The rate of fow of water through the xylem is regulated by?

Question

a) passive transport by the pith

b) the force of transpirational pull

c) the number of companion cells in the phloem

d) active transport by the sieve-tube members

e) active transport by tracheids and vessel elements

Answer 1

Transpiration generates the upward pull through the xylem so water is drawn from the roots by the evaporation at the leaf. It is regulated by stomatal closure.

http://www.emc.maricopa.edu/faculty/fara...

Clever animation of transport:

http://academic.kellogg.cc.mi.us/herbran...

In the phloem sucrose is actively moved and water passively follows from the xylem.