Edusaint

Transportation in Plants : NCERT Notes for Class 10th Biology

TRANSPORT IN PLANTS

      • The plants have two transport systems:

1. Xylem which carries water and minerals, and

2. Phloem which carries the food materials which the plant makes

TRANSPORT OF WATER AND MINERALS

      • The water and minerals dissolved in it move from the roots of the plant to its leaves through the two kinds of elements of the xylem tissue called xylem vessels and tracheid.

Xylem Vessels

      • The xylem vessel is a non-living, long tube which runs like a drainpipe through the plant
      • A xylem vessel is made of many hollow, dead cells (called vessel elements), joined end to end.
      • Xylem vessels do not contain the cytoplasm or nuclei.
      • In flowering plants, either only xylem vessels transport water or both xylem vessels and tracheid transport water.

Tracheids

      • Tracheids are long, thin, spindle shaped cells with pits in their thick cell walls.
      • Tracheids are dead cells with lignified walls but they do not have open ends, so they do not form vessels.
      • Although all the plants have tracheids, they are the only water conducting tissue in non-flowering plants.

Mechanism of Transport of Water and Minerals in a Plant

      • Ascent of Sap : The upward movement of water and minerals from roots to different plant parts is called ascent of sap.
      • Many factors are at play in the ascent of sap and it takes place in many steps.

They are explained as follows:

1. Root Pressure:

      • The walls of cells of root hairs are very thin. Water; from soil; enters the root hairs because of osmosis. Root pressure is responsible for movement of water up to the base of the stem.

2. Capillary Action:

      • A very fine tube is called capillary. Water: or any liquid; rises in the capillary because of physical forces and his phenomenon is called capillary action. Water; in stem; rises up to some height because of capillary action.

3. Adhesion-cohesion of Water Molecules:

      • Water molecules make a continuous column in the xylem because of forces of adhesion and cohesion among the molecules.

4. Transpiration Pull:

      • Loss of water vapour through stomata and lenticels; in plants; is called transpiration.
      • Transpiration through the stomata creates vacuum which creates a suction; called transpiration pull.
      • The transpiration pull sucks the water column from the xylem tubes and thus water is able to rise to great heights in even the tallest plants.

TRANSPORT OF FOOD AND OTHER SUBSTANCES

      • The transport of food from the leaves to other parts of the plant is called translocation.
      • Thus, phloem translocates the food (or sugar) made in the leaves.
      • Like Sieve tubes which form phloem are living cells which contain cytoplasm but no nucleus.
      • Each sieve tube cell has a companion cell next to its xylem vessels, phloem is made of many cells joined end to end to form long tubes.
      • The movement of food in phloem can be, however, upwards or downwards depending on the needs of the plant.

 

Scroll to Top