Question

How many types of ground tissues are there? What are they? Write about parenchyma.

Answer 1

• Ground tissue, also known as fundamental tissue system, forms the main bulk of the plant body. All tissues except the epidermis and vascular bundles are included underground tissue. There are three types of ground tissue:

1. CORTEX: It is the main zone that lies between the epidermis and pericycle. The thickness of this zone varies from few layers to many layers and is made up of primary tissues. In monocot stems and roots, the cortex is parenchymatous while in dicot stems, the cortex is differentiated into three sub-zones which are hypodermis, general cortex, and endodermis. The cortex serves as a protective zone and also stores food material in stems and roots. It also helps in absorption and translocation of water.
2. PERICYCLE: It is found just within the endodermis. Endodermis is the innermost layer of cortex having Casparian strips in roots.
   
3. MEDULLA OR PITH: It is the central part of the ground tissue which is mostly parenchymatous. Intercellular spaces may or may not be present. The pith forms the central part or core of the roots and stems. The pith of dicot stems is large and distinct whereas pith of dicot roots is very small. It serves as the storage organ for excretory substances of plants such as tannins, phenols, etc. and also for reserved food material.

• Parenchyma is the most abundant and commonly found tissue in plants. It is made up of thin-walled living cells having a distinct nucleus. The cells of parenchyma have intercellular spaces and are morphologically as well as physiologically unspecialized. The cells are typically isodiametric and may also be spherical, oval, rectangular etc.