In this article we will discuss about the definition and cell types of xylem tissue in plants. Definition of Xylem: Xylem can be defined as a complex tissue that is composed of four basic types of cell (tracheids, trachea, and xylem fibre and xylem parenchyma), remains in close association with phloem and has specialized functions like conduction of water and [...]
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 [...]
In this article we will discuss about:- 1. Origin of Xylem Parenchyma 2. Phylogeny of Ray Parenchyma 3. Phylogeny of Axial Parenchyma. Origin of Xylem Parenchyma: Xylem parenchymas cells are present both in primary and secondary xylem; accordingly their origin also differs. In primary xylem they originate from procambium. In secondary xylem ray parenchyma cells originate from the ray initials [...]