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Question
Study the graph which shows results of three different experiments P, Q and R.
What does this tell you about the factors limiting the rate of photosynthesis in the regions A-B and B-C of curve P?
Study the graph which shows results of three different experiments P, Q and R.
What does this tell you about the factors limiting the rate of photosynthesis in the regions A-B and B-C of curve P?Open in App
Solution
The correct option is A A- B was light intensity and temperature, B- C was temperature and CO2
Low light intensity lowers the rate of photosynthesis. As the intensity is increased the rate also increases. However, after reaching an intensity of 10,000 lux (lux is the unit for measuring light intensity) there is no effect on the rate. Very high intensity may, in fact, slow down the rate as it bleaches the chlorophyll. Normal sunlight (usually with an intensity of about 100,000 lux) is quite sufficient for a normal rate of photosynthesis. In the atmosphere, the concentration of carbon dioxide ranges from .03 to .04 %. However, it is found that 0.1% of carbon dioxide in the atmosphere increases the rate of photosynthesis significantly. An optimum temperature ranging from 25oC to 35oC is required for a good rate. At temperatures around 0oC the enzymes stop working and at very high temperatures the enzymes are denatured. Since both the stages of photosynthesis require enzyme activity, the temperature has an effect on the rate of photosynthesis. If we observe curve P, factors limiting the rate of photosynthesis in region A-B are the light intensity and temperature, as the intensity of light and temperature increases with increase in the rate of photosynthesis to a particular region. The light intensity and temperature both are less in curve P so, acts as limiting factors. The factors limiting the rate of photosynthesis in the region B-C of curve P are the temperature and CO2 concentration compared to curve P where temperature and CO2 concentrations are more in curve R and less in curve P.
So, the correct answer is option A.
A- B was light intensity and temperature, B- C was temperature and CO2
Low light intensity lowers the rate of photosynthesis. As the intensity is increased the rate also increases. However, after reaching an intensity of 10,000 lux (lux is the unit for measuring light intensity) there is no effect on the rate. Very high intensity may, in fact, slow down the rate as it bleaches the chlorophyll. Normal sunlight (usually with an intensity of about 100,000 lux) is quite sufficient for a normal rate of photosynthesis. In the atmosphere, the concentration of carbon dioxide ranges from .03 to .04 %. However, it is found that 0.1% of carbon dioxide in the atmosphere increases the rate of photosynthesis significantly. An optimum temperature ranging from 25oC to 35oC is required for a good rate. At temperatures around 0oC the enzymes stop working and at very high temperatures the enzymes are denatured. Since both the stages of photosynthesis require enzyme activity, the temperature has an effect on the rate of photosynthesis. If we observe curve P, factors limiting the rate of photosynthesis in region A-B are the light intensity and temperature, as the intensity of light and temperature increases with increase in the rate of photosynthesis to a particular region. The light intensity and temperature both are less in curve P so, acts as limiting factors. The factors limiting the rate of photosynthesis in the region B-C of curve P are the temperature and CO2 concentration compared to curve P where temperature and CO2 concentrations are more in curve R and less in curve P.
So, the correct answer is option A.
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