Transport in Plants Test - 4

Diffusion rates are affected by the gradient of concentration, the permeability of the membrane separating them, temperature and pressure

Two cells close to each other are called contiguous cells. Movement of water from one cell to other depends upon Diffusiion pressure deficit (DPD). DPD depends upon osmotic pressure and water pressure. So, movement of water from A to B will take place.

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

Water is essential for all physiological activities of the plant and plays avery important role in all living organisms. It provides the medium in which most substances are dissolved.

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.

The porinsare proteins that form huge pores in the outer membranes of the plastids, mitochondria and some bacteria allowing molecules up to the size of small proteins to pass through.

Root hairs absorb water from soil with the help of suction pressure created due to concentration difference of water and mineral ions present in soil.

Transport of water and mineral in plant take place through xylem tissue present in vascular bundles. Vessels and tracheids are main water conducting elements of xylem.

Movement by diffusionis passive, and may be from one part of the cell tothe other, or from cell to cell, or over short distances, say, from the intercellular spaces of the leaf to the outside.

Diffusion pressure deficit is equal to osmotic pressure minus water potential. Higher the DPD more faster osmosis will occur.(DPD = OP – WP).

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

Transpiration takes place through stomata. Decrease in light intensity closes the stomata that ultimately results into reduction in rate of transpiration.

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.

Some carrier or transport proteins allow diffusion only if two types of molecules move together. In a symport, both molecules cross the membrane in the same direction.

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.