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Study of the importance and practical utility of plasmolysis.

Importance of Plasmolysis:1. It is a vital phenomenon as it explains the process of osmosis.

2. Plasmolysis demonstrates the permeability of the cell wall and the semipermeable nature of the protoplasm.

3. It helps to detect whether a particular cell is living or dead as the plasmolysis does not take place in a dead cell.

4. Osmotic pressure of a cell can be determined by plasmolytic method.

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Let us make in-depth study of the importance and practical utility of plasmolysis.The shrinkage of the protoplast from its cell wall due to exosmosis under the influence of hypertonic solution is called plasmolysis.

The point at which protoplast just begins to shrink away from the cell wall is known as incipient plasmolysis .The stage when the cell wall has reached its limits of contraction and the protoplast has detached from cell wall attaining spherical shape is called evident plasmolysis (Fig. 1.5).

When a plsmolysed cell is placed in hypotonic solution, endosmosis takes place and the cell returns to its original state is known as de-plasmolysis. Temporary plasmolysis is not destructive to the cell. The cell can be restored quickly to its normal turgid condition simply by returning it to a dilute medium or water. However, plasmolysis prevents normal water balance and other functions of the plant as a whole, and thus plants cannot tolerate prolonged exposure to medium more concentrated than their own cells.

Importance of Plasmolysis:1. It is a vital phenomenon as it explains the process of osmosis.

2. Plasmolysis demonstrates the permeability of the cell wall and the semipermeable nature of the protoplasm.

3. It helps to detect whether a particular cell is living or dead as the plasmolysis does not take place in a dead cell.

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4. Osmotic pressure of a cell can be determined by plasmolytic method.

Practical Utility of Plasmolysis:Plasmolysis has many useful applications in our daily life. To quote a few:1. It plays most vital role in the preservation of meat, jellies and other food stuffs, and thereby prevents them from being destroyed by bacteria and fungi. Salting of food stuffs (to be preserved) raises the osmotic pressure of the preservation medium. Bacteria and fungi get plasmolysed and killed due to exosmosis.

2. Plasmolysis is also involved in killing of weeds in lawns, orchards and agricultural fields by chemical weedicides.

3. It helps in preventing the growth of plants in the cracks of the walls. Salting of such plants induces plasmolysis, and the unwanted plants are killed.

Movement of water from root hairs to xylem tissue

Ascent of sapThe ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root to the crown.

COHESSION AND ADHESSION THEORY

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Anti-transpirants are substances applied to the plants for the purpose of reducing transpiration (water loss) without causing a significant effect on other plant processes, such as photosynthesis & growth. They have been used with some success in horticulture, especially in the ornamental industry.

How they reduce Transpiration (water loss)?

Anti-transpirants may reduce transpiration in three different ways:

1. By reducing the absorption of solar energy and thereby reducing leaf temperatures and transpiration rates.

2. By forming thin transparent films which hinder the escape of water vapors from the leaves.

3. By promoting closure of stomata (by affecting the guard cells around the stomatal pore), thus decreasing the loss of water vapors from the leaf.

Types of Anti -transpirants:

1. Stomatal closing type: They induce stomatal closing or decrease size and number of stomata which subsequently reduce the photosynthesis. For example, when Phenyl Mercuric Acetate is sprayed at very low concentrations, results in a partial closure of stomata for 2 weeks.

2. Film forming type: Plastic and waxy material which form a thin colorless film over the leaf surface and result in a physical barrier. These glossy films then reduce water loss on plants while at the same time allow them to breathe normally. Colorless plastics, silicone oils & low viscosity waxes are some examples of film forming types.

3. Reflecting type: These are most commonly clay based and increase the reflection of light from leaf surface thus reducing leaf heating and water losses.

4. Growth retardant: These chemicals reduce shoot growth and increase root growth and thus enable the plants to resist drought. They may also induce stomatal closure.

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Mass Flow hypothesis/ Pressure flow hypothesis

Transport of Food through phloem elements