viability was significantly higher than in Calima (71.1% viability compared to 95.4% under control), and pollen successfully germinated and formed pollen tubes in the style under HS. It is concluded that HTA4 is heat tolerant and maintains a high level of reproductive output due to its ability to produce healthy pollen that is able to adhere to the stigma.

Does shading and ground cover of moss and litter improve germination and establishment of Betula pendula Roth, Salix caprea L. and Populus tremula L. seedlings during drought stress in climate change? – A greenhouse study

The climate change is leading to a significant increase in temperatures and dry periods in spring, for example in parts of middle and north Europe. Thus, the important factor for tree growth, the water availability, decreases on forest sites. It is to be expected that the successful establishment of pioneer tree species as pre-forests on large damaged areas will considerable be limited in the future. The phases of germination and establishment are the most dangerous phase in the life of trees. In this greenhouse study, we tested how different microsite conditions (open soil, moss and litter cover as well as different shading) under reduced water availability influence establishment success and growth of Betula pendula, Populus tremula and Salix caprea.The initial high germination success were reduced to 14%, 7% and 12% for Populus tremula, Salix caprea and Betula pendula, respectively, and the growth were significantly slower when the relevant soil water resource was just above the permanent wilting point. Therefore, in the first year the germination and establishment is linked to persistent moist conditions. If the soil dries out during germination, e.g. if there is no watering for more than 3 weeks, all seedlings died. Equivalent germination microsites (shading or ground cover) with comparable possible seedling densities to the moist open soil does not exist under water stress. Although moss and litter cover retain longer soil moisture under extremely dry conditions and guarantee significantly better seedling development than on open soil, initially significantly fewer seeds germinate on these substrate types.Radiation shows no influence on germination and seedling survival. The seedlings are able to survive radiation conditions of 3% and 27% of open area radiation. This makes establishment possible under (remaining) light canopy, at the edge of damaged areas or in small islands of remaining shelter trees on damaged areas. However, radiation had a significant effect on growth. With increasing radiation, shoot lengths and above ground biomasses are higher and the root collar diameter larger.Overall, Betula pendula is the most drought stress resistant of the tested tree species. While Populus tremula and Salix caprea already had problems establishing themselves on dry sites, the problem will become more serious under climate change. The lack of moist, vegetation-free open soils will result in a significant reduction of establishment success for tested pioneer tree species in climate change.

Counteracting effects of soil biota on emergence and growth of herbaceous plants

BackgroundPlants condition the biotic composition of their rhizosphere. In turn, this plant legacy on the soil biota may affect the performance of plants recruiting in their vicinity. Unravelling how plant-soil legacies drive plant recruitment is key to understand vegetation dynamics and plant community assembly. Studies on the topic usually focus on the effects of soil microbiota as a whole, while the relative role of different guilds of soil organisms in the plant recruitment processes is not usually dissected.AimsHere, we used soils of Mediterranean woody plant species to test whether arbuscular mycorrhizal fungi (AMF) and small-size microbiota (< 50 µm) (MB) affect the germination success and growth of eight herbaceous plants.ResultsWe documented a significant increase in seedling emergence probability when small-sized MB was present and no effect of AMF. In contrast, the aboveground plant biomass decreased with the presence of MB and increased with that of AMF. Interestingly, those plants growing in the absence of MB and in soils from woody plants associated with higher AMF richness developed higher aboveground biomass.ConclusionThis study brings new evidence on how soil microbial communities can determine the performance of their associated herb community, and also, how the effects of different microbial guilds may change across the plant ontogeny. Given these results, the differential effect of soil microbial functional guilds should be considered to better understand plant soil legacies and feedbacks, potentially driving plant recruitment and community assembly.

Incorporated cover crop residue suppresses weed seed germination

AbstractCover crops have been shown to be important integrated weed management tools. In addition to directly competing with weeds, cover crops can provide weed suppressive effects following incorporation through release of allelopathic compounds and/or changes to nutrient availability. Incorporation of a cover crop mixture may provide a synergistic or antagonistic effect on weed suppression by further altering nutrient dynamics. To investigate this phenomenon, we evaluated the suppressive effects following incorporation of annual ryegrass, buckwheat, brown mustard, and phacelia sown with and without field pea on germination and growth of several pernicious weed species. Further, we used the additive partitioning model to determine if pea synergistically improved biomass production and weed suppression of cover crops. Our results demonstrate that following incorporation, cover crop residues suppress weed germination and weed biomass production. According to the additive partitioning model, the addition of pea had an antagonistic effect on buckwheat and brown mustard biomass production and decreased buckwheat weed suppression by 8%. In contrast, the addition of field pea greatly enhanced biomass production of phacelia at a reduced seeding rate suggesting a positive biodiversity effect. Limited evidence was found for changes to nutrient availability following cover crop incorporation, however, a dose‐dependent effect of cover crop residue on weed suppression suggests allelopathy and/or nutrient availability may have a role on weed seed germination success. Together, our results support the use of incorporated cover crop residues as an integrated weed management tool.

Interactions between mammals and fruit of an endemic tree (Amphitecna montana, Bignoniaceae) with megafauna traits

ABSTRACT Several features in the fruit of some neotropical trees likely evolved in response to the interaction with the mammalian megafauna extinct in the late Pleistocene. However, few studies have assessed the interactions between these plants and mammals in the absence of megafauna. We conducted a camera-trapping study in the Reserve of El Triunfo, Chiapas, Southern Mexico, to record the fauna consuming the fruit of the endemic tree Amphitecna montana which has megafauna traits. We surveyed the abundance and the spatial distribution of trees, saplings, and seedlings in 10 transects totalizing 0.1 ha, analyzed the chemical composition of their fruit, and assessed the impact of seed manipulation on germination success and seedling establishment. We recorded 12 species of medium-large mammals but the most frequent consumers of fruit were squirrels. The relationship among trees, saplings, and seedlings did not indicate the existence of a regeneration limitation. All the plant stages showed a clustered spatial pattern, which is in agreement with squirrels being the main seed dispersers. Free seeds were the more successful to germinate and establish as seedlings. Despite the current lack of megafauna in our study area, the A. montana population does not show signs of declining.

Bloom development of toxic dinoflagellate Alexandrium catenella (Group I) in Jinhae-Masan Bay, Korea: Germination strategy of resting cysts in relation to temperature and salinity

To better understand the role of resting cysts in the outbreak of paralytic shellfish poisoning and bloom dynamics in Jinhae-Masan Bay, Korea, this study investigated the germination features of ellipsoidal Alexandrium cysts isolated from sediments collected in winter and summer under different combinations of temperature and salinity. Morphology and phylogeny of germling cells revealed that the ellipsoidal Alexandrium cysts belong to Alexandrium catenella (Group I). The cysts could germinate across a wide range of temperature (5–25 °C) with germination success within 5 days, indicating that continuous seeding for the maintenance of vegetative cells in the water column may occur through the year without an endogenous clock to regulate germination timing. In addition, the cyst germination of A. catenella (Group I) was not controlled by seasonal salinity changes. Based on the results, this study provides a schematic scenario of the bloom development of A. catenella (Group I) in Jinhae-Masan Bay, Korea.

The Ability of Ruppia polycarpa to Regenerate from Seed Depends on Seasonal Porewater Salinity Dynamics and Declining Winter Rainfall Could Delay Recruitment

For many plants, regeneration from seed is vital for population recovery. Climate change is modifying the global hydrological cycle and a primary factor controlling germination of marine plants: salinity. How altered salinity regimes, and especially altered porewater salinity regimes, will regulate early life history stages of estuarine seagrasses is poorly understood. Here, we quantified the porewater salinity dynamics in two ephemeral estuaries that are dominated by the cosmopolitan genus Ruppia. Seedbank, germlings (germinated seeds) and seedlings were found in salinities ranging from 5 to 110 over an annual cycle. To understand the germination ecology of the dominant species, Ruppia polycarpa, seeds were exposed to treatments simulating current salinity regimes and those predicted under climate change. Seeds underwent a Dormancy treatment (15, 60, 150) followed by a Germination treatment (10, 20, 80). Generally, early life history stages were positively affected by hypersaline dormancy conditions if the subsequent Germination salinity was ≤ 20. Germination success was significantly higher for seeds transferred to 10 (65%) compared to 20 (49%) whilst no seeds germinated in 80 highlighting the risk of lower germination as estuaries become drier and more hypersaline with declining winter rainfall. However, germlings were found in situ in salinities ≥ 80 suggesting aspects of the salinity dynamics, not captured by our experimental conditions, may broaden tolerances. Dormant seeds were continuously present in situ and seedlings were observed throughout the whole of the growing season. These results are indicative of bet-hedging strategies. Future research should explore the capacity of these strategies to afford resilience to R. polycarpa to salinity variability under climate change.

Dormancy-breaking treatments for enhancing seed germination in plant Kitaibela vitifolia Willd

Vine-leaved kitaibelia (Kitaibela vitifolia Willd.), also known as balkanmalva or chalice flower, is a critically endangered plant species with a high risk of extinction in the wild. A reason given for this is, among others, a low germination rate primarily caused by dormancy. The present study evaluated the seed germination and seedling growth parameters of vine-leaved kitaibelia in response to eight different pre-sowing treatments. The final germination percentage ranged from 0 % to 55 %, depending on the pre-sowing treatment. The most effective method for breaking dormancy and increasing vine-leaved kitaibelia seed germination was the treatment with seeds soaked in H2SO4 for 5 min. The mechanical scarification of vine-leaved kitaibelia seeds also improved germination as compared to control treatment, while treatments with nitric acid and gibberellic acid were not effective in enhancing seed germination. All evaluated seedling growth parameters were not affected by pre-sowing treatments. Considering that successful germination and seedling establishment are crucial for the regeneration of vine-leaved kitaibelia further studies are required in order to identify other pre-sowing treatments that could further enhance seed germination and, consequently, seedling development.

Severe Drought Still Affects Reproductive Traits Two Years Later in a Common Garden Experiment of Frangula alnus

Longer periods of intensified droughts in Western Europe are predicted due to ongoing climate change. Studying the responses of woody species during intense drought events can help toward understanding the consequences for forest ecosystems. We studied the effects of an intense summer water limitation on several reproductive traits, two years after the treatment, in Frangula alnus Mill. shrubs grown in a common garden. Drought-treated shrubs produced more berries one and two years after the drought event, while the height increment of the second post-treatment year was still significantly retarded. The mean weight of stones from berries picked two years after the drought treatment and their germination percentage, which was corrected for mean stone weight, were higher for the treated shrubs. These results indicate a resource re-allocation toward reproduction, rather than toward growth, which was still in action two years after the water limitation. The higher germination success, which is a transgenerational effect, and which has already been suggested to be an adaptation to survival in more stressful growth conditions, is also still detectable two years after the severe drought. F. alnus produces mature berries continuously during the whole summer. From the middle of July till the end of August, the counts of mature berries, the mean stone weight and the germination percentage, corrected for mean stone weight, decreased, whereas the timing of seedling emergence, also corrected for stone weight, advanced slightly. The timing of seedling emergence correlated weak but significantly with the timing of bud burst in the mother shrubs, with a variance analysis indicating a stronger genetic control for bud burst in comparison to seedling emergence. Several results corroborated previous findings. Population differentiation in the common garden was observed for mature berry counts and for several phenological traits. In conclusion, longer-term effects of drought on reproductive traits in woody species may add more complexity to the consequences of climate change on tree species distributions and survival of forest ecosystems.

Reviving Mung Bean Seeds: The Impact of Hydro Priming and Heat Shock on Germination Rates

Seed germination is a crucial stage of plant growth that can enhance yield by influencing seedling establishment. The speed and success of germination are key factors that determine the final yield of plants. This research aimed to investigate how hydro priming and heat shock affect the germination properties of green mung bean through a factorial experiment conducted in a completely randomized design with three replications at Parwan University's agronomic laboratory in 2022. The experimental treatments consisted of two temperature levels (35 and 25°C) and three moisture levels (8.5%, 10%, and 11.5%), with four categories of treatment: hydro prim, 30°C shock, 40°C shock, and control. Germination percentage, germination speed, seedling length, and dry weight were measured in the experiment. The results indicated that the triple interaction of temperature, moisture, and treatment was significant only for the germination speed trait at a 5% level. The main effect of temperature and the dual interaction of moisture and treatment at a 1% level were significant for stem length and dry weight. Additionally, the dual interaction between temperature, treatment, and temperature moisture level of 1 and 5% were significant for germination percentage, respectively. Moreover, the study found that hydro priming and thermal flushing treatment frequently improved seed storage capacity. Therefore, the study suggests that hydro priming and heat shock treatments can enhance seed germination and vigor, especially for seed lots stored under unfavorable conditions.

The influence of ammonium to nitrate ratio on the thermal responses of early life stages of the giant kelp Macrocystis pyrifera

The distribution and productivity of seaweeds, including kelps, are strongly influenced by changes in temperature and inorganic nitrogen (Ni) availability. However, their tolerances, sensitivities, and capacity to adjust to these changes can vary across their complex life cycle (microscopic and macroscopic stages). For the early life stages of Macrocystis, this study investigated the effect of the nitrate: ammonium ratio on physiological traits and gametophyte development at a range of temperatures (6.5 to 26.5 °C). Thermal performance curves (TPCs) were utilized to determine and predict the effect of temperature on meiospore germination success (%), gametophyte size (μm2), sex ratio and physiological traits (photosynthetic efficiency and nitrate and ammonium uptake rates). We found that the presence of NH4+ led to negative NO3− uptake rates in Macrocystis pyrifera gametophytes and reduced growth rates, and results suggest that thermal tolerance windows might vary between developmental stages and physiological traits. Our findings indicate that reduced meiospore germination and gametophyte size induced by suboptimal temperatures and increased NH4+concentrations can lead to lower physiological performance that might subsequently affect adult individuals and populations. Knowledge of the Ni uptake kinetics and source preferences across different life cycle phases can be crucial for conservation and aquaculture purposes as it might increase species productivity and persistence in a changing ocean.

Genome damage accumulated in seed ageing leads to plant genome instability and growth inhibition.

Successful germination and seedling establishment are important determinants of crop yields and plant survival in natural environments. Germination potential is compromised by suboptimal environmental conditions that result in seed ageing and high levels of genome damage. However, the mutagenic and growth inhibitory potential of DNA damage accumulated in seeds on subsequent seedling growth remains largely unknown. Arabidopsis seeds deficient in the chromosomal break repair factors DNA LIGASE 4 and DNA LIGASE 6 exhibited hypersensitivity to the effects of natural ageing, with reduced germination vigour and seedling biomass relative to wild type seed. Here we identify that aged Arabidopsis seed display elevated levels of programmed cell death (PCD) in the root meristem which persists into seedling establishment, with higher levels of cell death in lines deficient in DNA double strand break repair. Reporter lines determined the effects of seed ageing on mutation levels and intrachromosomal recombination frequencies. Seed deterioration resulted in strikingly elevated levels of frameshift mutations and genome instability in germinated seedlings. Thus, elevated levels genome damage incurred in the seed stage of the plant life cycle potentially impacts significantly on subsequent plant development. Furthermore, the mutagenic effects of seed ageing has potentially long-term implications on the genome stability of plant populations and ecosystem fitness. Collectively, we identify genome damage accumulated in suboptimal quality seed impacts on subsequent plant growth and genome stability, with associated implications for crop yields and plant survival under changing climates.

Determination of optimal plant growth regulators for breaking seed dormancy and micropropagation of Sorbus aucuparia L.

Sorbus aucuparia L. is an important forest tree used in the reforestation of high-altitude mountainous areas, which carries significant pharmaceutical, industrial, ornamental, food, and ecological properties. However, the seed propagation and micropropagation of mature trees of S. aucuparia L., presents various difficulties which are integral aspects for the re-propagation and breeding of novel cultivars. In this study, we isolated the mature embryo-containing seeds of selected varieties of S. aucuparia L. from their seed coat and used them directly as explants in vitro to investigate and determine the optimal dose of cytokinin in breaking seed dormancy and micropropagation. 3 mg/L of benzyl adenine (BA) in addition to different concentrations and combinations of kinetin (0.5, 1, and 2 mg/L), indole-3-butyric acid (IBA) (0, 1, 0.5, and 1 mg/L), and 1-naphthalene acetic acid (NAA) (0, 1, 0.5, and 1 mg/L) were applied within a Murashige and Skoog (1962) (MS) medium at germination inhibition, shoot elongation, and shoot proliferation. In the MS mediums containing BA and kinetin, germination was achieved at the end of 1 week, and shoot proliferation was achieved at the end of 3 weeks. The most successful germination (96%), tallest shoot length (mean 5.1 cm), most shoot proliferation (mean 7.2 pieces), and number of nodes (mean 9.7 pieces) were identified in the MS containing 3 mg/L BA and 1 mg/L kinetin. Direct root formation with shoot elongation occurred in 25% of explants which germinated in the MS medium. For shoots propagated without roots in this medium, 62% of these achieved rooting at the highest dose of 1 mg/L indole-3-acetic acid (IAA) using a two-stage rooting method. Rooted shoots were successfully transferred to an ex vitro medium. These results provide a basis for breaking seed dormancy of selected Sorbus L. genotypes quicker, leading to more effective clonal production. Keywords: Sorbus aucuparia L., rowanberry, tissue culture, seed dormancy, micropropagation, in vitro

Dispersal and establishment traits provide a colonization advantage for a polyploid apomictic plant.

Apomictic plants (reproducing asexually through seed) often have larger ranges and occur at higher latitudes than closely related sexuals, a pattern known as geographical parthenogenesis (GP). Explanations for GP include differences in colonizing ability due to reproductive assurance and direct/indirect effects of polyploidy (most apomicts are polyploid) on ecological tolerances. While life history traits associated with dispersal and establishment also contribute to the potential for range expansion, few studies compare these traits in related apomicts and sexuals. We investigated differences in early life history traits between diploid-sexual and polyploid-apomictic Townsendia hookeri (Asteraceae), which displays a classic pattern of GP. Using lab and greenhouse experiments, we measured seed dispersal traits, germination success, and seedling size and survival in sexual and apomictic populations from across the range of the species. While theory predicts that trade-offs between dispersal and establishment traits should be common, this was largely not the case in T. hookeri. Apomictic seeds had both lower terminal velocity (staying aloft longer when dropped) and higher germination success than sexual seeds. While there were no differences in seedling size between reproductive types, apomicts did, however, have slightly lower seedling survival than sexuals. These differences in early life history traits, combined with reproductive assurance conferred by apomixis, suggest that apomicts achieve a greater range through advantages in their ability to both spread and establish.