Transportation in Plants: Water Absorption in Plants, Active Absorption (For CBSE, ICSE, IAS, NET, NRA 2022)

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Water Absorption in Plants

Active Absorption

  • The osmotic process involves diffusion pressure deficit (DPD) of the cells.
  • The root hairs have more DPD as compared to soil solution.
  • There is an involvement of both Osmotic and non-osmotic mechanisms.
  • Symplastic movement of water in root hairs.
    • The water first enters the cell sap and then passes from one cell to another.
  • Root pressure, bleeding, and guttation, etc. are the evidences for active absorption.

Passive Absorption

  • It occurs due to the activity of the upper part of the plant such as shoot system.
  • The absorption is due to transpiration in the upper part.
  • Tension is created in the Xylem sap by transpiration pull.
  • Water moves through the free spaces or apoplast of root.
    • The water can reach up to endodermis through apoplast.
  • Even if all the roots are removed, the absorption of water is continued.

Driving Forces

Driving Forces

Transpiration

  • This driving force is behind uptake and transport of water.
  • The process of water evaporation through openings called stomata.
  • Due to the cohesive forces, the pull in the xylem tissues extends all the way down.
  • The negative water pressure eventually results in an increase of water uptake from the soil.

Force of Surface Tension

  • There is an increase in the curvature of the meniscus as more molecules evaporate from the water film.
  • To reduce the tension, water from the surrounding cell is pulled towards this area.

Water Potential Gradient

  • It is due to the water potential gradient; water moves from the roots to the leaves.
  • The water potential gradient is the highest in the water surrounding the roots.
  • The water potential gradient is the lowest in the airspace within the spongy parenchyma.

Hydrogen Bonding Force

  • By hydrogen bonds the water molecules stick to each other.
  • Within the xylem through the hydrogen bonds, the hydrogen bonding forces are communicated to water forces.

FAQs

Q 1. List out the different means of transportation in plants.

Answer:

The different means of transportation in plants are:

i) Simple diffusion

ii) Facilitated diffusion

iii) Osmosis

iv) Active transport

Q 2. How is the water and food transportation occur in plants?

Answer: Water transportation occurs through Xylem and Food transportation occurs through Phloem.

Q 3. What are the various driving forces responsible for transportation in plants?

Answer:

The various driving forces responsible for transportation in plants are:

i) Transpiration

ii) Force of surface tension

iii) Water potential gradient

iv) The force of hydrogen bonding between water molecules