CIE iGCSE Co-Ordinated Science B8.2 Water uptake Exam Style Questions Paper 3

(a)(i)

This is a tropic response called gravitropism (also accepted: geotropism).
The roots are growing downwards towards gravity to receive more water from the soil.
Roots are positively gravitropic — they grow in the direction of gravitational pull, which helps them anchor the plant and absorb water.

(a)(ii) Any two from:

1. Photosynthesis — water is a raw material for making glucose using light energy.
2. Support — water provides turgor pressure to keep plant cells firm and the plant upright.
(Also accepted: as a solvent; for germination; transport of minerals.)

(a)(iii) Root hair cell

Root hair cells have a large surface area due to their long thin extensions (root hairs), maximising water absorption from the soil.
Water enters by osmosis from the soil solution into the root hair cells.

(a)(iv) Xylem (vessels)

Xylem vessels are hollow, dead cells that form continuous tubes from root to leaf.
Water moves up through the xylem by transpiration pull (the movement of water due to evaporation from leaves).

(b) magnesium

Magnesium ions (\(\text{Mg}^{2+}\)) are essential for the synthesis of chlorophyll, the green pigment used in photosynthesis.
A magnesium deficiency causes yellowing of leaves (chlorosis) because chlorophyll cannot be produced.

(c) Three correct statements:

The other statements are incorrect: plants do respire; plants do not form the main part of a carnivore’s diet; and plants can reproduce both sexually and asexually.