小麦胚乳传递细胞发育的结构观察

Structure and Development of Endosperm Transfer Cells in Wheat

为从细胞学方面了解小麦产量和品质的形成机制,以扬麦5号为材料,利用光镜和透射电镜观察了小麦颖果发育过程中胚乳传递细胞的结构变化,并探讨了胚乳传递细胞的生理功能。结果表明：（1）胚乳传递细胞是胚乳发育过程中最早分化的细胞类型,它们发生在紧邻胚乳腔的胚乳表层,由位于外侧1~2层糊粉层传递细胞和位于内侧1~2层内胚乳传递细胞构成;（2）颖果发育成熟时,内胚乳传递细胞核衰亡,糊粉层传递细胞核依然完整;（3）胚乳传递细胞发育呈明显的极性,且具时空性;（4）糊粉层传递细胞胞质较浓,富含粗面内质网、线粒体、高尔基体和脂质体;质膜皱褶,在局部区域外翻,形成众多的原生质管;（5）内胚乳传递细胞胞质较稀,液泡化程度较高,富含淀粉体;（6）胚乳传递细胞未加厚以及未形成壁内突的壁区域分布有大量的胞间连丝;（7）胚乳传递细胞中线粒体呈极性分布,即质膜附近线粒体的密度较大。根据胚乳传递细胞的结构特点推测,经胚乳传递细胞的养分输送既可通过质外体途径又可通过共质体途径来完成。

In developing wheat caryopsis,grain filling nutrients transport into the endosperm via endosperm transfer cells（ETCs）.The developmental extent of ETCs is in close relation to yield and qualities of wheat.In this paper we investigated the developmental process and structural features of ETCs in wheat systematically by the combination of light microscopy and transmission electron microscopy.Main results were as follows：（1） ETCs occured in the endosperm epidermis bordering the endosperm cavity and were the first cell type histologically differentiated during endosperm development.ETCs could be divided into two subtypes： outer 1~2 layer of aleurone transfer cells and inner 1~2 layer of starchy endosperm transfer cells.（2） As caryopsis matured,the nuclei of starchy endosperm transfer cells disappeared,while the nuclei of aleurone transfer cells remained intact.（3） The development of ETCs showed obvious polarity and the pattern of temporal and spatial gradient.（4） Aleurone transfer cells had dense cytoplasm rich in rough endoplasmic reticulum,mitochondria,dictyosomes and lipid bodies;their plasma membrane wrinkled and in some region evaginated to form numerous plasmatubules.（5） Starchy endosperm transfer cells had sparse cytoplasm rich in amyloplasts and were highly vacuolated.（6） Lots of plasmodesmata penetrated into adjoining primary walls of ETCs where thickening and wall ingrowths didn＇t occur.（7） Mitochondria in ETCs showed polarized distribution,and most of them lied in the proximity of plasma membrane.The structural features of ETCs suggested that they may play a role in nutrients transportation into the endosperm both via apoplastic and symplastic pathway.