I was doing a Cambridge iGCSE past paper when I came across the question:
Describe the mechanism by which water flows through the xylem
I thought the correct answer would revolve around the xylem being composed of dead cells, thus allowing water to use capillary action to flow upwards, but it wasn't.
Instead, the mark scheme referred only to transpiration causing tension and so forth, not even mentioning capillary action.
Is capillary action not a valid answer? And if not, why not?