全日光强下5种植物叶片的UV-B防护

通过测定马尾松(Pinus massoniana)和荷木(Schima superba)，及黄果厚壳桂(Cryptocarw concinna)、藜蒴(Castanopsis fissa)和锥树(Castartopsis chinensis)叶片中甲醇提取物和细胞壁碱性酚类提取物中UV-B吸收物质的含量，以及叶片叶绿素含量和比叶面积，研究全日光强下植物对UV-B的防护策略。结果表明，在全日光强下植物叶片甲醇提取物的UV-B吸收能力较遮阴下的高，如藜蒴和锥树分别高出42．6％和32．6％，而马尾松仅高出4．2％。全日光强下的黄果厚壳桂和荷木叶片细胞壁碱性酚类提取物的UV-B吸收能力亦分别比遮阴下的高3596和11．7％，而马尾松、锥树和藜蒴则较遮阴下的低，可能这些树种在全日光下细胞壁UV-B吸收物质有部分转移到细胞质，以增强栅栏组织细胞的保护。全目光强下这几种植物叶片的叶绿素含量较遮阴下的低，但有较高的比叶面积，这可能有利于减少对光的吸收和对深层组织细胞器的保护。可见不同植物是采取不同的策略来适应增高的UV-B辐射。

UV-B Screening of the Leaves of Five Tree Species Grown under Full Sunlight

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 of cell wall-bound alkali extractable phenolics in leaves of C. concinna and S. superba grown under full sunlight was by 35% and 11.7% higher than that under shade, respectively. But it was lower in leaves of P. massoniana, C. chinensis and C. fissa grown under full sunlight than that under shade. It is likely that part of phenolics moved from cell wall into cytoplasm to enhance the protective effect of palisade tissue against UV-B. Besides, P. massoniana and the broad-leaved trees had lower chlorophyll content and higherspecific leaf area under full sunlight as compared to shading condition, which may have protective role for organelles in inner tissues.