l-Arginine Pretreatment Enhances Drought Resistance of Sunflower (Helianthus annuus L.) Plants by Increase in Polyamines Content

A significant reduction of fresh, dry biomass, shoot height, root length, succulent value, and leaf area were noticed as well as a significant accumulation of H2O2 and MDA contents in shoots and roots of sunflower plants in response to drought stress. Pretreatment of sunflower seeds with 2mM arginine (Arg) resulted in a significant increase in all growth parameters and reduced H2O2 and MDA contents in drought-stressed plants. This was accompanied with a significant increase of total polyamine contents (PAs) in shoots and roots. The results of this study indicate that Arg-pretreatment and the increase of PAs especially in roots might preventto some extentthe oxidative stress of H2O2 on plasma membranes and hence maintain the water status and growth of drought-stressed sunflower plants and reveal the role of polyamines as a strategy mechanism against drought stress.