Transport in plants：練習題

What is the main function of lignin in the cell walls of xylem vessel elements?

Which environmental conditions would result in the highest rate of transpiration for a typical mesophytic plant?

A plant is treated with a metabolic poison that inhibits the action of proton pumps in the plasma membranes of companion cells.

What would be the most immediate effect on the transport of materials in the phloem?

Which statement provides the most accurate definition of transpiration?

What causes the hydrostatic pressure gradient that drives the mass flow of solutes in the phloem sieve tubes?

State the specific name of the waxy, waterproof substance found in the Casparian strip of the endodermis that blocks the apoplast pathway.

Explain how hydrogen bonding between water molecules and the cell walls of xylem vessels contributes to the movement of water in the transpiration stream.

A transverse section of a leaf from a xerophytic plant shows specific anatomical adaptations. Explain how the presence of sunken stomata and a thick waxy cuticle specifically act to reduce the rate of transpiration.

Water moves from the soil into the xylem of a root through different pathways.
(a) Distinguish between the apoplast pathway and the symplast pathway.
(b) State the effect of the Casparian strip on the movement of water via the apoplast pathway.

The loading of sucrose into phloem sieve tubes is an active process involving specialized cells.

(a) Explain the role of proton pumps and cotransporter proteins in the transfer of sucrose from companion cells into phloem sieve tubes.
(b) Describe how the accumulation of sucrose in the sieve tube at the source leads to the mass flow of phloem sap towards the sink.