Plant Tissue Systems:

VASCULAR TISSUE

Vascular Tissue

Vascular tissue

apparently evolved as an adaptation to life on land. It consists of a series of elements that form tubes throughout the plant. It is made up of two different kind of tissues –xylem and phloem.

Xylem

Xylem consists of two types of cells known as tracheidsand vessel elements. Tracheids and vessel elements form tube-shaped structures that provide pathways for water and minerals to travel from the roots to the leaves. While tracheids are found in all vascular plants, vessels are found only in angiosperms.

Phloem

Phloem is composed mostly of cells called sieve-tube cells and companion cells. These cells assist in the transport of sugar and nutrients produced during photosynthesis from the leaves to other parts of the plant. While tracheid cells are nonliving, sieve-tube and companion cells of the phloem are living. Companion cells possess a nucleus and actively transport sugar into and out of sieve-tubes.

Xylem

Carries water and

nutrients that enter the plant in the root up through the stem and out to all parts of the leaf.

Phloem

Runs parallel to the xylem and carries sugar that is produced in the leaves, dissolved in fluid, to all parts of the plant.

• Phloem is the living tissue that carries organic nutrients to all parts of the plant where needed.

• Xylem transports water, but it also transports some nutrients.

• Vascular cambium is a type of meristem - a tissue consisting of embryonic (not specialized) cells which can produce other (and more differentiated) plant tissues originate.

Vascular

TissueXylem Tissue Phloem Tissue

Function • Conduct water and dissolved minerals

from root to leaves of plants

• Give mechanical strength (support) to the

plant body

• Conduct food and other organic

substances

Cell types Tracheids Vessel members Companion

cells

Sieve-tube

elements

Characteristics • elongated and lignified

• tapering end walls that overlap with adjacent tracheids

• They give support to the plant.

• Tracheids are dead cells with empty lumens when mature.

• cylindrical, tube-like structures

• very long and tubular structures (formed by the fusion of several cells end to end in a row)

• Vessels are dead at functional maturity and are perforated.

• parenchyma cells adjoining the sieve tube cells

• They assist the sieve tube cells in the conduction of food.

• They are living cells with elongated nucleus.

• elongated cells placed end to end to form a tube

• Their end walls have pores in them which forms the sieve plates.

• The main function of the sieve tubes is to carry food, especially carbohydrates.

Sources:

o http://biology.about.com/od/plantbiology/ss/plant-tissue-systems_2.htm

o http://www.phschool.com/science/biology_place/biocoach/plants/vascular.html

o http://www.ehow.com/list_7153104_functions-vascular-tissue-plants_.html

o http://www.phschool.com/science/biology_place/biocoach/plants/support.html

o http://www.phschool.com/science/biology_place/biocoach/plants/parenchyma.html

o http://tantebazar.com/gardening_histology_of_plant_part_2.php