The transpiration stream in a leaf

In plants, the transpiration stream is the uninterrupted stream of water and solutes which is taken up by the roots and transported via the xylem to the leaves where it evaporates into the air/apoplast-interface of the substomatal cavity. It is driven by capillary action and in some plants by root pressure.

because of

the growth of the plants is affected by the heat of the light. what is the student doing?