What would be a reason for saying that mycorrizhizal doesn't help a plant by passing on sugars to it.?

Question

I know the correct answer is that it does in certian situations but why would anyone put that it doesn't because some did.

Answer 1

mychorriza connections as far as I know are good for a plant cause it seems to substitute the tiny root hairs in many species.So the fungus takes water and nutrients from the ground and passes it to the plant and in return it gets some of the plants own synthetised substances(sugars) is what I have learnt.

Answer 2

The problem with this statement is that it is backward. The plant passes on sugars to the mycorrhizae. The hyphae of the mycorrhizae pass water and nutrients to the roots of the plant.