Parenchyma
Parenchyma is a tissue composed of polyhedral living cells having thin walls and is concerned with vegetative activities of the plant. The individual cells of the tissue are called parenchyma cells.
Types of parenchyma:
Assimilatory: parenchyma cells which take part in photosynthesis contain chloroplasts and form a tissue called Chlorenchyma. These cells have a single or many vacuoles.
Storage Parenchyma: Some parenchyma cells contain leucoplasts. Parenchyma cells may store reserve materials. Amides, proteins and sugars are found dissolved in cell sap, as in roots of sugar-beet. Starch, proteins and fats occur in cytoplasm in the form of small particles. Proteins, starch grains and oils are found in the endosperm and cotyledons of many plants. In succulent plants, parenchyma cells which store water are present. Such cells are large, thin-walled and have only a thin layer of cytoplasm.
Aerenchyma: The tissues with prominent intercellular spaces is called Aerenchyma, e.g., occurring in plants growing in waterlogged soils and aquatic environments.
Pseudo-parenchyma: These are thin walled and elastic and meristematic in nature.
Chromoplast Parenchyma: Chromoplast contain pigments and is common in petals of flowers, fruits etc.
Origin:
Parenchyma tissue of the primary plant body, i.e., parenchyma of the cortex and the pith, of mesophyll of leaves and of flower parts, differentiates from the ground meristem. The parenchyma associated with the primary and secondary xylem is formed from pro-cambium and the vascular cambium. Parenchyma also rise from the phellogen in the form of phelloderm.
Functions Of Parenchyma Tissues
In plant’s body or in its organs, the cell wall parenchyma appears as ground substance in which other tissues such as vascular tissues are embedded.
The apical meristems and the reproductive cells are parenchymatous. These are also involved in the phenomenon of wound healing and regeneration.
The parenchyma is also precursor of the other tissues. The parenchyma cells bring about the functions of photosynthesis, assimilation, respiration, storage, secretion, excretion, etc., as they have living protoplast.
The parenchyma cells associated with xylem and phloem are connected with transportation of food and water.
The intercellular larger portions of plants, such as pith, all or most, of the cortex of the root and shoot, the pericycle, the mesophyll of the leaf, and the fleshy parts of the root and shoot, the pericycle, the mesophyll of the leaf and the fleshy parts of the fruit consist of parenchyma cells. They are also present in xylem and phloem.
Explanation:
