In this study, Aquilaria sinensis ‘Qinan’, a strain of A. sinensis that easily forms agarwood, was selected and propagated by grafting seedlings. Existing research has mainly focused on the characteristics of agarwood formation, but little attention has been paid to the growth characteristics of A. sinensis ‘Qinan’. In this study, the growth rate, photosynthetic capacity, leaf size, carbon and nitrogen contents, and antioxidant capacity were evaluated during the early growth stage in A. sinensis ‘Qinan’ and A. sinensis grafted seedlings. Compared with A. sinensis, A. sinensis ‘Qinan’ exhibited higher net photosynthetic rate (9.2 μmol m⁻² s⁻¹ in A. sinensis ‘Qinan’ and 7.8 μmol m⁻² s⁻¹ in A. sinensis) in the mature leaf. There were higher contents of secondary metabolites such as flavonoids and phenols, with stronger antioxidant capacity in A. sinensis ‘Qinan’. Larger leaf area (43.9 cm² in A. sinensis and 30.1 cm² in A. sinensis ‘Qinan’), higher nitrogen content (24.9 mg kg⁻¹ in A. sinensis and 23.7 mg kg⁻¹ in A. sinensis ‘Qinan’) in young leaves, faster growth rate, and larger biomass were observed in A. sinensis. The results indicate that differences exist in nutrient distribution during the growth process of A. sinensis ‘Qinan’ and A. sinensis, with more substances being used to synthesize defensive secondary metabolites in A. sinensis ‘Qinan’.

Phosphorus (P) deficiency is a major nutritional constraint limiting the regeneration and large-scale cultivation of Homalium ceylanicum, a valuable tropical timber species in South and Southeast Asia. To identify an optimal P supply strategy for producing high-quality planting stock, we assessed the growth performance, photosynthetic characteristics, and nutrient status of one-year-old H. ceylanicum seedlings in response to exponential P fertilization at six levels: 0 (control), 25, 50, 100, 200 and 300 mg P per seedling. Seedlings supplied with 50 mg P per seedling performed best, with height, leaf biomass, and leaf area increasing by 57.5%, 152.0%, and 164.7%, respectively, relative to the unfertilized control. These enhancements were paralleled by significant improvements in net photosynthetic rate, chlorophyll content, photosystem II (PSII) photochemical efficiency, and gas exchange, indicating that enhanced photosynthetic carbon assimilation contributed to growth promotion. At the whole-plant level, this coordinated improvement in growth and photosynthesis was accompanied by a 171.04% increase in nitrogen (N) accumulation without inducing excessive P accumulation. In contrast, P supply above 100 mg per seedling reduced seedling height and root collar diameter, suppressed whole-plant biomass accumulation, and disrupted nutrient balance through excessive P accumulation and antagonistic effects on N and K (potassium). Vector analysis further confirmed 50 mg P per seedling as the optimal nutrient-loading dose, achieving effective P loading without inducing N or K excess or nutrient imbalance. In conclusion, exponential P fertilization at 50 mg P per seedling is a targeted nutritional strategy for producing high-quality planting stock, thereby supporting the plantation forestry of H. ceylanicum.