Objective To investigate the growth and physiological-biochemical responses of Neolamarckia cadamba seedlings under varying soil drought stress gradients, providing a scientific basis for water management in seedling cultivation.

Method A controlled pot experiment was conducted with four drought treatments: Control CK, 80%–85% field capacity (FC), light drought (LD, 65%–70% FC), moderate drought (MD, 50%–55% FC), and severe drought (SD, 35%–40% FC). Seedling height, ground diameter, root morphology, leaf morphological traits, osmoregulatory substances contents and antioxidant enzyme activities were measured. Fuzzy membership function analysis was used to comprehensively evaluate the adaptability of N. cadamba under different treatments

Result Drought stress significantly reduced leaf length, leaf width and leaf area (P < 0.05) but did not affect the length-to-width ratio. MD and SD significantly decreased seedling height, ground diameter, and superoxide dismutase activity, while significantly increased soluble protein and malondialdehyde contents (P < 0.05). LD had no significant impact. SD significantly reduced seedling biomass, root length, root surface area, and root volume (P < 0.05). Average root diameter, soluble sugar content, proline content, and peroxidase activity showed no significant differences among treatments. Comprehensive evaluation by fuzzy membership function analysis ranked the growth and physiological-biochemical performance of N. cadamba seedlings under different treatments as CK > LD > MD > SD.

Conclusion N. cadamba seedlings grow optimally under well-watered conditions, tolerate light drought with limited impact, but suffer significant growth inhibition and oxidative damage under moderate and severe drought. The species exhibits weak drought tolerance, and therefore prolonged moderate or severe soil drought should be avoided in cultivation.