13.2. Investigation of limiting factors
A subsection of Biology, 9700, through 13. Photosynthesis
Listing 10 of 75 questions
The rate of photosynthesis is affected by a number of environmental factors. shows the effect of light intensity on the rate of photosynthesis. rate of photosynthesis light intensity C A B State the limiting factor in region A of the graph. Explain what is meant by the term limiting factor. Explain why there is no further increase in the rate of photosynthesis beyond point C. For many plants living in temperate regions, the optimum temperature for photosynthesis is approximately 25 °C. Suggest reasons why the rate of photosynthesis decreases at temperatures above 25 °C.
9700_m16_qp_42
THEORY
2016
Paper 4, Variant 2
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An investigation was carried out to measure the rate of photosynthesis at different concentrations of carbon dioxide. Two different plants, barley and sugar cane, were tested at two different temperatures, 10 °C and 25 °C. The results are shown in . rate of photosynthesis / arbitrary units sugar cane at 25 °C carbon dioxide concentration / arbitrary units barley at 25 °C barley at 10 °C sugar cane at 10 °C Suggest why, in all four experiments, the rate of photosynthesis became constant as the carbon dioxide concentration increased. With reference to , describe the difference in the rate of photosynthesis, at 10 °C, between barley and sugar cane. Sugar cane is a C4 plant. Barley is not a C4 plant. Explain why, at 25 °C, sugar cane had a higher rate of photosynthesis than barley. Carbon dioxide for photosynthesis enters the leaves through open stomata. Stomata do not stay open all the time. Changes in environmental conditions can cause stomata to close. Describe these conditions and explain how stomatal closure benefits the plant.
9700_m17_qp_42
THEORY
2017
Paper 4, Variant 2
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Use shows the results of experiments investigating the effect of different light intensities on the rate of photosynthesis of cucumber plants measured as mm3 CO2 uptake per cm2 leaf area per hour. The experiments were carried out at two different temperatures and two different carbon dioxide concentrations. light intensity / arbitrary units rate of photosynthesis /mm3 cm-2 h-1 A B C key A 0.04% C02 20°C B 0.04% C02 30°C C 0.13% C02 30°C With reference to , describe the shape of curve A, Examiner’s Use explain the reasons for the difference between curves B and C. Suggest two ways in which a commercial grower of cucumbers may increase the yield of the growing crop.
9700_s06_qp_4
THEORY
2006
Paper 4, Variant 0
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shows the effect of temperature on the rate of photosynthesis of a plant at a constant light intensity and a carbon dioxide concentration of 0.03%. temperature / °C rate of photosynthesis Suggest and explain why the rate of photosynthesis of the plant decreases to zero just above 40 °C. Draw, on , the likely curve if the same experiment were carried out on a C4 plant, such as sorghum. Give reasons to explain your curve. Experiments were carried out to determine the effect of light intensity on the rate of photosynthesis of a species of the unicellular protoctist, Chlorella. A cell suspension of Chlorella was used. • The suspension of Chlorella was illuminated at a light intensity of 5 lux for 20 seconds. • The carbon dioxide uptake by Chlorella was measured at the end of the 20 second period of illumination. • The experiment was repeated at 10, 13 and 15 lux. • The suspension was maintained at a temperature of 20 °C. Table 8.1 shows the results of the experiments. Table 8.1 light intensity / lux total CO2 uptake after 20 seconds / μmol rate of photosynthesis / μmol s–1 1.8 Complete Table 8.1. Use the data in the table to plot a graph on the grid below to show the effect of light intensity on the rate of photosynthesis. With reference to photosynthesis, state what is meant by a limiting factor. State the limiting factor in these four experiments.
9700_s12_qp_41
THEORY
2012
Paper 4, Variant 1
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shows the effect of temperature on the rate of photosynthesis of a plant at a constant light intensity and a carbon dioxide concentration of 0.03%. temperature / °C rate of photosynthesis Suggest and explain why the rate of photosynthesis of the plant decreases to zero just above 40 °C. Draw, on , the likely curve if the same experiment were carried out on a C4 plant, such as sorghum. Give reasons to explain your curve. Experiments were carried out to determine the effect of light intensity on the rate of photosynthesis of a species of the unicellular protoctist, Chlorella. A cell suspension of Chlorella was used. • The suspension of Chlorella was illuminated at a light intensity of 5 lux for 20 seconds. • The carbon dioxide uptake by Chlorella was measured at the end of the 20 second period of illumination. • The experiment was repeated at 10, 13 and 15 lux. • The suspension was maintained at a temperature of 20 °C. Table 8.1 shows the results of the experiments. Table 8.1 light intensity / lux total CO2 uptake after 20 seconds / μmol rate of photosynthesis / μmol s–1 1.8 Complete Table 8.1. Use the data in the table to plot a graph on the grid below to show the effect of light intensity on the rate of photosynthesis. With reference to photosynthesis, state what is meant by a limiting factor. State the limiting factor in these four experiments.
9700_s12_qp_43
THEORY
2012
Paper 4, Variant 3
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A student investigated the effects of temperature and light intensity on the rate of photosynthesis of an aquatic plant. shows the results of the investigation. temperature / °C volume of oxygen released / mm3 h–1 high light intensity Key low light intensity With reference to : describe the results of the investigation suggest explanations for the results for high light intensity above 30 °C. Name the process in the light-dependent stage of photosynthesis that produces oxygen. Name the photosystem involved in the production of oxygen in the light-dependent stage. Explain why the volume of oxygen released from the plant does not give a true rate of photosynthesis.
9700_s13_qp_42
THEORY
2013
Paper 4, Variant 2
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The concentration of carbon dioxide in the atmosphere and the light intensity often limit the rate of photosynthesis. Explain what is meant by a limiting factor in relation to photosynthesis. Investigations were carried out in Florida, USA, into the effect of different concentrations of atmospheric carbon dioxide and of light intensity on the rate of photosynthesis of soybean plants. Plants were grown from seed in outdoor, computer-controlled growth chambers at different concentrations of carbon dioxide. The upper parts of the chambers were transparent so that the plants received natural sunlight. After the seedlings emerged, the air in the soil was separated from the air around the leaves by a gas-tight seal in each chamber. Suggest why the air in the soil and the air around the leaves of the plants were separated. In one investigation, two sets of plants, A and B, were grown from seed at different concentrations of carbon dioxide: • A – normal atmospheric concentration of carbon dioxide (0.033%) • B – normal atmospheric concentration of carbon dioxide ×2 (0.066%). Then, keeping each set of plants in its particular concentration of carbon dioxide, measurements were made of their rates of photosynthesis at different light intensities. The results are shown in on page 5. mean rate of photosynthesis per unit area of leaf / arbitrary units light intensity / arbitrary units set B set A With reference to : describe and explain, in terms of limiting factors, the results from the plants in set A explain the difference between the results of set A and set B at high light intensities. In a second investigation, two sets of plants, C and D, were grown from seed, as before, in different carbon dioxide concentrations: • C – normal atmospheric concentration of carbon dioxide (0.033%) • D – normal atmospheric concentration of carbon dioxide ×2 (0.066%). When the plants matured, conditions in the growth chambers were changed to investigate the rate of photosynthesis of each set of plants in different concentrations of carbon dioxide. The results are shown in . mean rate of photosynthesis per unit area of leaf / arbitrary units concentration of carbon dioxide / arbitrary units set D set C
9700_s16_qp_41
THEORY
2016
Paper 4, Variant 1
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The concentration of carbon dioxide in the atmosphere and the light intensity often limit the rate of photosynthesis. Explain what is meant by a limiting factor in relation to photosynthesis. Investigations were carried out in Florida, USA, into the effect of different concentrations of atmospheric carbon dioxide and of light intensity on the rate of photosynthesis of soybean plants. Plants were grown from seed in outdoor, computer-controlled growth chambers at different concentrations of carbon dioxide. The upper parts of the chambers were transparent so that the plants received natural sunlight. After the seedlings emerged, the air in the soil was separated from the air around the leaves by a gas-tight seal in each chamber. Suggest why the air in the soil and the air around the leaves of the plants were separated. In one investigation, two sets of plants, A and B, were grown from seed at different concentrations of carbon dioxide: • A – normal atmospheric concentration of carbon dioxide (0.033%) • B – normal atmospheric concentration of carbon dioxide ×2 (0.066%). Then, keeping each set of plants in its particular concentration of carbon dioxide, measurements were made of their rates of photosynthesis at different light intensities. The results are shown in on page 5. mean rate of photosynthesis per unit area of leaf / arbitrary units light intensity / arbitrary units set B set A With reference to : describe and explain, in terms of limiting factors, the results from the plants in set A explain the difference between the results of set A and set B at high light intensities. In a second investigation, two sets of plants, C and D, were grown from seed, as before, in different carbon dioxide concentrations: • C – normal atmospheric concentration of carbon dioxide (0.033%) • D – normal atmospheric concentration of carbon dioxide ×2 (0.066%). When the plants matured, conditions in the growth chambers were changed to investigate the rate of photosynthesis of each set of plants in different concentrations of carbon dioxide. The results are shown in . mean rate of photosynthesis per unit area of leaf / arbitrary units concentration of carbon dioxide / arbitrary units set D set C
9700_s16_qp_43
THEORY
2016
Paper 4, Variant 3
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Questions Discovered
75