Germination Requirements Research Articles

Microclimatic variation regulates seed germination phenology in alpine plant communities

Abstract For most terrestrial plants, regeneration depends on the ability of seeds to germinate in the most favourable climatic conditions. Understanding seed germination phenology is thus crucial for predicting plant responses to environmental changes. However, a substantial gap persists regarding how microclimatic conditions influence germination in seasonal ecosystems. Here, we investigate the germination phenology of alpine plants in snow‐related microclimates as a tool for predicting the resilience of plant communities to climate change. We conducted a continuous seasonal experiment with fresh seeds to investigate germination phenology in 54 co‐occurring species from temperate and Mediterranean alpine communities. Using long‐term field microclimatic data series, we precisely mimicked two contrasting microclimatic regimes in growth chambers: (1) windy exposed edges with a snow‐free period in winter and warmer temperatures in summer (‘fellfield’) and (2) sheltered areas with lengthy snow cover and cooler temperatures (‘snowbed’). We validated the laboratory results with field sowing experiments to provide a complete picture of germination phenology. The analysis of phenology traits demonstrated that both communities displayed similar responses to microclimatic variation. Small microclimatic differences of 2–3°C a week, accumulated across a whole year in the laboratory, resulted in a quantifiable germination phenology delay in snowbed regime, with an average of 60 and 45 days for temperate and Mediterranean alpine respectively. The results from climatic chambers under realistic microclimatic regimes were consistent with the germination phenology registered from field experiments. We also observed macroclimatic effects manifested as reduced dormancy and increased autumn germination in Mediterranean alpine species. Synthesis. This study combines novel laboratory and field experimentation to tackle the understudied topic of germination phenology in habitats with sharp microclimatic gradients. Specifically, our findings suggest a predictable phenological shift in the germination of alpine plants along microclimatic gradients. In warmer conditions with reduced snow cover, alpine species are expected to advance germination 52 days on average, with potential disrupting effects on cold‐adapted species with strict germination requirements. This highlights the role of germination phenology to determine plant‐environmental relationships in mid‐latitude ecosystems, with strong impact on plant establishment and extinction risks under local microclimatic gradients.

Macroclimatic Convergence and Habitat Specialisation Shape the Mediterranean Seed Germination Syndrome.

Ecological theory predicts that plant reproductive phenology in the Mediterranean regions is shaped by evolutionary processes driven by strong seasonality in precipitation-evaporation patterns. Thus, it can be expected that seed germination phenology has adapted to maximise recruitment during the season of highest water availability. Cold-cued and slow germination (i.e., the 'Mediterranean seed germination syndrome') has been hypothesised to be an adaptation to ensure that seedling emergence occurs in autumn/early winter, extending the growing season before the subsequent unfavourable summer drought. However, this hypothesis has been tested on individual species or local studies, without a proper synthesis for the whole Mediterranean region. Here we tested, for the first time, the Mediterranean seed germination syndrome using experimental data for 459 species (11,363 records, 59 families) occurring in the Mediterranean Basin. We performed a phylogenetically informed Bayesian meta-analysis to model the effect on germination proportions of seven key experimental cues: mean incubation temperature, alternating temperature regime, light and dormancy-breaking treatments (scarification, warm stratification and cold stratification) and the modulating role of seed mass on seed germination. We show that species from lowland zonal habitats of the Mediterranean align with the Mediterranean germination syndrome hypothesis, with their seeds responding positively to cool, constant temperatures and negatively to light. Yet, habitat specialists (i.e., species restricted to mountains, coasts and wetlands) deviate from the syndrome, showing nearly opposite germination requirements. Seed mass further influences the germination niche and phylogenetically related species exhibit similar germination responses. Cumulatively, these results suggest that evolutionary pressures from local habitat-related conditions override the macroclimatically imposed Mediterranean seed germination syndrome.

HTL/KAI2 signaling substitutes for light to control plant germination.

Plants monitor multiple environmental cues, such as light and temperature, to ensure they germinate at the right time and place. Some specialist plants, like ephemeral fire-following weeds and root parasitic plants, germinate primarily in response to small molecules found in specific environments. Although these species come from distinct clades, they use the same HYPOSENSITIVE TO LIGHT/KARRIKIN INSENSITIVE 2 (HTL/KAI2) signaling pathway, to perceive different small molecules suggesting convergent evolution on this pathway. Here, we show that HTL/KAI2 signaling in Arabidopsis thaliana bypasses the light requirement for germination. The HTL/KAI2 downstream component, SUPPRESSOR OF MAX2 1 (SMAX1) accumulates in the dark and is necessary for PHYTOCHROME INTERACTING FACTOR 1/PHYTOCHROME INTERACTING FACTOR 3-LIKE 5 (PIF1/PIL5) to regulate hormone response pathways conducive to germination. The interaction of HTL/KAI2 and light signaling may help to explain how specialist plants like ephemeral and parasitic weeds evolved their germination behaviour in response to specific environments.

Seed rain as a propagule source for restoration of semi‐arid floodplain old fields

AbstractAimsRevegetation of the world's abandoned agricultural land (old fields) is vital to promote biodiversity and restore ecosystem services. Natural regeneration, whereby vegetation regrows on its own via the propagules already within the landscape, is a cost‐effective restoration approach for old fields. It is vital that we understand how different seed sources contribute to the regenerative capacity of old fields to make informed management decisions. Little is known about seed rain as a propagule source for restoration within semi‐arid floodplains of eastern Australia.LocationWithin this study, we examined seed rain and extant vegetation in old fields and paired remnant sites across four regions in the northern Murray–Darling Basin, eastern Australia.MethodsSeed rain was surveyed using seed traps that were then subjected to a seedling emergence experiment.ResultsMinimal differences in seed rain composition, species richness, abundance, and plant functional groups were observed between old‐field and remnant sites, indicating similarities in seed dispersal within both land use histories. Larger distances to remnant patches and mean annual rainfall were found to drive the composition of old field's seed rain. The study found few emerged Eucalyptus seedlings despite seed traps being placed during peak seed release periods, which may be due to poor tree conditions from drought, interference with seed traps and the episodic germination requirements of Eucalyptus coolabah.ConclusionsThis study demonstrates that seed rain can contribute to the natural regeneration of understorey vegetation, with low abundances of exotic species, unlike other seed bank types. However, seed rain composition resembled little of the extant vegetation, suggesting a species pool facing barriers to germination and establishment, but likely linked to bet‐hedging strategies. Moving forward to promote natural regeneration via seed rain in old fields, protecting existing patches of vegetation within the landscape is vital to enable biotic connectivity.

Influence of Neltuma flexuosa and rainfall event on the germination of Leptochloa crinita and Pappophorum caespitosum in two different locations along a stress gradient in the central Monte desert

AbstractIn drylands, grass germination occurs after a large rainfall event. However, trees influence the water requirements for germination either by decreasing the rate of evaporation from soil surface or by interception rainfall with their canopy. The aim of this work was to evaluate the role of Neltuma flexuosa tree on the germination of Leptochloa crinita and Pappophorum caespitosum grasses in response to precipitation events of different sizes. The experiment was conducted in two locations within the Monte desert, Argentina: a semi‐arid location with an average annual precipitation of 345 mm and an arid location with an average annual precipitation of 156 mm. Six microsites were established under N. flexuosa canopies and six microsites in open areas at both locations. Within each microsite, 35 seeds of each grass species were exposed to precipitation events of varying sizes. This procedure was repeated 14 times across two growing seasons. Germinated seeds were counted in the laboratory. Generalized linear mixed models were then applied to evaluate the effects of accumulated precipitation and the microsite on the grass germination in both locations. Results showed that N. flexuosa did not influence the germination of either grass species in the arid location. However, in the semi‐arid location, N. flexuosa facilitated the germination of P. caespitosum only. Large precipitation events would act as an environmental signal for these perennial grasses, allowing them to germinate in favorable years regardless of the microsite or the location.

The influence of temperature on germination and seedling growth of sorghum

The extensification of agricultural activities to suboptimal areas, including dryland, is being considered. Sorghum as a drought-tolerant crop is usually cultivated in dryland areas in Indonesia. However local farmers are having difficulty in choosing quality seeds suitable for the specific area temperature condition. This study evaluated the physical quality of commonly used sorghum cultivars in Indonesia and their responses to several germination temperatures. The three sorghum cultivars used were Strong Brown (SB) Sorghum known as the local cultivar, Pale yellow (PY), and Light Brown (LB). The result revealed that each sorghum cultivar has specific seed characteristics, especially in the color, shape, and size of the seeds. The seeds of the Light Brown sorghum had the highest quality, followed by Strong Brown sorghum and PaleYellow sorghum cultivars based on both the tetrazolium test and the direct germination test. The optimum temperature for sorghum seed germination ranged from 25 to 35oC. Each sorghum cultivar has its specific temperature requirement for germination. Low temperature (20°C) potentially reduces the percentage of germination and delays the seed germination time of these three cultivars. LB cultivar has the highest relative growth rate (RGR) from the first week to the second week (R1), while the RGR from the first week to the third week (R2), LB sorghum cultivar is in the second position after the PY cultivar. Cultivar LB is suggested for cultivating in elevations 300-500 m asl, moreover cultivar SB elevations 50-250 m asl.

Longevity and persistence of arrowleaf sida seeds in soil and emergence modeling using thermal and hydrothermal time models

Arrowleaf sida (Sida rhombifolia L.) is a weed that has a fibrous stem, aggressive root system and waxy leaves that can hinder herbicide absorption. Based on knowledge of the environmental requirements for germination of this species, it is possible to predict emergence to assist in integrated management. The aim of this investigation was to characterize the air temperature and soil water potential requirements for arrowleaf sida germination, to model the emergence in the field using thermal and hydrothermal time models and to evaluate the longevity of the arrowleaf sida seed bank. Laboratory experiments were conducted to determine the temperature and water potential for seed germination by testing eight temperatures (10, 15, 20, 25, 30, 35, 40, and 45 °C) and 10 water potentials (0, −0.05, −0.1, −0.2, −0.4, −0.6, −0.9, −1.2, −1.5, and −2.0 MPa). Field experiments were conducted between 2014 and 2018 to model the emergence using three sampling times (starting on 10/20, 11/10, and 12/01), during which soybean seeds were sown. To evaluate the longevity and persistence of the seed bank, a factorial experiment was conducted, in which the first factor included three burial depths (0, 3, and 6 cm) and the second factor included five collection times (0, 1, 4, 10, and 16 months) after seed burial. The base, optimal and maximum temperatures for arrowleaf sida germination were 10.0, 24.8, and 42.5 °C, respectively, and the base water potential was −1.20 MPa. It is possible to predict the emergence of arrowleaf sida in the field by hydrothermal and thermal time models under different environmental conditions. In addition, this species has a persistent seed bank, with 30% of seeds being viable after 16 months of burial.

Seed germination requirements of the rare Helosciadium repens (aka Apium repens) determine persistence of seeds in the soil seed bank.

The rare and threatened Heliosciadium repens grows in moist grasslands and has a distinct life cycle. Plants reproduce both clonally, although ramets tend to be short-lived, and sexually, with seeds that can form a persistent soil seed bank. The germination requirements of H. repens were investigated, yielding important information for its habitat management and conservation. We examined the soil seed bank in three populations and carried out germination experiments and embryo growth measurements with fresh seeds in laboratory, greenhouse and outdoor conditions. We also investigated the effects of storage and burial of seeds. H. repens formed a long-term persistent (>6 years) soil seed bank with very pronounced primary dormancy, but no secondary dormancy or dormancy cycles. Seeds can germinate throughout the growing season when temperatures are sufficiently high. Embryo growth and seed germination are triggered by light and, to a lesser extent, daily temperature fluctuations. Seeds of H. repens seem to have developed a unique germination syndrome with several strategies to remain dormant in the soil until optimal conditions are present for seedling establishment and survival. Both sexual reproduction and seed bank formation are crucial for the long-term survival of the populations.

Seed dormancy, germination requirements, and implications of herbicides for Penstemon albidus and P. nitidus

Seed‐based restoration is dependent on seed germination, and poor germination can cause restoration failure. Many restoration failures can be attributed to a lack of knowledge of germination characteristics, species‐specific seed dormancy, or the effects of widely used herbicides on germination. White penstemon (Penstemon albidus) and Waxleaf penstemon (P. nitidus) are native to the Northern Great Plains region of North America, and increased germination of these species would contribute to improved restoration in the region. We performed two concurrent experiments to determine: (1) the germination requirements and dormancy class of these species; and (2) the effects of herbicides on germination. To determine germination requirements, we applied pretreatments (scarification, smoke, and KNO3) and three durations (2, 4, and 8 weeks) of cold and warm stratification. To test the effects of herbicides on germination, three commonly used herbicides (atrazine, trifluralin, and 2,4‐D) were applied at six concentrations (100, 50, 10, 1, 0.1, and 0% of the recommended field application rate). Germination characteristics indicate both species express physiological dormancy. Physiological dormancy denotes an embryo with low growth potential that is unable to overcome mechanical constraints but can be alleviated with proper temperature cues. Both species required cold stratification, with P. nitidus needing a longer period (8 weeks) than P. albidus (4 weeks). Final germination percentage of P. albidus decreased with higher doses of 2,4‐D but was not affected by atrazine or trifluralin. These experiments help to create protocol for the use of our study species, as well as other species, in restoration plantings.

Environmental factors that influence the germination of Bromeliadsseeds at a physiological level

Bromeliads are plants with epiphytic habits and in smaller quantities they develop on the ground. They are important at an ecological level since they function as indicators of environmental disturbance and intervene in nutrient and hydrological cycles. They also serve as hosts for arthropods and invertebrates, are ornamental,and have medicinal importance, which is why they are vulnerable to extraction by humans. If the germination of these plants in the wild is successful, their abundance and distribution willincrease. This review shows an analysis of the main factors that limit the germination of bromeliad seeds, a detaileddescription of the effect on germination of climatic factors such as light, temperature,and 71Revista Científica Vida NaturalUniversidad Autónoma de Chiriquírevistas.unachi.ac.paRevCient.VidNat, 2 (1) julio -diciembre, 2024, 70-81Revisión BibliográficaISSN L 2992-6424humidity is presented. In addition to some biotic factors that affect germination, which include the characteristics of the bark of the host tree, the allelopathic compounds that the bark can produce act as germination inhibitors, among others. Because bromeliads have very specific germination requirements, it is suggested that future studies explore topics in the physiology and ecology of germination processes, and thus have more detailed information on the factors that affect the germination of these seeds, both in the field and in the laboratory, tocollaborate in the conservation of these species.

Deep Simple Epicotyl Morphophysiological Dormancy in Seeds of Endemic Chinese Helleborus thibetanus

Helleborus thibetanus is an endemic species in China with important ornamental and medicinal value. However, the seeds have dormancy, and their germination percentage is low under natural conditions. This research was carried out to determine the seed germination requirements of H. thibetanus and to characterize the type of seed dormancy. The morphological post-ripening process of the seed embryo was studied according to the morphological anatomy, and the effects of temperature and gibberellic acid (GA3) on seed germination were investigated in H. thibetanus. The H. thibetanus seeds had a heart-shaped embryo at maturity. The embryo fully grew within the seed through warm stratification, and the embryo/seed ratio increased from 8.58% to 42.6%. The shortest time for a radicle to emerge (58.33 d) and the highest radicle emergence percentage (84.44%) were obtained at a temperature of 15 °C. The results showed that the H. thibetanus seeds had a morphophysiological dormancy. In addition, 300 mg/L GA3 treatments shortened the time of warm stratification and increased the radicle emergence percentage. Seeds with emerged radicles could not emerge epicotyl–plumule without cold stratification, which showed that the H. thibetanus seeds had epicotyl physiological dormancy. The length of the roots, cold stratification time, and GA3 markedly affected the release of the epicotyl physiological dormancy in H. thibetanus. The seeds with 2.5 cm roots required the shortest time to break their dormancy (50 d), and the epicotyl–plumule emergence percentage was the highest. Additionally, GA3 treatment also shortened the incubation time in cold stratification (5 °C) and successfully broke the epicotyl physiological dormancy. Our study showed that H. thibetanus seeds exhibited deep simple epicotyl morphophysiological dormancy. Temperature, GA3, and duration of stratification played vital roles in the seed germination of H. thibetanus. This research will provide valuable data for seed germination and practical dormancy-breaking techniques and will promote the cultivation and conventional crossbreeding of H. thibetanus.

Linking ex situ germination to in situ direct seeding for landscape scale restoration efforts in the semiarid Mallee region of Victoria, Australia

Direct seeding has high potential for arid revegetation, but success is limited by decreased germination and seedling emergence. Direct seeding success may be improved through developing an understanding of the germination biology and requirements of species used for these projects. This study looked into the germination temperature and moisture requirements of four semiarid species from Victoria's Mallee ecosystems to understand how their germination biology may advise strategies for future plantings. Temperature's effect on germination was analyzed by incubating the seeds under three different regimes: 30/20, 25/15, and 17/7°C. Moisture requirements were determined by germinating seeds along a water potential gradient created using polyethylene glycol 8000 solutions. Results showed three different strategies employed by the study species: (1) Acacia ligulata has a generalist approach, germinating well in all temperatures with a reasonable tolerance to water stress; (2) Eucalyptus calycongona and Melaleuca lanceolata germinate rapidly under higher germination temperatures and have generally higher water stress tolerance; while (3) Callitris gracilis germinates poorly in hot or dry conditions restricting germination to cooler and wetter conditions. Based on our results, A. ligulata would be the most widely applicable species for direct seeding work based on generalist germination habits. Callitris gracilis appears to do well if planted in cool, wet conditions where the species prefers to germinate but would be intolerant to warm‐weather planting. The ideal planting time for a mixed species planting based on germination requirements would be mid‐autumn, as that is when temperature and moisture levels would be optimal for germination.

Hot and fast: seed ecology for restoration relevant species in the Argyle region of the east Kimberley, Australia

This study investigates the germination requirements of 12 plant species native to the Argyle region of the east Kimberley, a biodiverse monsoonal tropical region characterized by high temperatures, high evaporation, and episodic seasonal rainfall. The research involved quality assessment of mature seeds, followed by dormancy alleviation and laboratory‐based germination to determine the responses of seeds to a range of temperatures (5–40°C) in terms of germination speed (T10), mean germination time, and maximum germination proportion. Data were then modeled to calculate the optimal temperature to support germination for each species. The results showed that germination rapidly commences in response to a wide range of temperatures typical of the wet season (November–February) in the east Kimberley, though germination for most species was still high (>50%) after exposure to temperatures as low as 15°C. Mean optimal temperature for germination across all species was 25.8 ± 1.5°C, with minimal variation between most species, the exception being Dodonaea physocarpa, which preferred cooler temperatures (Topt = 14.0°C). The speed of germination was also rapid (T10 = 1–3 days) across all species at the optimal germination temperature. The findings suggest that temperature is not a limiting factor for germination in this region and that the onset and intensity of the wet season are the most significant factors determining successful germination, emergence, and seedling establishment. The study underscores the importance of species‐specific understanding of environmental temperatures required for seed germination in seed‐based restoration efforts and informs the planning of direct seeding works, thus enhancing restoration outcomes.

Embryo growth and seed germination requirements in underdeveloped embryos of Elwendia caroides and E. wolfii (Apiaceae)

Elwendia wolfii and E. caroides are two herbaceous perennials that were initially classified in the Bunium genus and later transferred to the Elwendia genus. They are a rich source of bioactive and antioxidant compounds and have the potential to become sources of oil-bearing crops. The aim of this study was to investigate requirements for embryo growth, dormancy break and seed germination in these two species. The effects of gibberellic acid (GA3) and dry storage were also examined to determine the type of dormancy. The pericarps and seed coats of both species were water-permeable, and the embryos were small and differentiated but underdeveloped, with initial embryo lengths of 0.28 mm in E. wolfii and 0.96 mm in E. caroides, respectively. These underdeveloped embryos were either di (>98%) or tricotyledonous (<2%) and required cold temperatures to grow, indicating that these seeds had morphological dormancy (MD). The critical length required for germination was 3.44 mm for E. wolfii and 4.17 mm for E. caroides. However, seeds of both species reached less than 50% final germination if subjected only to cold incubation. Higher final germination was possible if seeds were pre-treated with dry cold storage (-22 ºC) or exposed to GA3, indicating the existence of physiological dormancy (PD) in part of the seed population. Therefore, both species had non-deep complex morphophysiological dormancy (MPD). This study demonstrates that E. caroides and E. wolfii share the same germination requirements, suggesting a common ecological strategy in their seed germination process.

Germination niche of co-occurring threatened native and alien species: a case study in Lindernia procumbens and L. dubia

Plant invasions have a negative impact on biodiversity and lead to species loss. Although studies on traits promoting invasiveness have been largely developed, comparative studies on germination traits of closely related native versus alien invasive species, which also take into account threatened species, are lacking. We analysed the germination requirements of two congeneric Lindernia species inhabiting paddy field in Northern Italy. Germination tests were conducted exposing seeds of both species across a broad range of temperature and conditions (i.e., cold-wet stratification, dark condition, alternate temperature, gibberellic acid). The invasive L. dubia showed higher and faster germination, occurring over a broader range of temperatures compared to the native threatened L. procumbens, along with a lighter non-deep physiological dormancy. These results show a competitive advantage of the alien species already in the early stages of plant regeneration and provide a comprehensive overview of the germination requirements, necessary for the development of future conservation and management plans.

Seed Dormancy Class and Germination Characteristics of Berberis amurensis var. latifolia Nakai, Native to Korea

Berberis amurensis var. latifolia Nakai is a plant native to the Ulleung Island in Korea. In this study, we aimed to identify seed dormancy-breaking and germination requirements of this species using water imbibition experiments, gibberellic acid (GA3) treatment (0, 10, 100, or 1000 mg/L), cold stratification (0, 2, 4, 8, or 12 weeks at 5 °C), move-along experiments, and phenological studies. In the water imbibition experiment, the seed weight increased by more than 120% after 24 h. Analysis of the internal morphological characteristics of the seeds revealed that the embryo in freshly matured seeds was fully grown and did not grow thereafter. The final germination percentages after 12 weeks of cold stratification at 5 °C were 49 ± 6.4% and 63 ± 3.4% under light and dark conditions, respectively. In move-along and phenological studies, a longer cold stratification treatment period resulted in a higher germination percentage; however, the warm stratification treatment did not affect germination significantly. The GA3 treatment had little effect on seed germination. Therefore, we concluded that B. amurensis var. latifolia seeds have intermediate physiological dormancy, and pre-treatment with cold stratification for 12 weeks and incubation in the dark are required for effective seed propagation.

Seed biology imperative for conservation and restoration of Swertia thomsonii C.B. Clarke-an endemic medicinal plant of Himalaya.

Endemic medicinal plants deserve immediate research priorities as they typically show a limited distribution range, represent few and fragmented populations in the wild and are currently facing anthropogenic threats like overharvesting and habitat degradation. One of the important aspects of ensuring their successful conservation and sustainable utilization lies in comprehending the fundamental seed biology, particularly the dormancy status and seed germination requirements of these plants. Here, we studied the seed eco-physiology and regeneration potential of Swertia thomsonii-an endemic medicinal plant of western Himalaya. We investigated the effect of different pre-sowing treatments, sowing media and sowing depth on seed germination parameters of S. thomsonii. Seeds of S. thomsonii exhibit morphophysiological dormancy (MPD), i.e. when the embryo of the seed is morphologically and/or physiologically immature. Wet stratification at 4°C for 20days, pre-sowing treatment with 50ppm GA3 and pre-sowing treatment with 50ppm KNO3 were found ideal for overcoming dormancy and enhancing the seed germination of S. thomsonii. Furthermore, seed germination and seedling survival were significantly influenced by pre-sowing treatments, sowing media and sowing depth. The percentage of seed germination and seedling survival got enhanced up to 84-86% and 73-75% respectively when seeds were pre-treated with GA3 or KNO3 and then sown in cocopeat + perlite (1:1) at a depth of 1cm. The information obtained in the present study outlines an efficient protocol for large-scale cultivation of S. thomsonii thereby limiting the pressure of overexploitation from its natural habitats and may also help in the restoration and conservation of this valuable plant species.

Modeling weed seedling emergence for time-specific weed management: a systematic review

Abstract Understanding the timing of weed emergence is crucial to effective management. Management practices implemented too early may fail to completely control late-emerging seedlings, whereas management practices implemented too late will suffer from low efficacy. Weed emergence times reflect biological factors, such as seed dormancy and germination requirements, as well as environmental conditions. We conducted a systematic review of studies that developed models to predict weed emergence temporal patterns. We screened 1,854 studies, 98 of which were included in the final dataset. Most of the studies included were conducted in North America (51%) or Europe (30%). A wide variety of weed species (102) and families (21) were included, and many studies modeled several weeds. Grass weeds (Poaceae) were modeled most frequently (83 instances). Most weeds (40%) had base temperature ${T_{\rm{b}}}$ values between 0 and 5 C, and 38% had base water potential ${{\rm{\psi }}_{\rm{b}}}$ ranging from −1.0 to −0.5 MPa. Most studies used empirical parametric models, such as Weibull (40%) or Gompertz (30%) models. Nonparametric and mechanistic models were also represented. Models varied in their biological and environmental data requirements. In general, empirical parametric models based on hydrothermal time (i.e., time above base temperature and water potential thresholds) represented a good balance between ease of use and prediction accuracy. Soft computing approaches such as artificial neural networks demonstrated substantial potential in situations with complex emergence patterns and limited data availability, although they (soft computing approaches) can be susceptible to overfitting. Our study also demonstrated variability in model performance and limited generalizability across species and regions. This finding underscores the need for context-specific and well-validated weed emergence models to inform management, especially in the context of climate change.

Germination Requirement and Suitable Storage Method of Hydrocharis dubia Seeds.

Understanding of seed germination requirements and storage methods is very important to successfully conserve and restore aquatic vegetation. The main question addressed by the research was germination requirements and suitable seed storage methods of Hydrocharis dubia seeds. Furthermore, the water content and respiration rate of H. dubia seeds were studied under different storage conditions. The study found that light and high seed clustering density had a positive effect on germination, while burial had a negative effect. Germination percentages were 60.67 ± 6.11% and 28.40 ± 6.79% in light and dark conditions, respectively. Under clustering densities of 1 and 50, germination percentages were 6.00 ± 2.00% and 59.33 ± 0.67%, respectively. Germination percentages were 50.40 ± 5.00%, 3.20 ± 3.20%, and 0.80 ± 0.80% at depths of 0, 2, and 3 cm, respectively. Oxygen, water level, and substratum had no significant effect on seed germination. Storage method had a significant effect on seed germination, moisture content, and respiration rate. The germination percentages were 64.00 ± 1.67%, 85.20 ± 5.04%, and 92.80 ± 4.27% under the storage conditions of 4 °C-Dry, 4 °C-Wet, and Ambient water temperature-Wet for 2 years, respectively. The seeds had no germination under the storage conditions of Ambient air temperature-Wet and Ambient air temperature-Dry. Overall, the study indicates that seed germination of H. dubia is restricted by light, burial depth, and seed clustering density. Additionally, it was found that H. dubia seeds can be stored in wet environmental conditions at ambient water temperature, similar to seed banks. Specifically, the seeds can be stored in sand and submerged underwater at ambient water temperatures ranging from 4 °C to 25 °C. This study will help with the conservation and restoration of aquatic plants, such as H. dubia.

Study of Germination and Seedling Growth of Piper guineense

Natural regeneration of black pepper (Piper guineense Schumach and Thonn) through seeds is poor and cultivation by local farmers is very limited since it is usually collected from the wild. High demand has put a pressure on its population in our declining forests and a call for domestication of non-timber forest plant species is ongoing. This study identified germination requirements, germination characteristics and seedling growth of Piper guineense with a view to providing information on its propagation from seeds. There were two major pre-sowing treatments - Fresh or dry fruits or seeds. Germination and seedling growth parameters were measured for all treatments. Results showed that Piper guineense seeds undergo epigeal germination, the radicle developing into three-legged hairy rootlets. The highest percentage germination, germination rate and germination index were recorded in the treatment with fresh seeds planted in petri dish. The dry seeds and fruits recorded no germination even after 38 days of planting. For seedling growth, the developing leaves have a higher sink strength between the fourth and fifth month of development and this stage may be crucial to the growth of the seedling. Piper guineense seeds must be sown fresh for germination to take place.