Vascular Tissue in Plants

Study Notes

Vascular tissue is a vital tissue in plants responsible for water and food transportation.
It is composed of arranged groups of cells that form a tissue system, which extends to every organ in the plant.
The vascular tissue connects water intake and food synthesis sites to plants' cell growth, development, and storage regions.

Primary xylem is present in young developing plants, but as the plants grow, secondary xylem is formed.
Secondary xylem comprises five components: rays, tracheid, vessels, xylem parenchyma, and xylem fibers.
Xylem transports water and mineral salts from the roots to the entire plant.
Water loss occurs through stomata, cuticle, and lenticels, with the majority of water loss through stomata.

Phloem transports metabolites such as sugars, amino acids, and other organic substances from the site of their production to other plant organs.
The components making up the phloem are sieve tubes, companion cells, fibers, and parenchyma cells.
Phloem is responsible for translocation, which is the transportation of soluble organic substances within the plant.

Vascular tissues are essential for plant survival.
Xylem tissue is responsible for water and mineral salts transportation, involving several forces, including cohesion, adhesion, capillarity attraction, transpiration pull, and root pressure.
Transpiration is beneficial in cooling the plants during hot weather, but excessive transpiration leads to wilting and eventually plant death.
Phloem is responsible for translocation, which occurs through the sieve tubes.

Xylem cells include:
- Xylem fibers, which form wood and are strengthened with lignin.
- Xylem parenchyma, which form the packaging tissues and are found between vessels.
- Tracheid, which have perforated cross-walls with tapering end walls and are dead at maturity.
Phloem cells include:
- Sieve cells, which are elongated and tapered in shape and conduct food elements in gymnosperms.
- Strasburger cells, which are elongated in shape and deliver substances such as ATP to sieve cells.
- Sieve-tube elements, which are also elongated and transport food substances in angiosperms.
- Companion cells, which are elongated in shape and have large nuclei and many mitochondria, and deliver food substances to sieve-tube elements.

The vascular bundle is continuous from roots to stems and leaves in both monocots and dicots.
The vascular cambium produces both the secondary phloem and xylem.
The secondary xylem is more complex than the primary xylem, especially in angiosperms, and is responsible for lateral growth.
The arrangement of the vascular bundle in the roots and stems differs between monocots and dicots.