Revision: 12th Std >> Plant-Water Relation MAH-MHT CET (PCM/PCB) Plant-Water Relation

The difference between the free energy of water molecules in pure water and the energy of water in any other system (e.g., water in a solution or in a plant cell or tissue) is called water potential.

The pressure exerted by the cell wall on the cell content is called wall pressure.

A cell is said to be turgid when it is fully distended by the maximum intake of water and can no longer accommodate more water.

The pressure of the cell contents on the cell wall is called turgor pressure.

Plasmolysis is the process in which the cytoplasm shrinks and the plasma membrane pulls away from the cell wall due to the loss of water when a plant cell is placed in a concentrated solution.

or

Plasmolysis is the contraction of cytoplasm from the cell wall caused due to the withdrawal of water when placed in a strong (hypertonic) solution. 

Flaccidity is the condition of a cell when it becomes limp due to plasmolysis, and the plasma membrane is no longer pressed tightly against the cell wall. It is the reverse of turgidity.

or

Flaccidity is the condition in which the cell content is shrunken and the cell is no more "tight'. The cell is then said to be flaccid. 

Turgidity is the condition in which a cell becomes fully swollen with water, exerting pressure on the cell wall.

or

Turgidity is the state of a cell in which the cell wall is rigid and stretched by an increase in the volume of vacuoles due to the absorption of water. The cell is then said to be turgid. 

The movement of soluble products of photosynthesis from the leaves to other parts of the plant through phloem is called translocation.

Loss of water vapour through the stomatal openings of the leaves of a plant is termed as transpiration.

Guttation is defined as the loss of water in the form of water droplets from the leaves of intact plants. It is also called exudation.

The largest amount of air that can be expelled following a maximum inspiration. It is the sum of TV, IRV, and ERV and ranges from 4100 to 4600 mL.

Transpiration is the process of loss of water in the form of water vapour from the leaves and other aerial parts of the plant.

The collapse of leaves and stems is frequently the result of excessive water loss through transpiration, which leads to wilting, the loss of turgidity in plant cells.