Collenchyma is a cell and tissue type in which the primary walls are unevenly thickened and consist of homogeneous, more or less elongated living cells; it provides mechanical support to the plant organs where present. i. Distribution: Collenchyma cells are present at the periphery of herbaceous stems, petioles (e.g. Begonia) and in the ribs of some leaves (e.g. Nerium). They [...]
Parenchyma (Figs. 8.1, 8.6) is a cell and tissue type in which the cells have only thin primary walls; the cells are unspecialized, lack the characteristic wall of collenchyma and the secondary walls of sclerenchyma; the cells have live nucleate protoplast concerned with various physiological activities in plants; the cells are meristematic, or permanent, simple homogeneous (i.e. composed of one [...]
Phloem consists of sieve cell, sieve tube, companion cell, phloem parenchyma and fibre. 1. Sieve Cell-Origin: The mother cells of sieve cells vary in shape. They are slender, short cylindrical to elongate with both ends tapering. Numerous primary pit fields occur on lateral walls. During differentiation the mother cells elongate. Vacuole appears in the cytoplasm that streams actively. The cell [...]