Explanation

Xylem is composed of four types of tissue (i) Tracheids Elongated or tube like cells with thick lignified walls and tapering ends. These are main water transporting elements (ii) Vessels A long cylindrical tube with lignified walls and large central cavity. It is a characteristic feature of angiosperms (iii) Xylem fibres have thickened walls and obliterated central lumen either septate or aseptate (iv) Xylem parenchyma is a thin cellulose and used to store food in the form of starch or fat