What are the objections raised against root pressure theory?

Explanation

The following objections have been raised against root pressure theory :
i. Root pressure is totally absent in gymnosperms, which includes some of the tallest plants.
ii. There is no relationship between the ascent of sap and root pressure. For example, in summer, the rate of the ascent of sap is more due to transpiration in spite of the fact that root pressure is very low. On the other hand, in winter when the rate of ascent of sap is low, a high root pressure is found.
iii. Ascent of sap continues even in the absence of roots.
iv. The magnitude of root pressure is about 2 atm, which can raise the water level up to few feet only, whereas the tallest trees are more than 100m high.