以日光温室内栽培的三年生油桃“早红艳”(PrunuspersicaL .var.nectarineAit“ZaoHongYan”)为试材 ,利用透射电子显微镜 (TEM)技术首次对处于正常光照条件和弱光条件下的源叶的韧皮组织进行了超微结构观察 ,重点研究了叶片超微结构对弱光的响应。结果表明 :在正常光照条件下 ,油桃源叶各级叶脉的筛管和伴胞的平均直径均比弱光条件下的大 ,表明光能影响细胞的发育 ,而弱光抑制了细胞的生长。在正常光照下的伴胞具有致密的细胞质 ,内含丰富的线粒体、内质网、多泡体、囊泡和质体 ,而弱光下的伴胞明显液泡化 ,同时含有少量的线粒体和内质网。在弱光条件下也观察到叶绿体基粒片层边缘紊乱 ,筛孔处于阻塞状态。在弱光下 ,邻近维管束鞘细胞的叶肉细胞内积累了大量的淀粉粒和少量的线粒体。淀粉粒的积累可能是由于光合同化产物的生产与输出之间的不平衡 ,这一观察结果有力地支持了大部分叶片是在光照条件下输出其大部分同化产物的观点。在筛管 伴胞、伴胞 韧皮薄壁细胞、韧皮薄壁细胞 韧皮薄壁细胞和韧皮薄壁细胞 维管束鞘细胞之间的胞间连丝密度都在弱光条件下下降 ,在正常光照强度下支脉筛管 伴胞和韧皮薄壁细胞 维管束鞘细胞之间可以观察到胞间连丝 ,而在弱光下几乎观察不到胞间连丝的存在 ,所以同化 Three-year nectarine “Prunus persica L.var. NectarineAit” ZaoHongYan was cultivated in sunlight greenhouse as the test material, and the transmission electron microscope (TEM) technique was used for the first time on the source under normal light and low light conditions The ultrastructure of the leaves of the phloem was observed, focusing on the leaf ultrastructure of the response to low light. The results showed that under normal light conditions, the mean diameters of the screen tubes and accessory cells in the leaf veins of nectarine leaves were higher than those in low light conditions, indicating that light energy affected the cell development and weak light inhibited the cell growth. Under normal light, the companion cells have a dense cytoplasm, which is rich in mitochondria, endoplasmic reticulum, multivesicular vesicles and plastids, while the accessory cells in the low light are obviously vacuolized with a small amount of mitochondria and inner Quality network. Under the weak light conditions, the edge of chloroplast grana tablets was also observed to be disordered, and the mesh was blocked. In low light, a large number of starch granules and a few mitochondria were accumulated in mesophyll cells adjacent to bundle sheath cells. The accumulation of starch grains may be due to an imbalance between production and output of photo-assimilation products, and this observation strongly supports the view that most leaves output most of their assimilates under light conditions. The cell density of the intercellular space between the sieve-tube companion cells, the accessory phloem parenchyma cells, the phloem parenchyma cells of phloem parenchyma cells and the bundle sheath cells of phloem parenchyma cells decreased in low light conditions, Under normal light intensity, the intercellular silkworms were observed between the branch vein sieve companion cells and the bundle sheath cells of the phloem parenchyma cells, whereas the existence of the interplasma filaments was hardly observed in the low light intensity. Therefore, the assimilation