Effects of Drought Stress on Growth and Physiological Characteristics of Michelia chapensis Seedlings

To investigate the growth and physiological adaptive mechanisms of Michelia chapensis seedlings under drought stress, a pot experiment with controlled watering was conducted. Four soil moisture treatments were established: CK, mild drought, moderate drought, and severe drought .After 60 days of treatment, growth, photosynthetic, and physiological-biochemical indices were measured. The results indicated that as drought stress intensified, the increments in plant height and ground diameter, along with leaf length, width, and area, decreased significantly. Under severe drought, root length and total biomass declined by over 30%. Net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, transpiration rate, and chlorophyll content were all reduced, with the severe drought group exhibiting significantly lower values than other treatments. Conversely, the contents of proline and soluble protein, as well as the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA), increased significantly with intensifying drought. The soluble sugar content exhibited a "V-shaped" trend, reaching the lowest level under moderate drought and then rising under severe drought.Correlation analysis revealed that the increment in plant height was significantly positively correlated with leaf morphological traits, but significantly negatively correlated with proline and MDA contents. Additionally, photosynthetic pigment content showed a significant negative correlation with soluble protein and MDA contents. These findings reveal that M. chapensis seedlings exhibit distinct stage-specific responses to drought stress: they can tolerate mild-to-moderate drought through morphological adjustments, photosynthetic down-regulation, and osmotic regulation; however, severe drought induces irreversible physiological damage. This study provides a theoretical basis for seedling cultivation and water management of this species in arid regions.