External factors affecting the rate of photosynthesis Flashcards
what are the three factors that affect the rate of photosynthesis?
-light intensity
-carbon dioxide
-temperature
what is the definition of a limiting factor?
-if a factor is limiting, increasing its amount will increase the rate of photosynthesis
what is the effect of increasing another factor that is not the limiting factor?
-increasing the rate of the other non limiting will not increase the rate of photosynthesis if the limiting factor is left unchanged
look at the graph in the book
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in most ecosystems when does light become a limiting factor? when is does light then not be a limiting factor anymore, after what time?
-as darkness approaches
-so photosynthesis will be unable to take place
-in early morning light usually ceases to be the limiting factor
what is the effect of light being a limiting factor in terms of the light dependent stage?
-not enough ATP and NADPH will be produced
what is the atmospheric level of carbon dioxide? what does increasing this level result in?
-0.04%
-this is sub optimal in for plants so increasing the level of CO2 can lead to higher levels of photosynthesis
when is CO2 the limiting factor?
-on a bright summers day when light intensity and temperature are high CO2 is the limiting factor
what is the effect of increasing CO2 levels in terms of the light independent stage?
-more CO2 would then be available for carboxylation of RuBP which then allows more glycerate phosphate to be formed
when does temperature become the limiting factor? How can this be changed?
-during winter
-glasshouse growers can produce optimum growing conditions by increasing temperature as necessary
what is the effect of increasing temperature in terms of the speed of the light independent stage?
-if temperature is increased to enzyme catalysed reactions of the light independent stage occur at a faster rate
what is one other factor that affects plants but not photosynthesis directly?
-water shortage
what happens if water is in short supply to the leaf?
-the stomata will close
-photosynthesis cannot occur then
-leaf will start to wilt
what does the net gain of photosynthesis mean?
-the difference between photosynthetic gains and respiratory losses
what is the equation for gross photosynthesis?
-net photosynthesis + respiration
what is the rate of respiration like in low light intensities?
-the rate of respiration exceeds the rate of photosynthesis so there is more CO2 given out than taken in
what is the compensation point?
-the rate of respiration and photosynthesis are equal
-the amount of CO2 given out and taken in is the same
look at graphs in book
