7b. Which value obtained from a light response curve could be used as a measure of O2 uptake in the leaf?


The y intercept of the linear part of the response curve shows O2 exchange extrapolated to darkness. Since the y-intercept is less than 0, this indicates a net uptake of O2. O2 uptake in leaves can result from two processes. One of these processes is cellular respiration, while the other is "photorespiration." Click here for a brief review of photorespiration.


7c. This is one way to estimate the rate of dark respiration in a leaf. What might be another way of using the photosynthesis apparatus to measure cellular respiration more directly?

A. Fill the leaf chamber with pure O2.

B. Eliminate all CO2 from the leaf chamber and then measure O2 evolution.

C. Cover half the leaf with foil and then run the experiment.

D. Cover the entire leaf chamber with foil and measure the change in O2 level.

Click here for explanation of question.


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Copyright (C) 1998, Steven R. Spilatro, spilatrs@marietta.edu. All rights reserved