The Effect of Exogenous Proline and Glycine Betaine on Phyto-biochemical Responses of Salt-stressed Basil Plants

SALINITY is one of the most problematic issues for agriculture in terms of abiotic stresses, particularly in semi-arid regions. Important osmolytes which accumulate in the cell include proline and glycine betaine. In the present investigation, the effect of the aforementioned osmolytes were assessed on sweet basil (Ocimum basilicum L.), the roles of exogenous applications were estimated at 50 100 or 200mM) and salinity stress (50,75 or 100mM NaCl). Results showed that all concentrations significantly increased growth parameters including number of branches/plants, height, fresh weight, leaves, and chlorophyll content, all of which decreased with increased NaCl. 100- and 200-mM glycine betaine had the most beneficial effect in both seasons. Similarly, severe salt conditions had a significant increase in endogenous proline content of basil leaves. Foliar application of 100- and 200-mM glycine betaine had the most beneficial effect in both seasons. When SDS-PAGE analysis was conducted it showed 19 bands with molecular weights (MW) ranging from 14.47 to 175.43kDa. Moderate and high salinity stress treatments of irrigation water (75 and 100mM) blocked the synthesis of a 175.429kDa polypeptide that was not restored by all foliar application of proline and glycine betaine. Highest NaCl level (100mM) alone induced the synthesis of new polypeptide (63.41kDa molecular weight). Exogenous proline and glycine betaine improved physiological parameters and reduced oxidative damage. Results suggest increased tolerance to oxidative damage caused by salinity, and these protectants rendered better performance, by upregulating their antioxidant defence system.