Contribution of structural and functional adaptations of hyper-accumulator Suaeda vera Forssk. ex J.F. Gmel. for adaptability across salinity gradients in hot desert.

The role of ionic excretions and hyper-accumulation of salts through alterations of structural and functional traits in five populations of Suaeda vera Forssk. ex J.F. Gmel., a halophytic salt-indicator species of saline environments, was explored. Differently adapted populations of S. vera exhibited specific structural and functional responses for the survival in hyper-saline conditions. Better growth in population from moderately saline habitat (25-30 dS m-1) was linked to high shoot and root K+ and increased ion selectivity (K+/Na+ and Ca2+/Na+). Increased excretion of Na+ and Cl- with increasing salinity level was a critical mechanism in maintaining ionic balance. Drastic differences were observed for anatomical characteristics in populations inhabiting differentially salt-affected lands. The plants from highly saline sites were characterized by narrow metaxylem vessels, low proportion of cortical parenchyma, and reduced phloem area leading to stunted growth. Contrariwise, root area significantly increased due to high proportion of sclerified xylem tissue, which was associated with easier conduction of solutes and protection of roots from collapsing. Root sclerification particularly at the highest salinity regime was a key factor in the survival of this species in salt-affected compact soils. Leaf anatomical characteristics showed reduction with increasing salinity, but the leaf thickness responded otherwise. This contributed to increased leaf succulence because of high proportion of storage parenchyma in populations colonizing hyper-saline habitats. It was concluded that moderate salinity conditions were more suitable for the growth of S. vera, though some populations of this species were able to tolerate much higher salinity levels.

Foliar Spray of Alpha-Tocopherol Modulates Antioxidant Potential of Okra Fruit under Salt Stress.

As an antioxidant, alpha-tocopherol (α-Toc) protects plants from salinity-induced oxidative bursts. This study was conducted twice to determine the effect of α-Toc as a foliar spray (at 0 (no spray), 100, 200, and 300 mg L-1) to improve the yield and biochemical constituents of fresh green capsules of okra (Abelmoschus esculentus L. Moench) under salt stress (0 and 100 mM). Salt stress significantly reduced K+ and Ca2+ ion concentration and yield, whereas it increased H2O2, malondialdehyde (MDA), Na+, glycine betaine (GB), total free proline, total phenolics, and the activities of catalase (CAT), guaiacol peroxidase (GPX), and protease in both okra varieties (Noori and Sabzpari). Foliar application of α-Toc significantly improved the yield in tested okra varieties by increasing the activity of antioxidants (CAT, GPX, SOD, and ascorbic acid), accumulation of GB, and total free proline in fruit tissues under saline and non-saline conditions. Moreover, α-Toc application as a foliar spray alleviated the adverse effects of salt stress by reducing Na+ concentration, MDA, and H2O2 levels and improving the uptake of K+ and Ca2+. Among the tested okra varieties, Noori performed better than Sabzpari across all physio-biochemical attributes. Of all the foliar-applied α-Toc levels, 200 mg L-1 and 300 mg L-1 were more effective in the amelioration of salinity-induced adverse effects in okra. Thus, we concluded that higher levels of α-Toc (200 mg L-1 and 300 mg L-1) combat salinity stress more effectively by boosting the antioxidant potential of okra plants.