Factors Affecting Photosynthesis Flashcards
Define the term light intensity
-level of light
Define the term water stress
-the condition a plant will experience when water supply becomes limiting
What are the factors that affect the rate of photosynthesis
-carbon dioxide
-water
-light intensity
-temperature
-turgidity of the cells
At a constant favourable temperature and constant suitable carbon dioxide concentration what becomes the limiting factor
-light intensity
When the light intensity is low what happens to the rate of photosynthesis
-the rate of photosynthesis is also low
How would you describe the relationship between light intensity and photosynthesis
-directly proportional
On a graph at a certain point the rate of photosynthesis will no longer increase even if light intensity increases and it will plateau, what does this mean
-that a factor other than light intensity is limiting the process
In bright light (high light intensity) what is the concentration of RuBP, TP and GP and explain why this is
-[RuBP]= high, because the light dependent reaction produces a lot of ATP and NADPH so more carbon is fixed and more TP is made meaning more RuBP is regenerated from TP
-[TP]= high, because the light dependent reaction produces a lot of ATP and NADPH so more carbon is fixed and more TP is produced
-[GP]= low, because more is reduced to TP
In dim light (low light intensity) what is the concentration of RuBP, TP and GP and explain why this is
-[RuBP]= low, because the levels of TP are low as GP cannot be reduced to it and so RuBP cannot be regenerated
-[TP]= low, because GP cannot be reduced to from TP as there is no ATP or NADPH
-[GP]= high, because it can’t be reduced to TP as there is little or no ATP and NADPH so GP accumulates
What effect would high carbon dioxide concentrations have on the Calvin cycle
-[GP]= high, because more CO₂ can be fixed to form GP
-[TP]= high, because if more GP is formed from CO2 being fixed then more GP can be reduced to form TP
-[RuBP]= low, because if CO₂ is abundant, more RuBP is used up quickly as it constantly reacts with CO₂. This means that the plant might not have enough time to regenerate RuBP as fast as it’s being used
What effect would low carbon dioxide concentrations have on the Calvin cycle
-[GP]= low, because less CO₂ can be fixed to form GP
-[TP]= low, because if less GP is formed from CO2 being fixed then less GP can be reduced to form TP
-[RuBP]= high, because if CO₂ isn’t abundant, less RuBP is used up as it doesn’t need to constantly react with CO₂
How does temperature affect the rate of photosynthesis
-the Calvin cycle involves many enzyme catalysed reactions and is sensitive to temperature
How does low temperature to temperatures of 25- 30°C affect the Calvin cycle
-From low temperatures to temperatures of 25-30°C, if plants have enough water and carbon dioxide and a sufficient light intensity, the rate of photosynthesis increases as temperature increases.
How do temperatures of above 30°C affect the Calvin cycle
-growth rates reduce due to photorespiration: oxygen competes with carbon dioxide for the enzyme RuBisCO’s active site
-reduces the amount of CO2 being accepted by RuBP and so the amount of GP and TP
How do temperatures of above 45°C affect the Calvin cycle
-enzymes involved in photosynthesis may be denatures which would reduce [TP] and [GP] and eventually RuBP
What 5 things happen when a plant becomes water stressed
1) the roots are unable to take up enough water to replace that lost via transpiration
2) cells lose water and become plasmolysed
3) plant roots produce abscisic acids that, when translocated to leaves causes stomata to close, reducing gaseous exchange
4) tissues become flaccid and leave wilt
5) the rate of photosynthesis greatly reduces
Which process photosynthesis or respiration is most affected by changes in temperature
-respiration because it uses a lot more enzymes in its process and therefore more stages can be affected by changes in the temperature
