The influence of heat shock on the rate of reserves allocated by wheat seeds for germination and growth

Abstract

We studied the accumulation and consumption of biomass by five-day-old seedlings of various wheat varieties (Triticum aestivum L.) grown from control and exposed to heat shock (HS) seeds. The suppression shoot and roots growth intensified with the temperature, which caused HS. With increasing the temperature (+50°С, +51°С, +52°С și +53°С) of HS, the biomass of the endosperm of the seeds transferred to the seedling, and spent on respiration during seed germination, and seedling growth decreased. Moreover, the effect of HS was more pronounced on the biomass of endosperm substances transferred to the seedling. To increase the resolution of separating wheat varieties according to their resistance to HS, we applied the optimal value (+52°С) of the HS temperature (HSo). The rate of dry matter transferred from the endosperm to the shoot, roots, and spent on respiration, made it possible to rank various wheat varieties following their resistance to high temperatures. The higher the resistance of a wheat cultivar to high temperatures, the higher the proportion of endosperm substances consumed by exposed to HSo seeds for seedling growth and respiration. With increasing the wheat varieties to high temperatures, the rate of endosperm biomass transferred to the seedling also increased, at the same time that spent on respiration on the contrary, decreased. After exposure to HSo, the seeds of the resistant to high temperatures varieties also showed higher metabolic efficiency than those of less resistant varieties. All parameters characterizing the resistance of leaves and roots to HS suggested that the high-temperature resistance of roots is lower than that of leaves. The method for determining the resistance of wheat varieties to high temperatures, based on the ability of seeds exposed to HSo, to mobilize reserve substances for germination and growth is fast, characterized by increased resolution, and ensures the distribution of wheat varieties according to their resistance to high temperatures.