A model leaf has a rate equal to the smaller of two numbers…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A model leaf has a rate equal to the smaller of two numbers. The light allows times the light intensity in percent of full sunlight, but never more than . The carbon dioxide allows times its concentration in microlitres per litre. Find the rate in each case. (a) Light percent, carbon dioxide . (b) Light percent, carbon dioxide . (c) Light percent, carbon dioxide .
Need a reminder? The key ideaShow
Photorespiration: RuBisCO binds oxygen when carbon dioxide is low and oxygen is high. RuBP and oxygen give one PGA and a 2-carbon compound. It involves the chloroplast, peroxisome and mitochondrion. It makes no sugar, no ATP and no NADPH, and it releases carbon dioxide. C4 plants lack it. Blackman's law of limiting factors: the factor nearest its minimum sets the rate. Light saturates at about 10 percent of full sunlight; carbon dioxide is the major limiting factor; temperature, water also matter.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Light allows . Carbon dioxide allows . The smaller is , and light is limiting.
Step 2. (b) Light allows , so only . Carbon dioxide allows . The rate is , and carbon dioxide is limiting.
Step 3. (c) Light allows . Carbon dioxide allows . The rate is , and carbon dioxide is limiting.
Answer: (a) ; (b) ; (c) .
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