FS561 – Physiology of Woody Plants Fall 2009
OBJECTIVES AND REFERENCES FOR November 3:
Photorespiration, A/Ci curves and mitochondrial respiration
Reading in Pallardy: For C3 vs. C4 plants, see pp. 17&18; for respiration see chapter 6; for photorespiration see pp. 179-180
Useful additional information:
Discussion of A/Ci curves from Lambers, Chapin and Pons (pp. 18-20)
Reich et al. 1998. Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups. Oecologia114: 471-482
Saxe et al. 2001. Tree and forest functioning in response to global warming. New Phytologist 149:369-400 (this is a great review paper that covers much more than respiration, but there are nice sections that deal specifically with both photorespiration and mitochondrial respiration)
On the web:
Role of respiration in desiccation tolerance
Other interesting links that are more tangentially related to this lecture:
Learning Objectives:
After this lecture and any supplementary reading you find useful, you should be able to:
1. Define and appropriately use these terms (at least to the degree of specificity used in the lecture): photorespiration vs. mitochondrial respiration, , C3 metabolism, C4 metabolism, Fick’s Law, leaf conductance, supply functions of C assimilation, demand functions of C assimilation
2. Describe how the carboxylase activity of the Rubisco enzyme is related to photorespiration
3. Describe the difference between photorespiration and mitochondrial respiration, and why these two very different processes are both termed "respiration"
4. Explain why photorespiration does not occur in C4 plants
5. Describe the three “rate limiting” steps of photosynthesis and how they correspond to A/Ci curves. Given an environmental “stressor” such as low nitrogen, low or high temperature, describe (at least to the degree of sophistication discussed in class) which of these steps is/are most likely to be affected (stressors can affect more than one of them).
6. Predict, given an A/Ci curve, how relative changes in assimilation rates vs. stomatal conductance affect Ci
7*. Define stomatal conductance mathematically in terms of Fick’s Law
8. Describe how rates of respiration may be controlled both by energy supply and energy demand in the plant. Can you come up with a mechanism by which increased respiration rates might result in a “feedback” regulation that increases rates of photosynthesis? Can you come up with a mechanism by which increased rates of photosynthesis might cause respiration rates to increase? (These topics will not be discussed in lecture - they are questions for you to think about ).
*Note: you are NOT expected to be able to answer questions about units of conductance! Also, you are not expected to be able to calculate stomatal conductance from A/Ci curves