Grade 10 general science – Transport in plants Quiz

Xylem vessels conduct water and dissolved mineral salts upward from roots to shoots and leaves; phloem transports organic food, cortex is for storage/transport within the root, and epidermis is outer protective layer.

Phloem conducts sugars and other organic compounds from sources (like leaves) to sinks (growing regions or storage organs); xylem carries water, cambium is a meristem, endodermis regulates water entry in roots.

Evaporation of water from leaf surfaces creates negative pressure (transpiration pull) that draws a continuous column of water up the xylem; phloem pressure moves sugars, roots do not actively pump water long distances.

Root hairs are thin extensions of root epidermal cells that greatly increase root surface area, enhancing water and mineral uptake; they do not make xylem, photosynthesise, or control stomata.

Osmosis is the passive movement of water through a semi-permeable membrane down its water potential gradient; the other options describe active transport, gas diffusion, and phloem translocation.

Cohesion (water molecules sticking to each other) and adhesion (water molecules sticking to xylem walls) maintain the continuous water column under tension; the other pairs are not the primary mechanisms.

In the pressure-flow model, sugars are loaded into phloem at sources (e.g., photosynthesizing leaves) and transported to sinks (growing tissues or storage organs) where they are unloaded.

A potometer measures water uptake by a cut shoot as an estimate of transpiration rate; the other instruments measure distance, heat energy, or light absorbance, not transpiration.

Guttation is the exudation of liquid water from leaf margins due to positive root pressure, usually at night when transpiration is low; transpiration is evaporation-driven.

The Casparian strip is a waxy barrier that forces water and dissolved minerals to enter endodermal cells via the symplast, allowing selective uptake and preventing uncontrolled leakage into the xylem.

Xerophytes reduce transpiration by having thick waxy cuticles and stomata set in pits (sunken) to reduce air movement; broad thin leaves and shallow roots increase water loss.

High temperature raises evaporation from leaf surfaces and wind removes the humid boundary layer, both increasing transpiration; high humidity or still air slow transpiration.

Active transport of ions into xylem vessels reduces water potential, causing water to move in by osmosis and creating positive root pressure; transpiration pull is a separate mechanism from leaves.

The pressure-flow model states that active loading of sugars into sieve tubes draws in water by osmosis, generating a pressure gradient that drives flow toward sinks where sugars are removed.

In light, guard cells actively accumulate K+ (and other solutes), water follows by osmosis, increasing turgor which causes the guard cells to bend and open the stomatal pore for gas exchange.

Xylem vessels have thickened, lignified walls that provide mechanical strength to resist negative pressures during transpiration; xylem vessels are non-living and lack nuclei.

Mineral ions are often taken up against concentration gradients by active transport mechanisms in root cell membranes, requiring metabolic energy; diffusion alone is insufficient for many ions.

Transpiration cools the plant and creates the transpiration stream for mineral transport; it does not produce food (photosynthesis does). The other options are incorrect descriptions of transpiration's role.

Cavitation is when air enters xylem and forms bubbles under tension, breaking the continuous water column and blocking water transport; it is not related to sugar changes or root hair growth.

Xylem primarily transports water and minerals upward from roots, while phloem transports sugars bidirectionally between sources and sinks depending on plant needs.

The apoplast pathway involves movement through cell walls and spaces outside the plasma membrane; the symplast goes via cytoplasm connected by plasmodesmata, transmembrane crosses membranes, and 'phloempast' is not a standard term.

The root cap shields the delicate meristem as the root grows through soil and secretes mucilage to ease movement; roots do not perform photosynthesis or primarily store sugars in the cap.

Girdling removes phloem around the stem, blocking downward translocation of sugars to roots; sugars therefore accumulate above the cut. Xylem is below the bark and usually remains functional.

High humidity raises the external water vapor pressure near leaves, reducing the gradient between leaf internal air spaces and outside air, so less water evaporates and transpiration falls.

By convention, pure water at atmospheric pressure has a water potential of zero; solutes reduce water potential (make it negative), driving osmosis toward areas of lower water potential.

Dye uptake visibly stains the xylem vessels and shows the upward water pathway; soil pH, bagging for fruit, or exposing roots to light do not directly trace water movement.

Most plants open stomata during daylight to permit CO2 entry for photosynthesis, though they close under stress; stomata are on leaves, not roots, and do not absorb minerals from air.

When conditions improve, positive root pressure and cellular processes can help dissolve or push out air from embolised vessels, restoring the water column; embolisms are not always permanent.