Moving Forward to Understand the Alteration of Physiological Mechanism by Seed Priming with Different Halo-agents Under Salt Stress

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.