Ground meristem the central region of the apical meristem from which the ground tissues of pith , cortex , medullary rays , and mesophyll differentiate . in root meristem it is also called periblem 基本分生组织：位于顶端分生组织的中部，髓、皮层、髓射线以及叶肉这些基本组织均是由基本分生组织分化而成。根部分生组织也称为皮层原。
