Effects Of Salicylic Acid Treatment On Physiological Characteristics Of Hydrangea Under High Light Stress

Hydrangea macrophylla is an important ornamental plant for both potted and ground grown plants.Its flower is bright and colorful,and its shape is beautiful.It is widely used and has broad market prospects.In summer,the intensity of light is too strong in China,which is far more than the light saturation point of the Hydrangea,producing light inhibition,which will cause the irreversible photooxidation damage of the photosynthetic organs.In this paper,the effect of salicylic acid treatment on the light resistance of Hydrangea under strong light stress was studied with Hydrangeapaniculata var.grandiflora and Hydrangea paniculata Sieb.et Zucc.The purpose is to provide a theoretical basis for the use of salicylic acid to improve the light resistance of Hydrangea.The main results are as follows:?1?The net photosynthetic rate of two Hydrangea leaves increased rapidly with the increase of Photosynthetically active radiation between 0 and 600 ?mol�m^-2 S^-1,and the rising amplitude was relatively slow after 600 ?mol�m^-2 S^-1,but the net photosynthetic rate values of different varieties were different.The light compensation point,light saturation point,the maximum net photosynthetic rate,dark respiration rate and apparent quantum yield of Hydrangeapaniculata var.grandiflora and Hydrangea paniculata Sieb.et Zucc are 6.890 and 7.955?mol�m^-2.S^-1,645.391 and 716.173 ?mol�m^-2�S^-1,6.582 and 7.428 ?molC02�m^-2�S^-1,0.294 and 0.289?molCO₂�m^-2�S^-1,0.044 and 0.037 ?mol�?mol^-1.?2?Salicylic acid treatment effectively improved the net photosynthetic rate under strong light stress.With the change of salicylic acid concentration,net photosynthetic rate increased first and then decreased,and salicylic acid treatment improved the photosynthetic capacity of Hydrangea.?3?Salicylic acid treatment effectively reduced the production rate of O₂^-� and the content of H₂O₂ under the strong light stress.It decreased and then increased with the change of SA concentration,and reduced the accumulation of active oxygen radicals in the Hydrangea.?4?Salicylic acid treatment effectively reduced the relative conductivity and malondialdehyde content of two kinds of Hydrangea under strong light stress,and decreased first and then increased with the change of Salicylic acid concentration,thus reducing the damage of membrane lipid peroxidation by strong light stress.?5?Salicylic acid treatment effectively improved the activity of superoxide dismutase,peroxidase and catalase under the strong light stress,and increased first and then decreased with the change of S A concentration,and increased the energy of scavenging oxygen free radicals by Hydrangea.?6?Comprehensive physiological and biochemical indexes,with 0.80 mmol�L^-1 and 0.60 mmol L^-1 salicylic acid treatment to improve the light resistance of Hydrangeapaniculata var.grandiflora and Hydrangea paniculata Sieb.et Zucc is the best,Hydrangeapaniculata var.grandiflora after salicylic acid treatment to improve the effect of light resistance is more significant.