CAIE IGCSE Biology 6 Plant Nutrition

Practise photosynthesis equations, leaf adaptations, limiting factors and experimental evidence for plant carbohydrate production.

Covered syllabus points

6.1 Photosynthesis 6.2 Leaf structure

[Maximum number: 1]

Which substance is used up in photosynthesis?

chlorophyll

light

oxygen

water

[Maximum number: 4]

Scientists investigated the effect of cuticle thickness on water loss from the leaves of the balsam fir tree, Abies balsamea.

The leaves were divided into three groups:

A - thick cuticle

B - medium cuticle

C - thin cuticle Samples of leaves from each group were weighed. The leaves were placed on a tray in dry air at $20^{\circ} \mathrm{C}$ . The samples of leaves were reweighed, at intervals, over 15 hours. The scientists calculated the mass of each sample of leaves as a percentage of the initial mass. mass of the leaves as a percentage of the initial mass

Fig. 5.1 shows the results.

(a)

Water is one of the raw materials needed for the production of sugars in photosynthesis.

[ 4 ]

(i)

State the name of the other raw material needed for photosynthesis.

[ 1 ]

(ii)

State three ways a plant uses the sugars produced in photosynthesis.

[ 3 ]

[Maximum number: 12]

(a)

Fig. 4.1 is a photomicrograph of a cross section of part of a leaf.

Fig. 4.1

[ 5 ]

(i)

Identify the tissue labelled A in Fig. 4.1.

[ 1 ]

(ii)

Identify the structure labelled C in Fig. 4.1.

[ 1 ]

(iii)

Describe how the tissue labelled B is adapted to maximise photosynthesis.

[ 3 ]

(b)

The effect of carbon dioxide concentration on the rate of oxygen production in an aquatic plant was measured.
- A lamp was used to keep the light intensity constant.
- The oxygen gas released by the plant was collected in a gas syringe.
- The plant was placed in water that was kept constant at $20^{\circ} \mathrm{C}$ .

Fig. 4.2 shows the results.

[ 5 ]

(i)

The rate of oxygen production was assumed to be the same as the rate of photosynthesis.

Suggest why the rate of oxygen production was not the same as the rate of photosynthesis.

Fig. 4.2

[ 2 ]

(ii)

Explain the results shown in Fig. 4.2.

[ 3 ]

1 carbon dioxide is required for photosynthesis ;

2 initially carbon dioxide concentration is limiting the rate of photosynthesis ;

3 (after $500 \mu \mathrm{~mol}$ per $\mathrm{dm}^{3}$ ) carbon dioxide concentration is not limiting the rate of photosynthesis / other factors are limiting the rate of photosynthesis ;

4 ref. to named limiting factor ;

(c)

The investigation was repeated with the same type of aquatic plant at $10^{\circ} \mathrm{C}$ .

Draw a line on Fig. 4.2 to predict the results at $10^{\circ} \mathrm{C}$ .

[ 2 ]

[Maximum number: 1]

Which structure contains the pigment that transfers energy from light into chemical energy?

chloroplast

mitochondrion

nucleus

ribosome

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Covered syllabus points

6. Plant nutrition question 1

6. Plant nutrition question 2

Question (a)

Question (i)

Question (ii)

6. Plant nutrition question 3

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (b)

Question (i)

Question (ii)

Question (c)

6. Plant nutrition question 4