Effect of heat stress during seed development and maturation on wheat (Triticum durum) seed quality. I. Seed germination and seedling vigor

Abstract

Two wheat cultivars, Marzak and Oum-rabia, were subjected to three temperature regimes (20/15, 28/21, 36/29 °C) beginning 10 d after anthesis to maturity. As expected, high temperature resulted in low values of both seed yield and physical traits of seed quality. The effect of temperature on seed germination was not consistent among the two cultivars. High temperature during seed development and maturity had no effect on seed germination of Oum-rabia, whereas it decreased seed germination of Marzak. In contrast to seed germination, seed vigor was adversely affected by heat stress. This decline in seed vigor was reflected in reduced shoot and root dry weight, increased shoot/root ratio, reduced root length, low root number per seedling, and high seed conductivity. Excised embryo culture showed marked differences in the embryo growth potential. Although embryos from all treatments had germinated, a delay of 24–48 h was observed in the germination of embryos excised from seeds grown under high temperature conditions. Also, their shoot and radicle development over time lagged behind that of embryos isolated from seeds grown under cool temperature conditions. Exposing seeds to high temperature during development and maturity also resulted in low embryo oxygen uptake. Results presented in this study show that the growing conditions, in this instance temperature, of the parent plant affect the quality of its seed. Key words: Embryo, germination, oxygen uptake, vigor, wheat, high temperature