A farmer grows bean plants in nutrient solution. Table 1 shows the mean height after 28 days when one mineral ion is omitted from the solution. All plants h...
Question 1 Report
A farmer grows bean plants in nutrient solution. Table 1 shows the mean height after 28 days when one mineral ion is omitted from the solution. All plants had equal light, water and starting height. The farmer needs to decide which mineral deficiency is most likely to affect crop yield and to explain why minerals are needed even though plants make their own food by photosynthesis.
| Solution provided | Mean plant height / cm | Leaf observation |
|---|---|---|
| Complete solution | 31 | dark green |
| Without nitrate ions | 14 | pale green |
| Without magnesium ions | 18 | yellow areas |
| Without phosphate ions | 22 | small leaves |
(a) State the mean height difference between plants given complete solution and plants without nitrate ions. [1]
(b) Name the mineral ion required to make chlorophyll. [1]
(c) Explain why plants without magnesium ions may have a lower photosynthesis rate. [2]
(d) Describe the evidence in the table that nitrate ions are important for growth. [2]
(e) Explain why a nitrate shortage can reduce protein production. [2]
(f) Give one reason why several plants should be used for each solution. [1]
Answer Details
(a) \[31\text{ cm}-14\text{ cm}=17\text{ cm}\] The mean height difference is 17 cm. [1]
(b) Magnesium ions are required to make chlorophyll. [1]
(c) Magnesium is needed to make chlorophyll. Less chlorophyll absorbs less light energy, so the rate of photosynthesis is lower. [2]
(d) Plants without nitrate ions have a mean height of 14 cm, compared with 31 cm for plants in complete solution. Their leaves are also pale green rather than dark green. These observations support the conclusion that nitrates are important for healthy growth. [2]
(e) Nitrates are needed to make amino acids, and amino acids are joined to make proteins. [2]
(f) Use several plants so a mean can be calculated, improving reliability and reducing the effect of natural variation. [1]
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