Abstract:UV-B absorbing capacities of methanol and cell-bound alkali extractable phenolics were measured in leaves of potted one-year-old seedlings of Pinus massoniana, Schima superba, Cryptocarya concinna, Castanopsis fissa and Castanopsis chinensis to investigate the UV-B protecting strategy in plants exposed to full sunlight. The results indicated that the UV-absorbing capacity of methanolic extracts was higher in plants grown under full sunlight than under shade regime. UV-B absorbing capacity of methanolic extracts in leaves of C．fissa, C. chinensis and P. massoniana under full sunlight was by 42．6％，32．6％ and 4．2％ higher than that under shade, respectively． The UV-B absorption ofcell wall-boun d alkali extractable phenolics in leaves ofC concinna and S．superba grown under full sunlight was by 35％and l1.7％higher than that under shade． respectively． But it was lower in leaves of P．massoniana, C．chinensis and C. fissa. grown under full sun light than that un der shade．It is likely that part ofphenolics moved from cell wall into cytoplasm to enhance the protective effect of palisade tissue against UV-B．Besides， massoniana and the broad-leaved trees had lower chlorophyll content and higher specific leaf area under full sunlight as compared to shading condition，which may have protective role for organelles in inner tissues.
