The important organ of the high level of plants

Roots and leaves
The major driving force of water uptake in a large tree is transpiration.Transpiration is the process  by which plants absorb water through the roots and release it as water vapor through the pores in their leaves. Once this water evaporates, a negative water vapor pressure is created or develops in the surrounding cells of the leaf.   when this happens, water is pulled into the leaf from the vascular system, the xylem, to replace the water that has been transpired from the leaf.This pulling of water, or tension, that occurs in the leaf, will extend through the rest of the xylem column of the tree right into the xylem of the roots as result of the cohesive force holding the water molecules  along the sides of the xylem tubing.The xylem is a continuous water column extending from the roots to the leaves.Finally, the negative water pressure that occurs even to the  roots will result in an increase of water uptake from the soil.

They must use the scientific method

It is platinum in the market value