Light and Nutrient Availability Drive Chlorophyll and Leaf Nutrient Traits in

Understanding the physiological responses of Dipterocarpus gracilis seedlings to nursery environmental conditions is essential for improving seedling quality and supporting conservation and reintroduction programs of this threatened dipterocarp species. This study aimed to evaluate the effect of light intensity and fertilization on relative chlorophyll content (SPAD) and leaf nutrient status of D. gracilis seedlings. The experiment was conducted for 90 days using a completely randomized design with two factors: shading level (30% and 60%) and NPK fertilizer doses (0 g and 1 g per seedling). Physiological parameters measured included relative chlorophyll content using a SPAD meter and leaf nutrient concentration including organic carbon (C), nitrogen (N), phosphorus (P), and potassium (K). The result showed that shading and fertilizer significantly affected relative chlorophyll content. Seedlings grown under 60% shade exhibited higher SPAD values (40.88) compared with those under 30% shade (32.14). NPK fertilization also increased SPAD value; however, no significant interaction between shading and fertilization was observed. Leaf nutrient analysis indicated that neither shading nor fertilization significantly affected leaf C, N, P, and K concentration. These fundings suggest that D. gracilis seedlings exhibit physiological acclimation to varying light condition through adjustments in chlorophyll content and gas exchange dynamics while maintaining relatively stable nutrient status. Such physiological plasticity is important for optimizing nursery management practice to produce high-quality seedlings for conservation and restoration programs.