In plants,the movement of water against gravitational force is due to

The most widely accepted explanation for the ascent of sap in trees is:

According to the transpiration-cohesion theory,the upward pull of water is transmitted to other water molecules by cohesion,which is caused by

Passive absorption of water by the root of a plant is affected by

Which of the following are objections to the root pressure theory of ascent of sap in plants?
$I$. It is not applicable to plants taller than $20 \ m$.
$II$. Ascent of sap occurs even in the absence of a root system.
$III$. Root pressure is almost zero in tall gymnosperms.
$IV$. Root pressure is the only mechanism explaining the ascent of sap.
$V$. Root pressure is not developed in actively transpiring plants.

When is the root pressure lowest?