风花菜根异常次生结构的解剖学观察

利用光镜观察了风花菜（Rorippa islandica (Oed.)Borb.）的根的发育过程中的解剖结构的变化，发现风花菜根具有异常次生结构，第一年早期次生结构中，在导管周围形成额外形成层并由额外形成层向内外分裂形成大量的薄壁组织，从而使根快速增粗，在根的横切面上，导管分散在薄壁组织当中。第一年晚期的次生结构中，由木质部中薄壁组织细胞反分化形成额外形成层，许多分散的额外形成层片段连接形成形成层环，形成层环向内向外分裂形成三生木质部及三生韧皮部，从而构成三生维管组织环，三生维管组织环形成方向由外向内,可以形成多环。第二年风花菜的韧皮部以及皮层中的薄壁组织反分化形成额外形成层，并且由额外形成层片段连接形成额外形成层环，进而分裂形成三生维管组织环，而且在皮层中可以形成多层，形成的方向为由内向外。风花菜根不同发育时期的异常次生结构是与其生理活动相适应的。

Anatomical observation of anomalous secondary structure in root of Rorippa islandica

Using light microscope to observe the change of the dissection structure of Rorippa islandica(Oed.)Borb in the development course of its root and finding that the root of Rorippa islandica(Oed.)Borb.has anomalous secondary structure.In the secondary structure in early period of the first year,formed supernumerary cambium in the surrounding of the vessel and from supernumerary cambium to inside and outside splitted and formed a lot of parenchyma,thus making the root increase thick fast,on the transverse section of the root,the vessel dispersed in the parenchyma.In the secondary structure in later period of the first year,using the dedifferentiation of the sells of parenchyma in the xylem to form supernumerary cambium,many dispersive supernumerary cambium snippets connected and formed cambium cylinder,cambium cylinder splitted into inside and outside and formed tertiary xylem and tertiary phloem,thus composing tertiary fibrovascular cylinder,the formative direction of the tertiary fibrovascular cylinder was from outside to inside and might form multicylinder.In the second year the parenchyma of the phloem and cortex of Rorippa islandica(Oed.)Borb.dedifferentiated and formed supernumerary cambium,and using supernumerary cambium snippets to connect and form supernumerary cambium cylinder,thus splitted and formed tertiary fibrovascular cylinder,and also formed multicylinder in the cortex,and its formative direction was form outside to inside.The anomalous secondary structure of Rorippa islandica(Oed.)Borb.in the different development period of its root corresponded to its physiological activities.