Effects of Light Condition on Growth and Physiological Characteristics of the Endangered Species Sedirea japonica under RCP 6.0 Climate Change Scenarios

This study was conducted to evaluate the physiological and growth responses of Sedirea japonica cultured in chambers under RCP 6.0 and different light conditions. S. japonica was grown in a soil–plant daylight system chamber under two treatments, a control (CO₂ = 400 ppm) and a climate change treatment (CCT) (CO₂ = 650 ppm, temperature = control + 3 °C), and three different shading treatments (60%, 90%, and no-shading). S. japonica showed the characteristics of typical Crassulacean acid metabolism (CAM) plants. As the shading rate increased, it increased chlorophyll content, leaf area, and leaf dry weight to efficiently absorb and use light. The CCT had a lower CO₂ absorption rate, stomatal conductance, and growth rate and slightly higher water utilization efficiency than the control. This was because stomatal closure occurred in the CCT to reduce water loss due to a relatively higher temperature. As CO₂ fixation decreased and consumption increased due to respiration, the overall growth was inhibited. The CCT without shading revealed a dynamic photoinhibition phenomenon showing a significant increase in ABS/RC, TRo/RC, ETo/RC, and DIo/RC and a decrease in PI _ABS and DF _ABS. In this group, leaf, root, and total dry weight, chlorophyll content, and carotenoid content were the worst growth indices.