Changes of Characteristics Related to Photosynthesis in Synurus deltoides under Different Shading Treatments

This study was conducted to investigate the changes of chlorophyll contents, chlorophyll fluorescence, photo- synthetic parameters, and leaf growth of Synurus deltoides under different shading treatments. S. deltoides was grown under non-treated (full sunlight) and three different shading conditions (Shaded 88~93%, 65~75%, and 45%~55%). Light com- pensation point (Lcomp), dark respiration (Dresp), maximum photosynthesis rate (Pnmax), photo respiration rate (Presp), car- boxylation efficiency (Φcarb), and photochemical efficiency were decreased with increasing shading level; However, CO2 compensation point (CO2 comp), total chlorophyll content, and specific leaf area (SLA) were shown the opposite trend. S. del- toides under 88~93% treatment showed the lowest photosynthetic activity such as maximum photosynthetic rate (Pnmax), photochemical efficiency, and CO2 compensation point (CO2 comp). Therefore, photosynthetic activity will be sharply decreased with a long period of 8~12% of full sunlight. With the shading level decreased, carotenoid content and non-photo- chemical fluorescence quenching (NPQ) increased to prevent excessive light damage. This result suggested that growth and physiology of S. deltoides adapted to high light intensity through regulating its internal mechanism.