O Level Biology: Plant nutrition and photosynthesis, questions with answers

Plants need magnesium ions to grow. Which compound in plants contains magnesium ions?

1. chlorophyll
2. cellulose
3. amino acids
4. starch

Which changes occur in the air spaces of a green leaf on a sunny day (carbon dioxide concentration / oxygen concentration)?

1. decreases / decreases
2. decreases / increases
3. increases / decreases
4. increases / increases

Scientists concluded that absorption of mineral ions in plants requires energy from respiration. Which observation best supports this?

1. Carbohydrate is stored in the roots.
2. Living roots give off carbon dioxide.
3. Root hairs have a large surface area.
4. Uptake of mineral ions is reduced in lower oxygen concentrations.

A small mountain lake has aquatic plants on the lake bed. After heavy rainfall the mud is stirred up and the water level rises. Why does this cause the rate of photosynthesis of these plants to fall?

1. extra carbon dioxide
2. extra dissolved nitrates
3. lower light intensity
4. lower oxygen concentration

Some plants have large leaves and grow well but the leaves are turning yellow. Which factor is likely causing this problem?

1. a lack of magnesium in the soil
2. a lack of water in the soil
3. not enough sunlight
4. too much nitrate in the soil

Plants growing in soil lacking magnesium ions have poor growth. What causes their poor growth?

1. They cannot form cellulose for new cell walls.
2. They cannot form chlorophyll for photosynthesis.
3. They cannot produce amino acids to form proteins.
4. They cannot take in mineral ions from the soil.