IGCSE Biology Plant nutrition topical questions

Complete the word equation for photosynthesis, and name the two conditions it needs.

1. (a)Complete: carbon dioxide + ______ → glucose + ______.[2]
2. (b)State the two conditions the reaction requires.[2]

State one use of the carbohydrates made in photosynthesis for each purpose.

1. (a)An energy store in the leaf.[1]
2. (b)Building cell walls.[1]
3. (c)Transport around the plant.[1]
4. (d)Attracting pollinating insects.[1]

A leaf is prepared and tested with iodine solution after 48 hours in daylight.

1. (a)State the positive result the student expects if photosynthesis happened.[1]
2. (b)The leaf is first boiled in water and then in ethanol. State why ethanol is used, and name the safety precaution taken when heating it.[2]
3. (c)State the nutrient whose presence the iodine test shows.[1]
4. (d)The presence of this nutrient proves photosynthesis happened. Explain why.[1]

An aquatic plant is kept in a tank of water. Its gas exchange is compared in bright light and in complete darkness.

1. (a)State which process releases oxygen in the leaf, and when it happens.[2]
2. (b)State which gases pass into and out of the plant in complete darkness, and name the process responsible.[2]
3. (c)State the gas a plant takes in during bright daylight, when photosynthesis is faster than respiration.[1]

Pondweed is placed under water in a bright funnel-and-beaker apparatus, and the oxygen bubbles it releases are counted at different light intensities.

1. (a)Describe the effect of light intensity on the rate of photosynthesis in these results.[2]
2. (b)The lamp is moved from 50 cm to 20 cm. Calculate the percentage increase in bubble rate.[2]
3. (c)Identify the gas in the bubbles and state where it comes from.[2]

Three tubes of hydrogencarbonate indicator are set up: tube P has an aquatic plant in the light, tube Q has the same plant in the dark, tube R has no plant. All start orange-red.

1. (a)State the expected colour of the indicator in tube P, with a reason.[2]
2. (b)State the expected colour in tube Q, with a reason.[2]
3. (c)State the purpose of tube R.[1]

Explain how two leaf structures, other than stomata, are each adapted for photosynthesis.

1. (a)Structure 1 — name it and explain its adaptation.[2]
2. (b)Structure 2 — name it and explain its adaptation.[2]

Pondweed is placed at different distances from a bright lamp and the bubble rate is recorded after two minutes at each distance.

1. (a)Calculate how many times greater the rate at 10 cm is than the rate at 20 cm.[1]
2. (b)Describe the trend in the data.[1]
3. (c)Explain why the rate rises when the lamp is closer.[1]
4. (d)Suggest why the rate changes only slightly between 30 cm and 40 cm.[2]
5. (e)State one variable, other than temperature, that should be kept the same.[1]

A grower measures the photosynthesis rate of a crop in full sunlight. At a carbon dioxide concentration of 0.04% the rate is 10 units; when the glasshouse air is enriched to 0.1% carbon dioxide, the rate rises to 25 units.

1. (a)Calculate the percentage increase in rate. Show your working.[2]
2. (b)Name the factor that was limiting the rate at 0.04% carbon dioxide, and state the evidence.[2]
3. (c)Explain why raising the light intensity further would not increase the rate at 0.04% carbon dioxide.[1]
4. (d)State two other factors the grower could control to raise the rate further.[1]

Seedlings are grown in water cultures: one with all ions, one lacking nitrate ions and one lacking magnesium ions. Their mean dry masses after four weeks are shown.

1. (a)Calculate the percentage decrease in dry mass caused by removing nitrate ions. Show your working.[2]
2. (b)Explain why growth is poor without nitrate ions.[2]
3. (c)Explain why the magnesium-starved seedlings are yellow and small.[2]

A greenhouse grower measures the photosynthesis rate of her crop under different conditions. All measurements are at the same time of day with the same crop.

1. (a)Compare A and B to identify the limiting factor in A.[2]
2. (b)Compare B and C to identify the limiting factor in B.[2]
3. (c)Explain why the rate in D is lower than in C even though CO₂ is enriched in both.[2]

A student grows two batches of lettuce in separate glasshouses over six weeks. Glasshouse 1 uses normal air; glasshouse 2 is enriched with carbon dioxide and receives extra lighting on dull days. Both are kept at the same warm temperature.

1. (a)Predict which glasshouse gives the greater yield, and explain why using the idea of limiting factors.[3]
2. (b)Explain why extra lighting raises the yield on dull days but would make little difference at night.[2]
3. (c)State one economic disadvantage of enriching a glasshouse with carbon dioxide.[1]
4. (d)Name the vascular tissue that carries the extra sugar produced away from the leaves, and state what it transports.[1]

The rate of photosynthesis of a crop is measured at different light intensities and two carbon dioxide concentrations. (Supplement)

1. (a)State the factor limiting the rate at 0 units of light, and explain your answer.[2]
2. (b)At 5 units of light, compare the two rates and name the factor that limits the lower one.[2]
3. (c)The 0.04% curve levels off near 30 units. State the factor most likely limiting it, giving a reason.[1]
4. (d)Predict what would happen to the 0.04% curve if the temperature were raised well above the optimum, and explain why.[1]

The balanced chemical equation for photosynthesis is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. (Supplement)

1. (a)Name the four substances in the equation.[2]
2. (b)State the energy transformation that happens in photosynthesis.[1]
3. (c)Show that the number of atoms of each element is the same on both sides of the equation.[2]
4. (d)Explain why the equation for aerobic respiration is the exact reverse of this one.[2]