Sameera O. Bafeel

Gibberellic acid (GA) and jasmonic acid (JA) are considered to be endogenous regulators that play a vital role in regulating plant responses to stress conditions. This study investigated the ameliorative role of GA, JA, and the GA + JA mixture in mitigating the detrimental effect of salinity on the summer squash plant. In order to explore the physiological mechanisms of salt stress alleviation carried out by exogenous GA and JA, seed priming with 1.5 mM GA, 0.005 mM JA, and their mixture was performed; then the germinated summer squash seedlings were exposed to 50 mM NaCl. The results showed that a 50 mM NaCl treatment significantly reduced shoot and root fresh and dry weight, water content (%), the concentration of carotenoid (Car), nucleic acids, K⁺, and Mg⁺⁺, the K⁺/Na⁺ ratio, and the activity of catalase (CAT) and ascorbate peroxidase (APX), while it increased the concentration of proline, thiobarbituric acid reactive substances (TBARS), Na⁺, and Cl⁻ in summer squash plants, when compared with the control. However, seed priming with GA, JA and the GA + JA mixture significantly improved summer squash salt tolerance by reducing the concentration of Na⁺ and Cl⁻, TBARS, and the Chl a/b ratio and by increasing the activity of superoxide dismutase, CAT, and APX, the quantities of K⁺ and Mg⁺⁺, the K⁺/Na⁺ ratio, and the quantities of RNA, DNA, chlorophyll b, and Car, which, in turn, ameliorated the growth of salinized plants. These findings suggest that GA and JA are able to efficiently defend summer squash plants from salinity destruction by adjusting nutrient uptake and increasing the activity of antioxidant enzymes in order to decrease reactive oxygen species accumulation due to salinity stress; these findings offer a practical intervention for summer squash cultivation in salt-affected soils. Synergistic effects of the GA and JA combination were not clearly observed, and JA alleviated most of the studied traits associated with salinity stress induced in summer squash more efficiently than GA or the GA + JA mixture.

This study explored the effectiveness of green zinc oxide nanoparticles (ZnO-NPs) foliar spray on tomato growth and oxidative stress relief under drought conditions. Tomato plant subjected to four water regimes (100, 75, 50, and 25% FC), and in the same while seedlings were sprayed with 25, 50, and 100 mg/L green ZnO-NPs. The results showed that tomato growth parameters reduced significantly by increasing drought stress levels, while ZnO-NPs enhanced plant growth under all studied drought levels. Out of three ZnO-NPs concentrations tested, 25 and 50 mg/L ZnO-NPs proved to be the optimum treatments for alleviating drought stress. They increased shoot and root biomass compared to untreated controls. Application of 25 and 50 mg/L ZnO-NPs enhanced shoot dry weight by about 2–2.5-fold, respectively, under severe drought conditions (25%) compared to ZnO-NPs untreated plants. The application of 25 and 50 mg/L green ZnO-NPs decreased the drought-induced oxidative stress as indicated by the reduction in malondialdehyde and hydrogen peroxide concentrations compared to untreated controls. While 100 mg/L ZnO-NPs further increased oxidative stress. The beneficial effects of ZnO-NPs were evident in the plants’ defensive state, in which the concentration of ascorbic acid, free phenols, and the activity of superoxide dismutase, catalase, and ascorbate peroxidase were maintained at higher levels compared to NPs-untreated plants. At severe drought conditions, 25 mg/L ZnO-NPs induced SOD, CAT, and APX activity by about 3.99-, 3.23-, and 2.82-fold of their corresponding controls, respectively. Likewise, at 25% FC, SOD, CAT, and APX activity increased with 50 mg/L ZnO-NPs by about 4.58-, 3.57-, and 3.25-fold consecutively compared with their respective controls. Therefore, foliar use of green ZnO-NPs at lower concentrations might be suggested as an efficient way for enhancing tomato tolerance to drought stress.

The aim of this study was todetect the expression profiles of salt-related genes in the leaf transcriptome of Jojoba (Simmondsia chinensis) to decipher the molecular mechanisms underlying salt stress tolerance in this plant species. The analyzed RNA-Seq data identified numerous differentially expressed genesthat were mostly upregulated under salt (NaCl) stress conditions. The genes varied in their ability to limit cellular damage under stress conditions by regulatingthe production of reactive oxygen species (ROS). Some genes demonstrated the use of methylation/demethylation followed by intergenerational transmission of a “stress memory”. Other genes are known for their potential to produce proteins with superoxide dismutase (SOD) activity, the ability to detoxify metal ions and to produce molecular chaperones. Additional activities include regulating signal transductionandthe ion transport processes, the reprogramming of selective gene expression andthe maintenance of balanced sucrose content, ethylene signaling and homeostasis, the regulating of plasmodesmal permeability, ubiquitination,and selective protein degradation. Moreover, genes were also identified to be associated with cell wall remodeling, alleviating chlorophyll content, and accumulatinglower levels of sodium (Na+) and chloride (Cl-), as well as increased levels of lignin that function to support a plant’s integrity under salt stress. Overall, these data provide new insights into the molecular mechanisms at play during conditions of salt stress. These mechanisms ensure a plant’s survival and help to maintain its natural chemical compounds. These findings may be beneficial in furthering the use of this economically important plant.

Success in the extension of crop production in the salt affected area may help to meet the demand of the world’s hunger. In plants, Na+ permeable HKT (High-affinity K + Transporter) gene family represents a primary mechanism for mediating salt tolerance. Better understanding of the relationship among HKT genes may provide a framework for the development of salt tolerance cultivars. In this study, phylogeny of plant- HKT gene family using the available nucleotide sequences in the current databases was examined. This study showed a total of 6 phylo-groups. Phylogenetic analyses based on HKT gene sequences demonstrated distinct lineages for monocots and eudicots. Group I, II and VI contained only monocots. Eudicots were clustered in group III, IV and V. A stable relationship was observed among the members of the group I (previously described as subfamily 2). Overall pairwise mean distance was very high (1.13), indicating the high level of diversity of the HKT gene family. Observed pairwise distances were: Group 4 (eudicots, 0.81) > group 6 (monocots, 0.52) > group 2 (monocots, 0.35) > group 1 (monocots, 0.33) ? group 5 (eudicots, 0.33) > group 3 (eudicots, 0.17).