Catalase is a key enzyme in seed recovery from ageing during priming

Cytological structures and physiological and biochemical characteristics of covered oat (Avena sativa L.) and naked oat (Avena nuda L.) seeds during high-temperature artificial aging

BACKGROUND

Seed aging, a natural and inevitable process occurring during storage. Oats, an annual herb belonging to the Gramineae family and pooideae. In addition to being a healthy food, oats serve as ecological pastures, combating soil salinization and desertification. They also play a role in promoting grassland agriculture and supplementing winter livestock feed. However, the high lipid and fat derivatives contents of oat seeds make them susceptible to deterioration, as fat derivatives are prone to rancidity, affecting oat seed production, storage, development, and germplasm resource utilization. Comparative studies on the effects of aging on physiology and cytological structure in covered and naked oat seeds are limited. Thus, our study aimed to determine the mechanism underlying seed deterioration in artificially aged 'LongYan No. 3' (A. sativa) and 'BaiYan No. 2' (A. nuda) seeds, providing a basis for the physiological evaluation of oat seed aging and serving as a reference for scientifically safe storage and efficient utilization of oats.

RESULTS

In both oat varieties, superoxide dismutase and catalase activities in seeds showed increasing and decreasing trends, respectively. Variance analysis revealed significant differences and interaction in all measured indicators of oat seeds between the two varieties at different aging times. 'LongYan No. 3' seeds, aged for 24-96 h, exhibited a germination rate of < 30%, Conductivity, malondialdehyde, soluble sugar, and soluble protein levels increased more significantly than the 'BaiYan No. 2'. With prolonged aging leading to cell membrane degradation, reactive oxygen species accumulation, disrupted antioxidant enzyme system, evident embryo cell swelling, and disordered cell arrangement, blocking the nutrient supply route. Simultaneously, severely concentrated chromatin in the nucleus, damaged mitochondrial structure, and impaired energy metabolism were noted, resulting in the loss of 'LongYan No. 3' seed vitality and value. Conversely, 'BaiYan No. 2' seeds showed a germination rate of 73.33% after 96 h of aging, consistently higher antioxidant enzyme activity during aging, normal embryonic cell shape, and existence of the endoplasmic reticulum.

CONCLUSIONS

ROS accumulation and antioxidant enzyme system damage in aged oat seeds, nuclear chromatin condensation, mitochondrial structure damage, nucleic acid metabolism and respiration weakened, oat seed vigor decreased. 'LongYan No. 3' seeds were more severely damaged under artificial aging than 'BaiYan No. 2' seeds, highlighting their heightened susceptibility to aging effects.

Seed longevity and genome damage

Seeds are the mode of propagation for most plant species and form the basis of both agriculture and ecosystems. Desiccation tolerant seeds, representative of most crop species, can survive maturation drying to become metabolically quiescent. The desiccated state prolongs embryo viability and provides protection from adverse environmental conditions, including seasonal periods of drought and freezing often encountered in temperate regions. However, the capacity of the seed to germinate declines over time and culminates in the loss of seed viability. The relationship between environmental conditions (temperature and humidity) and the rate of seed deterioration (ageing) is well defined, but less is known about the biochemical and genetic factors that determine seed longevity. This review will highlight recent advances in our knowledge that provide insight into the cellular stresses and protective mechanisms that promote seed survival, with a focus on the roles of DNA repair and response mechanisms. Collectively, these pathways function to maintain the germination potential of seeds. Understanding the molecular basis of seed longevity provides important new genetic targets for the production of crops with enhanced resilience to changing climates and knowledge important for the preservation of plant germplasm in seedbanks.

Telomere dynamics and oxidative stress in Arabidopsis grown in lunar regolith simulant

NASA envisions a future where humans establish a thriving colony on the Moon by 2050. Plants will be essential for this endeavor, but little is known about their adaptation to extraterrestrial bodies. The capacity to grow plants in lunar regolith would represent a major step towards this goal by minimizing the reliance on resources transported from Earth. Recent studies reveal that Arabidopsis thaliana can germinate and grow on genuine lunar regolith as well as on lunar regolith simulant. However, plants arrest in vegetative development and activate a variety of stress response pathways, most notably the oxidative stress response. Telomeres are hotspots for oxidative damage in the genome and a marker of fitness in many organisms. Here we examine A. thaliana growth on a lunar regolith simulant and the impact of this resource on plant physiology and on telomere dynamics, telomerase enzyme activity and genome oxidation. We report that plants successfully set seed and generate a viable second plant generation if the lunar regolith simulant is pre-washed with an antioxidant cocktail. However, plants sustain a higher degree of genome oxidation and decreased biomass relative to conventional Earth soil cultivation. Moreover, telomerase activity substantially declines and telomeres shorten in plants grown in lunar regolith simulant, implying that genome integrity may not be sustainable over the long-term. Overcoming these challenges will be an important goal in ensuring success on the lunar frontier.

Physiological and molecular changes of onion (Allium cepa L.) seeds under different aging conditions

BACKGROUND

Onion seeds have limited storage capacity compared to other vegetable seeds. It is crucial to identify the mechanisms that induce tolerance to storage conditions and reduce seed deterioration. To address this goal, an experiment was conducted to evaluate changes in germination, biochemical, physiological, and molecular characteristics of onion seed landraces (Horand, Kazerun landraces and Zargan cultivar) at different aging levels (control, three-days and six-days accelerated aging, and natural aging for one year).

RESULTS

The findings suggest that there was an increase in glucose, fructose, total sugar, and electrolyte leakage in the Horand (HOR), Kazerun (KAZ) landraces, and Zarghan (ZAR) cultivar, with Kazerun exhibiting the greatest increase. The percentage and rate of germination of Kazerun decreased by 54% and 33%, respectively, in six-day accelerated aging compared to the control, while it decreased by 12% and 14%, respectively, in Horand. Protein content decreased with increasing levels of aging, with a decrease of 26% in Kazerun landrace at six days of aging, while it was 16% in Horand landrace. The antioxidant activities of catalase, superoxide dismutase, and glutathione peroxidase decreased more intensively in Kazerun. The expression of AMY1, BMY1, CTR1, and NPR1 genes were lower in Kazerun landraces than in Horand and Zargan at different aging levels.

CONCLUSIONS

The AMY1, BMY1, CTR1, and NPR1 genes play a pivotal role in onion seed germination, and their downregulation under stressful conditions has been shown to decrease germination rates. In addition, the activity of CAT, SOD, and GPx enzymes decreased by seed aging, and the amount of glucose, fructose, total sugar and electrolyte leakage increased, which ultimately led to seed deterioration. Based on the results of this experiment, it is recommended to conduct further studies into the molecular aspects involved in onion seed deterioration. More research on the genes related to this process is suggested, as well as investigating the impact of different priming treatments on the genes expression involved in the onion seed aging process.

Beneficial effects of bio-fabricated selenium nanoparticles as seed nanopriming agent on seed germination in rice (Oryza sativa L.)

Climate change and increasing population pressure have put the agriculture sector in an arduous situation. With increasing demand for agricultural production overuse of inputs have accentuated the negative impact on environment. Hence, sustainable agriculture is gaining prominence in recent times with an emphasis on judicious and optimum use of resources. The field of nanotechnology can immensely help in achieving sustainability in agriculture at various levels. Use of nutrients and plant protection chemicals in nano-form can increase their efficacy even at reduced doses thus decreasing their pernicious impact. Seed priming is one of the important agronomic practices with widely reported positive impacts on germination, seedling growth and pathogen resistance. In the current study, the effect and efficacy of selenium nanoparticles synthesized using phyto-extracts as a seed priming agent is studied. This nanopriming enhanced the germination, hastened the seedling emergence and growth with an increase in seedling vigour and nutrient status. This eco-friendly and economical method of synthesizing nanoparticles of various nutrient minerals can optimize the resource use thus helping in sustainable agriculture by reducing environment damage without compromising on efficacy.

Herbal and chemical seed potentiations improve the redox health of aged seeds of indigenous aromatic rice cultivars through regulation of oxidative window, gene expression, and restoration of hormonal homeostasis

Previous studies associated with seed potentiation support the critical role of metabolic readjustment in restricting the loss of seed vigor and viability of aged seeds. However, their exact role in the regulation of 'oxidative windows' of potentiated seeds is rarely studied and hence is the subject of the present investigation. Seed potentiation of two contrasting indigenous aromatic rice cultivars, differing in sensitivity towards redox attributes (Oryza sativa L., Cultivars Tulaipanji and Jamainadu), with standardized doses of hydrogen peroxide (20 mM), triadimefon (250 μM), herbal extract (1% aqueous extract of Lantana camara flower) and distilled water before accelerated aging (RH 92% and 41 °C for 24 h) found to have significant impact on redox regulation of aged seeds and improvement of germination phenotypes. The efficacy of integrated RBOH-ascorbate-glutathione/catalase pathway, redox status and other redox fingerprints in the metabolic landscape of potentiated-aged seeds vis-a-vis non-potentiated-aged seeds corroborate the impact of seed potentiation on the regulation of 'oxidative window' of experimental rice seeds. Gene expression analysis of central redox hub enzymes (Osrboh, OsAPx2, OsGRase, OsCatA) strongly substantiates the impact of seed potentiation on transcriptional regulation of genes for redox homeostasis in accelerated aged seeds. The novelty of the current effort is that it suggests a positive nexus between seed potentiation-induced redox regulation and hormonal homeostasis. The efficacy of seed potentiation on the redox regulation of experimental accelerated aged seeds is found to be cultivar-specific and comparatively better in the cultivar Tulaipanji as compared to the cultivar Jamainadu and in the order herbal extract, hydrogen peroxide, hydropriming and triadimefon.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01375-9.

Germination of aged oat seeds associated with changes in antioxidant enzyme activity and storage compounds mobilization

Germination of aged seeds may be associated with specific metabolic changes. The objective of this study was to examine physiological and metabolic alterations before and after germination of control and aged oat (Avena sativa) seeds. The activity of antioxidant enzymes and the level of storage compounds were measured in the embryo and endosperm at 0, 4, 16, and 32 h of imbibition for control seeds and 0, 4, 16, 32, and 60 h of imbibition for medium vigor seeds after artificially accelerated aging; metabolomic changes were determined in embryos at 16 and 32 h of seed imbibition. In aged oat seeds, superoxide dismutase activity and catalase activity increased in the late imbibition stage. The content of soluble sugars decreased significantly in the later stages of imbibition, while the content of proteins increased in 32 h of seed imbibition eventually producing mannitol and proline. The mobilization of fat in deteriorated seeds was mainly through the sphingolipid metabolic pathway generated by cell growth-promoting dihydrosphingosine-1-phosphate. Ascorbic acid, avenanthramide and proline levels increased significantly at 60 h of imbibition, playing an important role in the germination of aged oat seeds.

Transcriptome Landscape Analyses of the Regulatory Network for Zygotic Embryo Development in Paeonia ostii

Paeonia ostii is a worldwide ornamental flower and an emerging oil crop. Zyotic embryogenesis is a critical process during seed development, and it can provide a basis for improving the efficiency of somatic embryogenesis (SE). In this study, transcriptome sequencing of embryo development was performed to investigate gene expression profiling in P. ostii and identified Differentially expressed genes (DEGs) related to transcription factors, plant hormones, and antioxidant enzymes. The results indicated that IAA (Indole-3-acetic acid), GA (Gibberellin), BR (Brassinosteroid) and ETH (Ethylene) were beneficial to early embryonic morphogenesis, while CTK (Cytokinin) and ABA (Abscisic Acid) promoted embryo morphogenesis and maturation. The antioxidant enzymes' activity was the highest in early embryos and an important participant in embryo formation. The high expression of the genes encoding fatty acid desaturase was beneficial to fast oil accumulation. Representative DEGs were selected and validated using qRT-PCR. Protein-protein interaction network (PPI) was predicted, and six central node proteins, including AUX1, PIN1, ARF6, LAX3, ABCB19, PIF3, and PIF4, were screened. Our results provided new insights into the formation of embryo development and even somatic embryo development in tree peonies.

Catalase: A critical node in the regulation of cell fate

Catalase (CAT) is an extensively studied if somewhat enigmatic enzyme that is at the heart of eukaryotic antioxidant systems with a canonical role in peroxisomal function. The CAT family of proteins exert control over a wide range of plant growth and defence processes. CAT proteins are subject to many types of post-translational modification (PTM), which modify activity, ligand binding, stability, compartmentation and function. The CAT interactome involves many cytosolic and nuclear proteins that appear to be essential for protein functions. Hence, the CAT network of roles extends far beyond those associated with peroxisomal metabolism. Some pathogen effector proteins are able to redirect CAT to the nucleus and recent evidence indicates CAT can traffic to the nucleus in the absence of exogenous proteins. While the mechanisms that target CAT to the nucleus are not understood, CAT activity in the cytosol and nucleus is promoted by interactions with nucleoredoxin. Here we discuss recent findings that have been pivotal in generating a step change in our understanding of CAT functions in plant cells.

Molecular Research of Lipid Peroxidation and Antioxidant Enzyme Activity of Comamonas testosteroni Bacterial Cells under the Hexachlorobenzene Impact

The species of Comamonas testosteroni is the most common human pathogen of the genus, which can be associated with acute appendicitis, infections of the bloodstream, the peritoneal cavity, cerebrospinal fluid, inflammatory bowel disease, and in general, bacteremia. According to the literature, Comamonas testosteroni has destructive activity to a wide range of toxic chemical compounds, including chlorobenzenes. The specified strains were isolated from the soil of the organochlorine waste landfill, where hexachlorobenzene (HCB) was predominant. These strains were expected to be capable of degrading HCB. Microbiological (bacterial enrichment and cultivating, bacterial biomass obtaining), molecular biology, biochemical (enzymatic activities, malondialdehyde measuring, peroxidation lipid products measuring), and statistical methods were carried out in this research. The reaction of both strains (UCM B-400 and UCM B-401) to the hexachlorobenzene presence differed in the content of diene and triene conjugates and malondialdehyde, as well as different catalase and peroxidase activity levels. In terms of primary peroxidation products, diene conjugates were lower, except conditions with 20 mg/L HCB, where these were higher up to two times, than the pure control. Malondialdehyde in strain B-400 cells decreased up to five times, in B-401, but increased up to two times, compared to the pure control. Schiff bases in strain B-400 cells were 2–3 times lower than the pure control. However, in B-401 cells Schiff bases under higher HCB dose were in the same level with the pure control. Catalase activity was 1.5 times higher in all experimental variants, compared to the pure control (in the strain B-401 cells), but in the B-400 strain, cells were 2 times lower, compared to the pure control. The response of the two strains to hexachlorobenzene was similar only in peroxidase activity terms, which was slightly higher compared to the pure control. The physiological response of Comamonas testosteroni strains to hexachlorobenzene has a typical strain reaction. The physiological response level of these strains to hexachlorobenzene confirms its tolerance, and indirectly, the ability to destroy the specified toxic compound.

Comparative analysis of wild-type accessions reveals novel determinants of Arabidopsis seed longevity

Understanding the genetic factors involved in seed longevity is of paramount importance in agricultural and ecological contexts. The polygenic nature of this trait suggests that many of them remain undiscovered. Here, we exploited the contrasting seed longevity found amongst Arabidopsis thaliana accessions to further understand this phenomenon. Concentrations of glutathione were higher in longer-lived than shorter-lived accessions, supporting that redox poise plays a prominent role in seed longevity. However, high seed permeability, normally associated with shorter longevity, is also present in long-lived accessions. Dry seed transcriptome analysis indicated that the contribution to longevity of stored messenger RNA (mRNAs) is complex, including mainly accession-specific mechanisms. The detrimental effect on longevity caused by other factors may be counterbalanced by higher levels of specific mRNAs stored in dry seeds, for instance those of heat-shock proteins. Indeed, loss-of-function mutant analysis demonstrated that heat-shock factors HSF1A and 1B contributed to longevity. Furthermore, mutants of the stress-granule zinc-finger protein TZF9 or the spliceosome subunits MOS4 or MAC3A/MAC3B, extended seed longevity, positioning RNA as a novel player in the regulation of seed viability. mRNAs of proteins with putative relevance to longevity were also abundant in shorter-lived accessions, reinforcing the idea that resistance to ageing is determined by multiple factors.

Dynamic Changes in Membrane Lipid Metabolism and Antioxidant Defense During Soybean (Glycine max L. Merr.) Seed Aging

Seed viability depends upon the maintenance of functional lipids; however, how membrane lipid components dynamically change during the seed aging process remains obscure. Seed storage is accompanied by the oxidation of membrane lipids and loss of seed viability. Understanding membrane lipid changes and their effect on the cell membrane during seed aging can contribute to revealing the mechanism of seed longevity. In this study, the potential relationship between oxidative stress and membrane lipid metabolism was evaluated by using a non-targeted lipidomics approach during artificial aging of Glycine max L. Merr. Zhongdou No. 27 seeds. We determined changes in reactive oxygen species, malondialdehyde content, and membrane permeability and assessed antioxidant system activity. We found that decreased non-enzymatic antioxidant contents and catalase activity might lead to reactive oxygen species accumulation, resulting in higher electrolyte leakage and lipid peroxidation. The significantly decreased phospholipids and increased glycerolipids and lysophospholipids suggested that hydrolysis of phospholipids to form glycerolipids and lysophospholipids could be the primary pathway of membrane metabolism during seed aging. Moreover, the ratio of phosphatidylcholine to phosphatidylethanolamine, double bond index, and acyl chain length of phospholipids were found to jointly regulate membrane function. In addition, the observed changes in lipid metabolism suggest novel potential hallmarks of soybean seed aging, such as diacylglycerol 36:4; phosphatidylcholine 34:2, 36:2, and 36:4; and phosphatidylethanolamine 34:2. This knowledge can be of great significance for elucidating the molecular mechanism underlying seed aging and germplasm conservation.

Genetic mechanisms of aging in plants: What can we learn from them?

Plants hold all records in longevity. Their aging is a complex process. In the presented review, we analyzed published data on various aspects of plant aging with focus on any inferences that could shed a light on aging in animals and help to fight it in human. Plant aging can be caused by many factors, such as telomere depletion, genomic instability, loss of proteostasis, changes in intercellular interaction, desynchronosis, autophagy misregulation, epigenetic changes and others. Plants have developed a number of mechanisms to increase lifespan. Among these mechanisms are gene duplication ("genetic backup"), the active work of telomerases, abundance of meristematic cells, capacity of maintaining the meristems permanently active and continuous activity of phytohormones. Plant aging usually occurs throughout the whole perennial life, but could be also seasonal senescence. Study of causes for seasonal aging can also help to uncover the mechanisms of plant longevity. The influence of different factors such as microbiome communities, glycation, alternative oxidase activity, mitochondrial dysfunction on plant longevity was also reviewed. Adaptive mechanisms of long-lived plants are considered. Further comparative study of the mechanisms underlying longevity of plants is necessary. This will allow us to reach a potentially new level of understanding of the aging process of plants.

The Seed and the Metabolism Regulation

Simple Summary

Seeds are the reproductive units of higher plants. They have a significant place in agriculture and plant diversity maintenance. Because they are dehydrated, they can remain viable in the environment for centuries. This review explores the dry seed as a metabolically inactive organism, but well organized to protect its components and enter intensive repair to restore metabolic activities upon imbibition for the completion of germination. Metabolism regulation is also critical for the most important seed traits, dormancy, and ageing recovery capacity.

Abstract

The seed represents a critical stage in the life cycle of flowering plants. It corresponds to a dry structure carrying the plant embryo in dormant or quiescent state. Orthodox seeds possess a very low water content, preventing biochemical reactions, especially respiration. If the desiccation of living organisms leads to a loss of homeostasis, structure, and metabolism, the seeds go through it successfully thanks to their structure, cellular organization, and growth regulation. Seeds set up a certain number of sophisticated molecules to protect valuable macromolecules or organelles from dehydration/rehydration cycles. Moreover, dormancy takes place in a coordinated process with environmental cues in order to ensure embryo development at the most appropriate conditions for the establishment of the new plant. Moreover, repair processes are programmed to be ready to operate to maximize germination success and seed longevity. This review focuses on the physiology of the seed as related to hydration forces, respiration, and biochemical reactions in the transition from thermodynamically undefined dry state to self-sustained living system. Such processes are of importance for basic knowledge of the regulation of metabolism of living organisms, but also for the control of germination in the context of climate change due to global warming.

Nitric Oxide as a Remedy against Oxidative Damages in Apple Seeds Undergoing Accelerated Ageing

Seed ageing is associated with a high concentration of reactive oxygen species (ROS). Apple (Malus domestica Borkh.) seeds belong to the orthodox type. Due to a deep dormancy, they may be stored in dry condition at 5 °C for a long time, without viability loss. In the laboratory, artificial ageing of apple seeds is performed by imbibition in wet sand at warm temperature (33 °C). The aim of the work was to study nitric oxide (NO) as a seed vigour preservation agent. Embryos isolated from apple seeds subjected to accelerated ageing for 7, 14, 21 or 40 days were fumigated with NO. Embryo quality was estimated by TTC and MDA tests. ROS level was confirmed by NBT staining. We analysed the alteration in transcript levels of CAT, SOD and POX. NO fumigation of embryos of seeds aged for 21 days stimulated germination and increased ROS level which correlated to the elevated expression of RBOH. The increased total antioxidant capacity after NO fumigation was accompanied by the increased transcript levels of genes encoding enzymatic antioxidants, that could protect against ROS overaccumulation. Moreover, post-aged NO application diminished the nitro-oxidative modification of RNA, proving NO action as a remedy in oxidative remodelling after seeds ageing.

Physiological responses of orchids to prolonged clinorotation

Creation of plant-based bioregenerative life support systems is crucial for future long-duration space exploring missions. Microgravity is one of the major stresses affecting plant growth and development under space flight conditions. Search for higher plant genotypes resilient to microgravity as well as revealing of biological features which could be used as markers of such resilience is rather urgently needed. The objective of this study was to analyze physiological and biochemical responses of three orchid species representing different life forms (terrestrial and epiphytic), growth types (monopodial and sympodial) and pathways of CO2 fixation to long-term (24 months) clinorotation which modeled the combined effect of two stress factors: hermetic conditions and microgravity. Three years old meristematic orchids Cypripedium flavum, Angraecum eburneum, Epidendrum radicans, representing different life forms, types of branching shoot system and pathways of CO2 fixation, were used as test-plants. The microgravity was simulated using three-dimensional (3-D) clinostat equipped with two rotation axes placed at right angles (rotation frequency was 3 rpm) in controlled conditions of air temperature, illumination, air humidity and substrate moisture. The control plants were grown in the similar plastic vessels but not hermetically sealed and without clinorotating in the same environmental conditions. The vital state of the test plants was assessed using characteristics of mineral nutrition, content of photosynthetic pigments, free amino acids, soluble proteins, DNA and RNA, enzymatic and non-enzymatic antioxidants. The results of this study confirmed that orchids grown under simulated microgravity and kept in hermetically-sealed vessels were subjected to oxidative stress, which could be responsible for the observed inhibition of basic physiological processes such as mineral nutrition, metabolism of aminoacids, protein biosynthesis and photosynthesis. Monopodial orchids C. flavum and A. eburneum demonstrated better adaptation to prolonged clinorotation as compared to sympodial E. radicans. In particular, the latter demonstrated some stimulation of mineral nutrition processes (i.e. K, N, Fe, Mn, Zn accumulation), content of photosynthetic pigments, proline and superoxide dismutase activity. Long-lasting clinorotation induced adaptive changes of antioxidant systems in the studied orchids (e.i. increase in carotenoids and proline content and stimulation of superoxide dismutase activity), which helped to maintain the main physiological functions at stable level in the above-mentioned stressful conditions. The following biochemical characteristics in the studied orchids could be considered as markers of resilience to simulated microgravity and hermetic conditions: 1) an increase in the accumulation of non-enzymatic (proline, carotenoids) and enzymatic antioxidants (superoxide dismutase); 2) ability to maintain stable balance of mineral nutrients; 3) increase in the content of photosynthetic pigments; 4) increase in the content of proteinogenic amino acids and soluble proteins; 5) increase in the DNA content or RNA/DNA ratio. Our studies have also demonstrated a correlation between orchid ecomorphological characteristics such as type of branching with their adaptive responses to prolonged clinorotation. We observed no correlation between the studied life form of orchids, ecotype or the pathway of CO2 fixation and their resilience to prolonged clinorotation. This research can be a starting point for studying the relationships between ecomorphological features of various orchids and their resilience to microgravity conditions in the search for biological markers of microgravity tolerance in species of higher plants.

Physiological responses of orchids to prolonged clinorotation

Creation of plant-based bioregenerative life support systems is crucial for future long-duration space exploring missions. Microgravity is one of the major stresses affecting plant growth and development under space flight conditions. Search for higher plant genotypes resilient to microgravity as well as revealing of biological features which could be used as markers of such resilience is rather urgently needed. The objective of this study was to analyze physiological and biochemical responses of three orchid species representing different life forms (terrestrial and epiphytic), growth types (monopodial and sympodial) and pathways of CO2 fixation to long-term (24 months) clinorotation which modeled the combined effect of two stress factors: hermetic conditions and microgravity. Three years old meristematic orchids Cypripedium flavum, Angraecum eburneum, Epidendrum radicans, representing different life forms, types of branching shoot system and pathways of CO2 fixation, were used as test-plants. The microgravity was simulated using three-dimensional (3-D) clinostat equipped with two rotation axes placed at right angles (rotation frequency was 3 rpm) in controlled conditions of air temperature, illumination, air humidity and substrate moisture. The control plants were grown in the similar plastic vessels but not hermetically sealed and without clinorotating in the same environmental conditions. The vital state of the test plants was assessed using characteristics of mineral nutrition, content of photosynthetic pigments, free amino acids, soluble proteins, DNA and RNA, enzymatic and non-enzymatic antioxidants. The results of this study confirmed that orchids grown under simulated microgravity and kept in hermetically-sealed vessels were subjected to oxidative stress, which could be responsible for the observed inhibition of basic physiological processes such as mineral nutrition, metabolism of aminoacids, protein biosynthesis and photosynthesis. Monopodial orchids C. flavum and A. eburneum demonstrated better adaptation to prolonged clinorotation as compared to sympodial E. radicans. In particular, the latter demonstrated some stimulation of mineral nutrition processes (i.e. K, N, Fe, Mn, Zn accumulation), content of photosynthetic pigments, proline and superoxide dismutase activity. Long-lasting clinorotation induced adaptive changes of antioxidant systems in the studied orchids (e.i. increase in carotenoids and proline content and stimulation of superoxide dismutase activity), which helped to maintain the main physiological functions at stable level in the above-mentioned stressful conditions. The following biochemical characteristics in the studied orchids could be considered as markers of resilience to simulated microgravity and hermetic conditions: 1) an increase in the accumulation of non-enzymatic (proline, carotenoids) and enzymatic antioxidants (superoxide dismutase); 2) ability to maintain stable balance of mineral nutrients; 3) increase in the content of photosynthetic pigments; 4) increase in the content of proteinogenic amino acids and soluble proteins; 5) increase in the DNA content or RNA/DNA ratio. Our studies have also demonstrated a correlation between orchid ecomorphological characteristics such as type of branching with their adaptive responses to prolonged clinorotation. We observed no correlation between the studied life form of orchids, ecotype or the pathway of CO2 fixation and their resilience to prolonged clinorotation. This research can be a starting point for studying the relationships between ecomorphological features of various orchids and their resilience to microgravity conditions in the search for biological markers of microgravity tolerance in species of higher plants.

Hydrotime analysis to explore the effect of H2O2-priming in the relationship between water potential (Ψ) and germination rate of Capsicum annuum L. seed under NaCl- and PEG-induced stress

Hydrogen peroxide (H2O2) priming was proved to be effective to boost salt and drought stress tolerance in Capsicum annuum L. Hither, hydrotime (HT) approach, a population-based threshold model-germination dependence on water availability, was introduced to account for the effects of reduced water potential on H₂O₂-primed seeds in progress toward germination. Pre-optimized H₂O₂ concentrations (1 and 10 mM for 24 h at 25 °C) were applied. Subsequently, seeds were germinated over a range of water potential (Ψ) (0 to -1.2 MPa) induced by sodium chloride (NaCl) and polyethylene glycol (PEG-6000) at 25 °C. We suggest that H₂O₂-priming affects differently the three derived items of HT model; induced lower hydrotime constant (θ_H) thus, revealed more rapid germination particularly evident with PEG, shifted the threshold or base water potential for 50% germination (Ψ_b(50)) towards a more negative value in NaCl culture, reflected a better salinity tolerance, though, the opposite effect was recorded with PEG, and reduced the standard deviation (σ_Ψb), proved a better uniformity of the germination process for both cultures. Thus, H₂O₂-priming increased GR_g (1/t_g) at all Ψ>Ψ_b(g) which is due to both a lower Ψ_b(50) and a smaller θ_H in the primed seeds for NaCl culture and primarily owing to reducing θ_H with no positive effect on Ψ_b(50) for PEG culture. A normalized time-scale, for comparing responses, was introduced and confirmed the aforementioned impact. Therefore, the crosstalk between H₂O₂ molecule and different cell pathways generates a constructive response in accordance with imposed stress.

Sustainable Agriculture through Multidisciplinary Seed Nanopriming: Prospects of Opportunities and Challenges

The global community decided in 2015 to improve people's lives by 2030 by setting 17 global goals for sustainable development. The second goal of this community was to end hunger. Plant seeds are an essential input in agriculture; however, during their developmental stages, seeds can be negatively affected by environmental stresses, which can adversely affect seed vigor, seedling establishment, and crop production. Seeds resistant to high salinity, droughts and climate change can result in higher crop yield. The major findings suggested in this review refer nanopriming as an emerging seed technology towards sustainable food amid growing demand with the increasing world population. This novel growing technology could influence the crop yield and ensure the quality and safety of seeds, in a sustainable way. When nanoprimed seeds are germinated, they undergo a series of synergistic events as a result of enhanced metabolism: modulating biochemical signaling pathways, trigger hormone secretion, reduce reactive oxygen species leading to improved disease resistance. In addition to providing an overview of the challenges and limitations of seed nanopriming technology, this review also describes some of the emerging nano-seed priming methods for sustainable agriculture, and other technological developments using cold plasma technology and machine learning.

Cathodic Water Enhances Seedling Emergence and Growth of Controlled Deteriorated Orthodox Seeds

All orthodox seeds eventually deteriorate during storage, a well-known problem in seed banking. Here we used a greenhouse study to test if priming deteriorated seeds with cathodic water can improve the emergence and subsequent seedling growth of three South African tree species, Bolusanthus speciosus, Combretum erythrophyllum and Erythrina caffra. Other priming solutions investigated were calcium magnesium (CaMg) solution and deionized water. In the present study, seeds were subjected to an artificial deterioration by increasing their water content to 14% and keeping them at 40 °C and 100% RH until they had lost 50% of their germination under laboratory conditions. Fresh and deteriorated seeds were primed with cathodic water, CaMg solution and deionized water, with non-primed fresh and deteriorated seeds as controls. Controlled deterioration significantly reduced total emergence and the biomass and photosynthetic parameters of the resulting seedlings. In one species (Bolusanthus speciosus), priming the deteriorated seeds with cathodic water significantly improved emergence parameters. However, in all species cathodic water significantly improved the total biomasses and other growth parameters of the seedlings derived from deteriorated seeds. Priming with CaMg solution and deionized water had little effect on emergence and while improving the growth of seedlings derived from deteriorated seeds, they were less effective than cathodic water. In fresh seeds, priming with all solutions resulted in small improvements in some parameters. Controlled deterioration of fresh seeds reduced the membrane stability index (MSI) in two of the three species and in all species increased the levels of the lipid oxidation products MDA and 4-HNE. Priming deteriorated seeds with cathodic water increased the MSI and reduced the MDA contents in all species and the 4-HNE content in one species. Other priming solutions were generally less effective in ameliorating oxidative stress. Results suggest that the strong antioxidative properties of cathodic water can explain its ability to ameliorate deterioration. In conclusion, the present study shows that priming with cathodic water is an effective way of invigorating deteriorated orthodox seeds and that it may have considerable potential in orthodox seed conservation.

Nanopriming with phytosynthesized zinc oxide nanoparticles for promoting germination and starch metabolism in rice seeds

The application of zinc oxide nanoparticles (ZnO NPs) in agricultural field is emerging and relatively new. In this work, a simple, cost-efficient, non-toxic and eco-friendly method for the green synthesis of ZnO NPs by Senna occidentalis leaf extract has been described. Techniques used to characterize nanoparticles (NPs) were X-ray diffractometer (XRD), UV visible spectroscopy, Particle size analyzer (PSA), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). In this study, green synthesized ZnO NPs at 20-40 mg/l solution was used to prime aged seeds of early flowering homozygous mutant (BM6) of Pusa basmati (Oryza sativa), which enhanced germination performance and seedling vigor significantly as compared to zinc sulphate (ZnSO₄) priming and conventional hydropriming. The effect of treatment was analyzed by measuring biophysical and biochemical parameter of germinating rice seeds. The seeds treated with ZnO NPs of 20 mg/l concentration showed more than 50 % stimulation in dry weight, relative water uptake of seeds and radicle length of seedling in comparison to other priming solution and control (hydro-primed). Significant growth was also observed in plumule length and fresh weight of seeds in ZnO NPs at 20 mg/l concentration in comparison to control and other priming treatments. At the same concentration of ZnO NPs, there was 23 % stimulation reported in total soluble sugar content and 45 % stimulation in amylase activity. There was also a substantial increase in antioxidant enzymes i.e. superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity. Seed priming represents an innovative user-friendly approach to enhance the germination rate, starch metabolic process and triggered zinc acquisition of rice aged seed as an alternative to the conventional priming method.

Is protein carbonylation a biomarker of seed priming and ageing?

For a long time, it has been known that seed priming allows the improvement of plant production and tolerance to abiotic stresses. However, a negative effect on the longevity of the seeds thus primed was observed; these mechanisms are still poorly understood. In addition, it has been shown by several authors that seed ageing is associated with the oxidation and particularly with carbonylation of protein. Our work consisted in studying the AOPP and carbonyl protein at the different parts of the embryo from freshly primed seeds and from those that have been primed for 4 years (after storage). We subjected Vigna unguiculata (L.) Walp. seeds to a single or double hydropriming. Our study showed that hydropriming, and more particularly a double cycle of hydration-dehydration, makes it possible to attenuate the oxidation of the protein while it favours a certain threshold of carbonylation in the freshly dehydrated seeds in order to better trigger the germination process. On the other hand, after a storage period of 4 years, these dehydrated seeds are characterised by a strong accumulation of the products of oxidation and especially carbonylated protein, compared with the untreated seeds, which could explain the decrease of the longevity of these seeds.

Influence of nanoscale micro-nutrient α-Fe2O3 on seed germination, seedling growth, translocation, physiological effects and yield of rice (Oryza sativa) and maize (Zea mays)

In the present study, nanoscale micronutrient iron (α-Fe₂O₃) has been prepared via co-precipitation using marine macro alga Turbinaria ornata. The nanoscale micronutrient iron has been used as priming agent for enhancing seed germination, seed quality, uptake, translocation, physiological effects and yield level of rice and maize crops. The physico-chemical characterization techniques results showed the successful preparation of nanoscale micronutrient iron. Seeds primed with nanoscale micronutrient iron at 25 mg/L significantly enhanced the seed germination and seedling parameters in comparison with conventional hydro-priming. ROS production in germinating nano-primed seeds of rice and maize enhanced the seed germination better than the conventional hydro-priming. Uptake and distribution of nanoscale micronutrient iron in rice and maize seedlings were studied using HR-SEM & ICP-MS analysis. Foliar application of low concentration (10 mg/L) nanoscale micronutrient iron under field conditions significantly increased the chlorophyll content, yield attributes of rice and maize crops.

Seed priming and foliar application with jasmonic acid enhance salinity stress tolerance of soybean (Glycine max L.) seedlings

BACKGROUND

Jasmonic acid (JA) is an important molecule that has a regulatory effect on many physiological processes in plant growth and development under abiotic stress. This study investigated the effect of 60 μmol L-1 of JA in seed priming (P) at 15 °C in darkness for 24 h, foliar application (F), and/or their combination effect (P + F) on two soybean cultivars - 'Nannong 99-6' (salt tolerant) and 'Lee 68' (salt sensitive) - under salinity stress (100 mmol L-1 sodium chloride (NaCl)).

RESULTS

Salinity stress reduced seedling growth and biomass compared with that in the control condition. Priming and foliar application with JA and/or their combination significantly improved water potential, osmotic potential, water use efficiency, and relative water content of both cultivars under salinity stress. Similarly, seed priming with JA, foliar application of JA, and/or their combination significantly improved the following properties under salinity stress compared with the untreated seedlings: net photosynthetic rate by 68.03%, 59.85%, and 76.67% respectively; transpiration rate by 74.85%, 55.10%, and 80.26% respectively; stomatal conductance by 69.88%, 78.25%, and 26.24% respectively; intercellular carbon dioxide concentration by 61.64%, 40.06%, and 65.79% respectively; and total chlorophyll content by 47.41%, 41.02%, and 55.73% respectively. Soybean plants primed, sprayed with JA, or treated with their combination enhanced the chlorophyll fluorescence, which was damaged by salinity stress. JA treatments improved abscisic acid, gibberellic acid, and JA levels by 60.57%, 62.50% and 52.25% respectively under salt stress compared with those in the control condition. The transcriptional levels of the FeSOD, POD, CAT, and APX genes increased significantly in the NaCl-stressed seedlings irrespective of JA treatments. Moreover, JA treatment resulted in a reduction of sodium ion concentration and an increase of potassium ion concentrations in the leaf and root of both cultivars regardless of salinity stress. Monodehydroascorbate reductase, dehydroascorbate reductase, and proline contents decreased in the seedlings treated with JA under salinity stress, whereas the ascorbate content increased with JA treatment combined with NaCl stress.

CONCLUSION

The application of 60 μmol L-1 JA improved plant growth by regulating the interaction between plant hormones and hydrogen peroxide, which may be involved in auxin signaling and stomatal closure under salt stress. These methods could efficiently protect early seedlings and alleviate salt stress damage and provide possibilities for use in improving soybean growth and inducing tolerance against excessive soil salinity. © 2020 Society of Chemical Industry.

A simple new method for aged seed utilization based on melatonin-mediated germination and antioxidant nutrient production

Seed deterioration, coupled with a decrease in nutrients, is unavoidable following long-term storage, and these seeds are therefore used as livestock fodder. Here, we developed a simple, rapid and efficient method of producing high amounts of antioxidants from deteriorated seeds via melatonin-induced germination. Legume seeds were subjected to high humidity at 55 °C for 12-36 h to obtain aged seeds with a 40% germination rate and severely reduced antioxidant nutrition (total phenolics content, ferric reducing power and 1,1-diphenyl-2-picryhydrazyl (DPPH) radical scavenging capacity). Aged seeds were then treated with 0.1 mM melatonin, resulting in the production of sprouts with a higher total phenolics content (fivefold), greater ferric reducing power (sevenfold) and greater DPPH radical scavenging capacity (twofold) compared to the aged seeds. These findings suggest that melatonin treatment efficiently converted aged seed reserve residues into antioxidant nutrients, providing an alternative use for deteriorated seeds in food production.

Relationship between mitochondrial changes and seed aging as a limitation of viability for the storage of beech seed (Fagus sylvatica L.)

Aging is one of the most fundamental biological processes occurring in all forms of eukaryotic life. Beech trees (Fagus sylvatica L.) produce seeds in intervals of 5–10 years. Its yearly seed yield is usually very low, so there is a need for long-term seed storage to enable propagation of this species upon demand. Seeds for sowing must be of high quality but they are not easy to store without viability loss. Understanding the mechanism responsible for seed aging is therefore very important. We observed the generation of reactive oxygen species (ROS) in mitochondria of embryonic axes and cotyledons of beech seeds during natural aging. The presence of ROS led to changes in compromised mitochondrial membrane integrity and in mitochondrial metabolism and morphology. In this study, we pointed to the involvement of mitochondria in the natural aging process of beech seeds, but the molecular mechanisms underlying this involvement are still unknown.

The efficacy of different seed priming agents for promoting sorghum germination under salt stress

Sorghum [Sorghum bicolor (L.) Moench] seed germination is sensitive to salinity, and seed priming is an effective method for alleviating the negative effects of salt stress on seed germination. However, few studies have compared the effects of different priming agents on sorghum germination under salt stress. In this study, we quantified the effects of priming with distilled water (HP), sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl₂), and polyethylene glycol (PEG) on sorghum seed germination under 150 mM NaCl stress. The germination potential, germination rate, germination index, vigor index, root length, shoot length, root fresh weight, shoot fresh weight, root dry weight, and shoot dry weight were significantly reduced by salt stress. Different priming treatments alleviated the germination inhibition caused by salt stress to varying degrees, and 50 mM CaCl₂ was the most effective treatment. In addition, the mitigation effect of priming was stronger on root traits than on shoot traits. Mitigation efficacy was closely related to both the type of agent and the concentration of the solution. Principal component analysis showed that all concentrations of CaCl₂ had higher scores and were clearly distinguished from other treatments based on their positive effects on all germination traits. The effects of the other agents varied with concentration. The priming treatments were divided into three categories based on their priming efficacy, and the 50, 100, and 150 mM CaCl₂ treatments were placed in the first category. The 150 mM KCl, 10% PEG, HP, 150 mM NaCl, 30% PEG, and 50 mM KCl treatments were placed in the second category, and the 100 mM NaCl, 100 mM KCl, 20% PEG, and 50 mM NaCl treatments were least effective and were placed in the third category. Choosing appropriate priming agents and methods for future research and applications can ensure that crop seeds germinate healthily under saline conditions.

High Drying Temperature Accelerates Sunflower Seed Deterioration by Regulating the Fatty Acid Metabolism, Glycometabolism, and Abscisic Acid/Gibberellin Balance

Sunflower seed storage is accompanied by the loss of seed vigor. Seed drying is a key link between seed harvest and seed storage; however, to date, the effect of seed drying on sunflower seed deterioration during storage remains unclear. The present study performed hot air drying for sunflower seeds with an initial moisture content of 30% to examine the manner in which drying temperature (35, 40, 45, 50, and 55°C) affects the drying performance and seed vigor following storage process (6 and 12 months). A drying temperature of 40°C was evidently safe for sunflower seeds, whereas the high drying temperatures (HTD, 45, 50, and 55°C) significantly lowered sunflower seed vigor by regulating the fatty acid metabolism, glycometabolism, and abscisic acid (ABA)/gibberellin (GA) balance. HDT significantly increased the seed damage rate and accelerated sunflower seed deterioration during natural and artificial aging process. Further biochemical analysis indicated that HDT significantly increased lipoxygenase and dioxygenase activities, leading to malonaldehyde and reactive oxygen species over-accumulation during storage. During early seed germination, HDT significantly inhibited fatty acid hydrolysis and glycometabolism by decreasing triacylglycerol lipase, CoA-SH oxidase, and invertase activities. Moreover, HDT remarkably increased ABA levels but reduced GA levels by regulating gene expressions and metabolic enzyme activities during early imbibitions. Cumulatively, the seed drying effect on sunflower seed vigor deterioration during the storage process may be strongly related to fatty acid oxidation and hydrolysis metabolism, toxic substance accumulation, and ABA/GA balance.

Differences in stress defence mechanisms in germinating seeds of Pinus sylvestris exposed to various lead chemical forms

Exposure to lead (Pb) can have serious toxic effects on the physiological and biochemical processes of plants. The chemical form of the metal determines the degree of its toxicity. In our research, we examined the effect of lead in the form of lead nitrate [Pb(NO3)2] and lead chloride (PbCl2) in concentrations of 12.5 mM and 25 mM on pine (Pinus sylvestris) seed germination. Nitrogen salt causes more severe changes than chloride salt. Increasing levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide were detected during germination processes. The high levels of ROS lead to redox changes in the cell. We observed a reduction in the level of the reduced form of glutathione (GSH), and at the same time observed increased levels of the oxidised form of glutathione (GSSG) depending on the concentration and also the time of exposure to lead compounds. At the beginning of germination processes, the effective non-enzymatic activity of the antioxidant cycle was dominant, and at the late stage the enzymatic activity was noticed in the presence of Pb compounds. CAT activity significantly increased after Pb compound exposition.

Revival of Ancient Marine Dinoflagellates Using Molecular Biostimulation

The biological processes involved in the preservation, viability, and revival of long-term dormant dinoflagellate cysts buried in sediments remain unknown. Based on studies of plant seed physiology, we tested whether the revival of ancient cysts preserved in century-old sediments from the Bay of Brest (France) could be stimulated by melatonin and gibberellic acid, two molecules commonly used in seed priming. Dinoflagellates were revived from sediments dated to approximately 150 years ago (156 ± 27, 32 cm depth), extending the known record age of cyst viability previously established as around one century. A culture suspension of sediments mixed with melatonin and gibberellic acid solutions as biostimulants exhibited germination of 11 dinoflagellate taxa that could not be revived under controlled culture conditions. The biostimulants revived some dinoflagellates from century-old sediments, including the potentially toxic species Alexandrium minutum. The biostimulants showed positive effects on germination on even more ancient cysts, showing dose-dependent effects on the germination of Scrippsiella acuminata. Concentrations of 1, 10, and 100 µM melatonin and gibberellic acid promoted germination. In contrast, 1,000 µM solutions, particularly for melatonin, drastically decreased germination, suggesting a potential noxious effect of high doses of these molecules on dinoflagellate revival. Our findings suggest that melatonin and gibberellic acid are involved in the stimulation of germination of dinoflagellate cysts. These biostimulants can be used to germinate long-term stored dinoflagellate cysts, which may promote studies of ancient strains in the resurrection ecology research field.

A multiscale approach reveals regulatory players of water stress responses in seeds during germination

Seed germination is regulated by environmental factors, particularly water availability. Water deficits at the time of sowing impair the establishment of crop plants. Transcriptome and proteome profiling was used to document the responses of sunflower (Helianthus annuus) seeds to moderate water stress during germination in two hybrids that are nominally classed as drought sensitive and drought tolerant. Differences in the water stress-dependent accumulation reactive oxygen species and antioxidant enzymes activities were observed between the hybrids. A pathway-based analysis of the hybrid transcriptomes demonstrated that the water stress-dependent responses of seed metabolism were similar to those of the plant, with a decreased abundance of transcripts encoding proteins associated with metabolism and cell expansion. Moreover, germination under water stress conditions was associated with increased levels of transcripts encoding heat shock proteins. Exposure of germinating seeds to water stress specifically affected the abundance of a small number of proteins, including heat shock proteins. Taken together, these data not only identify factors that are likely to play a key role in drought tolerance during seed germination, but they also demonstrate the importance of the female parent in the transmission of water stress tolerance.

Rocket Science: The Effect of Spaceflight on Germination Physiology, Ageing, and Transcriptome of Eruca sativa Seeds

In the 'Rocket Science' project, storage of Eruca sativa (salad rocket) seeds for six months on board the International Space Station resulted in delayed seedling establishment. Here we investigated the physiological and molecular mechanisms underpinning the spaceflight effects on dry seeds. We found that 'Space' seed germination vigor was reduced, and ageing sensitivity increased, but the spaceflight did not compromise seed viability and the development of normal seedlings. Comparative analysis of the transcriptomes (using RNAseq) in dry seeds and upon controlled artificial ageing treatment (CAAT) revealed differentially expressed genes (DEGs) associated with spaceflight and ageing. DEG categories enriched by spaceflight and CAAT included transcription and translation with reduced transcript abundances for 40S and 60S ribosomal subunit genes. Among the 'spaceflight-up' DEGs were heat shock proteins (HSPs), DNAJ-related chaperones, a heat shock factor (HSFA7a-like), and components of several DNA repair pathways (e.g., ATM, DNA ligase 1). The 'response to radiation' category was especially enriched in 'spaceflight-up' DEGs including HSPs, catalases, and the transcription factor HY5. The major finding from the physiological and transcriptome analysis is that spaceflight causes vigor loss and partial ageing during air-dry seed storage, for which space environmental factors and consequences for seed storage during spaceflights are discussed.

Reactive Oxygen Species as Potential Drivers of the Seed Aging Process

Seeds are an important life cycle stage because they guarantee plant survival in unfavorable environmental conditions and the transfer of genetic information from parents to offspring. However, similar to every organ, seeds undergo aging processes that limit their viability and ultimately cause the loss of their basic property, i.e., the ability to germinate. Seed aging is a vital economic and scientific issue that is related to seed resistance to an array of factors, both internal (genetic, structural, and physiological) and external (mainly storage conditions: temperature and humidity). Reactive oxygen species (ROS) are believed to initiate seed aging via the degradation of cell membrane phospholipids and the structural and functional deterioration of proteins and genetic material. Researchers investigating seed aging claim that the effective protection of genetic resources requires an understanding of the reasons for senescence of seeds with variable sensitivity to drying and long-term storage. Genomic integrity considerably affects seed viability and vigor. The deterioration of nucleic acids inhibits transcription and translation and exacerbates reductions in the activity of antioxidant system enzymes. All of these factors significantly limit seed viability.

Wheat seed ageing viewed through the cellular redox environment and changes in pH

To elucidate biochemical mechanisms leading to seed deterioration, we studied 23 wheat genotypes after exposure to seed bank storage for 6-16 years compared to controlled deterioration (CD) at 45 °C and 14 (CD14) and 18% (CD18) moisture content (MC) for up to 32 days. Under two seed bank storage conditions, seed viability was maintained in cold storage (CS) at 0 °C and 9% seed MC, but significantly decreased in ambient storage (AS) at 20 °C and 9% MC. Under AS and CS, organic free radicals, most likely semiquinones, accumulated, detected by electron paramagnetic resonance, while the antioxidant glutathione (GSH) was partly lost and partly converted to glutathione disulphide (GSSG), detected by HPLC. Under AS the glutathione half-cell reduction potential (E_GSSG/2GSH) shifted towards more oxidising conditions, from -186 to -141 mV. In seeds exposed to CD14 or CD18, no accumulation of organic free radicals was observed, GSH and seed viability declined within 32 and 7 days, respectively, GSSG hardly changed (CD14) or decreased (CD18) and E_GSSG/2GSH shifted to -116 mV. The pH of extracts prepared from seeds subjected to CS, AS and CD14 decreased with viability, and remained high under CD18. Across all treatments, E_GSSG/2GSH correlated significantly with seed viability (r = 0.8, p<.001). Data are discussed with a view that the cytoplasm is in a glassy state in CS and AS, but during the CD treatments, underwent transition to a liquid state. We suggest that enzymes can be active during CD but not under the seed bank conditions tested. However, upon CD, enzyme-based repair processes were apparently outweighed by deteriorative reactions. We conclude that seed ageing by CD and under seed bank conditions are accompanied by different biochemical reactions.

Combinative effects of Azospirillum brasilense inoculation and chemical priming on germination behavior and seedling growth in aged grass seeds

Germination of seeds during the transportation or after prolonged storage naturally and inevitably decreases because of ageing, but germination potential can be partially restored with seed priming treatments. A novel attempt was made to investigate the effects of combined treatments and to optimize the conditions for naturally aged seeds of tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.) and Russian wild rye (Psathyrostachys juncea (Fisch.) Nevski) using an orthogonal activity level experimental design [factor A: Azospirillum brasilense concentration, factor B: three seed priming treatments (H₂O, MgSO₄ and H₂O₂) and factor C: different priming times]. Multivariate regression model analysis was applied to determine the interactive effects of pairwise factors (A and C) and to optimize experimental conditions. The results showed that the mixed treatments positively affected seed germination and seedling growth. The three seed priming treatments were the dominant factors for germination promotion, whereas the bacterial concentration had the largest effect on seedling growth and the activity of superoxide dismutase (SOD), especially root elongation. The malondialdehyde content was reduced, the activities of SOD, peroxidase and catalase were triggered, and ascorbate peroxidase activity was also affected by the co-treatment. The combined results of all determined attributes showed that A. brasilense bio-priming with H₂O₂ priming constituted the optimal combination. The optimal bacterial concentration of A. brasilense and the time of seed priming were 52.3 × 10⁶ colony forming units (CFU) mL^-1 and 17.0 h, respectively.

Mitochondria Are Important Determinants of the Aging of Seeds

Seeds enable plant survival in harsh environmental conditions, and via seeds, genetic information is transferred from parents to the new generation; this stage provides an opportunity for sessile plants to settle in new territories. However, seed viability decreases over long-term storage due to seed aging. For the effective conservation of gene resources, e.g., in gene banks, it is necessary to understand the causes of decreases in seed viability, not only where the aging process is initiated in seeds but also the sequence of events of this process. Mitochondria are the main source of reactive oxygen species (ROS) production, so they are more quickly and strongly exposed to oxidative damage than other organelles. The mitochondrial antioxidant system is also less active than the antioxidant systems of other organelles, thus such mitochondrial 'defects' can strongly affect various cell processes, including seed aging, which we discuss in this paper.

The toxic effects of alizarin red S on catalase at the molecular level

Alizarin red S (ARS) is a widespread mordant dye derived from alizarin. However, it was reported to be mutagenic and carcinogenic probably because it could induce oxidative damages in organisms. Catalase (CAT) is an important antioxidant enzyme defensing oxidative damages induced by xenobiotics. The underlying mechanisms of ARS interacting with CAT have not been clarified yet. This study is conducted to characterize the functional and conformational changes on CAT by ARS and the binding details to further investigate their interaction mechanisms. Under exposure of ARS at 5 μM, CAT activity was significantly decreased to 76.2%. Inhibition of CAT probably resulted in promotion of intracellular oxidative stress and pro-oxidant property of ARS. The interaction between ARS and CAT was proved to be spontaneous and exothermic. However, limited structural changes were observed according to spectroscopic results. Results showed that ARS prefers to bind with residues buried in the active site and could alter the activity of CAT, which were agree with the molecular docking results. This work proves the adverse effects of ARS on CAT mainly at molecular level and further highlights its potential risks to heath.

Alizarin red S is confirmed to be toxic to catalase at molecular level attributing to the structural and functional changes of catalase.

Quantitative Interrelation between Atractylenolide I, II, and III in Atractylodes japonica Koidzumi Rhizomes, and Evaluation of Their Oxidative Transformation Using a Biomimetic Kinetic Model

Analytical methods based on ultraperformance liquid chromatography/ion-trap mass spectrometry (UPLC/ion-trap MS) were developed for quantification of atractylenolide I, II, and III in the methanol extract of Atractylodes japonica rhizomes with a C₁₈ column in an acidified water/acetonitrile gradient eluent in an LC system, and ion-trap MS coupled with electrospray ionization was employed under positive-ion mode. The three atractylenolides were quantified in all A. japonica samples, and the content of atractylenolide I, II, and III showed a significant correlation to each other. Such high correlation was explained by the mechanistic insights into the biosynthetic pathway of atractylenoide III and I from atractylenoide II by using the biomimetic cytochrome P450 model, [Fe(tmp)](CF₃SO₃) (tmp = meso-tetramesitylporphyrin). Atractylenolides could be transformed by oxidation via the oxidative enzyme in the A. japonica plant. The present study first reports the first oxidative transformation of atractylenolides using the heme iron model complex.

Suppression of LOX activity enhanced seed vigour and longevity of tobacco (Nicotiana tabacum L.) seeds during storage

The preservation of seed viability and quality in storage is an important trait both for commercial and germplasm usage. To better explore potential mechanisms of tobacco seed deterioration, seed packed in cloth bag (C) and vacuum bag (V) were stored under room temperature (RT) and low temperature (LT, 18°C), and sampled periodically for laboratory testing. Seed stored in low temperature with vacuum bag (LT/V) owned the highest seed vigour after 25 months of storage and in room temperature with cloth bag (RT/C) lost seed vigour and germination ability after 20-month storage. Meanwhile, seed in RT/C notably increased about 5-fold endogenous hydrogen peroxide (H₂O₂), 4-fold malondialdehyde (MDA) contents, 12-fold Lipoxygenases (LOX) activity and 2-fold the expression of NtLOX3 comparing with LT/V at the end of 15-month storage. In addition, regression analysis indicated that LOX activity was strongly negatively correlated with seed vigour as the R ² value reached 0.970 in RT/C. Furthermore, caffeic acid and catechin, the inhibitors of LOX activity, were applied to tobacco seeds pre-treatment and followed with artificial accelerated aging. Seeds pretreated with inhibitors, especially caffeic acid, reduced LOX activity by 50%, MDA and H₂O₂ contents by 40% and 20%, respectively, and increased more than 1.2-fold seed vigour and seedling quality comparing with seeds pretreated with H₂O after 6-day artificial aging, indicating a better seed storability after artificial accelerated aging. These results suggest that LOX accelerated seed aging, and suppression of LOX activity enhanced seed vigour and viability in accelerated aging tobacco seed, opening new opportunities for effective management of seed germplasm under long-term storage and conservation.

Seed priming and transgenerational drought memory improves tolerance against salt stress in bread wheat

This study was conducted to evaluate the potential of seed priming following terminal drought on tolerance against salt stress in bread wheat. Drought was imposed in field sown wheat at reproductive stage (BBCH growth stage 49) and was maintained till physiological maturity (BBCH growth stage 83). Seeds of bread wheat, collected from crop raised under terminal drought and/or well-watered conditions, were subjected to hydropriming and osmopriming (with 1.5% CaCl₂) and were sown in soil-filled pots. After stand establishment, salt stress treatments viz. 10 mM NaCl (control) and 100 mM NaCl were imposed. Seed from terminal drought stressed source had less fat (5%), and more fibers (11%), proteins (22%) and total soluble phenolics (514%) than well-watered seed source. Salt stress reduced the plant growth, perturbed water relations and decreased yield. However, an increase in osmolytes accumulation (4-18%), malondialdehyde (MDA) (27-35%) and tissue Na⁺ contents (149-332%) was observed under salt stress. The seeds collected from drought stressed crop had better tolerance against salt stress as indicated by better yield (28%), improved water relations (3-18%), osmolytes accumulation (21-33%), and less MDA (8%) and Na contents (35%) than progeny of well-watered crop. Seed priming, osmopriming in particular, further improved the tolerance against salt stress through improvement in leaf area, water relations, leaf proline, glycine betaine and grain yield while lowering MDA and Na⁺ contents. In conclusion, changed seed composition during terminal drought and seed priming improved the salt tolerance in wheat by modulating the water relations, osmolytes accumulation and lipid peroxidation.

Nanopriming technology for enhancing germination and starch metabolism of aged rice seeds using phytosynthesized silver nanoparticles

Application of nanomaterials for agriculture is relatively new as compared to their use in biomedical and industrial sectors. In order to promote sustainable nanoagriculture, biocompatible silver nanoparticles (AgNPs) have been synthesized through green route using kaffir lime leaf extract for use as nanopriming agent for enhancing seed germination of rice aged seeds. Results of various characterization techniques showed the successful formation of AgNPs which were capped with phytochemicals present in the plant extract. Rice aged seeds primed with phytosynthesized AgNPs at 5 and 10 ppm significantly improved germination performance and seedling vigor compared to unprimed control, AgNO₃ priming, and conventional hydropriming. Nanopriming could enhance α-amylase activity, resulting in higher soluble sugar content for supporting seedlings growth. Furthermore, nanopriming stimulated the up-regulation of aquaporin genes in germinating seeds. Meanwhile, more ROS production was observed in germinating seeds of nanopriming treatment compared to unprimed control and other priming treatments, suggesting that both ROS and aquaporins play important roles in enhancing seed germination. Different mechanisms underlying nanopriming-induced seed germination were proposed, including creation of nanopores for enhanced water uptake, rebooting ROS/antioxidant systems in seeds, generation of hydroxyl radicals for cell wall loosening, and nanocatalyst for fastening starch hydrolysis.

Nanopriming technology for enhancing germination and starch metabolism of aged rice seeds using phytosynthesized silver nanoparticles

Application of nanomaterials for agriculture is relatively new as compared to their use in biomedical and industrial sectors. In order to promote sustainable nanoagriculture, biocompatible silver nanoparticles (AgNPs) have been synthesized through green route using kaffir lime leaf extract for use as nanopriming agent for enhancing seed germination of rice aged seeds. Results of various characterization techniques showed the successful formation of AgNPs which were capped with phytochemicals present in the plant extract. Rice aged seeds primed with phytosynthesized AgNPs at 5 and 10 ppm significantly improved germination performance and seedling vigor compared to unprimed control, AgNO₃ priming, and conventional hydropriming. Nanopriming could enhance α-amylase activity, resulting in higher soluble sugar content for supporting seedlings growth. Furthermore, nanopriming stimulated the up-regulation of aquaporin genes in germinating seeds. Meanwhile, more ROS production was observed in germinating seeds of nanopriming treatment compared to unprimed control and other priming treatments, suggesting that both ROS and aquaporins play important roles in enhancing seed germination. Different mechanisms underlying nanopriming-induced seed germination were proposed, including creation of nanopores for enhanced water uptake, rebooting ROS/antioxidant systems in seeds, generation of hydroxyl radicals for cell wall loosening, and nanocatalyst for fastening starch hydrolysis.

Pulsed magnetic field improves seed quality of aged green pea seeds by homeostasis of free radical content

To elucidate the mechanism responsible for magnetic field induced seed invigoration in aged seeds an experiment was conducted on six year old garden pea seeds stored under controlled (20 °C and 40% RH) condition. Aged seeds were magnetoprimed by exposing to pulsed magnetic field (PMF) of 100 mT for 1 h in three pulsed modes. The 6 min on and off PMF showed significant improvement in germination (7.6%) and vigor (84.8%) over aged seeds. Superoxide and hydrogen peroxide production increased in germinating primed seeds by 27 and 52%, respectively, over aged seeds. Nicotinamide adenine dinucleotide (reduced) (NADH) peroxidase and superoxide dismutase involved in generation of hydrogen peroxide showed increased activity in PMF primed seeds. Increase in catalase, ascorbate peroxidase and glutathione reductase activity after 36 h of imbibition in primed seeds demonstrated its involvement in seed recovery during magnetopriming. An increase in total antioxidants also helped in maintaining the level of free radicals for promoting germination of magnetoprimed seeds. A 44% increase in level of protein carbonyls after 36 h indicated involvement of protein oxidation for counteracting and/or utilizing the production of ROS and faster mobilization of reserve proteins. Higher production of free radicals in primed seeds did not cause lipid peroxidation as malondialdehyde content was low. Lipoxygenase was involved in the germination associated events as the magnitude of activity was higher in primed aged seeds compared to aged seeds. Our study elucidated that PMF mediated improvement in seed quality of aged pea seeds was facilitated by fine tuning of free radicals by the antioxidant defense system and protein oxidation.

Seed priming with polyethylene glycol induces antioxidative defense and metabolic regulation of rice under nano-ZnO stress

The present study was carried out to investigate the beneficial impact of seed priming with polyethylene glycol (PEG) under different concentrations of zinc oxide nanoparticles (nano-ZnO), i.e., 0, 250, 500, and 750 mg L(-1) in two cultivars of Oryza sativa (Zhu Liang You 06 and Qian You No. 1). Physiological parameters were improved by priming with 30 % PEG in both cultivars under stress treatments. Seed priming with 30 % PEG improved α-amylase activities and total soluble sugar contents of both cultivars under nano-ZnO stress. In addition, glutathione reductase (GR) activity, reactive oxygen species (ROS) accumulation, and proline contents decreased after the priming treatment in both cultivars under different nano-ZnO concentrations. Expression of GR1, GR2, Amy2A, and Amy3A genes in shoots and roots of both cultivars increased and had higher transcription levels under the nano-ZnO stress condition. Fourier transform infrared spectroscopy (FTIR) analysis did not show any significant effects of the priming treatment on the band observed at 3400, 900, 1600, and 1000 cm(-1) corresponding to alkenyl stretch (C = C), carboxyl acid (O-H), nitrile (C = N), and aromatic (C-H), respectively, in both cultivars under nano-ZnO stress.

Molecular processes induced in primed seeds-increasing the potential to stabilize crop yields under drought conditions

Environmental stress factors such as drought, salinity, temperature extremes and rising CO₂ negatively affect crop growth and productivity. Faced with the scarcity of water resources, drought is the most critical threat to world food security. This is particularly important in the context of climate change and an increasing world population. Seed priming is a very promising strategy in modern crop production management. Although it has been known for several years that seed priming can enhance seed quality and the effectiveness of stress responses of germinating seeds and seedlings, the molecular mechanisms involved in the acquisition of stress tolerance by primed seeds in the germination process and subsequent plant growth remain poorly understood. This review provides an overview of the metabolic changes modulated by priming, such as the activation of DNA repair and the antioxidant system, accumulation of aquaporins and late embryogenesis abundant proteins that contribute to enhanced drought stress tolerance. Moreover, the phenomenon of "priming memory," which is established during priming and can be recruited later when seeds or plants are exposed to stress, is highlighted.

Quantitative Proteomic Analysis of Wheat Seeds during Artificial Ageing and Priming Using the Isobaric Tandem Mass Tag Labeling

Wheat (Triticum aestivum L.) is an important crop worldwide. The physiological deterioration of seeds during storage and seed priming is closely associated with germination, and thus contributes to plant growth and subsequent grain yields. In this study, wheat seeds during different stages of artificial ageing (45°C; 50% relative humidity; 98%, 50%, 20%, and 1% Germination rates) and priming (hydro-priming treatment) were subjected to proteomics analysis through a proteomic approach based on the isobaric tandem mass tag labeling. A total of 162 differentially expressed proteins (DEPs) mainly involved in metabolism, energy supply, and defense/stress responses, were identified during artificial ageing and thus validated previous physiological and biochemical studies. These DEPs indicated that the inability to protect against ageing leads to the incremental decomposition of the stored substance, impairment of metabolism and energy supply, and ultimately resulted in seed deterioration. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the up-regulated proteins involved in seed ageing were mainly enriched in ribosome, whereas the down-regulated proteins were mainly accumulated in energy supply (starch and sucrose metabolism) and stress defense (ascorbate and aldarate metabolism). Proteins, including hemoglobin 1, oleosin, agglutinin, and non-specific lipid-transfer proteins, were first identified in aged seeds and might be regarded as new markers of seed deterioration. Of the identified proteins, 531 DEPs were recognized during seed priming compared with unprimed seeds. In contrast to the up-regulated DEPs in seed ageing, several up-regulated DEPs in priming were involved in energy supply (tricarboxylic acid cycle, glycolysis, and fatty acid oxidation), anabolism (amino acids, and fatty acid synthesis), and cell growth/division. KEGG and protein-protein interaction analysis indicated that the up-regulated proteins in seed priming were mainly enriched in amino acid synthesis, stress defense (plant-pathogen interactions, and ascorbate and aldarate metabolism), and energy supply (oxidative phosphorylation and carbon metabolism). Therefore, DEPs associated with seed ageing and priming can be used to characterize seed vigor and optimize germination enhancement treatments. This work reveals new proteomic insights into protein changes that occur during seed deterioration and priming.