Showing papers on "Seedling published in 2019"

Heavy metal-induced oxidative stress on seed germination and seedling development: a critical review.

Abstract: Heavy metal contamination in soils can influence plants and animals, often leading to toxicosis. Heavy metals can impact various biochemical processes in plants, including enzyme and antioxidant production, protein mobilization and photosynthesis. Hydrolyzing enzymes play a major role in seed germination. Enzymes such as acid phosphatases, proteases and α-amylases are known to facilitate both seed germination and seedling growth via mobilizing nutrients in the endosperm. In the presence of heavy metals, starch is immobilized and nutrient sources become limited. Moreover, a reduction in proteolytic enzyme activity and an increase in protein and amino acid content can be observed under heavy metal stress. Proline, is an amino acid which is essential for cellular metabolism. Numerous studies have shown an increase in proline content under oxidative stress in higher plants. Furthermore, heat shock protein production has also been observed under heavy metal stress. The chloroplast small heat shock proteins (Hsp) reduce photosynthesis damage, rather than repair or help to recover from heavy metal-induced damage. Heavy metals are destructive substances for photosynthesis. They are involved in destabilizing enzymes, oxidizing photosystem II (PS II) and disrupting the electron transport chain and mineral metabolism. Although the physiological effects of Cd have been investigated thoroughly, other metals such as As, Cr, Hg, Cu and Pb have received relatively little attention. Among agricultural plants, rice has been studied extensively; additional studies are needed to characterize toxicities of different heavy metals on other crops. This review summarizes the current state of our understanding of the effects of heavy metal stress on seed germination and seedling development and highlights informational gaps and areas for future research.

High temperature and drought stress cause abscisic acid and reactive oxygen species accumulation and suppress seed germination growth in rice

Abstract: Seed germination is one of the most important biological processes in the life cycle of plants, and temperature and water are the two most critical environmental factors that influence seed germination. In the present study, we investigated the roles of the plant hormone abscisic acid (ABA) and reactive oxygen species (ROS) in high temperature (HT) and drought-induced inhibition of rice seed germination. HT and drought stress caused ABA accumulation in seeds and inhibited seed germination and seedling establishment. Quantitative real-time polymerase chain reaction analysis revealed that HT and drought stress induced the expression of OsNCED3, a key gene in ABA synthesis in rice seeds. In addition, ROS (O2•- and H2O2) and malondialdehyde contents were increased in germinating seeds under HT and drought stress. Moreover, we adopted the non-invasive micro-test technique to detect H2O2 and Ca2+ fluxes at the site of coleoptile emergence. HT and drought stress resulted in a H2O2 efflux, but only drought stress significantly induced Ca2+ influx. Antioxidant enzyme assays revealed that superoxide dismutase (SOD), peroxidase, catalase (CAT), and ascorbate peroxidase (APX) activity were reduced by HT and drought stress, consistent with the expression of OsCu/ZnSOD, OsCATc, and OsAPX2 during seed germination. Altogether, these results suggest that ABA and ROS accumulation under HT and drought conditions can inhibit rice seed germination and growth.

A quantitative trait locus, qSE3, promotes seed germination and seedling establishment under salinity stress in rice.

Abstract: Seed germination is a complex trait determined by both quantitative trait loci (QTLs) and environmental factors and also their interactions. In this study, we mapped one major QTLqSE3 for seed germination and seedling establishment under salinity stress in rice. To understand the molecular basis of this QTL, we isolated qSE3 by map-based cloning and found that it encodes a K+ transporter gene, OsHAK21. The expression of qSE3 was significantly upregulated by salinity stress in germinating seeds. Physiological analysis suggested that qSE3 significantly increased K+ and Na+ uptake in germinating seeds under salinity stress, resulting in increased abscisic acid (ABA) biosynthesis and activated ABA signaling responses. Furthermore, qSE3 significantly decreased the H2 O2 level in germinating seeds under salinity stress. All of these seed physiological changes modulated by qSE3 might contribute to seed germination and seedling establishment under salinity stress. Based on analysis of single-nucleotide polymorphism data of rice accessions, we identified a HAP3 haplotype of qSE3 that was positively correlated with seed germination under salinity stress. This study provides important insights into the roles of qSE3 in seed germination and seedling establishment under salinity stress and facilitates the practical use of qSE3 in rice breeding.

Effects of Two Trichoderma Strains on Plant Growth, Rhizosphere Soil Nutrients, and Fungal Community of Pinus sylvestris var. mongolica Annual Seedlings

Abstract: Trichoderma spp. are proposed as major plant growth-promoting fungi that widely exist in the natural environment. These strains have the abilities of rapid growth and reproduction and efficient transformation of soil nutrients. Moreover, they can change the plant rhizosphere soil environment and promote plant growth. Pinus sylvestris var. mongolica has the characteristics of strong drought resistance and fast growth and plays an important role in ecological construction and environmental restoration. The effects on the growth of annual seedlings, root structure, rhizosphere soil nutrients, enzyme activity, and fungal community structure of P. sylvestris var. mongolica were studied after inoculation with Trichoderma harzianum E15 and Trichoderma virens ZT05, separately. The results showed that after inoculation with T. harzianum E15 and T. virens ZT05, seedling biomass, root structure index, soil nutrients, and soil enzyme activity were significantly increased compared with the control (p < 0.05). There were significant differences in the effects of T. harzianum E15 and T. virens ZT05 inoculation on the growth and rhizosphere soil nutrient of P. sylvestris var. mongolica (p < 0.05). For the E15 treatment, the seedling height, ground diameter, and total biomass of seedlings were higher than that those of the ZT05 treatment, and the rhizosphere soil nutrient content and enzyme activity of the ZT05 treatment were higher than that of the E15 treatment. The results of alpha and beta diversity analyses showed that the fungi community structure of rhizosphere soil was significantly different (p < 0.05) among the three treatments (inoculated with T. harzianum E15, T. virens ZT05, and not inoculated with Trichoderma). Overall, Trichoderma inoculation was correlated with the change of rhizosphere soil nutrient content.

Treatment of Common Sunflower (Helianthus annus L.) Seeds with Radio-frequency Electromagnetic Field and Cold Plasma Induces Changes in Seed Phytohormone Balance, Seedling Development and Leaf Protein Expression.

Abstract: Treatment of plant seeds with electromagnetic fields or non-thermal plasmas aims to take advantage of plant functional plasticity towards stimulation of plant agricultural performance. In this study, the effects of pre-sowing seed treatment using 200 Pa vacuum (7 min), 5.28 MHz radio-frequency cold plasma (CP −2, 5, and 7 min) and electromagnetic field (EMF −5, 10, 15 min) on seed germination kinetics, content of phytohormones, morphometric parameters of seedlings and leaf proteome were assessed. CP 7 min and EMF 15 min treatments caused 19–24% faster germination in vitro; germination in the substrate was accelerated by vacuum (9%) and EMF 15 min (17%). The stressors did not change the seed germination percentage, with exception of EMF 5 min treatment that caused a decrease by 7.5%. Meanwhile both CP 7 min and EMF 15 min treatments stimulated germination, but the EMF treatment resulted in higher weight of leaves. Stressor-specific changes in phytohormone balance were detected in seeds: vacuum treatment decreased zeatin amount by 39%; CP treatments substantially increased gibberellin content, but other effects strongly varied with the treatment duration; the abscisic acid content was reduced by 55–60% after the EMF treatment. Analysis of the proteome showed that short exposure of seeds to the EMF or CP induced a similar long-term effect on gene expression in leaves, mostly stimulating expression of proteins involved in photosynthetic processes and their regulation.

A Mobile Auxin Signal Connects Temperature Sensing in Cotyledons with Growth Responses in Hypocotyls

Abstract: Plants have a remarkable capacity to adjust their growth and development to elevated ambient temperatures. Increased elongation growth of roots, hypocotyls, and petioles in warm temperatures are hallmarks of seedling thermomorphogenesis. In the last decade, significant progress has been made to identify the molecular signaling components regulating these growth responses. Increased ambient temperature utilizes diverse components of the light sensing and signal transduction network to trigger growth adjustments. However, it remains unknown whether temperature sensing and responses are universal processes that occur uniformly in all plant organs. Alternatively, temperature sensing may be confined to specific tissues or organs, which would require a systemic signal that mediates responses in distal parts of the plant. Here, we show that Arabidopsis (Arabidopsis thaliana) seedlings show organ-specific transcriptome responses to elevated temperatures and that thermomorphogenesis involves both autonomous and organ-interdependent temperature sensing and signaling. Seedling roots can sense and respond to temperature in a shoot-independent manner, whereas shoot temperature responses require both local and systemic processes. The induction of cell elongation in hypocotyls requires temperature sensing in cotyledons, followed by the generation of a mobile auxin signal. Subsequently, auxin travels to the hypocotyl, where it triggers local brassinosteroid-induced cell elongation in seedling stems, which depends upon a distinct, permissive temperature sensor in the hypocotyl.

The Rice Alpha-Amylase, Conserved Regulator of Seed Maturation and Germination

Abstract: Alpha-amylase, the major form of amylase with secondary carbohydrate binding sites, is a crucial enzyme throughout the growth period and life cycle of angiosperm. In rice, alpha-amylase isozymes are critical for the formation of the storage starch granule during seed maturation and motivate the stored starch to nourish the developing seedling during seed germination which will directly affect the plant growth and field yield. Alpha-amylase has not yet been studied intensely to understand its classification, structure, expression trait, and expression regulation in rice and other crops. Among the 10-rice alpha-amylases, most were exclusively expressed in the developing seed embryo and induced in the seed germination process. During rice seed germination, the expression of alpha-amylase genes is known to be regulated negatively by sugar in embryos, however positively by gibberellin (GA) in endosperm through competitively binding to the specific promoter domain; besides, it is also controlled by a series of other abiotic or biotic factors, such as salinity. In this review, we overviewed the research progress of alpha-amylase with focus on seed germination and reflected on how in-depth work might elucidate its regulation and facilitate crop breeding as an efficient biomarker.

Effects of Severe Water Stress on Maize Growth Processes in the Field

Abstract: In this study, we investigated the effects of water stress on the growth and yield of summer maize (Zea mays L.) over four phenological stages: Seedling, jointing, heading, and grain-filling. Water stress treatments were applied during each of these four stages in a water-controlled field in the Guanzhong Plain, China between 2013 and 2016. We found that severe water stress during the seedling stage had a greater effect on the growth and development of maize than stress applied during the other three stages. Water stress led to lower leaf area index (LAI) and biomass owing to reduced intercepted photosynthetically active radiation (IPAR) and radiation-use efficiency (RUE). These effects extended to the reproductive stage and eventually reduced the unit kernel weight and yield. In addition, the chlorophyll content in the leaf remained lower, even though irrigation was applied partially or fully after the seedling stage. Severe and prolonged water stress in maize plants during the seedling stage may damage the structure of the photosynthetic membrane, resulting in lower chlorophyll content, and therefore RUE, than those in the plants that did not experience water stress at the seedling stage. Maize plants with such damage did not show a meaningful recovery even when irrigation levels during the rest of the growth period were the same as those applied to the plants not subjected to water stress. The results of our field experiments suggest that an unrecoverable yield loss could occur if summer maize were exposed to severe and extended water stress events during the seedling stage.

Seedling traits predict drought-induced mortality linked to diversity loss.

Abstract: Trait-based approaches are increasingly used to predict ecological consequences of climate change, yet seldom have solid links been established between plant traits and observed climate-driven community changes. Most analyses have focused on aboveground adult plant traits, but in warming and drying climates, root traits may be critical, and seedlings may be the vulnerable stage. Relationships of seedling and root traits to more commonly measured traits and ecological outcomes are poorly known. In an annual grassland where winter drought-induced seedling mortality is driving a long-term decline in native diversity, using a field experiment during the exceptionally dry winter of 2017-2018, we found that seedling mortality was higher and growth of seedlings and adults were lower in unwatered than watered sites. Mortality of unwatered seedlings was higher in species with shorter seedling roots, and also in species with the correlated traits of small seeds, high seedling specific leaf area (SLA), and tall seedlings. Adult traits varied along an axis from short-stature, high SLA and foliar N, and early flowering to the opposite values, and were only weakly correlated with seedling traits and seedling mortality. No evidence was found for adaptive plasticity, such as longer roots or lower SLA in unwatered plants. Among these species, constitutive variation in seedling root length explained most of the variation in survival of a highly vulnerable life stage under winter drought. Selective loss of species with high adult SLA, observed in this community and others under drought stress, may be the byproduct of other correlated traits.

Origins of abrupt change? Postfire subalpine conifer regeneration declines nonlinearly with warming and drying

Abstract: Robust tree regeneration following high‐severity wildfire is key to the resilience of subalpine and boreal forests, and 21st century climate could initiate abrupt change in forests if postfire temperature and soil moisture become less suitable for tree seedling establishment. Using two widespread conifer species, lodgepole pine (Pinus contorta var. latifolia) and Douglas‐fir (Pseudotsuga menziesii var. glauca), we conducted complementary experiments to ask (1) How will projected early‐ to mid‐21st‐century warming and drying affect postfire tree seedling establishment and mortality? (2) How does early seedling growth differ between species and vary with warming and drying? With a four‐year in situ seed‐planting experiment and a one growing season controlled‐environment experiment, we explored effects of climate on tree seedling establishment, growth, and survival and identified nonlinear responses to temperature and soil moisture. In our field experiment, warmer and drier conditions, consistent with mid‐21ˢᵗ‐century projections, led to a 92% and 76% reduction in establishment of lodgepole pine and Douglas‐fir. Within three years, all seedlings that established under warmer conditions died, as might be expected at lower elevations and lower latitudes of species’ ranges. Seedling establishment and mortality also varied with aspect; approximately 1.7 times more seedlings established on mesic vs. xeric aspects, and fewer seedlings died. In the controlled‐environment experiment, soil temperatures were 2.0°–5.5°C cooler than the field experiment, and warming led to increased tree seedling establishment, as might be expected at upper treeline or higher latitudes. Lodgepole pine grew taller than Douglas‐fir and produced more needles with warming. Douglas‐fir grew longer roots relative to shoots, compared with lodgepole pine, particularly in dry soils. Differences in early growth between species may mediate climate change effects on competitive interactions, successional trajectories, and species distributions. This study demonstrates that climate following high‐severity fire exerts strong control over postfire tree regeneration in subalpine conifer forests. Climate change experiments, such as those reported here, hold great potential for identifying mechanisms that could underpin fundamental ecological change in 21st‐century ecosystems.

Drought stress has transgenerational effects on soybean seed germination and seedling vigor.

Abstract: Effects of environmental stressors on the parent may be transmitted to the F1 generation of plants that support global food, oil, and energy production for humans and animals. This study was conducted to determine if the effects of drought stress on parental soybean plants are transmitted to the F1 generation. The germination and seedling vigor of F1 soybean whose maternal parents, Asgrow AG5332 and Progeny P5333RY, were exposed to soil moisture stress, that is, 100, 80, 60, 40, and 20% replacement of evapotranspiration (ET) during reproductive growth, were evaluated under controlled conditions. Pooled over cultivars, effects of soil moisture stress on the parents caused a reduction in the seed germination rate, maximum seed germination, and overall seedling performance in the F1 generation. The effect of soil moisture stress on the parent environment induced seed quality that carried on the F1 generation seed gemination and seedling traits under optimum conditions and further exasperated when exposed to increasing levels of drought stress. Results indicate that seed weight and storage reserve are key factors positively associated with germination traits and seedling growth. Our data confirm that the effects of soil moisture stress on soybean are transferable, causing reduced germination, seedling vigor, and seed quality in the F1 generation. Therefore, optimal water supply during soybean seed formation period may be beneficial for seed producers in terms of optimizing seed quality and vigor characteristics of commodity seed.

Morpho-physiological and biochemical responses of tolerant and sensitive rapeseed cultivars to drought stress during early seedling growth stage

Abstract: The edible oil production in China is highly dependent on the screening and development of drought-resistant rapeseed cultivars especially in water stress areas. However, for the successful production of rapeseed, germination and early seedling growth is the key steps under drought stress, which are not fully understood up till now. To better predict about the adoption of rapeseed cultivars to drought stress, the current study explored the presumed roles of enzymatic, non-enzymatic antioxidants and osmolytes in improving drought tolerance in rapeseed. The comparative analysis in terms of germination and early sprouting growth of six rapeseed cultivars was assessed under normal (0.00 MPa) and osmotic stresses (− 0.1, − 0.2, − 0.3, − 0.4, and − 0.5 MPa simulated by polyethylene glycol 6000). Subsequently, based on the process of germination and early sprouting growth, Shenguang 127 (SG 127) and Zhongyou 36 (ZY 36) were chosen as drought-tolerant and -sensitive rapeseed varieties, correspondingly and further evaluated under − 0.3 MPa osmotic stresses. The results indicated that drought stress rigorously hindered germination and early seedling growth of rapeseed cultivars. On the other hand, SG 127 exhibited less reduction in seedling growth paralleled with ZY 36. SG 127 revealed lower levels of hydrogen peroxide (H2O2), lipids peroxidation (MDA), electrolyte leakage (EL %) and less reduction in chlorophyll (Chl) content than ZY 36. The drought tolerance of SG 127 may be correlated with enhanced activities of enzymatic (superoxide peroxidase, catalase, and dismutase), non-enzymatic antioxidants (ascorbic acid, glutathione), more accumulation of proline; total soluble sugar and total soluble protein. Furthermore, our study highlighted the significance of enzymatic and non-enzymatic antioxidants and osmolytes in the establishment of rapeseed seedlings under drought stress. Nevertheless, the better knowledge is crucial to be further investigated on genomic and molecular basis to deeply insight the detail mechanisms of drought tolerance in rapeseed.

Atmospheric-pressure plasma treated water for seed germination and seedling growth of mung bean and its sterilization effect on mung bean sprouts

Abstract: Plasma treated water (PTW), produced by atmospheric-pressure plasma treatment of water, usually contains various reactive oxygen and nitrogen species (RONS). This study aimed at evaluating the effectiveness of different types of PTW on seed germination, seedling growth and microbial sterilization during the germinated mung bean processing. Results showed that air-PTW possessed outstanding abilities in improving seed germination and seedling growth with a germination index of 95.50% and a vigor index of 1146.64, and in microbial decontamination. The physicochemical properties of the PTW were analyzed to better understand the PTW stressed germination. Some physiological parameters like the activity of superoxide dismutase (SOD), the contents of malondialdehyde (MDA) and phytohormone (indole acetic acid (IAA) and abscisic acid (ABA)) during germination were also evaluated. This study suggested that air-PTW treatment could indeed provide a green and effective mean of stimulating seed germination and plant growth, and thus accelerate the growth cycle. Industrial relevance Increasing the production of food by using both economical and environmentally friendly means has been deemed as an urgent matter to sustain the food demand of rapidly growing world population. The results of this study suggest that PTW presents a great opportunity to address this need by increasing seedling growth and viability. PTW treatment is an environment-friendly and low-cost mean of stimulating seed germination and plant growth, which possesses the potential of scale up or industrial applications in relevant fields.

Phosphate-Solubilizing Pseudomonas sp. Strain P34-L Promotes Wheat Growth by Colonizing the Wheat Rhizosphere and Improving the Wheat Root System and Soil Phosphorus Nutritional Status

Abstract: Rhizosphere colonization is a requirement for field applications of plant growth-promoting rhizobacteria (PGPR). Complex signal exchanges and mutual recognition occur between microbes and plants. Here, the phosphate-solubilizing strain Pseudomonas sp. P34, which is a type of PGPR with affinity to wheat, was isolated from a wheat rhizosphere via wheat germ agglutinin. A pTR102 plasmid harboring the luciferase luxAB gene was transferred into P34. The labeled strain (P34-L) was then used to track the temporal and spatial characteristics of rhizosphere colonization and examine the effects of colonization on wheat development. The transcript levels of the phosphate transporter gene TaPT4, a phosphorus deficiency indicator, in wheat roots were monitored by quantitative reverse transcription PCR (qRT-PCR). The results indicated that P34-L could survive within the wheat rhizosphere for a long time and colonize new spaces in the wheat rhizosphere following the elongation of wheat roots. Compared with uninoculated wheat plants, plants inoculated with P34-L exhibited significantly increased phosphorus accumulation in the leaves; seedling and root weight; total root length; root projection area; root surface area; and number of root tips, forks, and crossings, thus demonstrating the great value of applying this strain in wheat production by promoting root growth and dry matter accumulation. The downregulation of TaPT4 transcript levels in the wheat roots also suggested that a high-phosphorus environment was established by P34-L. These results lay a foundation for further research on the relationships between PGPR and their host plants. Moreover, a potentially ideal biofertilizer-producing strain for use in sustainable agriculture was developed.

DA-6 promotes germination and seedling establishment from aged soybean seeds by mediating fatty acid metabolism and glycometabolism.

Abstract: Soybean seeds contain higher concentrations of oil (triacylglycerol) and fatty acids than do cereal crop seeds, and the oxidation of these biomolecules during seed storage significantly shortens seed longevity and decreases germination ability. Here, we report that diethyl aminoethyl hexanoate (DA-6), a plant growth regulator, increases germination and seedling establishment from aged soybean seeds by increasing fatty acid metabolism and glycometabolism. Phenotypic analysis showed that DA-6 treatment markedly promoted germination and seedling establishment from naturally and artificially aged soybean seeds. Further analysis revealed that DA-6 increased the concentrations of soluble sugars during imbibition of aged soybean seeds. Consistently, the concentrations of several different fatty acids in DA-6-treated aged seeds were higher than those in untreated aged seeds. Subsequently, quantitative PCR analysis indicated that DA-6 induced the transcription of several key genes involved in the hydrolysis of triacylglycerol to sugars in aged soybean seeds. Furthermore, the activity of invertase in aged seeds, which catalyzes the hydrolysis of sucrose to form fructose and glucose, increased following DA-6 treatment. Taken together, DA-6 promotes germination and seedling establishment from aged soybean seeds by enhancing the hydrolysis of triacylglycerol and the conversion of fatty acids to sugars.

Research on the Physio-Biochemical Mechanism of Non-Thermal Plasma-Regulated Seed Germination and Early Seedling Development in Arabidopsis.

Abstract: Non-thermal plasma holds great potentials as an efficient, economical, and eco-friendly seed pretreatment method for improving the seed germination and seedling growth, but the mechanisms are still unclear. Therefore, a plant model organism Arabidopsis thaliana was used to investigate the physio-biochemical responses of seeds to non-thermal plasma at different treatment times by measuring the plant growth parameters, redox-related parameters, calcium (Ca2+) level and physicochemical modification of seed surface. The results showed that short-time plasma treatment (0.5, 1, and 3 min) promoted seed germination and seedling growth, whereas long-time plasma treatment (5 and 10 min) exhibited inhibitory effects. The level of superoxide anion (O2 •-) and nitric oxide (NO) and the intensity of infrared absorption of the hydroxyl group were significantly higher in short-time plasma treated Arabidopsis seeds, and the level of hydrogen peroxide (H2O2) was remarkably increased in long-time plasma treated seeds, indicating that O2 •-, ·OH, and NO induced by plasma may contribute to breaking seed dormancy and advancing seed germination in Arabidopsis, while plasma-induced H2O2 may inhibit the seed germination. The intensity of hydroxyl group and the contents of H2O2, malondialdehyde, and Ca2+ in Arabidopsis seedlings were obviously increased with the plasma treatment time. Catalase, superoxide dismutase, and peroxidase activities as well as proline level in short-time treated seedlings were apparently higher than in control. The etching effects of plasma on seed surface were dose-dependent, spanning from slight shrinkages to detached epidermis, which also significantly increased the oxidation degree of seed surface. Therefore, the improved activities of antioxidant systems, moderate ·OH, H2O2, and Ca2+ accumulation and seed surface modification induced by plasma all contribute to the enhanced seedling growth of Arabidopsis after short-time plasma treatment.

Advances in the Concept and Methods of Seed Priming

Abstract: The critical stages during the growth of crops are the uniform seed germination, early seedling growth, and uniform plant stand. Low crop yield is attributed to uneven seed germination and seedling growth. Therefore, the quality of seed can be improved through priming in addition to the field management techniques for better seed germination. Priming is a physiological technique of seed hydration and drying to enhance the pregerminative metabolic process for rapid germination, seedling growth, and final yield under normal as well as stressed conditions. The primed seeds show faster and uniform seed germination due to different enzyme activation, metabolic activities, biochemical process of cell repair, protein synthesis, and improvement of the antioxidant defense system as compared to unprimed seeds. There are many techniques of seed priming which are broadly divided into conventional methods (hydro-priming, osmo-priming, nutrient priming, chemical priming, bio-priming, and priming with plant growth regulators) and advanced methods (nano-priming and priming with physical agents). However, priming is strongly affected by various factors such as temperature, aeration, light, priming duration, and seed characteristics. This chapter highlights the priming mechanism and the available technologies as a tool for superficial seed germination and crop stand. An experiment with reference to the importance of priming toward vigor seed germination and seedling growth was conducted, and its results have been added in this chapter.

Influence of Heavy Metals on Seed Germination and Seedling Growth of Wheat, Pea, and Tomato

Abstract: Experiments were conducted under lead (Pb), cadmium (Cd), and copper (Cu) exposure to observe germination and seedling growth of wheat (Triticum aestivum L), pea (Pisum sativum), and tomato (Solanum lycopersicum L.). Metals were applied in five concentrations (20, 65, 110, 175, and 220 ppm) and Hoagland solution was used to feed the seedlings. Irrespective of the tested crop seeds, copper revealed maximum effect (51.2%) on germination followed by lead (47.5%) and cadmium (35.3%). Tomato seeds were most sensitive in germination stage followed by pea and wheat. In seedling stage, tomato also showed highest sensitivity to both Cd and Cu. However, pea seedlings showed higher tolerance to Pb and wheat seedlings had the highest tolerance to both Cu and Cd. Toxicity and tolerance of metals was found to vary with crops and growth stages. Higher transfer of metals (Pb, Cd, and Cu) in wheat seedling indicates higher risk of food chain contamination when grown in polluted soil. Higher mobility and uptake of Cd in tomato and wheat seedlings even under lower concentration of exposure needs further study.

Rice seed priming with sodium selenate: Effects on germination, seedling growth, and biochemical attributes

Abstract: The aim of this study was to determine the effects of sodium selenate (15, 30, 45, 60, 75, 90, and 105 mg kg−1) on the germination and seedling growth of Changnongjing 1 rice (Oryza sativa L.) at 25 °C and 30 °C. Low selenate concentrations induced shorter and more uniform germination periods than did ultrapure water at both temperatures. Seedlings primed with low selenate concentrations were superior to those primed with ultrapure water in terms of plant height, fresh weight, dry matter accumulation, and soluble carbohydrate and protein contents. Lower selenate concentrations (15–75 mg kg−1) induced higher chlorophyll and phenol contents in seedlings than did ultrapure water. Lower selenate concentrations also increased the superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), and glutathione peroxidase (GPx) contents in seedlings and significantly decreased the stress-related malondialdehyde (MDA) content compared to ultrapure water. In conclusion, rice seedling germination and growth were promoted by priming with low selenate concentrations (15–75 mg kg−1) but inhibited by priming with high selenate concentrations (90–105 mg kg−1).

Physiological mechanisms of exogenous calcium on alleviating salinity-induced stress in rice (Oryza sativa L.)

Abstract: Being more sensitive to salt stress among the cereals, growth of rice (Oryza sativa L.) has been habitually affected by salinity. Although, several practices have evolved to sustain the growth of rice under salinity, the enormous role of calcium (Ca2+) as a signalling molecule in salt stress mitigation is still arcane. Considering this fact, an experiment was performed aiming to explicate the mechanism of salt-induced growth inhibition in rice and its alleviation by exogenous Ca2+. At germination stage, 10 mM and 15 mM CaCl2 primed rice (cv. Binadhan-10 & Binadhan-7) seeds were grown in petri dishes for 9 days under 100 mM NaCl stress. At seedling stage, 9-day-old rice seedlings grown on sand were exposed to 100 mM NaCl alone and combined with 10 mM and 15 mM CaCl2 for 15 days. This research revealed that salinity radically slowed down growth of rice seedlings and Ca2+ treatment noticeably improved growth performances. At germination stage, 10 mM CaCl2 treatment significantly increased the final germination percentage, germination rate index (in Binadhan-7), shoot, root length (89.20, 67.58% in Bindhan-10 & 84.72, 31.15% in Bindhan-7) and biomass production under salinity. Similarly, at seedling stage, 10 mM CaCl2 supplementation in salt-stressed plants enhanced shoot length (42.17, 28.76%) and shoot dry weight (339.52, 396.20%) significantly in Binadhan-10 & Binadhan-7, respectively, but enhanced root dry weight (36.76%) only in Binadhan-10. In addition, 10 mM CaCl2 supplementation on salt-stressed seedlings increased the chlorophyll and proline content, and oppressed the accretion of reactive oxygen species thus protecting from oxidative damage more pronouncedly in Binadhan-10 than Binadhan-7 as reflected by the elevated levels of catalase and ascorbate peroxidase activity. The 15 mM CaCl2 somehow also enhanced some growth parameters but overall was less effective than 10 mM CaCl2 to alleviate salt stress, and sometimes showed negative effect. Therefore, supplementary application of calcium-rich fertilizers in saline prone soils can be an effective approach to acclimatize salt stress and cultivate rice successfully.