Microstructure and distribution of pathogenic fungi of root rot in the roots of Angelica sinensis were studied through freehand section,paraffin technology,ultramicrotomy technology and photomicrography technology.The results indicated that the secondary structure of the roots of A.sinensis consisted of the periderm and cylinders,and the peri-derm was composed of cork,cork cambium,arld phelloderm.The secondary phloem consisted of sieve cells,phloem parenehymas,phloem fibers and secretory canal,which occupied more than 60% of the diameter of root and the paren-chymas cells were abundant in starch grain and other inclusions.Vessels,xylary radials and parenchyma cells formed the secondary xylem,which had several ridges of pmtoxylem,xylary radial and the phloem ray were conspicuous.The path-ogenic fungi were colonized in the periderm and stele,they infected the phloem parenchymas through cork,cork cambi-um,and arld phelloderm,and then formed pelotons,and expanded their occupying area of phloem.They even invaded the xylem and destroyed vessels.Further study also found that starch grains was the main place for fungal colonization, pathogenic fungi penetrated or wrapped around them,utilizing their nutrition to grow and reproduce.%利用徒手切片、石蜡切片和超薄切片及显微摄像的方法，对当归根的显微结构及根腐病致病真菌的分布进行了研究。结果表明：当归的根由周皮和次生维管组织两部分组成，周皮由外向内依次分为木栓层、木栓形成层、栓内层；次生韧皮部占根径的比例在60％以上，主要成分包括筛胞、韧皮薄壁细胞、韧皮纤维和分泌道，薄壁细胞富含淀粉粒等营养物质；次生木质部由导管、木薄壁细胞和木射线组成，木质部呈多元形，木射线和韧皮射线明显。在根的周皮细胞和中柱中均有真菌分布，说明真菌由木栓层、木栓形成层、栓内层依次向里侵入到韧皮薄壁细胞，在薄壁细胞内定殖并形成菌丝结或团块状结构，进而扩展成一定的侵染区域；真菌不仅侵染周皮和韧皮部，而且还进一步侵染木质部并破坏导管。此外，研究还发现，淀粉粒是真菌定殖的主要场所，真菌穿透或缠绕在淀粉粒上，并利用其营养不断地生长与繁殖。
展开▼
