Vascular Bundle
Vascular bundles are present in vascular tissue system and are distributed in the stele. The stele is the central column of Dicol stems. Each vascular bundle may be made up of both xylem tissue and phloem tissue with a cambium as in dicot stems or without cambium as in Monocot stems or of one kind of tissue xylem or phloem as in roots.
Vascular bundle may be regularly arranged in a ring as in the stems of most dicotyledons and in all roots or they may be scattered in the ground tissue as in stems of Monocotyledons.
Elements of Vascular Bundle
Vascular bundle of Dicot stem when fully formed consists of there well defined tissues (1) Xylem or wood (2) Phloem or bast (3) Cambium. They have different kinds of tissue elements.
(1) Xylem or wood
This lies towards the centre and is composed of (i) Trachae or vessels (ii) sone tracheids, (iii) a number of wood fibres and (iv) a small patch of wood parenchyma. Vessels are of various kinds such as spiral, annular, scalariform, and reticulate and pitted (with simple or bordered pits). Some tracheids also lie associated with the vessels. Wood fibres and wood parenchymatous cells lying associated with the wood or xylem provided with simple pits in their walls.
Xylem vessels and tracheids are used for conduction of water and numeral salts from roots to the leaves and other parts of the plant. Xylem parenchyma assists them in their task and also serves for food storage and wood fibres give proper rigidity to the xylem. Except wood parenchyma all other xylem elements are thick walled, lignified and dead and hence they also give mechanical strength to the plant body. The first formed xylem or Protoxylem consists of annular, spiral and scalariform vessels. It lies towards the centre of the stem and its vessels have smaller cavities. The later formed xylem or Metaxylem consists of reticulate and pitted vessels and some trachieds. It lies away from the centre and its vessels have much bigger cavities. Xylem is endarch in
Vascular bundle may be regularly arranged in a ring as in the stems of most dicotyledons and in all roots or they may be scattered in the ground tissue as in stems of Monocotyledons.
Elements of Vascular Bundle
Vascular bundle of Dicot stem when fully formed consists of there well defined tissues (1) Xylem or wood (2) Phloem or bast (3) Cambium. They have different kinds of tissue elements.
(1) Xylem or wood
This lies towards the centre and is composed of (i) Trachae or vessels (ii) sone tracheids, (iii) a number of wood fibres and (iv) a small patch of wood parenchyma. Vessels are of various kinds such as spiral, annular, scalariform, and reticulate and pitted (with simple or bordered pits). Some tracheids also lie associated with the vessels. Wood fibres and wood parenchymatous cells lying associated with the wood or xylem provided with simple pits in their walls.
Xylem vessels and tracheids are used for conduction of water and numeral salts from roots to the leaves and other parts of the plant. Xylem parenchyma assists them in their task and also serves for food storage and wood fibres give proper rigidity to the xylem. Except wood parenchyma all other xylem elements are thick walled, lignified and dead and hence they also give mechanical strength to the plant body. The first formed xylem or Protoxylem consists of annular, spiral and scalariform vessels. It lies towards the centre of the stem and its vessels have smaller cavities. The later formed xylem or Metaxylem consists of reticulate and pitted vessels and some trachieds. It lies away from the centre and its vessels have much bigger cavities. Xylem is endarch in