Plant and water relationship

This post describe relationship between plant and water absorption.

PostPlant and water relationship
TypeDescriptive questions
Major subjectPlant physiology
CategoryPlant physiology

Also read: Multiple Choice Questions On Plant (crop) Physiology (MCQ)

Questions on plant and water relation

Question 01. How is water taken up by a plant?

The absorption of water takes place in the terminal portion of roots. Roots hairs are responsible for water uptake. These type of roots are more developed in xerophytes. These are absent in hydrophytes.

Question 02. What are the different types of water absorption?

There are two types of water absorption. These are as follows:

  • Active absorption
  • Passive absorption

Active absorption: In active absorption, water is absorbed due to activities of roots. Metabolic energy is spend in non osmotic absorption. Only a small portion of water is absorbed by active absorption.

Passive absorption: It is controlled by activities of areal portion. Example is shoots of plant. Plant absorbs most of water by passive absorption. It occurs due to osmosis.

Question 03. What is ascent of sap?

It is the upward movement of water from stem base to top.

Question 04: What are the different theories of ascent of sap?

The different theories of ascent of sap are as follows:

  • Vital theories
  • Root pressure theory
  • Physical theories

Vital theories

  • Relay (clambering pump) theory: It was given by Godlewski in 1984.
  • Pulsation theory: It was given by Sir J.C. Bose in 1884.

Root pressure theory

  • It was coined by Stephan Hales in 1727
  • Root pressure is the hydrostatic pressure developed due to the accumulation of water which is absorbed by the roots.
  • We measure root pressure by using manometer.

Physical theories

Capillarity theory by Boehm (1809): Water rises in narrow tubes due to surface tension.
Imbibitional theory: According to Sachs (1878), the imbibition activities of cell walls of xylem is responsible of ascent of sap.

Transpiration pull theory

  • It is the most accepted theory.
  • Also known as cohesion and adhesion theory.

Plant physiology questions

Question 05. Explain the loss of water in plant

There are two ways of loss of water

  • Transpiration
  • Guttation

5.1: What is transpiration?

  • Transpiration is the loss of water from aerial parts of plant in the form of vapour. It cools down the leaf surface of plant.
  • The loss of water due to transpiration is 90%.
  • Hence, it is a necessary evil.
  • It is unavoidable.
  • Transpiration is regulated by stomatal activities.

5.2: What are the different types of foliar transpiration?

Foliar transpiration is of two types:

  1. Stomatal transpiration which is 80-90%.
  2. Cuticular transpiration which is up to 20%.

5.3: Describe stomata and its mechanism

Stomata are specialized epidermal cells which are present all over the leaf surface. In terrestrial plants, it is found mainly on lower surface, hence 97% of transpiration take place from the lower surface of leaves.


  • Stomatal movement is governed by turgor pressure.
  • Opening of stomata: Increase in turgor pressure.
  • Closing of stomata: Decrease in turgor pressure.

5.4: How is the rate of transpiration determined?

Rate of transpiration is determined by Photometer.

5.4: What is guttation?

Guttation is the exudation of water with salt minerals through hydathode. Root pressure causes guttation. It usually occurs in light. The term guttation was given by Burgerstein.

5.5: What is hydathode?

It is a structure present at tips of veins of leaves.

Leave a Comment