Moving forward to understand the alteration of physiological mechanism by seed priming with different halo-agents under salt stress

Abstract

Soil salinity hampers the survival and productivity of crops. To minimize salt-associated damages in plant, better salt management practices in agriculture have become a prerequisite. Seed priming with different halo-agents is a technique, which improves the primed plant's endurance to tackle sodium. Salt tolerance is achieved in tolerant plants through fundamental physiological mechanisms- ion-exclusion and tissue tolerance, and salt-tolerant plants may (Na⁺ accumulators) or may not (Na⁺ excluders) allow sodium movement to leaves. While Na⁺ excluders depend on ion exclusion in roots, Na⁺ accumulators are proficient Na⁺ managers that can compartmentalize Na⁺ in leaves and use them beneficially as inexpensive osmoticum. Salt-sensitive plants are Na⁺ accumulators, but their inherent tissue tolerance ability and ion-exclusion process are insufficient for tolerance. Seed priming with different halo-agents aids in 'rewiring' of the salt tolerance mechanisms of plants. The resetting of the salt tolerance mechanism is not universal for every halo-agent and might vary with halo-agents. Here, we review the physiological mechanisms that different halo-agents target to confer enhanced salt tolerance in primed plants. Calcium and potassium-specific halo-agents trigger Na⁺ exclusion in roots, thus ensuring a low amount of Na⁺ in leaves. In contrast, Na⁺-specific priming agents favour processes for Na⁺ inclusion in leaves, improve plant tissue tolerance or vacuolar sequestration, and provide the greatest benefit to salt-sensitive and sodium accumulating plants. Overall, this review will help to understand the underlying mechanism behind plant's inherent nature towards salt management and its amelioration with different halo-agents, which helps to optimize crop stress performance.

Keywords: Glycophyte; Halophyte; Optimization of crop performance; Salinity; Sodium accumulator; Sodium excluder; Tissue tolerance.