Differential Radiation Sensitivities of Arabidopsis Plants at Various Developmental Stages

Abstract

Arabidopsis plants were exposed to γ-rays of 200 Gy at one vegetative and three reproductive stages such as 23, 30, 36, and 43 days after sowing the seeds (DAS). The plants irradiated at certain reproductive stages, 30 and 36 DAS, showed a marked delay in leaf senescence in spite of inhibited growth of inflorescence stems and abnormalities in leaf morphology. The delay in leaf senescence was first characterized as increased levels of chlorophylls and carotenoids. The irradiated leaves also showed higher values in the maximum apparent electron transport rate, ETRmax, than the control ones. Moreover, microscopic analysis revealed the increased number of chloroplasts and the integrity of thylakoid membranes in the irradiated leaves of the 30 and 36-DAS plants at the later reproductive stage after ?-irradiation. The obtained results suggest that radiation-induced responses of Arabidopsis plants would be strongly dependent on the developmental stage including differential effects in leaf senescence.