Effects of Weak Light on the Ultrastructural Variations of Phloem Tissues in Source Leaves of Three-Year-Old Nectarine Trees(Prunus persica L.var. nectarina Ait.)  

弱光对三年生油桃源叶韧皮组织超微结构的影响(英文)

作　　者：王秀芹[1] 黄卫东[1] 

机构地区：[1]中国农业大学,北京100083

出　　处：《Acta Botanica Sinica》2003年第6期688-697,共10页Acta Botanica Sinica（植物学报：英文版）

基　　金：国家自然科学基金 (3 0 0 70 5 3 1)~~

摘　　要：Leaves from three_year_old solar greenhouse nectarine trees ( Prunus persica L. var. nectarina Ait. “Zao Hong Yan”) were used as materials in this study. It was the first time that the ultrastructural characteristics of phloem tissues of source leaves were observed and compared in normal and weak light intensities using the transmission electron microscopy. Results showed that the average diameters of companion cells (CC) and sieve elements (SE) of all kinds of veins were bigger in normal than that in weak light intensity, indicating that light could influence the cell development and growth. Dense cytoplasm with abundant mitochondria, endoplasmic reticulums, multivesicular bodies, vesicles and plastids were observed in normal light intensity. On the contrary, CC with small vacuolar structures and few mitochondrias, endoplasmic reticulums were shown in weak light. Misalignment of grana thylakoid margins of nectarine leaves also was seen in weak light. The sieve pores of SEs were obstructed in weak light. Chloroplasts with numerous starch grains and few mitochondrias were noticed in the mesophyll cell (MES) surrounding the bundle sheath in weak light. The storage of starch grains appeared to result from an unbalance between photosynthate production and export of photosynthates. This observation provided a strong support to the point that most leaves export the most of assimilates in the light time. Plasmodesmal densities between SE/CC, CC/PP (phloem parenchyma cell), PP/PP and PP/BSC (bundle_sheath cell) decreased in weak light. Plasmodesmata were observed between CC/SE (NS) (nacreous_walled sieve element), PP/BSC in branch veins in normal light intensity, but not in weak light. Thus apoplasmic pathway may be the main mode of transport of assimilates in weak light, however symplasmic pathway may be the main mode of transport of assimilates in normal light intensity. These results demonstrated that the solar greenhouse nectarine trees could be adapted to the weak light via the ultrastructure variation of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 。

关 键 词：nectarine (Prunus persica L.var. nectarina Ait.) phloem tissue ultrastructure weak light SE/CC complex phloem loading 

分 类 号：S662.1[农业科学—果树学]