The ameliorative effect of salicylic acid (SA) on cadmium (Cd) toxicity in sunflower plants was studied by investigating leaves protein content and fatty acid composition. Sunflower plants in two leaves stage were exposed to CdCl2 treatment (0, 50,100,150 and 200 μM) and then were treated with salicylic acid (0, 250 and 500 μM) as foliage spraying. One week after the last salicylic acid treatment, plants were harvested and growth parameters and protein content were measured. Oil of leaf was extracted in a Soxhlet system and fatty acid composition were measured by gas chromatography (GC). Statistical analyses showed excess Cd reduced fresh weight and number of leaves and SA increased them compared with the control. Maximum reduction in these parameters was at 200 μmol Cd and 0μmol of SA. Protein content in leaves of sunflower was decreased with increasing concentrations of Cd. Exogenous application of SA increased the amount of protein in sunflower plants exposed to Cd stress. Cd×SA interaction on protein content in leaves was significant. Cd caused a shift in fatty acids composition, resulting in a lower degree of their unsaturation and an increase in saturated fatty acids in sunflower leaves,whereas SA improved them. SA, particularly increased the percentage of linolenic acid and lowered that of palmitic acid by the same proportion. These results suggest that SA alleviated the inhibitory effects of Cd on protein content and could be used as a stabilizer of membrane integrity due to lipids protection of cadmium-induced oxidative stress to improve plant resistance to Cd stress.
