Photosynthetic capacity of plant - Experimental control

[vertciel]

Hello everyone,

I have posted the image of the question and my thoughts below. The image for some reason is cut off, so the original image can be found here: http://i42.tinypic.com/15s0g79.jpg

Thank you for your help.

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38. A useful control for the experiment would have included which of the following?

I. Expose the plant to 32 hours of continuous moderate light and measure rates of carbon dioxide uptake and tissue starch concentration.

II. Expose the plant to 32 hours of continuous dark and measure rates of carbon dioxide uptake and tissue starch concentration.

III. Measure the chlorophyll concentration in the plant's leaf tissue.

a) I only
b) II only
c) III only
d) I and II only
e) I, II, and III


I answered d) because I do not see how e) would be a control; chlorophyll is not explicitly in the equation for photosynthesis and the controls should be to see if there are extraneous variables in the dark and light hours.