In this study, three-year-old seed-derived seedlings of Horsfieldia hainanensis Merr. were subjected to 0%, 25%, 50%, and 75% shade treatments in a nursery shade-net experiment from October 2025 to June 2026. Each treatment included three replicates, with three seedlings per replicate. The results showed that the light environment significantly affected growth. Seedlings under 0% shade showed severe wilting and mortality; therefore, this treatment was treated as a mortality outcome and excluded from subsequent statistical comparisons, which were conducted among the 25%, 50%, and 75% shade treatments. Within this range, plant height, ground diameter, crown width, leaf traits, and above- and belowground biomass increased with shade level, with the highest values observed under 75% shade. The 75% shade treatment was associated with higher maximum net photosynthetic rate (Pmax), apparent quantum yield (AQY), initial carboxylation efficiency (α), and CO₂-saturated net photosynthetic rate (Amax), together with lower light compensation point (LCP) and carbon dioxide compensation point (CDCP), indicating improved light- and CO₂-response performance within the tested shade range. Leaf thickness, epidermal thickness, and palisade and spongy parenchyma thicknesses increased with shade level, whereas variation in stomatal traits was mainly reflected in stomatal density. Chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids increased under stronger shading, showing clear variation in pigment accumulation along the shade gradient. Growth, biomass, photosynthetic capacity, leaf anatomical traits, and pigment contents were positively correlated, whereas the light saturation point (LSP), LCP, carbon dioxide saturation point (CDSP), and CDCP were generally negatively associated with these traits. Among the surviving treatments tested, the 75% shade treatment produced the best seedling performance and may be suitable for nursery cultivation, although further validation at different sites and in different seasons is needed. These findings provide practical guidance for artificial propagation, seedling production, plantation establishment, and light-environment management of this species.

To examine differences in resource use and functional traits between the narrow-ranged Camellia longzhouensis and its widespread congener Camellia gigantocarpa, we compared their light and CO₂ responses, leaf anatomy, stomatal traits, photosynthetic pigments, and trait correlations under common nursery conditions. In both species, net photosynthetic rate increased rapidly with increasing irradiance and then gradually approached a plateau. The maximum net photosynthetic rate of C. gigantocarpa was significantly higher and was 4.10 times that of C. longzhouensis, whereas apparent quantum yield, light saturation point, light compensation point, and dark respiration rate did not differ significantly between the two species. As intercellular CO₂ concentration increased, net photosynthetic rate increased and then gradually leveled off in both species. Initial carboxylation efficiency was significantly higher in C. gigantocarpa, whereas the other CO₂-response parameters showed no significant differences between species. Leaf thickness and lower epidermal thickness were similar between species, but C. gigantocarpa had a thicker upper epidermis and palisade tissue and a higher palisade-to-spongy tissue thickness ratio, whereas C. longzhouensis had thicker spongy tissue and higher stomatal density. Stomatal length, width, and area did not differ significantly between species. C. gigantocarpa had significantly higher chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents, as well as a higher chlorophyll a-to-b ratio, whereas the ratio of carotenoids to total chlorophyll did not differ significantly between species. Trait correlations indicated coordinated variation among photosynthetic performance, leaf anatomy, stomatal characteristics, and photosynthetic pigments. Overall, the two species exhibited distinct combinations of leaf structural and photosynthetic functional traits under common nursery conditions, providing baseline ecophysiological information on their resource-use differences and for germplasm conservation of C. longzhouensis.