胚根鞘

根和根冠被一鞘状结构，即胚根鞘所覆盖。

Both root and root cap are covered by a sheath-like structure called the coleorhiza .

胚基具有生长带，纵向伸长长度大，胚基的上部参与形成胚根鞘，其余部分干缩后附在胚根鞘末端。

As to the hypoblast there is a growth belt , which promotes elongation of the hypoblast . Eventually the upper portion of the hypoblast contributes to the formation of the coleorhiza and the remainder dries up , sticking to the end of the coleorhiza .

药理学实验证实，低浓度的GABA能够促进玉米种子萌发及其幼苗胚根、胚芽鞘的生长，高浓度则起抑制作用，其抑制效应可能与内源乙烯水平升高有关。

Pharmacological experiments indicated that low concentration of GABA could promote the growth of radicle and coleoptile and high concentration of GABA could restrained their growth , Presumedly the inhibitory effect had something to do with increase of endogenous ethylene level .