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Salinity is an agro-environmental problem limiting plant growth and development in the arid to semi-arid regions of the world and becomes the predicament of serious concern. Plants exposed to salt stress may undergo osmotic stress, ion toxicity and nutritional imbalance which results in production of reactive oxygen species (ROS). The ability of plants to detoxify radicals under conditions of salt stress is probably the most critical requirement and is determined by multifarious morpho-physiological and biochemical pathways like initial entry of salt to roots, intercellular compartmentation, synthesis of osmoprotectants (sugars, amino acids, proline and upgradation of antioxidant system) that results in maintaining ion homeostasis. This paper also revealed the plant responses to salinity stress with emphasis on physiological and biochemical mechanisms of salt tolerance which may help in interdisciplinary studies to assess the ecological consequence of salt stress. Moreover, the application of potassium helps the plants to cope with the hazardous effects of salinity by improving the morphological, physiological and biochemical attributes.

Generation of ROS seems to be unavoidable under normal conditions and the activity of antioxidant enzymes in plants varies in terms of ROS generation under salt stress. However, the data indicate that plants subjected to salt stress-induced oxidative stress and the low concentrations of chitosan exhibited positive effects on salt stress alleviation through the reduction of enzyme activity in both crops.

Summary Under dehydration in plants, antagonistic activities of histone 3 lysine 4 (H3K4) methyltransferase and histone demethylase maintain a dynamic and homeostatic state of gene expression by orientating transcriptional reprogramming toward growth or stress tolerance. However, the histone demethylase that specifically controls histone methylation homeostasis under dehydration stress remains unknown. Here, we document that a histone demethylase, JMJ17, belonging to the KDM5/JARID1 family, plays crucial roles in response to dehydration stress and abscisic acid (ABA) in Arabidopsis thaliana. jmj17 loss‐of‐function mutants displayed dehydration stress tolerance and ABA hypersensitivity in terms of stomatal closure. JMJ17 specifically demethylated H3K4me1/2/3 via conserved iron‐binding amino acids in vitro and in vivo. Moreover, H3K4 demethylase activity of JMJ17 was required for dehydration stress response. Systematic combination of genome‐wide chromatin immunoprecipitation coupled with massively parallel DNA sequencing (ChIP‐seq) and RNA‐sequencing (RNA‐seq) analyses revealed that a loss‐of‐function mutation in JMJ17 caused an ectopic increase in genome‐wide H3K4me3 levels and activated a plethora of dehydration stress‐responsive genes. Importantly, JMJ17 bound directly to the chromatin of OPEN STOMATA 1 (OST1) and demethylated H3K4me3 for the regulation of OST1 mRNA abundance, thereby modulating the dehydration stress response. Our results demonstrate a new function of a histone demethylase under dehydration stress in plants.

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A pot experiment was conducted to investigate the role of potassium (K) in extenuating the injurious effect of salt stress on maize hybrids differing in salt tolerance at different growth stages. One salt-sensitive viz. 8441 and one salt-tolerant viz. 26,204 maize hybrids were sown in pots having 12 kg soil. The recommended dose of nitrogen and phosphorus @ 200 and 150 kg ha -1 with different rate of potassium (75, 150 and 300 kg ha -1 ) and salinity level (10 dS m -1 ) was developed in soil before filling the pots. Salinity stress reduced plant growth by affecting plant morphological characteristics, reducing relative water contents and membrane stability index, decreasing photosynthetic activities, altering K ? /Na ? ratios and antioxidant activities of both maize hybrids at all three growth stages. However, results also depicts that maximum relative water contents, membrane stability index, gas exchange attributes, photosynthetic pigments, antioxidant enzymes activities and proline contents was observed at reproductive growth stage as compared to vegetative and grain development growth stages in both hybrids. The inhibitory effect of salt stress was more pronounced on maize hybrid 8441 than 26,204. But, addition of potassium significantly alleviates harmful effect of salinity by improving the plant growth, gas exchange parameters, enhancing K ? /Na ? ratios and antioxidant activities of both maize hybrids. Potassium application (300 kg K ha -1 ) was found more effective in alleviating perilous effect of salinity as compared to other two levels. Salt tolerant maize hybrid (26,204) produced more biomass, less shoot Na ? concentration, high K ? concentration, exhibited more chlorophyll contents, gas exchange parameters and antioxidant enzymes activities under salt stress condition at all growth stages as compared to salt sensitive maize hybrids (8441). These results suggested that potassium application counteracted the unfavorable effects of salinity on growth of maize by civilizing photosynthetic capacity of maize plants against salinity-induced oxidative stress and maintaining ion homeostasis, however, these alleviating effects were cultivar specific.

Trithorax-group proteins (TrxGs) play essential regulatory roles in chromatin modification to activate transcription. Although TrxGs have been shown to be extensively involved in the activation of developmental genes, how the specific TrxGs function in the dehydration and abscisic acid (ABA)-mediated modulation of downstream gene expression remains unknown. Here, we report that two evolutionarily conserved Arabidopsis thaliana TrxGs, ARABIDOPSIS TRITHORAX4 (ATX4) and ATX5, play essential roles in the drought stress response. atx4 and atx5 single loss-of-function mutants showed drought stress-tolerant and ABA-hypersensitive phenotypes during seed germination and seedling development, while the atx4 atx5 double mutant displayed further exacerbation of the phenotypes. Genome-wide RNA-sequencing analyses showed that ATX4 and ATX5 regulate the expression of genes functioning in dehydration stress. Intriguingly, ABA-HYPERSENSITIVE GERMINATION 3 (AHG3), an essential negative regulator of ABA signaling, acts genetically downstream of ATX4 and ATX5 in response to ABA. ATX4 and ATX5 directly bind to the AHG3 locus and trimethylate histone H3 of Lys 4 (H3K4). Moreover, ATX4 and ATX5 occupancies at AHG3 are dramatically increased under ABA treatment, and are also essential for RNA polymerase II (RNAPII) occupancies. Our findings reveal novel molecular functions of A. thaliana TrxGs in dehydration stress and ABA responses.

Soil pollution caused by heavy metals is one of the major problems throughout the world. To maintain a safe and healthy environment for human beings, there is a dire need to identify hyperaccumulator plants and the underlying genes involved in heavy metals stress tolerance and accumulation. The goal of this research is to explore the potential of hemp as a decontaminator of heavy metals by identifying the two important heavy metals responsive genes, glutathione-disulfidereductase (GSR) and phospholipase D-a (PLDa). The results revealed heavy metals accumulation; Cu (1530 mg kg ) in hemp plants' leaves collected from the contaminated site. This shows the ability of the hemp plant to tolerate heavy metals, perhaps due to the presence of stress tolerance genes. In this study, partial sequences of putative GSR (215 bp) and PLDa (517 bp) genes were identified, responsive to heavy metals stress in hemp leaves. Both genes exhibited 40-60% sequence identity to previously reported genes from other plant species. Glutathione binding residues and conserved arginine residues were found identical in a putative GSR gene to those of other plant species, while the phospholipids binding domain and catalytic domain were found in the PLDa gene. These results will help to improve our understanding about the phytoremediation potential of hemp as well as in manipulating GSR and PLDa genes in breeding programs to produce transgenic heavy-metals-tolerant varieties.