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

本文研究了桃儿七Sinopodophyllum hexandrum根的显微结构及其真菌分布。结果表明,桃儿七的根为根状茎,节状,不定根形成的须根系发达。根的结构主要由表皮、皮层、维管柱三部分构成,其中,皮层所占比例最大,超过80%。根的木质部有四原型和五原型两种类型,五原型较为常见;四原型的根和五原型的根在皮层细胞形态上存在一定差异。在桃儿七的不定根和其上的侧根观察到真菌菌丝分布,其数量和种类与根的直径有关,在不定根较细(先端)的部位真菌以暗色有隔内生真菌(DSE真菌)为主,侵染率为77.9%;而较粗根中真菌菌丝为无隔菌丝为主,分布很少且仅存在于皮层细胞的一至二层,不侵染皮层深部和维管柱。不定根侧根中真菌以丛枝菌根真菌为主,丛枝菌根常常占据大部分的皮层细胞,侵染率高达90%以上。桃儿七根中没有发现根毛存在,因此,侧根中共生的丛枝菌根真菌可能是桃儿七养分和水分吸收的主要途径。

Microstructure and mycorrhizal fungus distribution of the root of endangered and officinal plant Sinopodophyllum hexandrum

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.