iGCSE Biology (0610)-8.2 Water uptake - iGCSE Style Questions Paper 3

Question

Fig. 3.1 is a photomicrograph of a section through the stem of a plant.

(a) Use a label line and label to identify and name a structure that transports sucrose in Fig. 3.1.

(b) Complete the sentences about water uptake in a plant using words or phrases from the list. You may use the words or phrases once, more than once or not at all.

active transport cuticle mesophyll osmosis photosynthesis respiration root cortex root hair stomata transpiration

Plants absorb water molecules from the soil through …………. cells by the process of …………. Water molecules then move into …………. cells and then into the xylem. From the xylem, the water molecules move into …………. cells in the leaf. Water vapour diffuses out of the leaves through the …………. The loss of water vapour from leaves is called …………. .

▶️ Answer/Explanation

Solution

Ans:

(a)
The structure that transports sucrose is the phloem, as shown in the labeled diagram below:

(b)
Plants absorb water molecules from the soil through root hair cells by the process of osmosis. Water molecules then move into root cortex cells and then into the xylem. From the xylem, the water molecules move into mesophyll cells in the leaf. Water vapour diffuses out of the leaves through the stomata. The loss of water vapour from leaves is called transpiration.

Detailed Explanation:

Part (a): The phloem is responsible for transporting sucrose and other organic nutrients in plants. It is identified in the photomicrograph as a distinct vascular tissue.

Part (b): Water uptake follows a specific pathway:
1. Root hair cells absorb water via osmosis due to their high surface area.
2. Water moves into the root cortex and then into the xylem for upward transport.
3. In leaves, water enters mesophyll cells and evaporates, exiting through stomata in a process called transpiration.

Question

(a) Fig. 6.1 is a diagram showing the pathway of water into a plant. The arrows show the direction of water movement.

(i) State the name of the cell labelled A in Fig. 6.1.

(ii) State the name of cell B and describe how it is adapted for absorption of water.

(iii) State the name of the process by which cell B absorbs water.

(b) State two uses of water in plants.

▶️ Answer/Explanation

Solution

(a)(i) (root) cortex (cell)

Explanation: The cell labelled A is part of the root cortex, which is the region of parenchyma cells between the epidermis and vascular tissue in plant roots. These cells store starch and help in the movement of water and minerals from the epidermis to the vascular tissue.

(a)(ii) root hair (cell); large surface area / elongated shape

Explanation: Cell B is a root hair cell, which is specialized for water absorption. Its key adaptation is its elongated shape that creates a large surface area to maximize absorption of water and minerals from the soil. The thin cell wall also facilitates this absorption process.

(a)(iii) osmosis

Explanation: Root hair cells absorb water through osmosis, which is the passive movement of water molecules from an area of higher water potential (soil) to an area of lower water potential (root hair cell) across a partially permeable membrane.

(b) Any two from: photosynthesis / metabolic processes; support; solvent; transport; germination

Explanation: Water has multiple crucial roles in plants. It’s essential for photosynthesis as a raw material and maintains turgor pressure for support. As a universal solvent, it transports minerals and nutrients. Water is also vital for metabolic processes and is required for seed germination.

(c) Any two from: wind(speed); temperature; humidity; light intensity

Explanation: Environmental factors significantly affect transpiration rates. Wind increases water loss by removing humid air around leaves. Higher temperatures accelerate evaporation. Low humidity creates a steeper water potential gradient. Light intensity affects stomatal opening, thus influencing transpiration.

iGCSE Biology (0610)-8.2 Water uptake – iGCSE Style Questions Paper 3

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