Microstructure and mycorrhizal fungus distribution of the root of endangered and officinal plant Sinopodophyllum hexandrum
濒危药用植物桃儿七根的显微结构及其菌根真菌分布研究

Microstructure and fungus distribution in the adventitious roots and lateral roots of Sinopodophyllum hexandrum were studied through permanent paraffin-cut section and optical microscope photography. Annual increments of the rhizomes were distinct, and there were developed adventitious roots in S. hexandrum root system. The adventitious roots consisted of epidermis, cortex and vascular cylinder, and the cortex occupied more than 80% of the transverse section of roots. There were two types of xylem of the adventitious roots, namely tetrarch and pentarch. The structure of cortex cells of tetrarch and pentarch roots showed significant different. Fungal hyphae were colonized in cortex of the adventitious roots. In adventitious roots, the fungi were dark-septate endophytic (DSE) fungus which were mainly distributed in the root apex (D<1.5mm). The fungal hyphae in thicker part (D>1.5mm) of roots were unseptate and they were only located in the first and second layer of the exodermis. In lateral roots of adventitious roots, arbuscular mycorrhizal fungi were dominant, which often occupied most part of cortex, and the colonization rate was as high as 90%. No root hairs are observed, suggesting that the plant absorbs nutrition and water through the symbiotic arbuscular mycorrhizal fungi.