Influence Seedling Emergence Research Articles

Pachycereus pringlei seedling emergence and establishment under different lighting conditions

Cactus early life stages, especially in arid ecosystems, are typically the most vulnerable; seedlings face various abiotic and biotic filters to achieve survival and successful integration into their habitat. Thus, Pachycereus pringlei – endemic to Mexican Sonoran Desert – plays a crucial role in the arid areas of Baja California Sur, Mexico acting as a refuge and food source for wildlife. The present study evaluates P. pringlei emergence, survival, and seedling growth under different solar exposure (open and shaded areas) levels, both in greenhouse and natural conditions. The results indicated that natural conditions and moisture significantly influenced seedling emergence and survival. Lack of soil moisture led to compaction, which may have reduced porous spaces and restricted air and water circulation, thereby affecting root growth during the establishment phase. Conversely, the emerged seedling proportion under greenhouse shade was higher than in natural conditions. Additionally, these seedlings exhibited superior stem development, while those exposed to sunlight notably developed root systems. Low water potential was recorded, reaching down to -5.1 MPa for seedlings exposed to higher light levels. However, relative water content (RWC) values in tissues exceeded 70 %. No significant relationship was found between photosynthetic pigment concentration and different light conditions. Despite adapting cacti to xeric environments, the results suggest they may not be fully prepared to withstand prolonged drought episodes during the seedling stage. Nevertheless, some morphological traits, such as stem length, spines, and root area showed significant variations under different light conditions, facilitating photosynthesis light capture.

Environmental Effects during Early Life-History Stages and Seed Development on Seed Functional Traits of an Australian Native Legume Species.

Understanding how seed functional traits interact with environmental factors to determine seedling recruitment is critical to assess the impact of climate change on ecosystem restoration. This study focused on the effects of environmental factors on the mother plant during early plant life history stages and during seed development. Desmodium brachypodum A. Gray (large tick trefoil, Fabaceae) was used as a model species. Firstly, this study analyzed seed germination traits in response to temperature and moisture stress. Secondly, it investigated how seed burial depth interacts with temperature and soil moisture to influence seedling emergence traits. Finally, it determined if contrasting levels of post-anthesis soil moisture could result in changes in D. brachypodum reproductive biology and seed and seedling functional traits. The results showed that elevated temperature and moisture stress interacted to significantly reduce the seed germination and seedling emergence (each by >50%), while the seed burial improved the seedling emergence. Post-anthesis soil moisture stress negatively impacted the plant traits, reducing the duration of the reproductive phenology stage (by 9 days) and seed production (by almost 50%). Unexpectedly, soil moisture stress did not affect most seed or seedling traits. In conclusion, elevated temperatures combined with low soil moisture caused significant declines in seed germination and seedling emergence. On the other hand, the reproductive output of D. brachypodum had low seed variability under soil moisture stress, which might be useful when sourcing seeds from climates with high variability. Even so, a reduction in seed quantity under maternal moisture stress can impact the long-term survival of restored plant populations.

Under drought conditions, fungicide seed coating does not increase emergence of two native grass species in sagebrush stands of the Intermountain West, U.S.A.

Coating seeds with amendments to increase germination, emergence, and establishment is a promising strategy for dryland restoration. Seed coatings containing fungicides offer a potential solution in regions where fungal pathogens cause seed mortality during the winter stratification period between late fall seeding and spring germination. The effectiveness of the fungicide treatment, however, may be dictated by weather and within‐site microenvironment. We tested how fungicide coating influenced seedling emergence of native grasses within sagebrush stands by planting untreated seeds and seeds coated (encrusted) with and without active fungicide ingredients in furrows that extended from the canopy edge of sagebrush plants (Artemisia tridentata ssp. wyomingensis) into the interspace. This was replicated at four sites across the Intermountain West in two successive years. We planted two native grasses, bottlebrush squirreltail (Elymus elymoides) and bluebunch wheatgrass (Pseudoroegneria spicata). Emergence was extremely low in both years, with a complete seeding failure (i.e. zero emergence) at two sites in the first year and three sites in the second year. At one site where emergence was sufficient for statistical analysis: (1) the coating on the fungicide and blank treatments inhibited emergence under anomalously dry conditions and (2) across seed treatments, proximity to a sagebrush canopy slightly increased seedling emergence. The variable emergence patterns across sites and years (i.e. the highest emergence was for the site–year combination with the lowest precipitation) highlight the sensitivity of seeding outcomes to, and dependence of fungicide seed coatings on, site conditions, and the necessity of repeating experiments across different weather years.

CONCEPT OF SEED DETERIORATION: REASON, FACTORS, CHANGES DURING DETERIORATION AND PREVENTIVE MEASURES TO OVERCOME SEED DEGRADATION

Seed deterioration is when a seed loses its vigor and eventually loses viability. Seed viability is an important trait that directly influences seedling emergence and crop yield. The rate of seed deterioration varies on several factors. Our main aims were to express the methods for testing seed deterioration, factors influencing seed aging, stages of seed deterioration, changes associated with seed deterioration, Practical approaches to overcome seed deterioration, and the role of reactive oxygen species during seed aging. From this investigation, it can be concluded that high temperatures and high relative humidity can hasten the degradation of seeds. An increase in the loss of seed leachate, a drop in respiration rates and ATP production, a loss of enzyme activity, and organelle structural breakdown are often seen as changes as seeds age. Various factors can cause seed aging, but the main cause is probably oxidative damage brought on by free radicals and reactive oxygen species (ROS). Protein oxidation, lipid peroxidation, chromosomal abnormalities, and DNA damage can all be induced by ROS, which can have critical interactions with any macromolecule of biological significance. In the early stages of imbibition, some repairs may occur, and seeds will lose their viability within a short period. Seed deterioration can be retrieved through different priming and exogenous application of plant growth regulators.

Effects of gibberellin priming on seedling emergence and transcripts involved in mesocotyl elongation in rice under deep direct-seeding conditions.

Mesocotyl elongation is a key trait influencing seedling emergence and establishment in direct-seeding rice cultivation. The phytohormone gibberellin (GA) has positive effects on mesocotyl elongation in rice. However, the physiological and molecular basis underlying the regulation of mesocotyl elongation mediated by GA priming under deep-sowing conditions remains largely unclear. In the present study, we performed a physiological and comprehensive transcriptomic analysis of the function of GA priming in mesocotyl elongation and seedling emergence using a direct-seeding japonica rice cultivar ZH10 at a 5-cm sowing depth. Physiological experiments indicated that GA priming significantly improved rice seedling emergence by increasing the activity of starch-metabolizing enzymes and compatible solute content to supply the energy essential for subsequent development. Transcriptomic analysis revealed 7074 differentially expressed genes (false discovery rate of <0.05, |log2(fold change)| of ≥1) after GA priming. Furthermore, gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses revealed that genes associated with transcriptional regulation, plant hormone biosynthesis or signaling, and starch and sucrose metabolism were critical for GA-mediated promotion of rice mesocotyl elongation. Further analyses showed that the expression of the transcription factor (TF) genes (v-myb avian myeloblastosis viral oncogene homolog (MYB) alternative splicing 1 (MYBAS1), phytochrome-interacting factors 1 (PIF1), Oryza sativa teosinte branched 1/cycloidea/proliferating cell factor 5 (OsTCP5), slender 1 (SLN1), and mini zinc finger 1 (MIF1)), plant hormone biosynthesis or signaling genes (brassinazole-resistant 1 (BZR1), ent-kaurenoic acid oxidase-like (KAO), GRETCHEN HAGEN 3.2 (GH3.2), and small auxin up RNA 36 (SAUR36)), and starch and sucrose metabolism genes (α-amylases (AMY2A and AMY1.4)) was highly correlated with the mesocotyl elongation and deep-sowing tolerance response. These results enhance our understanding of how nutrient metabolism-related substances and genes regulate rice mesocotyl elongation. This may facilitate future studies on related genes and the development of novel rice varieties tolerant to deep sowing.

English

Three experiments were conducted to optimize boron (B) delivery through seed coating for improving wheat yield and biofortification to fight against the malnutrition in the most consumable crop. First experiment was conducted in Petri plates kept in laboratory at room temperature. Seed were coated with 0, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 g B kg-1 seed by boric acid (H3BO3) and borax (Na2B4O7) as source of B. Results of this experiment revealed that least mean germination time (MGT) was recorded in seed coated with 0.05 g B kg-1 using borax as source of B (2.06 days) than control (2.34 days) followed by 0.25 g B kg-1 seed using same source and 0.25, 0.50 g B kg-1 seed using boric acid. Higher final germination percentage (FGP) was also recorded in 0.25, 0.50 g B kg-1 seed by using boric acid (100% and 98.8% respectively) and 0.25, 0.50 g B kg-1 seed by using borax (100% and 100% respectively). Moreover, higher shoot length (10.68 cm) was recorded in seed coated with 0.25 g B kg-1 seed using boric acid, while higher root length and seedling dry weight (13.49 cm and 17.88 mg respectively) was recorded in seed coated with 0.25 g B kg-1 seed using borax. Optimized seed coating treatments 0.25 ad 0.50 g B (as boric acid and borax) kg-1 seed were further evaluated against uncoated control seed in 2nd experiment which was conducted in sand filled small cups kept in laboratory at room temperature. Seed coated by 0.25 and 0.50 g B (as borax) kg-1 seed resulted in higher seedling growth i.e., root length, shoot length and seedling dry weight, than control. In 3rd experiment seed were coated with 0.25 and 0.50 g B (as borax) kg-1 seed. This experiment was conducted in soil filled clay pots kept in glass house in room temperature. Results of this experiment showed that treatments did not influence seedling emergence; nonetheless, seed coating using 0.25 g B kg-1 seed enhanced grain yield (13.75 g per pot) and grain B concentration (1.76 µg g -1 ). In conclusion, wheat seed may be coated with 0.25 g B (as borax) kg-1 seed to mend seedling growth, grain yield and grain B concentration of wheat. Increased B concentration wheat grain may play a significant role to eliminate malnutrition in humans if adapted in the wheat cultivation.

24-epibrassinolide confers tolerance against deep-seeding stress in Zea mays L. coleoptile development by phytohormones signaling transduction and their interaction network

ABSTRACT Coleoptile/mesocotyl elongation influence seedling emergence and establishment, is major causes of maize deep-seeding tolerance (DST). Detailed analyses on molecular basis underlying their elongation mediated by brassinosteroid under deep-seeding stress (DSS) could provide meaningful information for key factors controlling their elongation. Here we monitored transcriptome and phytohormones changes specifically in elongating coleoptile/mesocotyl in response to DSS and 24-epibrassinolide (EBR)-signaling. Phenotypically, contrasting maize evolved variant organs to positively respond to DST, longer coleoptile/mesocoty of K12/W64A was a desirable organ for seedling under DSS. Applied-EBR improved maize DST, and their coleoptiles/mesocotyls were further elongated. 15,607/20,491 differentially expressed genes (DEGs) were identified in W64A/K12 coleoptile, KEGG analysis showed plant hormone signal transduction, starch and sucrose metabolism, valine, leucine, and isoleucine degradation were critical processes of coleoptile elongation under DSS and EBR signaling, further highly interconnected network maps including 79/142 DEGs for phytohormones were generated. Consistent with these DEGs expression, interactions, and transport, IAA, GA3, ABA, and Cis-ZT were significantly reduced while EBR, Trans-ZT, JA, and SA were clearly increased in coleoptile under DSS and EBR-signaling. These results enrich our knowledge about the genes and phytohormones regulating coleoptile elongation in maize, and help improve future studies on corresponding genes and develop varieties with DST.

Emergencia y crecimiento de plántulas de Piscidia piscipula (L.) Sarg. en condiciones de vivero

Las fabáceas dominan los bosques del sureste de México: en la Península de Yucatán se encuentra el jabín (Piscidia piscipula L.) como especie arbórea dominante. Sin embargo, su manejo está poco documentado. Por lo anterior, el objetivo del presente trabajo fue describir aspectos de su manejo en vivero. Para esto, se evaluó la emergencia de plántulas posterior a la escarificación de semillas en soluciones de ácido clorhídrico y en agua a 100 °C, contra otras sin escarificar. Las plántulas obtenidas fueron fertilizadas con las fórmulas NPK (Nitrógeno, Fósforo y Potasio) (17-17-17, 46-00-00 y 18-46-00) y un testigo blanco. La emergencia de las plántulas se contabilizó durante 20 días y el crecimiento durante un mes, registrando la altura y diámetro. El análisis de los datos se realizó con el método no paramétrico de Kruskal Wallis aplicado en ambos experimentos. Los resultados no mostraron diferencias estadísticas entre tratamientos de escarificación; la altura fue favorecida por las fórmulas NPK 17-7-17 y 18-46-00, mientras que el mayor diámetro se obtuvo con la fórmula NPK 46-00-00. Esto indica que, estadísticamente, la escarificación no influye en la emergencia de plántulas y que la fertilización de plántulas de jabín debería contener mayor nitrógeno y fósforo.

Assessment of the Role of Different Soil Properties on Crust Strength by Linear Regression Models

Soil crust strength influences seedling emergence, penetration and morphology of plant roots, and, consequently, crop yields. A study was carried out to assess the role of different soil properties on crust strength atHisar, Haryana, India. The soil samples from 0-5 and 5-15 cm depths were collected from 21 locations from farmer’s fields, having a wide range of texture.Soil propertieswere evaluated in the laboratory and theirinfluence on the modulus of rupture (MOR), which is the measure of crust strength, was evaluated.The MOR of texturally different soils was significantly correlated with saturated hydraulic conductivity at both the depths. Dispersion ratio was found to decrease with an increase in fineness of the texture of soil and the lowest value was recorded in silty clay loam soil,which decreased with depth. The modulus of rupture was significantly negatively correlative with the dispersion ratio.There was no role of calcium carbonate in influencing the values of MOR of soils. Similarly,the influence of pH, EC and SAR of soil solution on MOR was non-significant.A perusal of thevalues of the correlations between MOR and different soil properties showed that the MOR of soils of Haryana are positively correlated with silt + clay (r = 0.805) followed by water-stable aggregates (r = 0.774), organic carbon (r = 0.738), silt (r = 0.711), mean weight diameter (r = 0.608) and clay (r = 0.593) while negatively correlated with dispersion ratio (r = - 0.872), sand (r = -0.801) and hydraulic conductivity (r = -0.752) of soils.

Effects of climate warming and prolonged snow cover on phenology of the early life history stages of four alpine herbs on the southeastern Tibetan Plateau.

Much research has focused on plant responses to ongoing climate change, but there is relatively little information about how climate change will affect the early plant life history stages. Understanding how global warming and changes in winter snow pattern will affect seed germination and seedling establishment is crucial for predicting future alpine population and vegetation dynamics. In a 2-year study, we tested how warming and alteration in the snowmelt regime, both in isolation and combination, influence seedling emergence phenology, first-year growth, biomass allocation, and survival of four native alpine perennial herbs on the southeastern Tibetan Plateau. Warming promoted seedling emergence phenology of all four species and biomass per plant of two species but reduced seedling survival of three species. Prolonged snow cover partly mediated the affects of warming on Primula alpicola (survival and biomass), Pedicularis fletcheri (phenology, biomass, and root:shoot ratio) and Meconopsis integrifolia (survival). For the narrowly distributed species M. racemosa, seedling growth was additively decreased by warming and prolonged snow cover. Both warming and alteration of the snow cover regime can influence plant recruitment by affecting seedling phenology, growth, and survival, and the effects are largely species-specific. Thus, climate change is likely to affect population dynamics and community structure of the alpine ecosystem. This is the first experimental demonstration of the phenological advancement of seedling emergence in the field by simulated climate warming.

Factors influencing seedling emergence of three global invaders in greenhouses representing major eco-regions of the world.

Successful germination and seedling emergence in new environments are crucial first steps in the life history of global plant invaders and thus play a key role in processes of range expansion. We examined the germination and seedling emergence success of three global plant invaders - Lupinus polyphyllus, Senecio inaequidens and Verbascum thapsus - in greenhouses and climate chambers under climate regimes corresponding to seven eco-regions. Seed materials were collected from one non-native population for L.polyphyllus and S.inaequidens, and from 12 populations for V.thapsus (six natives and six non-natives). Experimental climates had significant effects on species responses. No species germinated in the dry (humidity ≤ 50%) and cool (≤ 5°C) experimental climates. But all species germinated and emerged in two moderately cool (12-19°C) and in three warm (24-27°C) experimental climates. In general, V.thapsus showed higher fitness than S.inaequidens and L.polyphyllus. The climate of the seed source region influenced responses of native and non-native populations of V. thapsus. Non-native populations of V.thapsus, originating from the warmer seed source, showed higher performance in warm experimental climates and lower performance in moderately cool experimental climates compared to native populations. Responses of V.thapsus populations were also related to precipitation of the seed source region in moderately dry experimental climates. The warm, semi-arid and humid experimental climates are suitable for the crucial first steps of invasion success for L.polyphyllus, S.inaequidens and V.thapsus. The species adaptation to its source region modified the responses of our studied plants under different experimental climates representing major eco-regions of the world.

Influences of fine-scale disturbance on germinant success in a treeline ecotone

ABSTRACTFine-scale disturbance can increase seed access to suitable substrates, facilitating germinant emergence and survival, which are necessary elements for treeline advance. We conducted an experiment to test this hypothesis in a white spruce (Picea glauca) treeline ecotone in southwest Yukon, Canada. Sixty seed germination quadrats were established at two elevations (treeline and alpine tundra) and subjected to three levels of simulated disturbance. We sowed 125 seeds in half of the quadrats (30) and measured their emergence and survival over 3 years. Soil temperature, moisture, and organic depth were recorded in all treatments. Treeline quadrats had significantly greater seedling emergence and survival than alpine tundra quadrats. Mean soil temperature, moisture, and organic layer depth were all greater in treeline quadrats. Partially scarified quadrats had the highest germinant emergence compared to unscarified and completely scarified quadrats. Completely scarified quadrats had the highest temperature range and the lowest soil moisture. The results indicate that moderate levels of disturbance can positively influence seedling emergence, while more severe disturbance can lead to high temperature ranges and moisture loss that negate the benefits of lower interspecific competition. Collectively, our findings suggest that fine-scale disturbance can play a significant role in influencing seedling presence in treeline ecotones.

Dynamic transcriptome and phytohormone profiling along the time of light exposure in the mesocotyl of rice seedling

Mesocotyl elongation is an important trait influencing seedling emergence and establishment in rice direct-seeding cultivation and is immediately inhibited after light exposure. Detailed researches on the molecular basis and biological processes underlying light repression of mesocotyl growth could probably provide useful information for key factors controlling this trait. Here we monitored the transcriptome and endogenous phytohormone changes specifically in the elongating mesocotyl in response to light exposure with a time-course. It was revealed that 974 transcripts were significantly differentially expressed (FDR < 0.05, |log2 (L/D) | ≥2) after light exposure. Most of the differential expression genes associated with the responses to hormone. Metabolic pathway analysis using the KEGG system suggested plant hormone signal transduction, α-linolenic acid metabolism and diterpenoid biosynthesis were critical processes of mesocotyl growth inhibited by light. Consistent with DEGs, the endogenous IAA, tZ and GA3 content was significantly reduced while JA level was dramatically increased, which indicated that light inhibited rice mesocotyl growth through decreasing IAA, tZ and GA3 content and/or increasing JA level. The present results enriched our knowledge about the genes and phytohormones regulating mesocotyl elongation in rice, which may help improve future studies on associated genes and develop new varieties tolerance to deep sowing.

The value of trophic interactions for ecosystem function: dung beetle communities influence seed burial and seedling recruitment in tropical forests.

Anthropogenic activities are causing species extinctions, raising concerns about the consequences of changing biological communities for ecosystem functioning. To address this, we investigated how dung beetle communities influence seed burial and seedling recruitment in the Brazilian Amazon. First, we conducted a burial and retrieval experiment using seed mimics. We found that dung beetle biomass had a stronger positive effect on the burial of large than small beads, suggesting that anthropogenic reductions in large-bodied beetles will have the greatest effect on the secondary dispersal of large-seeded plant species. Second, we established mesocosm experiments in which dung beetle communities buried Myrciaria dubia seeds to examine plant emergence and survival. Contrary to expectations, we found that beetle diversity and biomass negatively influenced seedling emergence, but positively affected the survival of seedlings that emerged. Finally, we conducted germination trials to establish the optimum burial depth of experimental seeds, revealing a negative relationship between burial depth and seedling emergence success. Our results provide novel evidence that seed burial by dung beetles may be detrimental for the emergence of some seed species. However, we also detected positive impacts of beetle activity on seedling recruitment, which are probably because of their influence on soil properties. Overall, this study provides new evidence that anthropogenic impacts on dung beetle communities could influence the structure of tropical forests; in particular, their capacity to regenerate and continue to provide valuable functions and services.

Effect of methyl salicylate (MeSA), an elicitor on growth, physiology and pathology of resistant and susceptible rice varieties.

Methyl salicylate (MeSA) is a volatile organic compound synthesized from salicylic acid (SA) a plant hormone that helps to fight against plant disease. Seed treatment with MeSA, is an encouraging method to the seed industry to produce more growth and yield. The aim of our study is to find out the growth, development and disease tolerance of rice seed treated with different concentrations of MeSA. Also the seed treatments were studied to determine whether they directly influenced seedling emergence and growth in rice (Oryza sativa L) cultivars ‘IR 20, IR 50, IR 64, ASD 16, ASD 19 and ADT 46’ under greenhouse condition. MeSA seed treatments at 25, 50, 75 and 100 mg/L significantly increased seedling emergence. Effects were stronger in IR 50, and IR 64 and the effects were dose dependent, although the relationship between dose and effect was not always linear. MeSA seed treated rice plant against bacterial blight were analyzed. Bacterial blight was more effectively controlled by the seed treated with 100 mg/L than others. These results suggest that seed treatment with MeSA alters plant physiology in ways that may be useful for crop production as well as protection.

Effects of litter, seed position, and water availability on establishment of seedlings for two semiarid grass species

We conducted a field investigation and controlled experiments in a glasshouse to determine how litter, seed position, and/or water supply affect seedling emergence and the establishment of two native grass species (Leymus chinensis (Trin.) Tzvel. and Bromus inermis Leyss) in northern China. Both water supply and seed position dramatically influenced seedling emergence and growth, as well as the accumulation of biomass for these two species. For L. chinensis, the quantity of litter had a significant impact on seedling survival, height increment, and biomass production when grown in either the glasshouse or the field while that component had little influence on B. inermis seedling emergence or survival. The effects of litter were physical but not biological or chemical, suggesting that this component is important only in the first year of seedling establishment. Therefore, longer-term experiments are probably necessary to examine the biological and chemical impacts that litter has on seedling performance.

Seed-germination responses of Calotropis procera (Asclepiadaceae) to temperature and water stress in northern Australia

Understanding the seed biology of the introduced weed rubber bush (Calotropis procera (Aiton, W.T.Aiton)) is critical to its management in northern Australia. We examined the numbers of seeds produced and the effects of environmental temperature and water stress on germination performance (germinability G; mean germination time MGT) of rubber bush seeds from across northern Australia. Germination trials were conducted using seeds from wild populations monitored for 3 years. Seed numbers per fruit did not vary significantly among the six populations studied (mean ± s.e. = 433.2 ± 19.0), but seed mass did (range from 8.32 ± 0.24 to 5.24 ± 0.06 mg), with no negative correlation between the measures. Maximum seed germination (68–100%) occurred at 30°C, associated with a mean germination time of 2.58 days. Under water stress, the proportion of germinated seeds declined significantly with increasing temperature from 92.5 ± 1.1% at 20°C and 0 MPa to 2.8 ± 1.7% at 40°C and –0.4 MPa respectively. Seeds were unable to germinate at ambient temperatures ≥40°C, but remained quiescent and hence viable. Planting depth influenced seedling emergence, with minimal germination of seeds on the surface (5.8%) but 88.5% germination at 3-cm depth. The effect of water stress was dependent on temperature, with water stress inducing a reduction in optimum germination temperature from 30°C to 20°C. Phenotypic plasticity in G and MGT did not show clear patterns among populations or years. Short MGTs increase seedling survival by rapid transition from endosperm resources to photosynthesis, whereas seed quiescence (cf. dormancy) optimises germination opportunities in a semiarid environment. Thus, the germination traits reported in the present study are likely to promote seedling survival and potential spread of rubber bush in semiarid Australia.

Effects of burial depth and water depth on seedling emergence and early growth of Scirpus planiculmis Fr. Schmidt

Seed burial and water regime are both crucial factors influencing seedling emergence and plant growth in wetlands and thus exert important effects on revegetation in degraded wetlands. We conducted a pot experiment to determine the effects of burial depth and water depth on the seedling emergence and growth of Scirpus planiculmis Fr. Schmidt. Seeds of S. planiculmis were buried at 0, 0.5, 1 and 2cm depths in plastic pots with non-sterilized sediment under exposed (−5cm), waterlogged (0cm) and submerged (5 and 10cm water depths relative to sediment surface) water regimes. The results showed that the percentage of seedling emergence at a burial depth of 0cm was enhanced under 10cm and 5cm water depths (78.89% and 81.37%, respectively) in comparison to the results under −5cm and 0cm water depths (0 and 2.22%, respectively). Seedlings did not grow through the water to the surface and no tuber formed when covered by 10cm of water. The total biomass per seedling was generally higher at 0.5cm or 1cm burial depths than that at other burial depths. The tuber number per seedling was highest at a 0.5cm burial depth, while the value was lowest at a 0cm burial depth. Our results provide valuable guidance for the establishment of S. planiculmis from seeds in wetland revegetation programs.

Intraspecific seed interactions alter seedling emergence of Lespedeza cuneata under field conditions

AbstractThere is growing recognition that seeds influence one another prior to, or shortly after, germination. Both interspecific and intraspecific seed–seed interactions have been reported, but for the latter, the evidence is almost exclusively from laboratory and greenhouse studies so that it is unclear whether such intraspecific seed interactions occur under field conditions. We tested how Lespedeza cuneata seed density influenced seedling emergence within a native grassland located in Kansas, USA and whether this response was related to seed leachate. The percentage of L. cuneata seedlings that emerged under field conditions was negatively related to seed density. After confirming this pattern in the greenhouse, we found that at low seed densities, addition of seed leachate had similar effects on seedling emergence as high seed densities in the absence of leachate. Our results provide some of the best evidence to date, that intraspecific seed density can influence seedling emergence in the field and that these effects are likely linked to seed leachate.

Seed handling behaviours of native and invasive seed‐dispersing ants differentially influence seedling emergence in an introduced plant

Myrmecochory, or ant‐mediated seed dispersal, is an important ecological interaction in which ants benefit by gaining nutrition from lipid‐rich elaiosomes attached to seeds and plants benefit from having their seeds dispersed away from parent plants. Most research on the benefits of myrmecochory focuses on primary dispersal, in which ants move seeds to nests, or secondary dispersal, in which ants deposit intact seeds in middens after consuming elaiosomes. Less is known about how ants handle seeds inside nests and if handling influences plant fitness. The seed handling behaviours of a native ‘keystone disperser’, Aphaenogaster rudis s.l., and an invasive seed‐disperser, Myrmica rubra L., on an introduced herb, Chelidonium majus L., were compared. We conducted a greenhouse experiment to test if handling by ants, manual removal of elaiosomes, or no handling (controls) influenced seedling emergence. Colony‐level differences in handling behaviours and plant responses were also examined. Aphaenogaster rudis retained seeds inside nests longer than M. rubra, but there was no difference in the amount of elaiosome removed by the two species. There was no difference in the proportion of seedlings that emerged among treatments, but seedlings emerged earlier when handled by A. rudis. Additionally, more seedlings emerged and seedlings emerged earlier the longer seeds were retained inside ant nests. This study suggests that handling by ants may be a benefit of myrmecochory. This is probably not due to elaiosome removal; rather favourable nest conditions may enhance emergence. Also, functional differences in ant species may result in different outcomes for plant partners.