Seed Priming and Its Role in Mitigating Heat Stress Responses in Crop Plants

Abstract

Rise in temperature beyond threshold level that causes irreversible damage in plants is heat stress while heat stress during reproductive or grain filling period is regarded as terminal heat stress. Heat stress significantly alters plant growth and metabolic activities and makes them struggle for survival. Terminal heat stress obstructs growth and development of crops by disturbing their physiological and biochemical progressions of reproductive stages like grain/pod filling, their development, maturation, ripening and ultimately conferring yield loss. However, one of the easiest and low-priced advanced techniques to diminish this loss is seed priming. In this technique, seeds are soaked in different nutrient-enriched solutions to improve their quality for establishing uniform and rapid seed germination, resulting in healthy and vigorous seedlings. This method of seed soaking elicits pre-germinative metabolic responses inside seed that leads to early germination and fastens crop establishment process. Various priming techniques have been adapted that include hydropriming, halopriming, osmopriming, sand matric priming and nutripriming (priming with water, salt, osmoticum, moist sand and nutrient). Seed priming has an important role to alleviate terminal heat stress by inducing the activity of many enzymes during pre-soaking period as various enzymes require hydration energy for activation. Seed priming also sometimes increases production and activity of heat shock proteins (HSPs) and molecular chaperones to ensure proper protein folding and prevent protein denaturation during heat stress condition. Despite positive responses of various seed priming techniques, these have been less applied in the area of crop production in the field condition. Considering these facts, this review depicts responses of the plants under heat stress and its management through seed priming techniques, especially under field condition, and to associate the same with enhanced crop production under the stressful situations.