Transport in Plants Test - 10

The behaviour of the plant cells (or tissues) with regard to water movement depends on the surrounding solution. If the external solution is more dilute than the cytoplasm, it is hypotonic Cells swell in hypotonic solutions.

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 ψp.

The fungus provides minerals and water to the roots, inturn the roots provide sugars and N-containing compounds to themycorrhizae. Some plants have an obligate association with themycorrhizae.

Relative humidity of atmosphere also influence the opening and closing of stomata. If relative humidity of atmosphere comes below 50% stomata close down.

In plants capillarity is aided by the small diameter of the tracheary elements – the tracheids and vessel elements.

In angiosperms and gymnosperms (but not in ferns and lycopsids), Accumulation of ABA triggers closing of the stomata when soil water is insufficient to keep up with transpiration.

Imbibition is a special type of diffusion when water is absorbed by solids-colloids causing an enormous increase in volume. Examples include the absorption of water by seeds and dry wood.

The excess water collects in the form of droplets around special openings of veins near the tip of grass blades, and leaves of many herbaceous parts. Such water loss in its liquid phaseis known as guttation.

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.

Solute potential of a solution is always less than 0 as solute potential of distilled water is 0 and addition of solute decrease the solute potential.