细叶马先蒿根系发育形态学研究

STUDY ON DEVELOPMENTAL MORPHOLOGY OF PEDICULARIS STRIATA PALL.

细叶马先蒿（ＰｅｄｉｃｕｌａｒｉｓｓｔｒｉａｔａＰａｌｌ．）为玄参科多年生草本植物。年生长周期明显缩短。根系营养生长至花期为粗壮主根与纤细侧根并存，果期侧根几乎全部枯萎脱落，所存留根系皆呈乳白色。由胚根形成的初生主根根毛密集，初生木质部二原型。侧生分生组织只有形成层而无木栓形成层。根表皮细胞经解离后略呈不规则方形片状，横切面为平周长梭形，进行垂周分裂增加梭形根表皮细胞长度，以适应根的增粗生长。根表皮脱落时，外皮层以同样生长方式代替脱落的表皮。在年生长后期，随着侧根的大部脱落，产生大量越冬根原基。就其年发育节律而言，属局部更替型，其特点为不限于吸收根而是全部细侧根参与更替。

Pedicularis striata Pall. is a perennial herb in Scrophulariaceae. The yearly growth cycle shorten obviously. During nutritive growth and blooming stages all the thick main root and its fine banches exist. But the latter is almost withering and fall off completely in fruit stage. It is very rare that the survive root system is milk white. The primary root is covered with root hairs densely. The primary xylem is diarch. There is only vascular cambium but no cork cambium in lateral meristem. The epidermis cell divides anticlinally within mother cell and elongates periclinally in cross section. It can be seen that the shape of the whole epidermis cell is irregular square when it is dissociated. The root perimeter can be prolonged by this special growth type to adapt root thickening. The exodermis cell takes the place of epidermis cell with the same way when epidermis fall off. To accompany fine branches withering,a lot of winter root primodia arise at the end of growing period. According to its yearly developmental rhythm,the root system is partial renewal type and withering not only absorb roots but also fine branches.