小麦颖果腹部维管束韧皮部细胞的超微结构与功能分析

利用透射电镜技术，对小麦颖果发育过程中韧皮部细胞的超微结构进行了观察和分析。结果表明，在颖果发育的早期和中期，韧皮薄壁细胞与伴胞、中间细胞间，以及韧皮薄壁细胞之间都有丰富的胞间连丝。筛分子（SE）与伴胞（CC）间、SE/CC复合物之间、筛分子与韧皮薄壁细胞间缺少胞间连丝。但SE和CC与中间细胞间、以及中间细胞相

Ultrastructure and Its Function of Phloem Cell in Abdominal Vascular Bundle of Wheat Caryopsis

The ultrastructure of phloem cell in developing wheat( Triticum aestivum L )caryopsis was investigated and analyzed by transmission electron microscopy during the entire developmental process of the fruit. The results showed that, during the early and middle developmental stages of caryopsis, numerous plasmodesmata were found between phloem parenchyma cells and companion cells (CCs), between intermediary cells, and between phloem parenchyma cells. There was short of plasmodesma between SE and CC, between SE/CC complexes and between SEs and phloem parenchyma cells; but there were numerous plasmodesmata between SEs and intermediary cells, between CCs and intermediary cells. The SEs were rich in mitochondria, P type plastids, and some SEs had nacreous wall. CCs contained electron-dense protoplasm and nucleus. Intermediary cells also contained electron-dense protoplasm distribution along intermediary cell wall. Numerous plasmodesmata were found between intermediary cells and surrounding cells, and there were some furcated plasmodesmata channels between two intermediary cells, indicating that intermediary cells might act as some special companion cells that suited to symplastic transport. During the later developmental stage of caryopsis, the substance in SEs disappeared and the number of mitochondria decreased. The CCs and phloem parenchyma cells contained electron-light protoplasm, but intermediary cells still contained numerous mitochondria to form a similar structure to SE, suggesting that intermediary cell had an important function during later filling stage. The photoassimilate unloading and transport path in phloem was analyzed according to the ultrastructure of phloem cells and the distribution of plasmodesmata.