Showing papers on "Seedling published in 2021"

Effect of Salinity Stress on Physiological Changes in Winter and Spring Wheat

Abstract: Salinity is a leading threat to crop growth throughout the world. Salt stress induces altered physiological processes and several inhibitory effects on the growth of cereals, including wheat (Triticum aestivum L.). In this study, we determined the effects of salinity on five spring and five winter wheat genotypes seedlings. We evaluated the salt stress on root and shoot growth attributes, i.e., root length (RL), shoot length (SL), the relative growth rate of root length (RGR-RL), and shoot length (RGR-SL). The ionic content of the leaves was also measured. Physiological traits were also assessed, including stomatal conductance (gs), chlorophyll content index (CCI), and light-adapted leaf chlorophyll fluorescence, i.e., the quantum yield of photosystem II (Fv′/Fm′) and instantaneous chlorophyll fluorescence (Ft). Physiological and growth performance under salt stress (0, 100, and 200 mol/L) were explored at the seedling stage. The analysis showed that spring wheat accumulated low Na+ and high K+ in leaf blades compared with winter wheat. Among the genotypes, Sakha 8, S-24, W4909, and W4910 performed better and had improved physiological attributes (gs, Fv′/Fm′, and Ft) and seedling growth traits (RL, SL, RGR-SL, and RGR-RL), which were strongly linked with proper Na+ and K+ discrimination in leaves and the CCI in leaves. The identified genotypes could represent valuable resources for genetic improvement programs to provide a greater understanding of plant tolerance to salt stress.

Achieving similar root microbiota composition in neighbouring plants through airborne signalling

Abstract: The ability to recognize and respond to environmental signals is essential for plants. In response to environmental changes, the status of a plant is transmitted to other plants in the form of signals such as volatiles. Root-associated bacteria trigger the release of plant volatile organic compounds (VOCs). However, the impact of VOCs on the rhizosphere microbial community of neighbouring plants is not well understood. Here, we investigated the effect of VOCs on the rhizosphere microbial community of tomato plants inoculated with a plant growth-promoting rhizobacterium Bacillus amyloliquefaciens strain GB03 and that of their neighbouring plants. Interestingly, high similarity (up to 69%) was detected in the rhizosphere microbial communities of the inoculated and neighbouring plants. Leaves of the tomato plant treated with strain GB03-released β-caryophyllene as a signature VOC, which elicited the release of a large amount of salicylic acid (SA) in the root exudates of a neighbouring tomato seedling. The exposure of tomato leaves to β-caryophyllene resulted in the secretion of SA from the root. Our results demonstrate for the first time that the composition of the rhizosphere microbiota in surrounding plants is synchronized through aerial signals from plants.

Influence of nano-priming on seed germination and plant growth of forage and medicinal plants

Abstract: Plant growth and development are vastly affected by different abiotic and biotic stresses. Seed priming is an effective tool for increasing seed germination and plant growth that will eventually increase productivity under different environmental conditions and stresses. Efficient seed germination promotes successful establishment and deep root system of plants. Among the different seed priming methods, nano-priming is more effective mainly because of its small size and unique physicochemical properties. Since plant species are physiologically different, they differ in their uptake of nanoparticles in nano-priming, and hence in their rate and manner of growth. Most previous studies have separately investigated the effect of nanomaterial on seed germination, growth, and development of one plant at a time. However, very few studies have reported nano-priming effects using different particles on seed germination and seedling growth of forage and medicinal plants together. Therefore, this review summarizes studies of nano-priming effects using various particles on seed germination and seedling growth of forage and medicinal plants. Furthermore, the effect of different nanoparticles on the most important characteristics of germination, morphology and physiology affecting the establishment, growth and production of these plants are reviewed. In general, nano-priming increased seed germination, seedling growth and development, vigor, rate of seedling emergence and subsequent performance in most of the medicinal and forage plants. While the use of nanoparticles enhanced environmental stress resistance of these plants, negative effects of nano-priming on seed germination, seedling and plant growth traits were observed. In addition, future research areas of focus are discussed briefly.

Combined Application of Arbuscular Mycorrhizal Fungi and Exogenous Melatonin Alleviates Drought Stress and Improves Plant Growth in Tobacco Seedlings

Abstract: Studies have shown that the application of arbuscular mycorrhizal (AM) fungi or exogenous melatonin (MT) can alleviate drought stress and improve plant growth, but the additive effects of both treatments on plants grown under drought stress are largely unknown. In this study, we conducted a pot experiment to investigate the effects of AM inoculation (Funneliformis mosseae BGC XJ01) and/or MT application on tobacco (Nicotiana tabacum L. cv. Yuyan No. 6) seedling growth, photosynthetic and chlorophyll fluorescence parameters, antioxidant enzymatic activity, osmotic adjustment substance accumulation, and nutrient uptake under three water conditions (75–80%, 50–55%, and 30–35% of the maximum moisture retention capacity). The results show that applying either the AM inoculant or MT alone significantly increased tobacco seedling growth and decreased the negative effects of drought stress. Furthermore, AM inoculation alone promoted root function (root biomass, root/shoot ratio, root system architecture), facilitated the capture and conversion of solar energy (photosynthetic rate, ΦPSII), and increased nutrient uptake more effectively than MT. In contrast, exogenous MT application alone was more effective at increasing peroxidase and catalase activity and decreasing H2O2 and MDA accumulation, which in turn enhanced the adaptation of seedlings to drought stress by improving their antioxidant capacity and reducing oxidative damage. Nevertheless, applying exogenous MT significantly enhanced the AM colonization rate under AM inoculation conditions but had no obvious effect on AM colonization under noninoculated conditions. The combined application of AM and MT had an additive effect and produced the largest increases in tobacco seedling growth, photosynthetic ability, antioxidant enzymatic activity, and N, P, and K uptake and the largest decreases in H2O2 and MDA contents of all the treatments. The results suggest that AM inoculation in combination with exogenous MT application may render plants more productive and more tolerant of drought stress.

Drought and crop yield.

Abstract: Episodes of water shortage occur in most agricultural regions of the world. Their durations and intensities increase, and their seasonal timing alters with changing climate. During the ontogenic cycle of crop plants, each development stage, such as seed germination, seedling establishment, vegetative root and shoot growth, flowering, pollination and seed and fruit development, is specifically sensitive to dehydration. Desiccation threatens yield and leads to specific patterns, depending on the type of crop plant and the harvested plant parts, e.g. leafy vegetables, tubers, tap roots or fruits. This review summarizes the effects of drought stress on crop plants and relates the dehydration-dependent yield penalty to the harvested organ and tissue. The control of shoot transpiration and the reorganization of root architecture are of core importance for maintaining proper plant water relationships. Upon dehydration, the provision and partitioning of assimilates and the uptake and distribution of nutrients define remaining growth activity. Domestication of crops by selection for high yield under high input has restricted the genetic repertoire for achieving drought stress tolerance. Introgression of suitable alleles from wild relatives into commercial cultivars might improve the ability to grow with less water. Future research activities should focus more on field studies in order to generate more realistic improvements to crops. Robotic field phenotyping should be integrated into genetic mapping for the identification of relevant traits.

Halotolerant Microbial Consortia for Sustainable Mitigation of Salinity Stress, Growth Promotion, and Mineral Uptake in Tomato Plants and Soil Nutrient Enrichment

Abstract: Salinity significantly impacts the growth, development, and reproductive biology of various crops such as vegetables. The cultivable area is reduced due to the accumulation of salts and chemicals currently in use and is not amenable to a large extent to avoid such abiotic stress factors. The addition of microbes enriches the soil without any adverse effects. The effects of microbial consortia comprising Bacillus sp., Delftia sp., Enterobacter sp., Achromobacter sp., was evaluated on the growth and mineral uptake in tomatoes (Solanum Lycopersicum L.) under salt stress and normal soil conditions. Salinity treatments comprising Ec 0, 2, 5, and 8 dS/m were established by mixing soil with seawater until the desired Ec was achieved. The seedlings were transplanted in the pots of the respective pH and were inoculated with microbial consortia. After sufficient growth, these seedlings were transplanted in soil seedling trays. The measurement of soil minerals such as Na, K, Ca, Mg, Cu, Mn, and pH and the Ec were evaluated and compared with the control 0 days, 15 days, and 35 days after inoculation. The results were found to be non-significant for the soil parameters. In the uninoculated seedlings’ (control) seedling trays, salt treatment significantly affected leaf, shoot, root dry weight, shoot height, number of secondary roots, chlorophyll, and mineral contents. While bacterized seedlings sown under saline soil significantly increased leaf (105.17%), shoot (105.62%), root (109.06%) dry weight, leaf number (75.68%), shoot length (92.95%), root length (146.14%), secondary roots (91.23%), and chlorophyll content (−61.49%) as compared to the control (without consortia). The Na and K intake were higher even in the presence of the microbes, but the beneficial effect of the microbe helps plants sustain in the saline environment. The inoculation of microbial consortia produced more secondary roots, which accumulate more minerals and transport substances to the different parts of the plant; thus, it produced higher biomass and growth. Results of the present study revealed that the treatment with microbial consortia could alleviate the deleterious effects of salinity stress and improve the growth of tomato plants under salinity stress. Microbial consortia appear to be the best alternative and cost-effective and sustainable approach for managing soil salinity and improving plant growth under salt stress conditions.

Symbiosis of AMF with growth modulation and antioxidant capacity of Caucasian Hackberry (Celtis Caucasica L.) seedlings under drought stress

Abstract: Beside climate changes, drought stress has become a serious limitated factor for plant production and seedling growth. Arbuscular mycorrhizal fungi (AMF) symbiosis has proposed to improve the growth and water efficiency under limited-water condition. For this purpose, Caucasian Hackberry (Celtis Caucasica L.) seedlings inoculate with mycorrhizal fungi Rhizophagus intraradices and Funneliformis mosseae under well-watered and water deficient conditions. The mycorrhizal and non-mycorrhizal seedlings were treated under 75 % FC (as control), 50 and 25 % FC for 90-days. The data were analyzed by using two-way ANOVA (SAS 9.2). In order to determine the significance of means, Duncan’s multiple-range test (DMRT) was performed using SAS 9.2 software at P ≤ 0.05. A principal component analysis (PCA) was conducted to assess the distribution of water and AMF treatments across a biplot figure by Past software. As well as, cluster analysis was performed using d3heatmap, dendextend, and gplots packages in R according to the Ward method to classify traits and applied treatments. The Result showed that the plant growth parameters dry shoot weight, leaf area, seedling height, dry root weight, length of root, number of secondary root, and chlorophyll content were greater in mycorrhizal seedlings in comparison with non-inoculated seedlings under normal irrigation and drought treatments. AMF symbiosis decreased H2O2 and malondialdehyde (MDA) content in leaves, while the activity of antioxidant enzymes catalase and superoxide dismutase raised in the host mycorrhiza-inoculated seedlings. The positive correlation was observed between colonization rate and plant growth as well as antioxidant enzymes activity, remarkably. These results suggest that AMF symbiosis is a potential tool to alleviating the detriment created by drought stress on Caucasian Hackberry young seedling by elevating plant growth, reducing membrane lipid peroxidation, raising cell wall stability and increasing the activity of antioxidant enzymes.

Variable influences of soil and seed-associated bacterial communities on the assembly of seedling microbiomes.

Abstract: Plants grown in distinct soils typically harbor distinct microbial communities, but the degree of the soil microbiome influence on plant microbiome assembly remains largely undetermined. We also know that the microbes associated with seeds can contribute to the plant microbiome, but the magnitude of this contribution is likely variable. We quantified the influence of soil and seed microbiomes on the bacterial community composition of seedlings by independently inoculating seeds from a single cultivar of wheat (Triticum aestivum) with 219 unique soil slurries while holding other environmental factors constant, determining the composition of the seed, soil, and seedling bacterial communities via cultivation-independent methods. Soil bacterial communities exert a strong, but variable, influence on seedling bacterial community structure, with the extent of the soil bacterial contribution dependent on the soil in question. By testing a wide range of soils, we were able to show that the specific composition of the seedling microbiome is predictable from knowing which bacterial taxa are found in soil. Although the most ubiquitous taxa associated with the seedlings were seed derived, the contributions of the seed microbiome to the seedling microbiome were variable and dependent on soil bacterial community composition. Together this work improves our predictive understanding of how the plant microbiome assembles and how the seedling microbiome could be directly or indirectly manipulated to improve plant health.

Use of microbial biostimulants to increase the salinity tolerance of vegetable transplants

Abstract: Vegetable plants are more sensitive to salt stress during the early growth stages; hence, the availability of poor-quality brackish water can be a big issue for the nursery vegetable industry. Microbial biostimulants promote growth and vigor and counterbalance salt stress in mature plants. This study aimed to evaluate the application of plant growth-promoting microorganisms for improving salt tolerance of lettuce and tomato seedlings irrigated with different water salinity levels (0, 25, and 50 mM NaCl) during nursery growth. Two commercial microbial biostimulants were applied to the substrate before seeding: 1.5 g L−1 of TNC BactorrS13 containing 1.3 × 108 CFU g−1 of Bacillus spp.; 0.75 g L−1 of Flortis Micorrize containing 30% of Glomus spp., 1.24 × 108 CFU g−1 of Agrobacterium radiobacter, Bacillus subtilis, Streptomyces spp. and 3 × 105 CFU g−1 of Thricoderma spp. Many morpho-physiological parameters of lettuce and tomato seedlings suffered the negative effect of salinity. The use of the microbial biostimulants modified seedling growth and its response to salt stress. They had a growth-promoting effect on the unstressed seedlings increasing fresh and dry biomass accumulation, leaf number, and leaf area and were successful in increasing salinity tolerance of seedlings especially when using Flortis Micorizze that enhanced salinity tolerance up to 50 mM NaCl. The inoculation of the substrate with microbial biostimulants could represent a sustainable way to improve lettuce and tomato transplant quality and to use brackish water in vegetable nurseries limiting its negative effect on seedling growth.

Exogenous Melatonin Modulates Endogenous H2S Homeostasis and L-Cysteine Desulfhydrase Activity in Salt-Stressed Tomato (Solanum lycopersicum L. var. cherry) Seedling Cotyledons

Abstract: Although melatonin has been reported to function as a stress signaling molecule, not much information is available on the biochemical and molecular events associated with probable melatonin-hydrogen sulfide crosstalk in plants. Present work provides evidence on the role of melatonin in the modulation of H2S homoeostasis during NaCl stress in dark-grown tomato (Solanum lycopersicum L. var. cherry) seedlings. NaCl stress (120 mM) inhibits hypocotyl elongation, promotes primary root growth and enhances electrolytic leakage from tomato seedlings. Treatment with H2S donor (100 µM; NaHS) tends to reverse these effects, all the more so (additive effect) in the presence of melatonin. NaCl stress and exogenous melatonin (30 µM) treatments modulate endogenous H2S accumulation and positively upregulate the activity of L-cysteine desulfhydrase (L-DES; EC 4.4.1.15; cytosolic). Melatonin has been observed to temporally modulate the activity of specific isoforms of H2S biosynthesizing enzyme, L-DES in seedling cotyledons. Zymographic analysis of L-DES isoforms in tomato seedling cotyledons has provided novel findings in plant system. Melatonin treatment decreases H2S accumulation in NaCl-stressed seedling cotyledons which is accompanied by a contrasting increase in L-DES activity. Melatonin, therefore, regulates endogenous H2S concentration in seedling cotyledons (NaCl treated), thus indicating the role of H2S catabolism pathways in H2S homoeostasis. Present findings thus reveal that exogenous melatonin modulates early H2S signaling in cotyledons of tomato seedlings subjected to NaCl stress. Furthermore, exogenous melatonin and H2S in combination (additive effect) ameliorate NaCl stress-induced growth changes in tomato seedlings.

Low-Temperature Plasma-Assisted Nitrogen Fixation for Corn Plant Growth and Development

Abstract: Nitrogen fixation is crucial for plants as it is utilized for the biosynthesis of almost all biomolecules. Most of our atmosphere consists of nitrogen, but plants cannot straightforwardly assimilate this from the air, and natural nitrogen fixation is inadequate to meet the extreme necessities of global nutrition. In this study, nitrogen fixation in water was achieved by an AC-driven non-thermal atmospheric pressure nitrogen plasma jet. In addition, Mg, Al, or Zn was immersed in the water, which neutralized the plasma-treated water and increased the rate of nitrogen reduction to ammonia due to the additional hydrogen generated by the reaction between the plasma-generated acid and metal. The effect of the plasma-activated water, with and without metal ions, on germination and growth in corn plants (Zea Mays) was investigated. The germination rate was found to be higher with plasma-treated water and more efficient in the presence of metal ions. Stem lengths and germination rates were significantly increased with respect to those produced by DI water irrigation. The plants responded to the abundance of nitrogen by producing intensely green leaves because of their increased chlorophyll and protein contents. Based on this report, non-thermal plasma reactors could be used to substantially enhance seed germination and seedling growth.

Effect of Nitric Oxide on Seed Germination and Seedling Development of Tomato Under Chromium Toxicity

Abstract: Nitric oxide (NO), a signaling molecule with diverse physiological functions, improves immunity of the plant against different environmental stresses. Heavy metal stress-induced structural and functional damages in cells are common consequences. Seed germination and seedlings development are crucial phases in the life cycle of a plant. The present experiment was designed to investigate how NO suppresses hexavalent chromium Cr(VI)-provoked impairment in the key processes during seed germination and seedlings development of tomato. This study reports that Cr(VI) stress significantly impaired seed germination attributes and the activity of hydrolyzing enzymes, such as α-amylase (α-A) and protease (Pr). However, exogenous NO donor sodium nitroprusside substantially improved seed germination parameters and upregulation of α-A and Pr. Furthermore, NO improved the content of nitrogen (N), NO, and proline (Pro), and modulated the activity of enzymes involved in Pro and N-assimilation. Under Cr(VI) toxicity conditions, NO improved the content of metal ligation compounds (non-protein thiols and total thiols), ascorbate and glutathione (GSH), and maintained higher content of GSH in glutathione pool (GSH:GSSG) and suppressed the formation of 4-hydroxy-2-nonenal and protein carbonylation, and electrolyte leakage. It may be concluded that NO improved the activity of hydrolyzing and Pro and N-metabolism enzymes. Application of NO also enhanced non-enzymatic antioxidants, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity under Cr(VI) toxicity conditions, thereby improved enhanced seed germination and seedlings vigor.

Salinity Duration Differently Modulates Physiological Parameters and Metabolites Profile in Roots of Two Contrasting Barley Genotypes.

Abstract: Hordeum maritimum With is a wild salt tolerant cereal present in the saline depressions of the Eastern Tunisia, where it significantly contributes to the annual biomass production In a previous study on shoot tissues it was shown that this species withstands with high salinity at the seedling stage restricting the sodium entry into shoot and modulating over time the leaf synthesis of organic osmolytes for osmotic adjustment However, the tolerance strategy mechanisms of this plant at root level have not yet been investigated The current research aimed at elucidating the morphological, physiological and biochemical changes occurring at root level in H maritimum and in the salt sensitive cultivar Hordeum vulgare L cv Lamsi during five-weeks extended salinity (200 mM NaCl), salt removal after two weeks of salinity and non-salt control H maritimum since the first phases of salinity was able to compartmentalize higher amounts of sodium in the roots compared to the other cultivar, avoiding transferring it to shoot and impairing photosynthetic metabolism This allowed the roots of wild plants to receive recent photosynthates from leaves, gaining from them energy and carbon skeletons to compartmentalize toxic ions in the vacuoles, synthesize and accumulate organic osmolytes, control ion and water homeostasis and re-establish the ability of root to grow H vulgare was also able to accumulate compatible osmolytes but only in the first weeks of salinity, while soon after the roots stopped up taking potassium and growing In the last week of salinity stress, the wild species further increased the root to shoot ratio to enhance the root retention of toxic ions and consequently delaying the damages both to shoot and root This delay of few weeks in showing the symptoms of stress may be pivotal for enabling the survival of the wild species when soil salinity is transient and not permanent

Deciphering Plantago ovata Forsk Leaf Extract Mediated Distinct Germination, Growth and Physio-Biochemical Improvements under Water Stress in Maize (Zea mays L.) at Early Growth Stage

Abstract: Use of Plantago ovata Forsk leaf (also known as blond plantain or isabgol) extract is a novel approach for ameliorating water stress in various agronomic crops such as maize (Zea mays L.). To examine the potential roles of P. ovata extract (0, 20 and 40%) in increasing seed germination, plant growth, photosynthetic measurements, stomatal properties, oxidative stress and antioxidant response, ions uptake and the relationship between studied parameters, we investigated the impacts of its short-term seed priming on Z. mays L. elite cultivar “Cimmyt-Pak” under a control environment and a water deficit stress environment (induced by PEG). It was evident that water deficit stress conditions induced a negative impact on plant growth, stomatal properties and ion uptake in different organs of Z. mays. The decrease in growth-related attributes might be due to overproduction of oxidative stress biomarkers, i.e., malondialdehyde (MDA) contents, hydrogen peroxide (H2O2) initiation, and electrolyte leakage (%), which was also overcome by the enzymatic antioxidants, i.e., superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) and non-enzymatic antioxidants, which increased under the water stress environment. However, seed priming with P. ovata extract positively increased germination rate and growth profile, and protected photosynthetic apparatus and stomatal properties by decreasing oxidative stress indicators and increasing activities of antioxidant compounds. Our results also depicted that the optimum concentration of P. ovata extract for Z. mays seedlings under water stress conditions was 20%, while a further increase in P. ovata extract (40%) induced a non-significant negative impact on growth and biomass of Z. mays seedling. In addition, the effect was more promising on Z. mays seedlings when grown under controlled conditions. Here, we concluded that the understanding of the role of seed priming with P. ovata extract in the increment of growth-related attributes, photosynthetic apparatus (Pn, Gs, Ts and Ci) and nutrient uptake (Ca2+, Fe2+, P and Mg2+) introduces new possibilities for their effective use in water deficit stress environments and shows a promising foundation for Z. mays tolerance against water deficit stress conditions.

Evaluation of the Impact of Cold Atmospheric Pressure Plasma on Soybean Seed Germination.

Abstract: The present study aims to define the effects of Cold Atmospheric Pressure Plasma (CAPP) exposure on seed germination of an agriculturally important crop, soybean. Seed treatment with lower doses of CAPP generated in ambient air and oxygen significantly increased the activity of succinate dehydrogenase (Krebs cycle enzyme), proving the switching of the germinating seed metabolism from anoxygenic to oxygenic. In these treatments, a positive effect on seed germination was documented (the percentage of germination increased by almost 20% compared to the untreated control), while the seed and seedling vigour was also positively affected. On the other hand, higher exposure times of CAPP generated in a nitrogen atmosphere significantly inhibited succinate dehydrogenase activity, but stimulated lactate and alcohol dehydrogenase activities, suggesting anoxygenic metabolism. It was also found that plasma exposure caused a slight increment in the level of primary DNA damage in ambient air- and oxygen-CAPP treatments, and more significant DNA damage was found in nitrogen-CAPP treatments. Although a higher level of DNA damage was also detected in the negative control (untreated seeds), this might be associated with the age of seeds followed by their lower germination capacity (with the germination percentage reaching only about 60%).

Gibberellic acid and nitrogen efficiently protect early seedlings growth stage from salt stress damage in Sorghum.

Abstract: Salinity one of environmental factor that limits the growth and productivity of crops. This research was done to investigate whether GA3 (0, 144.3, 288.7 and 577.5 μM) and nitrogen fertilizer (0, 90 and 135 kg N ha-1) could mitigate the negative impacts of NaCl (0, 100, and 200 mM NaCl) on emergence percentage, seedling growth and some biochemical parameters. The results showed that high salinity level decreased emergence percentage, seedling growth, relative water content, chlorophyll content (SPAD reading), catalase (CAT) and peroxide (POD), but increased soluble protein content, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. The SOD activity was decreased by nitrogen. However, the other measurements were increased by nitrogen. The interactive impact between nitrogen and salinity was significant in most parameters except EP, CAT and POD. The seedling length, dry weight, fresh weight, emergence percentage, POD, soluble protein and chlorophyll content were significantly affected by the interaction between GA3 and salinity. The GA3 and nitrogen application was successful mitigating the adverse effects of salinity. The level of 144.3 and 288.7 μm GA3 and the rate of 90 and 135 kg N ha-1 were most effective on many of the attributes studied. Our study suggested that GA3 and nitrogen could efficiently protect early seedlings growth from salinity damage.

Transmission of Seed and Soil Microbiota to Seedling

Abstract: The seed microbial community constitutes an initial inoculum for plant microbiota assembly. Still, the persistence of seed microbiota when seeds encounter soil during plant emergence and early growth is barely documented. We characterized the encounter event of seed and soil microbiota and how it structured seedling bacterial and fungal communities by using amplicon sequencing. We performed eight contrasting encounter events to identify drivers influencing seedling microbiota assembly. To do so, four contrasting seed lots of two Brassica napus genotypes were sown in two soils whose microbial diversity levels were manipulated by serial dilution and recolonization. Seedling root and stem microbiota were influenced by soil but not by initial seed microbiota composition or by plant genotype. A strong selection on the seed and soil communities occurred during microbiota assembly, with only 8% to 32% of soil taxa and 0.8% to 1.4% of seed-borne taxa colonizing seedlings. The recruitment of seedling microbiota came mainly from soil (35% to 72% of diversity) and not from seeds (0.3% to 15%). Soil microbiota transmission success was higher for the bacterial community than for the fungal community. Interestingly, seedling microbiota was primarily composed of initially rare taxa (from seed, soil, or unknown origin) and intermediate-abundance soil taxa. IMPORTANCE Seed microbiota can have a crucial role for crop installation by modulating dormancy, germination, seedling development, and recruitment of plant symbionts. Little knowledge is available on the fraction of the plant microbiota that is acquired through seeds. We characterize the encounter between seed and soil communities and how they colonize the seedling together. Transmission success and seedling community assemblage can be influenced by the variation of initial microbial pools, i.e., plant genotype and cropping year for seeds and diversity level for soils. Despite a supposed resident advantage of the seed microbiota, we show that transmission success is in favor of the soil microbiota. Our results also suggest that successful plant-microbiome engineering based on native seed or soil microbiota must include rare taxa.

Arabidopsis seedling establishment under waterlogging requires ABCG5-mediated formation of a dense cuticle layer

Abstract: Germination requires sufficient water absorption by seeds, but excessive water in the soil inhibits plant growth. We therefore hypothesized that tolerance mechanisms exist that help young seedlings survive and develop in waterlogged conditions. Many ATP-BINDING CASSETTE TRANSPORTER subfamily G (ABCG) proteins protect terrestrial plants from harsh environmental conditions. To establish whether any of these proteins facilitate plant development under waterlogged conditions, we observed the early seedling growth of many ABCG transporter mutants under waterlogged conditions. abcg5 seedlings exhibited severe developmental problems under waterlogged conditions: the shoot apical meristem was small, and the seedling failed to develop true leaves. The seedlings had a high water content and reduced buoyancy on water, suggesting that they were unable to retain air spaces on and inside the plant. Supporting this possibility, abcg5 cotyledons had increased cuticle permeability, reduced cuticular wax contents, and a much less dense cuticle layer than the wild-type. These results indicate that proper development of plants under waterlogged conditions requires the dense cuticle layer formed by ABCG5 activity.

Seed Halo-Priming Improves Seedling Vigor, Grain Yield, and Water Use Efficiency of Maize under Varying Irrigation Regimes

Abstract: Water-deficit stress poses tremendous constraints to sustainable agriculture, particularly under abrupt climate change. Hence, it is crucial to find eco-friendly approaches to ameliorate drought tolerance, especially for sensitive crops such as maize. This study aimed at assessing the impact of seed halo-priming on seedling vigor, grain yield, and water use efficiency of maize under various irrigation regimes. Laboratory trials evaluated the influence of seed halo-priming using two concentrations of sodium chloride solution, 4000 and 8000 ppm NaCl, versus unprimed seeds on seed germination and seedling vigor parameters. Field trials investigated the impact of halo-priming treatments on maize yield and water use efficiency (WUE) under four irrigation regimes comprising excessive (120% of estimated crop evapotranspiration, ETc), normal (100% ETc), and deficit (80 and 60% ETc) irrigation regimes. Over-irrigation by 20% did not produce significantly more grain yield but considerably reduced WUE. Deficit irrigation (80 and 60%ETc) gradually reduced grain yield and its attributes. Halo-priming treatments, particularly 4000 ppm NaCl, improved uniformity and germination speed, increased germination percentage and germination index, and produced more vigorous seedlings with heavier dry weight compared with unprimed seeds. Under field conditions, the plants originated from halo-primed seeds, especially with 4000 ppm NaCl, had higher grain yield and WUE compared with unprimed seeds under deficit irrigation regimes. The long-lasting stress memory induced by seed halo-priming, particularly with 4000 ppm NaCl, promoted maize seedling establishment, grain yield, and WUE and consequently mitigated the devastating impacts of drought stress.

Chromium (VI)-Induced Alterations in Physio-Chemical Parameters, Yield, and Yield Characteristics in Two Cultivars of Mungbean (Vigna radiata L.).

Abstract: Chromium (Cr) presently used in various major industries and its residues possess a potent environmental threat. Contamination of soil and water resources due to Cr ions and its toxicity has adversely affected plant growth and crop productivity. Here, deleterious effects of different levels of Cr (VI) treatments i.e., 0, 30, 60, 90, and 120 μM on two mungbean cultivars, Pusa Vishal (PV) and Pusa Ratna (PR), in hydroponic and pot conditions were evaluated. Germination, seedling growth, biomass production, antioxidant enzyme, electrolytic leakage, oxidative stress (hydrogen peroxide and malondialdehyde), and proline content were determined to evaluate the performance of both cultivars under hydroponic conditions for 15 days. The hydroponic results were further compared with the growth and seed yield attributes of both the genotypes in pot experiments performed over 2 years. Seedling growth, biomass production, total chlorophyll (Chl), Chl-a, Chl-b, nitrogen content, plant height, seed protein, and seed yield decreased significantly under the 120 μM Cr stress level. Activities of antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase and peroxidase increased in the leaves following Cr exposure at 60-90 μM but declined at 120 μM. Cr-induced reductions in growth and seed yield attributes were more in the sensitive than in the tolerant cultivar. Cr accumulation in the roots, stems, leaves, and seeds increased with an increase in Cr concentrations in the pot conditions. Furthermore, for both cultivars, there were significant negative correlations in morpho-physiological characteristics under high Cr concentrations. Overall results suggest that (PR) is more sensitive to Cr stress (PV) at the seedling stage and in pot conditions. Furthermore, (PV) can be utilized to study the mechanisms of Cr tolerance and in breeding programs to develop Cr-resistant varieties.

Allelopathic effect of Artemisia argyi on the germination and growth of various weeds.

Abstract: Allelopathy means that one plant produces chemical substances to affect the growth and development of other plants. Usually, allelochemicals can stimulate or inhibit the germination and growth of plants, which have been considered as potential strategy for drug development of environmentally friendly biological herbicides. Obviously, the discovery of plant materials with extensive sources, low cost and markedly allelopathic effect will have far-reaching ecological impacts as the biological herbicide. At present, a large number of researches have already reported that certain plant-derived allelochemicals can inhibit weed growth. In this study, the allelopathic effect of Artemisia argyi was investigated via a series of laboratory experiments and field trial. Firstly, water-soluble extracts exhibited the strongest allelopathic inhibitory effects on various plants under incubator conditions, after the different extracts authenticated by UPLC-Q-TOF-MS. Then, the allelopathic effect of the A. argyi was systematacially evaluated on the seed germination and growth of Brassica pekinensis, Lactuca sativa, Oryza sativa, Portulaca oleracea, Oxalis corniculata and Setaria viridis in pot experiments, it suggested that the A. argyi could inhibit both dicotyledons and monocotyledons not only by seed germination but also by seedling growth. Furthermore, field trial showed that the A. argyi significantly inhibited the growth of weeds in Chrysanthemum morifolium field with no adverse effect on the growth of C. morifolium. At last, RNA-Seq analysis and key gene detection analysis indicated that A.argyi inhibited the germination and growth of weed via multi-targets and multi-paths while the inhibiting of chlorophyll synthesis of target plants was one of the key mechanisms. In summary, the A. argyi was confirmed as a potential raw material for the development of preventive herbicides against various weeds in this research. Importantly, this discovery maybe provide scientific evidence for the research and development of environmentally friendly herbicides in the future.