The Dermal Tissue System: The Dermal Tissue System

Dermal Tissue System

The dermal tissue system consist of epidermis and periderm whose cells contain protoplasm and nucleus without intercellular spaces. The dermal tissue system is theprotective outer layer for the whole part of plant. It acts like human skin which forms the first line of defence against physical damage and pathogen.A single tissue called epidermis, is a layer of tightly packed cell usually found in non-woody plant or herbaceous plants. The epidermis forms a protective cover in plant organs like stem, flower, fruits and leaves. Epidermis possesses numerous minute openings called stomata, thesmall gated pores that are formed bythe guard cells and their subsidiary cellswhose main function is the exchange of gases between the

The ground tissue system is composed of all the tissues of a plant body except dermal and vascular tissues (Chawla, 2002). Tissues that are neither dermal nor vascular are part of the ground tissue system. The internal ground tissue is known as pith, whereas the external one is called cortex. The ground tissue system is not just filler. It involves various cells specialized for functions such as storage, photosynthesis, and support.

There are three simple tissues namely, parenchyma, collenchyma, and sclerenchyma. Parenchyma is thought of as the ground tissue of an axis since it occurs in greatest abundance and is the tissue in which the vascular tissues are embedded. Parenchyma cells may be isodiametric in both the pith and the cortex, but are more mostly longitudinally elongated in the cortex. They have comparatively thin walls. Wall layers are continuously shaped regions. These simple pits usually occur opposite each other, forming pit-pairs in the walls of contiguous cells. Plasmodesmata (specialized strands of endoplasmic reticulum) form interconnections with the protoplasts of adjacent living cells through simple

The secondary walls of sclerenchyma cells are thick and contain abundant lignin. This relatively indigestible strengthening polymer accounts for more than a quarter of the dry mass of wood. Lignin is present in all vascular plants, but not in bryophytes. Sclerenchyma cells stop growing in length when mature and cannot elongate any further. They are so specialized for support that many are dead at functional maturity, but they produce secondary walls before the protoplast (the living part of the cell) dies. In some cases, the rigid walls remain as a ‘skeleton’ that support the plant for hundreds of