EFFECT OF HEAT-STRESS DURING SEED DEVELOPMENT AND MATURATION ON WHEAT(TRITICUM-DURUM) SEED QUALITY .1. SEED-GERMINATION AND SEEDLING VIGOR

Two wheat cultivars, Marzak and Oum-rabia, were subjected to three tem perature regimes (20/15, 28/21, 36/29 degrees C) beginning 10 d after anthesis to maturity. As expected, high temperature resulted in low va lues of both seed yield and physical traits of seed quality. The effec t of temperature on seed germination was not consistent among the two cultivars. High temperature during seed development and maturity had n o effect on seed germination of Oum-rabia, whereas it decreased seed g ermination of Marzak. In contrast to seed germination, seed vigor was adversely affected by heat stress. This decline in seed vigor was refl ected in reduced shoot and root dry weight, increased shoot/root ratio , reduced root length, low root number per seedling, and high seed con ductivity. Excised embryo culture showed marked differences in the emb ryo growth potential. Although embryos from all treatments had germina ted, a delay of 24-48 h was observed in the germination of embryos exc ised from seeds grown under high temperature conditions. Also, their s hoot and radicle development over time lagged behind that of embryos i solated from seeds grown under cool temperature conditions. Exposing s eeds to high temperature during development and maturity also resulted in low embryo oxygen uptake. Results presented in this study show tha t the growing conditions, in this instance temperature, of the parent plant affect the quality of its seed.