Given below is a picture of a tree. Mention the scientific phenomena occurring in the parts labelled (a), (b) and (c).
Topic: Processes occurring in a tree
Answer
(a) ROOTS — ABSORPTION of water and dissolved minerals from the soil, chiefly by OSMOSIS through the root hairs. (b) STEM — CONDUCTION (ascent of sap): the upward movement of water and minerals through the XYLEM to the leaves. (c) LEAVES — TRANSPIRATION: the loss of water as vapour, mainly through the stomata. (Photosynthesis also occurs here.)
One mark per part. Name the PROCESS, not just the organ — the question asks for the phenomena.
THE THREE TOGETHER FORM ONE CONTINUOUS SYSTEM, and saying so is what lifts the answer: water absorbed at the roots is carried up the stem and evaporates from the leaves. The evaporation at the top creates a suction — the TRANSPIRATION PULL — which is what draws the whole unbroken column of water up the xylem, sometimes to the top of a very tall tree.
This is why transpiration, although it looks like a wasteful loss of water, is essential: it is the engine that lifts water and minerals against gravity, and it also cools the leaf.