Morphological and physiological responses of Ardisia crenata seedlings under different light intensities

Changes in the morphology, biomass, and physiology of Ardisia crenata seedlings were studied under different light environments (100%, 52%, 33%, 15%, and 6% relative light intensities). Results showed that the biomass of individual A. crenata seedlings was significantly higher under 52% light treatment than that under other treatments. The proportion of biomass allocated to leaves under 15%-52% light treatment was also higher than that under 100% and 6% light treatment. The root shoot ratio was not affected by light intensity, indicating that the structural plasticity of A. crenata was relatively low. The concentrations of nitrate increased with the decrease in light intensity and increased significantly under 6% light treatment. The change in nitrate reductase activity with light intensity was consistent with the change in nitrate content. Furthermore, the A. crenata seedlings adapted to different light environments by changing the leaf area and specific leaf area and by regulating the photosynthetic pigment. Analysis of chloroplast ultrastructure also showed that chloroplast number and cellular structure under 15%-52% light treatment were intact. However, under 100% and 6% light treatment, the number of the chloroplasts decreased significantly, the cellular structure was damaged, and plasmolysis occurred. Therefore, the most suitable growth conditions for A. crenata seedlings were under 15%-52% relative light intensities, though the best growth was achieved under 33%-52% relative light treatment.