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Drought stress exposure adversely affects plant growth and productivity. Various seed priming techniques are experimented to mitigate the adverse effect of drought stress on plant performance. It is a low-cost and sustainable technology that proved to be of immense potential to enhance drought tolerance and increase crop productivity. Drought episodes are followed by recovery through rain or irrigation and help the plants to recuperate from the damages caused by drought stress. The severity of drought-associated damages determines the recovery kinetics of plants. Under the recurrent cycle of drought events, recovery kinetics has immense importance in predicting the stress tolerance potential and survival status of a plant. Many processes like DNA damage repair, de-novo synthesis of nucleic acids and proteins, osmotic adjustment through the accumulation of osmolytes, the potential activity of antioxidant machinery occurring during seed priming play a significant role during recovery from drought stress. Alleviation of the severity of drought stress through the accumulation of osmolytes, the augmented activity of antioxidant machinery, improved photosynthetic performance, and the upregulated expression of stress-responsive genes attributed by seed priming will complement the recovery from drought stress. Although the beneficial effects of seed priming on drought tolerance are well explored, priming influenced recovery mechanism has not been well explored. There is a lacuna in the field of research related to the beneficial effects of seed priming for recovery from drought stress, and that is the focus of this paper.

As an essential element, copper (Cu) is involved in various metabolic processes in plants. However, this metal becomes a potential stress factor when the concentration reaches the threshold level. A comparative analysis was conducted to investigate the potential role of two cytokinins [kinetin (KIN) and 6-benzylaminopurine (BAP)] in Cu stress alleviation in Ricinus communis seedlings by assessing the metal bioaccumulation, antioxidation mechanisms, anatomical changes as well as analysis of various essential elements and bioactive compounds in the cotyledonary leaves. Application of KIN and BAP regulated the Cu toxicity in castor seedlings via modulation of metal uptake and antioxidation mechanisms. The increase in antioxidant enzyme activities during Cu stress was further increased upon exposure to cytokinin treatments, and the enhancement reached up to 25 folds for CAT, 16 folds for POD, and 8 folds for SOD over the control, which helps the plant to alleviate the toxic effects of Cu stress. The FTIR analysis of the cotyledonary leaves revealed that the functional groups associated with cell wall materials contributed to the Cu sequestration in the cell wall, supported by the xylem wall thickening as observed in the SEM analysis. The GCMS analysis revealed that most of the secondary metabolites identified were phenolic and flavonoid compounds with antioxidant properties, which help the castor seedlings withstand the Cu stress, and the presence of these compounds was more prominent in cytokinin-treated seedlings. Findings revealed that BAP was more effective than KIN to withstand the Cu stress effects in castor seedlings.

The concentrations of cadmium (Cd) and zinc (Zn) in arable lands exceed the maximum permissible levels due to the excessive use of phosphorus fertilizers and fungicides by farmers. The increasing issues related to the application of agrochemicals have lead to the demand for the implementation of sustainable agricultural approaches. Association of arbuscular mycorrhizae with crop plants is an appropriate strategy due to the potential of these microorganisms to augment the metals tolerance of plants through the immobilization of Cd and Zn in an eco-friendly manner. In the present study, 45 d old Zea mays (var. CoHM6) plants inoculated with AM fungi (Claroideoglomus claroideum) were exposed to 1.95 g Zn Kg−1 soil and 0.45 g Cd Kg−1 soil. The major objective of this study was to determine the metabolic alterations in the leaves and roots of mycorrhizal and non-mycorrhizal plants exposed to CdCl2 and ZnSO4. Both non AM and AM plants exhibited alterations in the quantity of primary and secondary metabolites on exposure to Zn and Cd toxicity. Moreover, Zn and Cd-induced accumulation of γ-sitosterol reduced the quantity of neophytadiene (a well-known terpenoid) and aided the production of 3-β-acetoxystigmasta-4,6,22-triene in maize leaves. Mycorrhization and heavy metal toxicity induced significant metabolic changes in the roots by producing 4,22-stigmastadiene-3-one, eicosane, 9,19-cyclolanost-24-en-3-ol, pentacosane, oxalic acid, heptadecyl hexyl ester, l-norvaline, and n-(2-methoxyethoxycarbonyl). In addition, the metal-induced variations in leaf and root lignin composition were characterized with the aid of the FTIR technique. Mycorrhization improved the tolerance of maize plants to Cd and Zn toxicity by stabilizing these metal ions in the soil and/or limiting their uptake into the plants, thus ensuring normal metabolic functions of their roots and shoots.

Seed priming is a cost-effective, practical, environmental, and farmer-friendly method to improve seed germination that can potentially increase the growth and yield of plants. The priming process enhances various physiological and biochemical mechanisms of defense and empowers the seeds or seedlings to overcome different environmental stresses. However, under critical circumstances, plants are hindered from absorbing specific chemical priming reagents owing to their larger size, molecular structure, or lack of carriers. Therefore, nanoscale materials having exceptional physiochemical properties and a large surface/volume ratio are expected to be better absorbed by the seeds/seedlings as priming agents in comparison to bulk chemicals and can trigger enhanced molecular interactions at the cellular level. Further, the flexibility in altering the surface chemical properties of the nanomaterials can facilitate better interaction with the seeds/seedlings while inhibiting the wastage of priming agents. In this review, we have systematically discussed the potentiality of various nanostructured materials as priming agents in alleviating the adverse effects of various abiotic stresses, viz., drought, salinity, high temperature, cold temperature, and heavy metals, by studying the growth parameters and physiological and biochemical response of various crop plants subjected to these stress conditions. Also, we have highlighted the molecular mechanism and activation of genes involved in enabling abiotic stress tolerance in plants after being primed with nanostructured materials.

Heavy metal toxicity and drought stresses are two growing concerns of the global population as these have a disastrous effect on the agriculture sector, creating oxidative stress in plants and leads to deleterious effects, which end up causing a major decline in yield. Hence, carving out the best candidate for combating both these stresses have become the prime objective of researchers. Plectranthus amboinicus (Lour.) Spreng., a medicinal plant, is regarded as one such candidate that can tolerate both drought and zinc stressors by the elicitation of metabolic changes. Variation in the composition of primary and secondary metabolites of P. amboinicus was evaluated in the leaf tissues of the plants subjected to drought and ZnSO4 (4 mM) treatments. Drought stress resulted in the accumulation of amino acids and sugars in the leaves of plants exposed to this stress. Similarly, zinc stress exhibited a remarkable impact on the synthesis of secondary metabolites like alkaloids, phenols, and flavonoids. Further, on carrying out GC–MS profiling, the compositional variation of secondary metabolites produced in P. amboinicus implicated its inherent potential to survive environments of these two stresses. Compounds like 2-methoxy-4-ethyl-6-methylphenol, gamma-sitosterol, hexadecanoic acid, alpha-amyrin, and ethyl linalool were some of the major secondary metabolites developed in leaves of plants under drought, whereas during ZnSO4 treatment, the major compounds developed were trans-alpha-bergamotene, squalene, 1,5-dimethyl-1-vinyl-4-hexenyl isovalerate, and spathulenol. This in turn makes the plant more compatible with the stressful environmental conditions, aiding it with better survival and protection. At the same time, the enhancement in the content of these metabolites in this medicinal plant under the influence of these stressors may have applications in the pharmaceutical industry, necessary for the development of novel drugs.

More than 2 billion people worldwide suffer from micronutrient malnutrition, sometimes known as hidden hunger. Zn malnutrition affects around a third of the world's population. The physicochemical features of soil, which limit the availability of Zn to plants, cause Zn deficiency. The eating habits of certain populations are more depended on Zn-deficient staple foods. Due to the high expense and certain interventions such as diet diversification, zinc supplementation and food fortification cannot be achieved in disadvantaged populations. Biofortification is the most practical technique for alleviating Zn malnutrition. Seed priming with nutrients is a promising biofortification approach for edible crops. Seed nutripriming with zinc is a cost-effective and environmentally benign approach of biofortification. Seeds can be nutriprimed with Zn using a variety of methods such as Zn fertilisers, Zn chelated compounds and Zn nanoparticles. Nutripriming with nanoparticles is gaining popularity these days due to its numerous advantages and vast biofortification potential. Seeds enriched with Zn also aid plant performance in Zn-deficient soil. Zn an essential trace element can regulate physiological, biochemical and molecular processes of plant cells and thus can enhance germination, growth, yield and bioavailable Zn in edible crops. Moreover, zinc emerges as an important element of choice for the management of COVID-19 symptoms.

The contamination of lands and water by heavy toxic metal(loid)s is an environmental issue that needs serious attention as it poses a major threat to public health. The persistence of heavy metals/metalloids in the environment as well as their potentially dangerous effects on organisms underpins the need to restore the areas contaminated by heavy toxic metal(loid)s. Soil restoration can be achieved through a variety of different methods. Being more cost-effective and environmentally sustainable, phytoremediation has recently replaced traditional processes like soil washing and burning. Many plants have been intensively explored to eliminate various heavy metals from polluted soils through phytoextraction, which is a commonly used phytoremediation approach. The ability of chelants to enhance phytoextraction potential has also received wide attention owing to their ability to elevate the efficiency of plants in removing heavy metal(loid)s. Chelants have been found to improve plant growth and the activity of the defense system. Several chelants, either non-biodegradable or biodegradable, have been reported to augment the phytoextraction efficiencies of various plants. The problem of the leaching of heavy metal(loid)s and secondary pollution caused by non-biodegradable chelants can be overcome by the use of biodegradable chelants to an extent. This review is a brief report focusing on recent articles on chelate-assisted phytoextraction of heavy metal (loids) As, Cd, Cu, Cr, Hg, Ni, Pb, U, and Zn.The review

Biostimulants can be used as an alternative to fertilizers to overcome the effect of nutrient deficiency in plants. Yeast is a biostimulant, having the capacity to modify physiological processes in plants by improving germination and seedling growth under environmental stress. The effects of yeast extract, a sustainable biostimulant derived from yeast (Saccharomyces cerevisiae) containing all the nutritive values, amino acids, vitamins, and growth factors, were investigated in rice (Oryza sativa). Various growth parameters, Chlorophyll a fluorescence, PS II, metabolites accumulation, and antioxidative function of enzymatic (SOD, CAT, APX, GPOX) as well as non-enzymatic (phenol, AsA, and GSH) antioxidant were analyzed in two rice varieties (Hraswa-tolerant and Manu ratna-sensitive) in both yeast extract primed and non-primed seeds subjected to nutrient-deficient soil conditions. The application of the biostimulant (yeast extract) as a priming agent increased the biomass, photosynthetic pigment, modified chlorophyll a fluorescence-related parameters, and also enhanced the photosystem activities of seedlings, supported by decreased content of ROS and MDA in primed seeds when compared to non-primed ones. These changes were accompanied by a significant enhancement in osmolytes and non-enzymatic antioxidants (AsA, GSH, and total phenolics). In general, yeast priming under nutrient-deficient conditions appeared to stimulate the activities of SOD, CAT, and APX in var. Hraswa while GPOX was dramatically upregulated in var. Manu ratna. Thus, these results speculate that yeast priming under nutrient-deficient conditions maintained cell homeostasis and provided better adaptation to the stress conditions in both tolerant as well as sensitive varieties of rice seedlings.

Bioenergy plants that are better adapted to metal-contaminated lands can be used for phytoremediation purposes and also can be additionally used to produce biofuels such as bioethanol, biodiesel, a...

Photosynthetic efficiency is significantly affected by both qualitative and quantitative changes during light exposure. The properties of light have a profound effect on electron transport and energy absorption in photochemical reactions. In addition, fluctuations in light intensity and variations in the spectrum can lead to a decrease in photosystem II efficiency. These features necessitate the use of a simple and suitable tool called chlorophyll

NaCl and polyethylene glycol-6000 (PEG) stressors are the major limitation factors for successful seedling establishment in rice. The present study was carried out to investigate the role of UV-B priming on the augmentation of stress tolerance in tolerant and sensitive rice seedlings exposed to NaCl and PEG stresses. The result shows that the severity of drought than salinity stress was experienced by emerging rice seedlings as evidenced from increased content of H2O2, O2− and MDA. However, the seed priming with UV-B results in the enhanced production of defense agents, there by activating innate tolerance potential of the seedlings. UV-B priming reduces excess ROS accumulation during NaCl and PEG stresses and thus eliminates the chance of oxidative stress in the rice seedlings. This was possible by enhancing the crucial role of innate immune system, which imparts tolerance toward NaCl and PEG stresses. UV-B seed priming maintained maximal photochemical efficiency of PSI and PSII as well as mitochondrial activity of tolerant and sensitive varieties under NaCl and PEG stresses due to the increased activity of osmolytes and non-enzymatic antioxidants as well as induced expression of enzymatic antioxidants (Cu/Zn SOD, CatA and APx1) and stress-related proteins (Hsp90 and Group3 LEA) in tolerant variety at large, followed by sensitive variety.

Plants are exposed to various abiotic stresses and there exists sophisticated mechanisms within them for tolerating these stresses. The present study clearly revealed the efficacy of UV-B priming at both seed and seedling stage in tolerant (Kanchana) and sensitive (Aiswarya) rice varieties, to tolerate UV-B stress, polyethylene glycol-6000 (PEG) and NaCl stresses. Increase in UV stress specific characters such as accumulation of UV absorbing compounds [flavonoids (242–368%) and anthocyanin (367–386%) content],increased activity of phenylalanine ammonia lyase (116–210%) and increased leaf cuticular wax content (382–403%) was observed in UV-B primed seedlings of rice subjected to UV-B, NaCl and PEG stresses. The increase in the levels shown as percent increase were highest in seedlings subjected to UV-B stress followed by NaCl and PEG stresses. The influence of priming imprints was more effective in seeds and seedlings of the tolerant rice variety (Kanchana) than the sensitive variety (Aiswarya). Functional groups variation in wax content was more prominent in PEG stress conditions than UV-B and NaCl stresses and it was mainly observed in Aiswarya than in Kanchana. Additionally our results suggests the UV-priming mediated enhancement of the stress tolerance potential of a tolerant variety seems to be more successful than the sensitive variety.

NaCl and PEG stresses have negative impacts on seed germination and early seedling establishment in Oryza sativa. The present study was designed to ascertain the influence of different priming techniques (Hydro priming-HyP, Halo priming-HP, UV-B priming-UP) in enhancing oxidative and anti-oxidative mechanisms during seed germination phase in response to NaCl and PEG stresses tolerance of three rice varieties (Neeraja, Vaisakh and Vyttila 6). NaCl and PEG stresses caused delayed germination rate, enhanced reactive oxygen species content and thereby increased lipid peroxidation rate. Different priming techniques significantly hastened the metabolites/non enzymatic antioxidant contents (total sugars, total phenolics, free amino acids, proline, ascorbate and glutathione) as well as activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase), and thus reduced oxidative stress damages caused by NaCl and PEG stresses in rice seedlings. Seed priming techniques imparted abiotic stress tolerance not only to sensitive varieties but also additional tolerance potential to tolerant varieties. All three priming techniques protects the plants from toxicity caused by NaCl and PEG stresses but halo priming had proved to be more successful.

Arable lands getting contaminated with heavy metals have a very high negative impact on crop plants. The establishment of the mycorrhizal association with crop plants is a sustainable strategy to overcome metal toxicity. The major aim of this study was to analyze mycorrhizae-mediated alterations on the physiology and metabolism of Oryza sativa, as well as the impact of these alterations in the metal tolerance potential of the host on exposure to cadmium (Cd) and zinc (Zn) stresses. For this, 45 d old O. sativa (var. Varsha) plants inoculated with Claroideoglomus claroideum were exposed to 1.95 g Zn kg

Drought stress is a major stress constraint for the growth and establishment of rice seedlings. The objective of this study was to investigate the effects of UV-B and halo priming induced physiochemical changes in the seedling stage of drought-sensitive rice variety exposed to drought stress and recovery. The seedlings of Oryza sativa L. var. Neeraja were UV-B and halo primed and was further subjected to drought stress and recovery. Drought stress induced reactive oxygen species leads to the accumulation of carbonyl content indicating the impairment of photosynthetic machinery and various cellular activities. However, the seed priming resulted in the enhanced production of various metabolites such as proline, amino acids, soluble protein, total phenolics and total soluble sugar. Moreover, it increased the activities of antioxidant enzymes such as superoxide dismutase, catalase and ascorbate peroxidase in rice seedlings exposed to drought stress. After re-watering, all the increased physiochemical parameters of primed and non-primed rice seedlings returned to the levels as in control. The retention of priming memory in seedlings emerged from primed seeds make them more tolerant towards drought and rapid recovery occurs in response to re-watering. Thus, these results suggest that halo and UV-B priming of Oryza sativa seeds is an effective means for reducing drought stress impacts and enhancing the recovery rate from drought at the seedling stage .

Physio-anatomical modifications and elemental distribution pattern in Acanthus ilicifolius subjected to Zn stress were analysed in this study. Survival of A. ilicifolius plants under a high concentration of ZnSO4 was compensated by the reduction in the photosynthetic efficacy. Micro and macro-elemental distribution pattern in the root tissues was significantly influenced by heavy metal exposure. Tolerance towards the excess toxic metal ions in the tissue of A. ilicifolius was aided by the modified anatomical features. Moreover, the increased deposition of Zn around the central vasculature of the root confirms the complexation of Zn2+ in the xylem vessels. Metal induced molecular level changes of root and leaf samples indicate the presence of OH, NH2, and CH3 deformation as well as C-O-H and C-O-C stretch. A prominent band corresponding to CH3 deformation, pointing hemicellulose fortification, occurs in the cell walls of the xylem, aiding in Zn localization. The phytostabilisation potential of A. ilicifolius is dependent on the coordinated responses which endow with phenotypic plasticity necessary to cope with Zn toxicity.

The concentrations of cadmium (Cd) and zinc (Zn) in arable lands exceed the maximum permissible levels due to the excessive use of phosphorus fertilizers and fungicides by farmers. The increasing issues related to the application of agrochemicals have lead to the demand for the implementation of sustainable agricultural approaches. Association of arbuscular mycorrhizae with crop plants is an appropriate strategy due to the potential of these microorganisms to augment the metals tolerance of plants through the immobilization of Cd and Zn in an eco-friendly manner. In the present study, 45 d old Zea mays (var. CoHM6) plants inoculated with AM fungi (Claroideoglomus claroideum) were exposed to 1.95 g Zn Kg

Potassium (K) is an essential element for the growth and development of plants; however, its scarcity or excessive level leads to distortion of numerous functions in plants. It takes part in the control of various significant functions in plant advancement. Because of the importance index, K is regarded second after nitrogen for whole plant growth. Approximately, higher than 60 enzymes are reliant on K for activation within the plant system, in which K plays a vital function as a regulator. Potassium provides assistance in plants against abiotic stress conditions in the environment. With this background, the present paper reviews the physiological functions of K in plants like stomatal regulation, photosynthesis and water uptake. The article also focuses upon the uptake and transport mechanisms of K along with its role in detoxification of reactive oxygen species and in conferring tolerance to plants against abiotic stresses. It also highlights the research progress made in the direction of K mediated signaling cascades.

The carcinogenic attribute of arsenic (As) has turned the world to focus more on the decontamination and declining the present level of As from the environment especially from the soil and water bodies. Phytoremediation has achieved a status of sustainable and eco-friendly approach of decontaminating pollutants, and in the present study, an attempt has been made to reveal the potential of As remediation by a halophyte plant, Acanthus ilicifolius L. Special attention has given to analyse the morphological, physiological and anatomical modulations in A. ilicifolius, developed in response to altering concentrations of Na