Physiological and biochemical indexes of exogenous salicylic acid on chrysanthemum seedlings with high temperature stress

To study the relief of salicylic acid (SA) on thermal damage in chrysanthemum seedlings with high temperature stresses of 0, 24, 48, and 72 h, cuttings from 40-day-old summer chrysanthemum seedlings were used as materials. Leaves were sprayed with different concentrations of SA (0, 15, 30, 45, and 60 mmol·L-1). Then the content of chlorophyll, malondialdehyde (MDA), proline, free soluble sugar, and free soluble protein, were studied along with activities of superoxide dismutase (SOD), peroxidase (POD), and hydrogen peroxide (CAT) enzyme. Results showed that compared with the controls, the 30 mmol·L-1 salicylic acid treatment on the leaf for 72 h reduced leaf chlorophyll content 1.7%, have significant difference (P < 0.05). After high temperature treatment, best results were with the 30 mmol·L-1 salicylic acid treatment where compared to the control the MDA content increased 86.8%, have significant difference(P < 0.05). The content of proline (94.3%), free soluble sugar (112.1%), and free soluble protein (80%) significantly increased than other treatments (P < 0.05). SOD activity first increased, then decreased, whereas POD and catalase (CAT) activity increased. The 30 mmol·L-1 SA concentration had the greatest effect on SOD and POD, and 15 mmol·L-1 SA had the greatest effect on CAT. Thus, a short duration of high temperature stress damaged chrysanthemum leaves, but SA could play a protective role mitigating the damage. [Ch, 4 fig. 14 ref.]