Test: Transport in Plants

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.

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

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 influencetheopening 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.

For preserving food stuff vinegar, salt and sugar is used. Ethanol is antiseptic in nature but not used for preserving food stuff.

Osmotic Pressure is the right option. As because roots need water for transportation. They dont have water at first but the surrounding soil does have. So, due to hypertonic state, roots absorb water by osmosis.

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 process of movement of water and minerals from roots to leaves in plant through xylem tissues is called ascent of sap. The most accepted theory of ascent of sap is cohesion-tension theory

The flow of water upward through the xylem in plants can achieve fairly high rates, up to 15 metres per hour. The water is mainly pulled through the plant and that the driving force for this process is transpiration from the leaves. This is referred to as the cohesion-tension-transpiration pull model.

Water molecules are attracted to each other in the liquid phase more than to water in the gas phase due to surface tension.

The lenticels functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases.The lenticels help in the gaseous exchange between the atmosphere and the internal tissue of the stem. The lenticels also helps in transpiration called as the lenticular transpiration.Lenticels are a portions of periderm with numerous intercellular spaces and loosely organized cells

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.

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 freewater and the concentration of water decreases, reducing its water potential.

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.

Stomatal index is the ratio of number of stomata to the total number of epidermal cells and stomata per unit area of leaf.

As various ions from the soil are actively transported into the vascular tissues of the roots, water follows (its potential gradient) and increases the pressure inside the xylem. This positive pressure is called rootpressure, and can be responsible for pushing up water to small heights.

The cells surrounding the stomata pore is called guard cell. It is bean shaped in dicots and dumbbellshape in monocots. Cellulose microfibrils are arranged radially in guard cell.

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 intercellularspaces of the leaf to the outside.

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.

Neighbouring cells are connected through cytoplasmic strands that extend through plasmodesmata. During symplastic movement, the water travels through the cells – their cytoplasm; intercellular movement is through the plasmodesmata.

When two solution are separated by a semipermeable membrane, water enters the sugar solution. Themovement of water always occurs from higher concentration to lower concentration. Such solution are called osmotically active.

The concentration of minerals in the soil is usually lower than the concentration of minerals in the root.

The margin and tips of leaves contain special structure made up of parenchyma tissues and water pores through which guttation take place is called hydathodes.

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