Study of biochemical traits of Mexican lime (Citrus aurantifolia L. var. Mexican lime) to low temperature after treatment by glycine betaine

Glycine betaine (GB) is an important compatible solute that acts as a substitute for water molecules release protein and membrane protection and also acts as active oxygen scavengers. In some plants، accumulation of this compound causes resistance to various stresses such as low temperature. In this experiment، the effect of exogenous application of GB and low temperature stress was investigated on Mexican lime in factorial experiment based on complete randomized design with three replications. Glycine betaine was applied at five levels (0، 2. 5، 5، 7. 5 and 100 mM) and also plants were subjected to five temperature treatments (2، 0، -2، -4 and -6°C). Results showed that spraying by 7. 5 and 10 mM GB as compared to other concentrations apart from the temperature at 2°C significantly increased the activity of peroxidase (POD) during the stress. Also، 10 mM of GB increased the total protein during the low temperatures in leaf tissues significantly. However، different concentrations of GB had not any clear effact on other characteristics such as lipid peroxidation (MDA)، ion leakage (EC)، total antioxidant capacity (DPPH sc%) and superoxide dismutase (SOD). It seemed that GB had protected the proteins such as peroxidase. In this study SOD content did not change during treatments that may depended on the low duration of stress. In addition، GB without antioxidant role in Mexican lime، could not protect the membrane from proxidation.