Response to X-rays of dormant and non-dormant seeds of Triticum durum desf

Abstract

The X-ray sensitivity of dry seeds of durum wheat at different levels of dormancy was examined. Two doses of X-ray exposures (1000 and 5000 R) were utilized and analysis was carried out on cells from root to tip meristems of seeds allowed to germinate on moistened filter paper for different times. The results showed that the 1000 R dose did not increase the spontaneous chromosome damage in deep dormant seeds, while inducing a 100% increase in chromosome damage in lightly dormant and in non-dormant seeds. The deep dormant seeds irradiated with 5000 R showed a chromosome damage lower than that of both lightly dormant and non-dormant seeds. The chromosome damage was of chromatid type (B′) at 1000 R, irrespective of the physiological condition of the seeds. On the contrary, the lightly dormant or non-dormant seeds irradiated with 5000 R showed both chromatid and chromosome (B″) damage; the deep dormant seeds exhibited B′ damage only. The lack of B″ damage in root meristems from deep dormant seeds is likely to be due to (i) the physiological state of seeds which causes a slow germination and a possible delay of mitosis initiation at germination, (ii) a more efficient repair process or a greater radiation resistance bound to the metabolic condition of the deep dormant seeds.