摘要
本研究揭示,白芨(Bletilla striata)种子为兰科中容易萌发的种子类型。胚的大型薄壁细胞中富含淀粉及脂类等贮藏物质,是种子在常规条件下萌发的主要营养来源。但种子伴菌播种处理,相适应的真菌侵染种子后,可提高种子的发芽势,尤其是对萌发后原球茎的叶片、假根等分化有显著促进作用。超微结构观察表明,真菌从侧壁加厚的种皮细胞间穿过到达种胚,自胚柄处侵入胚细胞,分布在胚柄端的几层胚细胞中。被真菌侵染的胚细胞,细胞质及细胞器逐渐消失,质膜内陷产生的囊状体包围并消化菌丝。菌丝通过白芨细胞壁时,顶端常膨大,靠其细胞质产生的膨压在白芨细胞中穿越。另外有的菌丝细胞壁明显比侵入前加厚,被加厚的物质来源于胚细胞质,最终这些菌丝完全被水解,作为白芨种子萌发生长的营养。邻近染菌细胞的未染菌的白芨细胞表现了旺盛的代谢活动。
Aided by the techniques of ultrathin section and electron microscopy,the changes of cell ultrastructure of seed germination of Bletilla striata was investigated.It was found that the seeds of B.striata were germinated easily among Orchidaceae,the large thin-wall cells of embryo contained a great amount of starch and lipid materials which were nutrients of seed germination.The differentiation and growth of the nutritive organ of B.striata would be ac- celerated after fungus infection.Fungus could penetrate seed coat in cell interstice,invaded embryo through suspensor,and interspersed in several layers of embryonic cells.Cytoplasm and organelles of embryo would disappear after the cells infected by fungus,and then endocytic plasmalemma produces some sacs enclosing and digesting hyphae.The hyphae with its tip in- flation,relying on expansion-pressure of its cytoplasm,could penetrate cell wall of embryo.In addition,after invasion hyphae wall was significantly thickened by the deposition of the em- bryonic cytoplasm.In the end,the hyphae would be wholly collapsed and its degradated mate- rials were used as nutrient for germination.The cells without penetration by hyphae show vigrous metabolism activity in protocorms.
关键词
白芨
真菌侵染
种子萌发
超微结构
Bletilla striata
Fungus infection
Seed germination
Ultrastructure
