Grade 10 biology – Transport Quiz

Xylem conducts water and dissolved mineral ions upward from the roots to the rest of the plant; phloem transports sugars and other organic materials.

Phloem transports assimilates (sugars) from sources (like leaves) to sinks (roots, growing tips) by the process called translocation.

Vessel elements join end-to-end with perforation plates to form continuous vessels that allow efficient water flow; both vessel elements and tracheids are dead at maturity and transport water.

Transpiration at the leaf creates tension (negative pressure) that pulls water up; cohesion between water molecules maintains a continuous column through xylem vessels.

Active transport of ions into the xylem lowers water potential, so water enters by osmosis and can create a positive pressure (root pressure) that pushes water upward, especially at night.

The Casparian strip (a waxy band) prevents water and dissolved substances from bypassing the plasma membrane, ensuring selective uptake by endodermal cells.

Sieve tube elements lose their nucleus to make room for transport of sap and rely on companion cells for metabolic support and loading/unloading of sugars.

Sugars are actively loaded into phloem at sources, drawing water in and creating high pressure; unloading at sinks lowers pressure, driving bulk flow from source to sink.

In light, guard cells actively take up potassium ions; water follows by osmosis, increasing turgor and opening the stomatal pore.

Transpiration depends on the difference in water vapour concentration between the leaf air spaces and the outside air; high external humidity lowers this gradient and reduces transpiration.

Guttation happens at night or early morning when stomata are closed and high root pressure forces water out through special pores (hydathodes) as droplets.

Adhesion pulls water along the walls while cohesion keeps molecules together, enabling capillary rise in narrow tubes like xylem vessels.

Plasmodesmata are microscopic channels connecting the cytoplasm of neighboring cells, allowing water, ions and small molecules to move along the symplast pathway.

Water flows from areas of higher water potential (closer to zero) to areas of lower (more negative) water potential; this concept explains osmosis and movement in plants.

Wind carries away moist air near the leaf, increasing the vapour concentration gradient and therefore increasing transpiration rate.

In the apoplast route water moves through cell walls and intercellular spaces without entering the cytoplasm until blocked by the Casparian strip.

Mineral ions are often at lower concentration in soil than in root cells, so roots use energy (ATP) to actively transport ions into root cells against concentration gradients.

Companion cells are metabolically active cells closely associated with sieve tube elements; they help load sugars into phloem and maintain the function of sieve tubes.

Cavitation creates air embolisms that break the continuous water column in xylem, reducing the plant's ability to transport water and potentially causing wilting.

A thick waxy cuticle on the leaf surface reduces water loss by limiting evaporation from the epidermis, an important adaptation in dry conditions.

Root hairs are extensions of epidermal cells that greatly increase root surface area, improving uptake of water and mineral ions from the soil.

Mycorrhizal fungi form networks of hyphae that reach beyond the root zone, helping the plant absorb water and nutrients (especially phosphorus) more efficiently.

Sieve plates are porous end walls between sieve tube elements that permit the flow of phloem sap along the phloem.

Pressure potential (turgor) is the pressure of the cell contents pushing against the cell wall; it raises water potential and influences water movement in plants.

A potometer measures water uptake by a plant shoot; under steady conditions water uptake approximates transpiration loss, so the device estimates transpiration rate.