Physiological and Biochemical Characteristics of Salt Tolerance in Xanthoceras sorbifolium Under Drought Stress

In order to explore the effect of drought on salt tolerance physiological and biochemical characteristics of two-year-old Xanthoceras sorbifolium seedlings, the physiological and biochemical indicators of leaf organic osmotic adjustment system, inorganic ion concentration, and membrane system were studied under 15% concentrated PEG 6000 and different concentrations of salt(NaCl) stress treatment. The results showed that these indicators, such as the soluble sugar, proline, soluble protein, sodium ion(Na⁺) content, relative electrical conductivity, and malondialdehyde(MDA) content of seedling leaves, showed an upward trend with intensification of stress level under drought stress and single salt stress. The contents of soluble sugar and soluble protein increased first and then decreased with the extension of the stress time, the other indicators except potassium which decreased showed an upward trend. Under drought and salt cross stress, the change trend of physiological and biochemical indexes of X. sorbifolium leaves with salt concentration and with the extension of stress time were the same as the overall change trend under drought stress and single salt stress. Under low salt concentration, compared with single salt stress and drought and salt cross treatment, except for potassium ion content, all other indicators of leaves treated with 15% PEG 6000 were lower than those without PEG 6000. When the concentration of NaCl reached 0.45%, the result was the opposite. The above results showed that X. sorbifolium could resist the stress by increasing soluble sugar, proline and soluble protein in a certain salt concentration range, while the increase of relative conductivity, malondialdehyde, sodium ion and the decrease of potassium ion were not conducive to its resistance to the stress. When the salt concentration exceeded the tolerance range of the seedlings or the salt stress time was too long, its physiological metabolism would be unbalanced, which would cause the content of soluble sugar, soluble protein and other substances to decrease. At the low salt concentration , it was beneficial to the resistance of X. sorbifolium to salt damage that was treated by 15% PEG 6000.