Physiological Response of Vitex trifolia var. simplicifolia from Different Provenances Under Drought Stress and Evaluation of Drought Tolerance

Using cutting seedlings of Vitex trifolia var. simplicifolia from 19 different provenances as test materials, this research investigated the physiological and morphological indices of leaf protective enzymes (CAT, SOD, POD), proline, soluble sugar, soluble protein, malondialdehyde (MDA) content, and the growth of branch and leaf area under different water gradient conditions (75%−80%, 35%−40%, 15%−20%). The results showed that when the drought stress increased, the growth of branch and leaf area decreased; the activity of CAT and SOD from most of the provenances decreased; the activity of POD increased; the content of proline, soluble protein and MDA increased, and the content of soluble sugar showed different trend. The variation trend of each index varied with different provenance, and drought stress had significant influence on the physiological and morphological indices ofV. trifolia var. simplicifolia, with significant difference between provenances. Using the method of cluster analysis, seedlings of V. trifolia var. simplicifolia from the 19 different provenances were divided into 3 categories of strong, medium and weak for drought resistance. Investigation of more accurate identification and comparison for drought resistance of the 19 different provenances were carried out using subordinate function values analysis. The results showed that the highest drought resistance of the 19 different provenances were: Rongcheng (D₁₉)、Rizhao (D₁₁)、Xingfulinchang (D₁₃), and the most drought sensitive provenances were Dayao (D₈)、Dalian (D₁₅)、Xiangshan (D₁₂).