Test: Transport in Plants - A Level MCQ

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

Transport over longer distances proceeds through the vascular system(the xylem and the phloem) and is called translocation.

Terrestrial plants take up huge amount water daily but most of it is lost to the air through evaporation from the leaves, i.e., transpiration.

An important aspect that needs to be considered is the direction of transport organic and mineral nutrients however, undergo multidirectional transport.

The cytoplasm of two adjacent cells are connected through a bridge plasmodesmata. Movement of substance in plants takes place through thisplasmodesmata.

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.

Distilled water do not contain any kind of salt in it so its water potential is 0. Addition of solute results into further decrease in water potential in negative term.

A cell dipped in 0.5 M sucrose has no effect due to osmosis as concentration of sucrose is more of equal to cytoplasm but 0.5 M NaCl cause exosmosis that leads to plasmolysis.

The transpiration driven ascent of xylem sap depends mainly on the physical properties of water. Cohesion– mutual attraction between water molecules.

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.

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

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

The cell wall is nonliving and cannot regulate the entry and exit of solute or solvent molecules. When a cell is kept in hypertonic solution, it readily crosses the cell wall and fills the space between the cell wall and cell membrane. This hypertonic solution in direct contact with the cell membrane causes plasmolysis and extracts water from the cytoplasm of the cell.
So, the correct answer is option B.

Transpirational or gravitational pull exert strain so they are factors that can cause rupture of the column. 

Lignified walls are only present for structural support.

Cohesion ( attraction of water molecules towards each other) and adhesion (attraction of water molecules and the walls of the tube ) is the reason why  the column doesn't break as these attractive forces overcome the strain developed by Transpiration pull. 

So the correct answer is 'Cohesion and adhesion'.

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

Reverseosmosis is the movement of pure water form a solution through a semi permeable membrane under the influence of pressure higher than the osmotic pressure. This process is used to obtain drinking water from salty water.

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

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

Water potential of a cell is affected by both solute and pressure potential. The relationship between them is as follows: ψw=Ψs+Ψp

The apoplastis the system of adjacent cell walls that iscontinuousthroughout the plant, except at the casparianstrips of the endodermis in the roots. The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells.

Rate of transpiration is influenced by wind speed, availability of water and temperature. Rate of transpiration is highest when soil is wet and air is dry.

A sudden increase in carbon dioxide gas concentration around a leaf will cause decrease in transpiration due to closure of stomata.

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

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.

Plasmolysis is the shrinking of cell membrane due to exosmosis. Plasmolysis shows that cell membrane is semipermeable and elastic but do not show that cell wall is semipermeable.