Filippou Manolis, Fasseas Costas, Karabourniotis George
Laboratory of Electron Microscopy, Department of Agricultural Biotechnology, Agricultural University of Athens, Iera Odos 75, 11855 Botanikos Athens, Greece.
Tree Physiol. 2007 Jul;27(7):977-84. doi: 10.1093/treephys/27.7.977.
Functional and structural characteristics of corticular photosynthesis of sun-exposed bark of olive tree (Olea europaea L.) were examined. Stomata are only sporadically present during stem primary growth. Light transmission through the phellem was age dependent, decreasing rapidly in stems older than five years of age. Light transmission was also low in pubescent 1-year-old stems. Light transmission was about 50% higher in wet phellem than in dry phellem. Photosynthetic capacity on a unit area basis (measured with an oxygen disc electrode at 27 degrees C and about 5% CO(2) on chlorophyllous tissue discs isolated from the stem) was higher in 1-, 20- and 30-year-old stems compared with 2-10-year-old stems. Low chlorophyll a/b ratio and light compensation points were recorded in olive stems with low phellem light transmission, in accordance with the shade acclimation hypothesis. The intrinsic photochemical efficiency of photosystem II of all stems, especially young stems, was less than that of the leaves. Our results show that olive tree bark possesses an efficient photosynthetic mechanism that may significantly contribute not only to the reduction in concentrations of CO(2) in the inner bark, but also to whole-tree carbon balance.
对橄榄树（油橄榄）暴露于阳光下的树皮皮层光合作用的功能和结构特征进行了研究。在茎的初生生长过程中，气孔仅偶尔出现。通过木栓层的光透射率与年龄有关，在年龄超过5年的茎中迅速降低。在1年生有柔毛的茎中，光透射率也较低。湿木栓层的光透射率比干木栓层高约50%。与2 - 10年生的茎相比，1年生、20年生和30年生茎的单位面积光合能力（在27摄氏度和约5%二氧化碳条件下，用氧盘电极在从茎中分离出的含叶绿素组织圆盘上测量）更高。根据遮荫适应假说，在木栓层光透射率低的橄榄茎中记录到低叶绿素a/b比值和光补偿点。所有茎，尤其是幼茎的光系统II的内在光化学效率低于叶片。我们的结果表明，橄榄树皮具有一种高效的光合机制，这不仅可能显著有助于降低内皮层中二氧化碳的浓度，而且有助于整棵树的碳平衡。
