The ground tissue system synthesizes organic compounds, supports the plant and functions in food manufacture and storage. It is mostly made up of plant cells called parenchyma cells but can also include some collenchyma and sclerenchyma cells as well. Parenchyma cells synthesize and store organic products in a plant. Most of the plant’s metabolism takes place in these cells. Parenchyma cells in leaves control photosynthesis. Collenchyma cells have a support function in plants, particularly in young plants. These cells help to support plants while not restraining growth due to their lack of secondary cell walls and the absence of a hardening agent in their primary cell walls. Sclerenchyma cells also have a support function in plants, but unlike collenchyma cells, they have a hardening agent and are much more rigid.
The ground tissue is the layer which lies inner to dermal tissue. In leaves, the ground tissue is the mesophyll that contains the photosynthetic cells.
Ground tissue layer is divided into following parts:
It is situated below the epidermis. It is multilayered and made up of parenchymatous and sclerenchymatous cells.
- General Cortex
This consists of parenchymatous cells with or without chloroplasts. This may be differentiated into hypodermis and inner cortex.
Endodermis is single layered made up of parenchymatous cells. The radial and internal walls of endodermal cell are thickened; a band of lignin or suberin knows as casparian strip is sometimes found on the radial and transverse wall of every cell.
It is single or multilayered and is situated in between endodermis and vascular bundles. It is made up of sclerenchymatous and parechymatous cells.
The central portion in stems and roots is called pith or medulla. It is made up of parenchymatous cells with intercellular spaces. In dicot stem the pith is large and well developed; in dicot roots the pith is either absent or small; in monocot roots large pith is present; in monocot stem the vascular bundles are scattered and the ground tissue is not marked into different parts.