The structure of these cells is roughly spherical, through some may be elongated.
The main function of parenchyma is to act as a packing tissue, it provides support in herbaceous plants.
These cells are metabolically active and are the sites for many of the vital activity of the plant body.
The air spaces between the cells of these tissue allow gaseous exchange to take place between the living cell and the environment.
Parenchyma is distributed in Cortex, pith, medullary rays in wood and as packing tissue in xylem and phloem.
The structure of collenchyma is similar to parenchyma but it is characterized by the deposition of extra cellulose at the corners of the cells.
Collenchyma is a mechanical tissue, its main function is to provide support to those organs where it is found.
It is found in the outer regions of cortex (stems, petioles).
The structure of these cells are roughly spherical, although it may vary considerably in size and shape, the primary cell wall is thickened with the deposits of lignin.
Their main function is to provide mechanical support and are most commonly found in the cortex, pith phloem, fruits and seeds.