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  • The study of various vital activities and metabolism of plants is known as Plant physiology.
  • Stephan Hales is known as the father of plant physiology.
    Fig: Stephen Hales
    Fig: Stephen Hales
  • J.C. Bose is known as the Father of Indian Plant physiology.
  • Plants grow in soil and absorb water and minerals, which are available in the soil. So that water has great importance for plants. Water forms 80-90% of the fresh weight of the plant body. The method or technique, plant cells obtain water, comes under the heading of Water relation.

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What is the study of various vital activities and metabolism of plants known as?
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To understand the plant water relations, we should know the following process-

Diffusion


“The movement of molecules or atoms or ions of materials from an area of higher concentration to an area of their lower concentration is called diffusion.

Diffusion in Plants | Biology for JAMB

                                                                 Fig: Diffusion

The diffusion is continue till the dynamic equilibrium is established. At this stage, the net movement of the molecule is equal in both directions.


  • The kinetic energy, which is present in the molecules of material is distributed equally in their available space by their nature.

Diffusion rate → Gas > Liquid > Solid

Diffusion pressure:

“The diffused molecules or ions exert a pressure on the substance or medium in which diffusion take place, known as Diffusion pressure.”

  • This is developed due to differences in the concentration of molecules of the material. The diffusion pressure of a pure solvent (1236 atm) is always higher than its solution.
  • Water molecules move from their higher concentration to their lower concentration in plants.
  • The rate of diffusion decrease with the increasing size of molecules.


Factors affecting Diffusion in Plants


1. Diffusion Pressure Gradient: The difference in the diffusion pressure determines the rate of diffusion. The rate of diffusion is directly proportional to the difference in concentration of the molecules in the two regions.

2. Temperature: The rate of diffusion is directly proportional to the increase in temperature.

3. Density: The rate of diffusion is inversely proportional to the square root of the density of the gas.

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What determines the rate of diffusion in plant water relations?
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Significance of diffusion

  • The exchange of gases like CO2, O2 takes place through diffusion.
  • The distribution of hormones in the plants takes place through diffusion.
  • The process of transpiration is a diffusion process. The evaporation of water from the intercellular spaces is linked with diffusion during transpiration.
  • The ions of the minerals may diffuse into the plant body.
  • The process of osmosis is a special type of diffusion of solvent molecules through a semi-permeable membrane.
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FAQs on Diffusion in Plants - Biology for JAMB

1. What is diffusion and how does it occur in plants?
Ans. Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In plants, diffusion occurs in various processes such as gas exchange in leaves, movement of water and nutrients in roots, and transport of sugars in phloem. It happens through small openings in the leaves called stomata, specialized structures in roots called root hairs, and through the sieve tubes in the phloem.
2. What are the factors that affect diffusion in plants?
Ans. Several factors can affect diffusion in plants. Some of the key factors include the concentration gradient, temperature, surface area available for diffusion, distance over which diffusion occurs, and the nature of the diffusing substance. A steeper concentration gradient, higher temperature, larger surface area, shorter distance, and smaller diffusing substances all facilitate faster diffusion in plants.
3. How is diffusion significant for plants?
Ans. Diffusion plays a crucial role in various physiological processes in plants. It is essential for gas exchange, allowing plants to take in carbon dioxide for photosynthesis and release oxygen. Diffusion also facilitates the movement of water and nutrients from the soil to the roots and further to other parts of the plant. Additionally, diffusion is involved in the transport of sugars and other organic compounds in plants.
4. How does diffusion occur in leaves of plants?
Ans. In leaves, diffusion occurs through small openings called stomata. The stomata are surrounded by guard cells that control their opening and closing. During photosynthesis, carbon dioxide enters the leaf through the stomata and diffuses into the cells where it is utilized. At the same time, oxygen produced during photosynthesis diffuses out of the cells and exits through the stomata.
5. How does diffusion contribute to the movement of water in plants?
Ans. Diffusion is one of the primary mechanisms by which water moves in plants. Water molecules move from an area of higher concentration to an area of lower concentration through a process called osmosis. This movement occurs through specialized structures in plant roots called root hairs, which have a large surface area and are in close contact with soil water. The water then moves upward through the plant's vascular system, primarily driven by transpiration and capillary action.
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