Effects of Drought Stress on the Growth and Physiology of Purple-leaf Lagerstroemia indica Container Seedlings

To investigate how drought stress affects the physiology and growth of purple-leaf Lagerstroemia indica container seedlings, two-year-old L. indica‘Ebony Embers’container seedlings, 5 drought stress treatments were created to ascertain the impact of various treatments on the growth and physiological indicators. The findings demonstrated the considerable effects of drought stress on the physiology and growth of container seedlings of purple-leaf L. indica. The drought stress intensity increased, and the purple-leaf L. indica container seedlings' relative water content, peroxidase activity, superoxide dismutase activity, soluble protein content, net photosynthetic rate, stomatal conductance, and transpiration rate all showed a general declining trend, these indicators significantly decreased by 21.45%, 40.45%, 31.92%, 3.30%, 81.25%, 89.29%, and 87.17% respectively during severe drought compared to normal water supply, falling to their lowest values in extremely severe drought. When drought stress intensified, the levels of soluble sugar, proline, and malondialdehyde consistently increased. In severe drought, these levels significantly increased when compared to normal water supply by 122.92%, 74.98%, and 288.34%, respectively, and reached their maximum value in extremely severe drought. Catalase activity, relative chlorophyll content, and water use efficiency showed an increasing and then decreasing trend with the intensity of drought stress. In moderate drought, catalase activity was highest, relative chlorophyll content and water use efficiency were highest, and in very severe drought, they were all lowest. Intercellular CO₂ concentration decreased and then increased with the intensification of drought stress, with the highest intercellular CO₂ concentration in normal water supply and the lowest in moderate drought. Purple-leaf L. indica container seedlings may tolerate a moderate amount of drought. However, timely irrigation and watering of the seedlings is required when the relative soil moisture content falls to 35% to 30%.