Transport in Plants Test - 3

The diffusion of water across a semi-permeable membrane from high concentration of water (or low solute concentration) to low concentration of water (or high solute concentration) is called osmosis.

The net direction and rate of osmosis depends on two factors: concentration gradient and pressure gradient.

Water drops comes out from theinjured leaf edges of leaves. This oozing of water drop from injured leaf edges is called leaf bleeding.

Potometer is used for measuring rate of transpiration in plant. Loss of water in form of water vapour is called transpiration.

Repeated question

Difference between osmotic pressure is called diffusion pressure deficit (DPD). It is the reduction of diffusion pressure of water in solution or cell over its pure state due to presenceof solute.

Plasmolysis is the process of shrinkage or contraction of the protoplasm of a plant cell as a result of loss of water from the cell.

Plasmolysis is one of the results of osmosis and occurs very rarely in nature, but it happens in some extreme conditions.

In diffusion, molecules move in a random fashion, the net result being substances moving from regions of higher concentration to regions of lower concentration.

Pressure potential is usually positive, though in plants negative potential or tension inthe water column in the xylem plays a major role in water transport up a stem. Pressure potential is denoted as ψ_p.

The water potential of pure water at standard temperatures, which is not under any pressure, is taken to be zero. If some solute is dissolved in pure water, the solution has fewer free water and the concentration of water decreases, reducing its water potential.

Absorption of water by root system is passive due to tension in sap created by transpiration. No energy molecule is required in this process, so it is passive in nature.

Plant-water relations, an understanding of certainstandard terms is necessary. Water potential (Ψw) is a concept fundamental to understand water movement. Solute potential(Ψs) and pressure potential (Ψp) are the two main components that determine water potential.