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Class 10, Science, Chapter-5, Lecture-4, Transportation (Notes)

THE CONDUCTING TISSUES FOR TRANSPORTATION IN PLANTS:

  1. Xylem for water
    Two types of xylem tissues
    (i)Tracheids in non-flowering plants
    (ii)Vessels in flowering plants
  2. Phloem for food
    Phloem cells consist of Sieve tubes and Companion cells.

TRANSPIRATION:

The loss of water in vapour form from the leaf through the stomata into the atmosphere is called transpiration.

TRANSPORTATION OF WATER IN PLANTS: 

Xylem of roots, stems and leaves are interconnected to form a continuous column. 
The cells in contact with soil actively take up ions and causes difference in the ion concentration between the roots and the surrounding soil. Water from the soil diffuses in to the root due to the difference in the ion concentration. 
The water column created in the root xylem causes root pressure which tends to push water upwards. Transpiration creates suction force pulling up water from root xylem.

The various cells through which water moves upwards to reach the leaves:

  1. Epidermis
  2. Root cortex
  3. Endodermis
  4. Xylem

Transpiration Helps In Upward Movement of Water:

Explanation:

Evaporation of water molecules from cells of a leaf, during transpiration, creates SUCTION which helps in upward movement of water and dissolved salts and minerals from roots.

Transpiration Is Necessary.

Reason:

All the parts of plants need water for various activities but cannot absorb water.
Only the roots can absorb water from the earth.
Transpiration helps in upward movement of water by creating suction.
So, transpiration is necessary to facilitate all the parts with water.

TRANSLOCATION:

The transport of food in dilute aqueous form from leaves to other parts of the plant through phloem tubes is termed as translocation.

Movement of food in Plants: 

The food produced during photosynthesis in the leaves is first entered into the phloem tissue by using energy from ATP. 
As a result of this osmotic pressure of the tissue increases and water moves in to dissolve the food. 
The solution of the food then moves through the sieve tubes with the help of adjacent companion cells in the phloem tube to the needed parts.

Translocation Is Necessary.

Reason:

All the parts of plant need food for obtaining energy and biosynthesis but cannot produce food.
Only the green leaves can synthesise food.
So, translocation is necessary to facilitate all the parts with food.

DIFFERENCES BETWEEN:

Movement of water (Ascent of sap)

Movement of food (Translocation)

Water and minerals are transported to different parts of the plant.

Food is transported to different parts of the plant.

It results in movement of water in upward direction only.

It results in movement of food in both upward and downward directions.

It takes place in xylem tissue.

It takes place in the phloem tissue.

Energy is not required.

Energy is required.