Abstract
Irradiation stress adversely affects plant growth and development. No radioprotective activity of glycinebetaine (GB) has yet been reported in plants. When applied pre-sowing to dry seeds of fenugreek, gamma rays at doses of 0, 25, 50, 100 and 150 Gray (Gy) from a cobalt ( 60 Co) source with a strength of 500 Ci and a dose rate of 0.54 Gy/min significantly reduced the chlorophyll content, total protein, photosynthetic efficiency ( 14 CO 2 fixation), total dry weight, and accumulation of reducing, non-reducing and total soluble sugars in comparison with the un-irradiated control. It also significantly repressed the activities of hydrolytic enzymes (α-amylase and invertase) and the carboxylating enzyme (ribulose-1,5-bisphosphate-carboxylase/oxygenase) in the fenugreek plants. Soaking irradiated seeds with glycinebetaine (50 mM) for 24 hours partially alleviated the depression effects of irradiation in these parameters. Gamma irradiation significantly increased the H 2 O 2 content, while pre-soaking irradiated seeds with GB significantly decreased the H 2 O 2 level. The magnitude of the reversal declined as the irradiation dose increased.Gamma irradiation induced a significant decrease in the level of nucleic acids (DNA and RNA), accompanied by a corresponding induction of the hydrolytic activities of DNase and RNase in comparison with the un-irradiated control. These changes were more significant at higher γ-ray doses. Post-treatment of irradiated seeds with GB partially alleviated the adverse effects of radiation, significantly increasing nucleic acid levels and repressing the activities of DNase and RNase. The protective role played by glycinebetaine was more significant at lower γ-ray doses. Pre-treatment of seeds with GB may play an effective role in the radio-repair mechanism.
Published Version
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