Root pressure, transpiration pull, translocation, cohesive force pick the odd one out and mention the category

Dear Student

Ans. Translocation is the odd one out. 
That is because the other options are involved in the transport of water and minerals in plants from the roots to the leaves whereas translocation refers to the transport of the food prepared by leaves to other parts of the plant. 

Root pressure generates when water moves from soil into the root hairs and from them to the cells of xylem. The xylem vessels has lower water potential. Root pressure pushes the water up the xylem vessels.
Generation of root pressure is an active process. It is because root pressure is generated when in a xylem vessel, minerals are accumulated against the concentration gradient by active absorption resulting in lowering in water potential of surrounding xylem vessels. 

Due to evaporation of water from the cells present on the surface of the leaves (transpiration) a vacuum space is created. To fill that vacuum water droplets from the other cells rush inside. This rush of water towards the vacuum creates a mechanical force that enables to pull up water absorbed by the roots through the stems. These antis gravitational force that results in upward movement of water through the xylem is known as transpiration pull. In tall trees transpiration pull can draw water up to 50 meter height.

Translocation is the process of movement of materials from leaves to all other parts of the plant body. Leaves of the plants perform photosynthesis and produce carbohydrates (organic solutes) which are translocated to the non photosynthetic parts (roots, flowers, fruits) of the plant through special tissues called phloem.

The attractive forces which exist between molecules of the same substance and cause a tendency in liquids to resist separation are called cohesive forces. The water molecules are attracted to each other due to cohesion which forms a continuous channel. Water molecules are also attracted by xylem elements due to adhesion. So cohesive and adhesive forces are responsible to form a continuous channel between roots and the leaves.


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