Ungerminated Seeds Research Articles

Population histories of variable reproductive success and low winter precipitation correlate with risk-averse seed germination in a mediterranean-climate winter annual.

Seed germination involves risk; post-germination conditions might not allow survival and reproduction. Variable, stressful environments favor seeds with germination that avoids risk (e.g., germination in conditions predicting success), spreads risk (e.g., dormancy), or escapes risk (e.g., rapid germination). Germination studies often investigate trait correlations with climate features linked to variation in post-germination reproductive success. Rarely are long-term records of population reproductive success available. Supported by demographic and climate monitoring, we analyzed germination in the California winter-annual Clarkia xantiana subsp. xantiana. Sowing seeds of 10 populations across controlled levels of water potential and temperature, we estimated temperature-specific base water potential for 20% germination, germination time weighted by water potential above base (hydrotime), and a dormancy index (frequency of viable, ungerminated seeds). Mixed-effects models analyzed responses to (1) temperature, (2) discrete variation in reproductive success (presence or absence of years with zero seed production by a population), and (3) climate covariates, mean winter precipitation and coefficient of variation (CV) of spring precipitation. For six populations, records enabled analysis with a continuous metric of variable reproduction, the CV of per-capita reproductive success. Populations with more variable reproductive success had higher base water potential and dormancy. Higher base water potential and faster germination occurred at warmer experimental temperatures and in seeds of populations with wetter winters. Geographic variation in seed germination in this species suggests local adaptation to demographic risk and rainfall. High base water potential and dormancy may concentrate germination in years likely to allow reproduction, while spreading risk among years.

High density promotes the germination of the recalcitrant seeds of submerged macrophyte Vallisneria natans

Seed germination is a critical process in the seed life cycle, especially for annual submerged macrophytes Vallisneria natans which is a model species for the restoration of degraded shallow lakes. Fresh seeds of V. natans have a very high germination rate but with no significant responses to the aggregation effect; meanwhile, these recalcitrant seeds quickly lose seed viability under dry storage. This study aims to explore the response of seed germination of V. natans after dry storage to aggregation effect by several microcosm experiments. We observed that seed aggregation has a significant positive effect on germination, and among the seven experimental densities between 10 ∼ 640 seeds, higher seed densities resulted in significantly enhanced germination. In contrast, daily removal of germinated seeds led to a significant decrease in the overall germination rate, suggesting that germinated seeds may secrete chemicals that promote the germination of ungerminated seeds. However, further experiments indicated that ethylene and gibberellins had no noticeable impact on seed germination, which was consistent with additional experiment results from spectrophotometer and high-throughput targeted metabolomics. We concluded that the promoting effect of aggregation on the seed germination of V. natans may be an adaptation of this species to its natural habitat but detailed mechanisms warranted further study.

Germination Promotes Flavonoid Accumulation of Finger Millet (Eleusine coracana L.): Response Surface Optimization and Investigation of Accumulation Mechanism.

Germination is an effective measure to regulate the accumulation of secondary metabolites in plants. In this study, we optimized the germination conditions of finger millet by response surface methodology. Meanwhile, physiological characteristics and gene expression were measured to investigate the mechanism of flavonoid accumulation in finger millet at the germination stage. The results showed that when germination time was 5.7 d, germination temperature was 31.2 °C, and light duration was 17.5 h, the flavonoid content of millet sprouts was the highest (7.0 μg/sprout). The activities and relative gene expression of key enzymes for flavonoid synthesis (phenylalanine ammonia-lyase, 4-coumarate-coenzyme a ligase, and cinnamate 4-hydroxylase) were significantly higher in finger millet sprouts germinated at 3 and 5 d compared with that in ungerminated seeds (p < 0.05). In addition, germination enhanced the activities of four antioxidant enzymes (catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase) and up-regulated the gene expression of PAL and APX. Germination increased malondialdehyde content in sprouts, which resulted in cell damage. Subsequently, the antioxidant capacity of the sprouts was enhanced through the activation of antioxidant enzymes and the up-regulation of their gene expression, as well as the synthesis of active substances, including flavonoids, total phenolics, and anthocyanins. This process served to alleviate germination-induced cellular injury. These findings provide a research basis for the regulation of finger millet germination and the enhancement of its nutritional and functional properties.

Enhancing Seed Germination Test Classification for Pole Sitao (Vigna unguiculata (L.) Walp.) Using SSD MobileNet and Faster R-CNN Models

The classification of germinated pole sitao (Vigna unguiculata (L.) Walp.) seeds is important in seed germination tests. The automation of this process has been explored for different grain and legume seeds but is only limited to binary classification. This study aimed to develop a classifier system that can recognize three classes: normal, abnormal, and ungerminated. SSD MobileNet and Faster R-CNN models were trained to perform the classification. Both were trained using 1500 images of germinated seeds at fifth- and eighth-day observations. Each class had 500 images. The trained models were evaluated using 150 images per class. The SSD MobileNet model had an accuracy of 0.79 while the Faster R-CNN model had an accuracy of 0.75. The results showed that the average accuracies for the classes were significantly different from one another based on one-way ANOVA at a 95% confidence level with an F-critical value of 3.0159. The SSD MobileNet model outperformed the Faster R-CNN model in classifying pole sitao seeds, with improved precision in identifying abnormal and ungerminated seeds on the fifth day and normal and ungerminated seeds on the eighth day. The results confirm the potential of the SSD MobileNet model as a more reliable classifier in germination tests.

Effect of salt-alkali stress on seed germination of the halophyte Halostachys caspica

The increasing global phenomenon of soil salinization has prompted heightened interest in the physiological ecology of plant salt and alkali tolerance. Halostachys caspica belonging to Amaranthaceae, an exceptionally salt-tolerant halophyte, is widely distributed in the arid and saline-alkali regions of Xinjiang, in Northwest China. Soil salinization and alkalinization frequently co-occur in nature, but very few studies focus on the interactive effects of various salt and alkali stress on plants. In this study, the impacts on the H. caspica seed germination, germination recovery and seedling growth were investigated under the salt and alkali stress. The results showed that the seed germination percentage was not significantly reduced at low salinity at pH 5.30–9.60, but decreased with elevated salt concentration and pH. Immediately after, salt was removed, ungerminated seeds under high salt concentration treatment exhibited a higher recovery germination percentage, indicating seed germination of H. caspica was inhibited under the condition of high salt-alkali stress. Stepwise regression analysis indicated that, at the same salt concentrations, alkaline salts exerted a more severe inhibition on seed germination, compared to neutral salts. The detrimental effects of salinity or high pH alone were less serious than their combination. Salt concentration, pH value, and their interactions had inhibitory effects on seed germination, with salinity being the decisive factor, while pH played a secondary role in salt-alkali mixed stress.

Salinity effects on germination of Portulaca oleracea L.: A multipurpose halophyte from arid rangelands

Salt resistance studies have, unfortunately, mainly been focused on conventional crops, with very few studies being conducted on the potential of available halophytes as new crops in the future. Portulaca oleracea L. has been listed as one of the most used medicinal plants by the World Health Organization as an edible halophyte. It is a fast-growing herbaceous annual with high nutritional relevance. The present work was designed to determine the effect of six soluble salts (NaCl, Na2SO4, KCl, CaCl2, CaCO3, and MgCl2) on germination of P. oleracea seeds. The effect of salinity was tested on final germination percentage (FGP%), and germination tolerance index (GTI%) using five concentrations (0, 200, 300, 400, and 600 mM) of each salt. In addition, laboratory experiments were conducted to assess the effects of salinity on germination recovery from high saline conditions (600 mM). Salinity level and salt composition significantly influenced germination attributes. P. oleracea seeds were non-dormant, exhibited approximately 100% germination in distilled water. Both FGP and GTI gradually decreased with increasing salinity. This study showed that seeds of P. oleracea can germinate under 300 mM in all tested salts. The salts causing germination inhibition exhibited specificity, with an increasing trend observed in the following sequence: MgCl2 > Na2SO4 > NaCl > KCl > CaCl2 > CaCO3. Transferring ungerminated seeds from 600 mM to distilled water recovered their germination ability. Based on these results, we can conclude that P. oleracea is a high salt-tolerant species that can tolerate a variety of salts found in soil. Therefore, P. oleracea may be considered a promising species for improving ecological balance in saline soils.

Germination: A Powerful Way to Improve the Nutritional, Functional, and Molecular Properties of White- and Red-Colored Sorghum Grains.

This study explored the effects of the germination of red and white sorghum grains (Sorghum bicolor [Moench (L.)]) for up to seven days on various properties of the grain. Germination enriched sorghum's nutritional and sensory qualities while mitigating existing anti-nutritional factors. The study employed Fourier-transformed infrared spectroscopy (FT-IR) and scanning electron microscopy techniques to support its findings. Germination increased protein and lipid content but decreased starch content. White sorghum grains showed elevated calcium and magnesium but decreased iron, potassium, and zinc. Red sorghum grains showed a consistent decrease in mineral content during germination. Germination also increased fiber and lignin values in both sorghum varieties. The results of the FT-IR analysis demonstrate that germination induced significant changes in the molecular structure of white sorghum samples after 24 h, whereas this transformation was observed in red sorghum samples at four days. Total phenolic content (TPC) in red sorghum ranged from 136.64 ± 3.76 mg GAE/100 g to 379.5 ± 6.92 mg GAE/100 g. After 72 h of germination, the germinated seeds showed a threefold increase in TPC when compared to ungerminated seeds. Similarly, the TPC of white sorghum significantly increased (p < 0.05) from 52.84 ± 3.31 mg GAE/100 g to 151.76 mg GAE/100 g. Overall, during the 7-day germination period, all parameters showed an increase, and the germination process positively impacted the functional properties that contributed to the health benefits of white and red sorghum samples.

Draba verna L. (Brassicaceae/Cruciferae): A salt averse taxon

In this study, it was aimed to determine whether Draba verna L. (=Erophila verna (L.) Chevall. subsp. verna (L.) DC.), which is a relative of model organism Arabidopsis thaliana (L.) Heynh. and distributing around saline areas, is a halophyte or not and to research the salinity tolerance during germination period. D. verna seeds were germinated at distilled water and different NaCl concentrations (100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 mM) at 8ºC/16ºC 12/12 h photoperiodism (light intensity 12000 lux ±%10) for 20 days. The NaCl concentrations and the germination percentages were as follows distilled water 100%, 100 mM NaCl 83%, 200 mM NaCl 2%, 300 mM NaCl 1% and no germination over 300 mM NaCl. Un-germinated seeds were taken into recovery and show 87.3% mean germination, and the ones still ungerminated were tested for viability. Increase in salinity, cause decrease in germination rate which means that D. verna is not resistant to salinity but salinity has important pressure on germination. The tolerance of D. verna seeds to salinity, although it has a wide distribution area at saline areas, is result of decrease in soil salinity during germination period. It can be concluded that D. verna is not a halophyte it is a salt avoider.

Germination Strategy of Chenopodium acuminatum Willd. under Fluctuating Salinity Habitats

Germination events of plants often occur after rainfall in saline environments where the soil salinity is diluted, viz recovery germination. Previous germination studies have rarely considered the duration of exposure to salt stress, and none of them have investigated recovery germination under low-salt concentration, other than in distilled water. The main objective of this study was to investigate the effects of salinity, exposure duration and low-salt recovery solutions on seed germination of the weed Chenopodium acuminatum to get a clear insight about the germination strategy exhibited by this species in a saline habitat. Seeds were initially exposed to 0–400 mM NaCl for 10, 20 and 30 d. The subsequent recovery experiment was conducted differently. For those initially treated with 100 and 200 mM NaCl, the recovery solution was distilled water, while for those initially treated with 300 and 400 mM NaCl, the recovery solution was distilled water, at 50 and 100 mM NaCl. Results showed that the recovery germination percentage and rate significantly decreased when the exposure duration extended. Seeds could subsequently recover to germinate at high percentages at recovery salt solution concentrations for a short duration, but the recovery percentages and rates in high salinity, combined with high exposure duration and relatively high recovery salt concentrations, were remarkably lower. More than 30% of the ungerminated seeds were viable after the recovery experiment. We suggest that Ch. acuminatum exhibits a ‘cautious’ strategy of germination to avoid injury from long-term salt stress and ensure survival for the subsequent continuation of its population under unfavorable saline conditions.

Vacuolar Sugar Transporter TMT2 Plays Crucial Roles in Germination and Seedling Development in Arabidopsis

Vacuolar sugar transporters transport sugar across the tonoplast, are major players in maintaining sugar homeostasis, and therefore play vital roles in plant growth, development, and biomass yield. In this study, we analyzed the physiological roles of the tonoplast monosaccharide transporter 2 (TMT2) in Arabidopsis. In contrast to the wild type (WT) that produced uniform seedlings, the tmt2 mutant produced three types of offspring: un-germinated seeds (UnG), seedlings that cannot form true leaves (tmt2-S), and seedlings that develop normally (tmt2-L). Sucrose, glucose, and fructose can substantially, but not completely, rescue the abnormal phenotypes of the tmt2 mutant. Abnormal cotyledon development, arrested true leaf development, and abnormal development of shoot apical meristem (SAM) were observed in tmt2-S seedlings. Cotyledons from the WT and tmt2-L seedlings restored the growth of tmt2-S seedlings through micrografting. Moreover, exogenous sugar sustained normal growth of tmt2-S seedlings with cotyledon removed. Finally, we found that the TMT2 deficiency resulted in growth defects, most likely via changing auxin signaling, target of rapamycin (TOR) pathways, and cellular nutrients. This study unveiled the essential functions of TMT2 for seed germination and initial seedling development, ensuring cotyledon function and mobilizing sugars from cotyledons to seedlings. It also expanded the current knowledge on sugar metabolism and signaling. These findings have fundamental implications for enhancing plant biomass production or seed yield in future agriculture.

Seed Germination and Seedling Growth in Suaeda salsa (Linn.) Pall. (Amaranthaceae) Demonstrate Varying Salinity Tolerance among Different Provenances.

Salinity is a pressing and widespread abiotic stress, adversely affecting agriculture productivity and plant growth worldwide. Seed germination is the most critical stage to seedling growth and establishing plant species in harsh environments, including saline stress. However, seed germination characteristics and stress tolerance may vary among geographical locations, such as various provenances. Suaeda salsa (Linn.) Pall. (S. salsa) is a halophytic plant that exhibits high salt tolerance and is often considered a pioneer species for the restoration of grasslands. Understanding the germination characteristics and stress tolerance of the species could be helpful in the vegetation restoration of saline-alkali land. In this study, we collected S. salsa seeds from seven different saline-alkali habitats (S1-S7) in the Songnen Plain region to assess the germination and seedling growth responses to NaCl, Na2CO3, and NaHCO3, and to observe the recovery of seed germination after relieving the salt stress. We observed significant differences in germination and seedling growth under three salt stresses and among seven provenances. Resistance to Na2CO3 and NaHCO3 stress was considerably higher during seedling growth than seed germination, while the opposite responses were observed for NaCl resistance. Seeds from S1 and S7 showed the highest tolerance to all three salt stress treatments, while S6 exhibited the lowest tolerance. Seeds from S2 exhibited low germination under control conditions, while low NaCl concentration and pretreatment improved germination. Ungerminated seeds under high salt concentrations germinated after relieving the salt stress. Germination of ungerminated seeds after the abatement of salt stress is an important adaptation strategy for black S. salsa seeds. While seeds from most provenances regerminated under NaCl, under Na2CO3 and NaHCO3, only seeds from S4 and S7 regerminated. These findings highlight the importance of soil salinity in the maternal environment for successful seed germination and seedling growth under various salinity-alkali stresses. Therefore, seed sources and provenance should be considered for vegetation restoration.

Impact of Environmental Conditions on Seed Germination of Glossy Buckthorn (Frangula alnus (Mill)) in Eastern Canada

Understanding seed characteristics, germination, and seedling establishment patterns is essential for formulating effective management strategies to control invasive species. Glossy buckthorn (Frangula alnus) is a shrub or small tree from Eurasia that has become invasive in North America, and which has negative impacts on plant communities and ecosystems. In this study, we analyzed the germination response of glossy buckthorn seeds to different temperatures (12, 14, 16, 18, 20, 24, and 28 °C), various stratification lengths (4 to 20 weeks), and scarification conditions to measure the impact on breaking seed dormancy, and the effect of light in triggering germination. Analysis using distinct time-to-event approaches, including the Kaplan–Meier estimator and Cox proportional hazard model, was employed to interpret germination data. Glossy buckthorn seeds exhibited physiological dormancy and required cold stratification to germinate. At 12 °C, only 14% of the seeds could germinate. At warmer temperatures, germination rates increased, reaching a peak of 70% at 20 °C. At 24 °C and 28 °C, germination declined, and seeds were probably induced into secondary dormancy. Scarified seeds had a higher probability of germination than non-scarified ones, even at the lowest temperatures. Darkness had a negative impact on germination at all tested temperatures. This study significantly advances our understanding of how temperature, light, stratification, and scarification impact glossy buckthorn seeds, elucidating the species’ seasonal germination patterns in North America. The results emphasize that glossy buckthorn utilizes seed banks as a primary strategy for invading and establishing in new habitats. The ungerminated seeds form persistent seed banks, ensuring F. alnus’ survival and bolstering its chances of successful establishment and invasion. As climate change drives temperature increases, it may affect seeds in the soil, altering stratification periods and consequently shifting the timing of germination.

Identificación molecular y prevalencia de contaminantes fúngicos en semillas de cultivos semestrales

Seed quality is affected by fungal contamination. These cause abortion, rot, or necrosis of the seed, as well as seedling damage that results in the development of diseases in later stages of growth. Their identification and characterization are essential to establish appropriate management. The objective of this work was to identify and determine the prevalence of fungal contaminants present in the seed of thirteen plant varieties of rice, soybean, corn, and forage sweet sorghum produced in the municipality of El Espinal, Tolima, Colombia. This research was carried out at the Tibaitatá Research Center of the Colombian Agricultural Research Corporation AGROSAVIA (Cundinamarca, Colombia) during the second semester of 2021. By means of a blotter test, fungal contaminants and their prevalence in germinated and non-germinated seeds were identified. A total of 65 fungal isolates were obtained, which were grouped into twenty-eight molecularly identified morphotypes (44 soybean, 5 rice, 7 sorghum and 9 corn). The genera Diaporthe and Fusarium were the ones with the highest total prevalence and in ungerminated seeds. The fungi found include possible pathogens such as Fusarium spp, Curvularia spp and Diaporthe spp. and saprophytic fungi such as Penicillium spp and Aspergillus spp. The isolates of Fusarium equiseti and Diaporthe sp. in soybean seed, Curvularia penniseti in rice seed, Diaporthe melonis in sorghum seed and Fusarium verticillioides in corn seed can be considered as potential seed-borne pathogens that caused a negative effect on germination capacity.

Identification of potential fungal biocontrol agents for the management of ripgut brome

Ripgut brome (Bromus diandrus) is a significant weed in arable systems with cereals being negatively impacted through yield reduction and contamination of harvested grain. There are limited herbicide options for its control, and reduction of the weed seed bank is a key part of its management. Ripgut brome seeds were incubated in three soils known to harbour a range of plant pathogens, and a range of fungi were subsequently isolated from ungerminated seeds. The most prevalent putative fungal pathogens isolated were Fusarium spp. and Marasmius sp. Selected isolates were cultured on artificial media and tested for their ability to inhibit germination of ripgut brome seeds in a series of in vitro assays, with many isolates completely inhibiting germination. When isolates were tested for their activity against non-target arable species in plant assays, three of five Fusarium spp. isolates significantly inhibited germination of oats and barley while a Marasmius sp. isolate had no effect on germination of these species. Further plant assays using four Marasmius sp. isolates against a wider range of plant species (oats, barley, ryegrass, brome, cocksfoot, and prairie grass) indicated some variability between Marasmius sp. isolates, with two isolates slightly inhibiting germination of some plant species, while two isolates (W14, W17) had no adverse effects. Sequencing of the ITS region of the Marasmius sp. isolates indicated that they were closely related but distinct from M. graminum, which is known to have some phytopathogenic activity and M. oreades which has not yet been reported as a plant pathogen. Further investigation of the Marasmius isolates as potential biocontrol agents for ripgut brome seed is warranted.

Seed dormancy loss from dry after-ripening is associated with increasing gibberellin hormone levels in Arabidopsis thaliana.

The seeds of many plants are dormant and unable to germinate at maturity, but gain the ability to germinate through after-ripening during dry storage. The hormone abscisic acid (ABA) stimulates seed dormancy, whereas gibberellin A (GA) stimulates dormancy loss and germination. To determine whether dry after-ripening alters the potential to accumulate ABA and GA, hormone levels were measured during an after-ripening time course in dry and imbibing ungerminated seeds of wildtype Landsberg erecta (Ler) and of the highly dormant GA-insensitive mutant sleepy1-2 (sly1-2). The elevated sly1-2 dormancy was associated with lower rather than higher ABA levels. Ler germination increased with 2-4 weeks of after-ripening whereas sly1-2 required 21 months to after-ripen. Increasing germination capacity with after-ripening was associated with increasing GA4 levels in imbibing sly1-2 and wild-type Ler seeds. During the same 12 hr imbibition period, after-ripening also resulted in increased ABA levels. The decreased ABA levels with after-ripening in other studies occurred later in imbibition, just before germination. This suggests a model where GA acts first, stimulating germination before ABA levels decline, and ABA acts as the final checkpoint preventing germination until processes essential to survival, like DNA repair and activation of respiration, are completed. Overexpression of the GA receptor GID1b (GA INSENSITIVE DWARF1b) was associated with increased germination of sly1-2 but decreased germination of wildtype Ler. This reduction of Ler germination was not associated with increased ABA levels. Apparently, GID1b is a positive regulator of germination in one context, but a negative regulator in the other.

Metabolomics and chemometrics depict the changes in the chemical profile of white lupine (Lupinus albus L.) bioactive metabolites during seed germination

The current study attempts to illustrate how the chemical and biological profile of white lupine seeds varies throughout the course of various germination days using UHPLC-QqQ-MS combined to chemometrics. Abscisic acid showed maximum level in the un-germinated seeds and started to decline with seed germination accompanied by an increase in the levels of gibberellins which were undetectable in un-germinated seeds. Coumaronochromones were the most prevalent constituents detected in un-germinated seeds while day 2 sprouts showed significant accumulation of flavones. The levels of alkaloids showed significant increase upon germination of the seeds reaching its maximum in day 14 sprouts. The OPLS model coefficients plot indicated that lupinalbin D and F, apigenin hexoside, kaempferol hexoside, albine, and hydoxylupanine showed strong positive correlation to the alpha amylase inhibitory activity of the tested samples while lupinalbin A, lupinisoflavone, lupinic acid and multiflorine were positively correlated to the inhibition of alpha glycosidase activity. The results obtained indicated that seed germination has a profound effect on the chemical profile as well as the in-vitro antidiabetic activity of lupine seeds.

Comparative effects of NaCl and Na2SO4 on germination and early seedling stages of the halophyte Carthamus tinctorius L.

Salinity is one of the primary environmental problems limiting the agricultural productivity and affecting soil physicochemical properties, especially on arid and semi-arid areas. Hence, early screening of salt-tolerant species is a promising strategy for the recovery of salt affected lands. Safflower (Carthamus tinctorius L.), is a medicinal plant used as a laxative, pain relieving, antipyretic and an antitoxin against poisoning. It provides an interesting perspective in becoming a salt-tolerant and high-value crop at saline conditions. In this regard, the aim of the present investigation was to evaluate the effect of salt stress on the germination and early seedling stages of safflower. A laboratory experiment was carried out in a phytotron at a temperature of 25 °C and in the dark for 7 days. The seeds were germinated in Petri dishes treated with various concentrations 0 (control) to 600 mM of NaCl and Na2SO4, with 4 repetitions. The presented results indicate that increasing salinity delayed the beginning of germination and gradually reduced germination percentages. At salt levels beyond 400 mM Na2SO4 and 500 mM NaCl germination was completely inhibited. The germination stress tolerance index displayed that seed germination of safflower was restricted more with Na2SO4 compared to NaCl. Ungerminated seeds in high salt treatments (≥ 300 mM Na2SO4 and ≥ 400 mM NaCl) when transferred to distilled water recovered and kept their ability to germinate. Although, total germination percentages progressively decreased with increasing salinity levels, suggesting that the adverse impact of these treatments were osmotic effect and specific ion toxicity. In addition, increasing salinity concentrations led to a significant decrease in the seedling vigor index by means of reduced radicle and hypocotyl growth irrespective of the salt agents applied. These findings suggest that safflower may be considered as a promising species for saline soil rehabilitation and by consequence for ecological balance improvement.

Distribution of sexually reproductive eelgrass (Zostera marina) seeds in microhabitats of eelgrass beds in intertidal zones

Eelgrass (Zostera marina) seedling establishment based on the sexually reproductive seed bank depends on habitat factors, and there are different microhabitats in eelgrass beds. Seedling abundance varies with microhabitat. Why is the distribution pattern of seedlings so? Is there an edge effect of eelgrass patches on seedling distribution? To clarify the distribution and variation patterns of ungerminated seeds, germinated seeds and seedlings in microhabitats, field investigations were conducted from December 2020 to April 2021. The density of the total seed bank varied with microhabitat except in March. In April, the density of germinated seed banks in the highland, low-lying area edge and low-lying area was 0.00 ± 0.00, 0.33 ± .33 and 7.44 ± 0.96 seeds.cm−3, respectively, and the density in the low-lying area was higher than that in the other microhabitats. The order of density of the seedling bank was highland < low-lying area edge < low-lying area in April. The relative proportion of germinated seeds in the low-lying area was higher than that in the highland from March to April, during which the increase rate in the seedling bank of the highland was lower than that of other microhabitats. The distribution pattern of eelgrass seeds varies with microhabitat. The change characteristics of germinated seeds or seedling banks are related to microhabitats. There are edge effects of eelgrass patches on the distribution of germinated seeds and seedlings. All these factors contribute to the formation of seedling distribution. Sowing eelgrass seeds in the edge area of a continuously distributed eelgrass bed can promote the seedling establishment rate.

Uticaj različitih vrsta višegodišnjeg malča na banku semena korova u voćnjaku

Mulching is an agrotechnical measure often used in orchards and it means covering the soil with the organic or inorganic material in order to prevent the germination of the weeds. The other positive effects imply: the improvement of the physical and chemical soil characteristics, decrease of soil erosion and water loss, the prevention of the soil crusting, etc. The research of the weed seed bank under the different types of mulch was conducted during the growing season of 2021. in a plum orchard located at Rimski Šančevi. The black and white agrotextile and white mulch film, unlike the other mulches, left the surfaces clean, without the weeds. The analysis of the weed seed bank revealed the seeds of 20 weed species, of which 12 were not found to be present in the orchard during the experimental year. The overall germination rate of the obtained weed seeds is low because in the three-year experiment with mulches, there was no influx of new weed seeds for several years, while the old ones lost their germination. The highest germination percentage was noted for the seeds of the following species: Amaranthus retroflexus, Stellaria media and Solanum nigrum, due to their ability to retain germination for a long period of time. The highest number of the seeds per m2 was found in the inter-row space due to the large influx of the seeds during the growing season. The highest germination rate was observed in case of the seeds found under the sawdust mulch. None of the ungerminated seeds showed the viability, as determined by the Crush test.

Different Traits Affect Salinity and Drought Tolerance during Germination of Citrullus colocynthis, a Potential Cash Crop in Arid Lands

Citrullus colocynthis, a native plant with potential uses as a feedstock for edible oil, biodiesel, and animal feed make it a potential cash crop. The importance of propagating this species under saline arid habitats necessitates understanding environmental factors affecting salinity and drought tolerance during the germination stage. Here, we assessed the impacts of seed collection time, the temperature of incubation on salinity, and drought tolerance during the seed germination stage of different accessions growing in the botanical garden of the University of Sharjah. No previous study assessed the interactive effects of these factors on the drought and salinity tolerance of this species. Three accessions (9, 10, and 13) differed in fruit and seed size and color, and germination behavior, and were selected from an earlier study. Seeds that matured in summer and winter on these accessions were treated with three salinities (0, 50, and 100 mM NaCl), and PEG levels (0, −0.3, and −0.6 MPa) and incubated at two temperatures (20/30 and 25/35 °C). The results showed significant effects of all factors (collection time, temperature, drought, and salinity) and their interactions on germination percentage. Seeds of C. colocynthis were very sensitive to salinity and drought stress, and the sensitivity depended on the time of seed collection, accession, and incubation temperature. The overall germination and tolerance to salinity and drought were significantly greater in seeds of accession 10, seeds that matured in summer, and seeds incubated at 25/35 °C. The germination in NaCl solutions was greater than in PEG solutions, indicating that seed germination was more sensitive to osmotic stress created by PEG than NaCl. Moreover, when transferred from NaCl, the recovery of ungerminated seeds was greater than in PEG solutions. This result indicates that the detrimental effect of salinity in C. colocynthis could be mainly attributed to osmotic rather than ion-toxicity effects. To adopt C. colocynthis as a cash crop or to restore degraded desert habitats, it is recommended to use seeds of drought- and salt-tolerant accessions (e.g., 10), especially those that mature in summer.