Home › ICAR JRF › Plant Sciences › Plant Form and Physiology › How does the direction of flow in the xylem diff…
How does the direction of flow in the xylem differ from that in the phloem?
AXylem flow can reverse, while phloem flow cannot
BBoth tissues carry material in both directions
CXylem flow is always one way, phloem is not
DBoth tissues carry material in one direction
Answer & Solution
Correct answer: C. Xylem flow is always one way, phloem is not
1. The highest leaves send photosynthates upward to the growing shoot tip.
2. Lower leaves direct photosynthates downward to the roots, and intermediate leaves send products both ways.
3. Flow in the xylem, by contrast, is always unidirectional, running soil to leaf to atmosphere.
4. So the phloem is the tissue with two possible directions and the xylem is the one way route.
5. Saying both tissues behave alike misses the contrast that products are delivered to the nearest sink.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.5 Transport of Water and Solutes in Plants_
Related questions
Which defence compound of the cassava root becomes toxic only after a herbivore eats it?A tree exposed to constant strong wind shows which developmental response?Jasmonates elicit the synthesis of volatile compounds that attract which agents?In ripening fruit, ethylene stimulates which conversion?Low soil moisture raises the level of abscisic acid, which then does what?Gibberellins are described as a group of about how many closely related hormones?The effect of cytokinins was first reported after adding what to plant embryos in culture?Which is the only naturally occurring auxin that shows physiological activity?