Investigating the Impact of Drought Stress on the Growth and Physicochemical Properties of the Endangered Species Malania oleifera Seedlings

Endemic to China, the endangered tree species Malania oleifera possesses significant medicinal, ecological, and economic importance. However, there is a paucity of research on the physiological responses of M. oleifera seedlings to drought stress. We utilized one-year-old seedlings to investigate the morphological alterations and physiological reactions under simulated natural drought conditions in this study. The findings revealed significant variations in root length, plant height, stem diameter, and root count between drought-stressed and control groups. As the severity of drought increased, M. oleifera exhibited an initial increase followed by a decrease in root length, while plant height and fresh weight showed a notable decline. Chlorophyll content (a + b, a, b) was found to be reduced under drought conditions compared to the control, with further reduction as the duration of stress extended. The levels of malondialdehyde (MDA) and soluble sugars progressively increased with prolonged stress exposure. Similarly, the concentrations of soluble proteins, proline, and the activities of protective enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) initially rose but then declined as drought stress intensified. In summary, the morphology, physiology and biochemistry of M. oleifera seedlings under drought stress have undergone significant changes, such as significant inhibition of seedling growth, root development, reduction of chlorophyll content, and significant increase in malondialdehyde content. In particular, the accumulation of osmotic regulators such as proline and the enhancement of enzyme defense systems to varying degrees alleviate the adverse effects of drought.