C4 photosynthesis and water stress
1Centre for Plant and Food Science, University of Western Sydney, South Penrith DC, NSW, Australia. o.ghannoum@uws.edu.au
Annals of Botany
|June 17, 2008
Summary
C(4) photosynthesis is highly sensitive to water stress, declining through stomatal and non-stomatal phases. Elevated CO(2) can alleviate drought effects in C(4) plants by improving water status.
Area of Science:
- Plant Physiology
- Photosynthesis Research
- Drought Stress Studies
Background:
- C(4) photosynthesis, crucial for global carbon and food security, is less understood under water stress than C(3) photosynthesis.
- C(4) plants utilize a CO(2)-concentrating mechanism to enhance photosynthesis and reduce photorespiration.
- This review examines C(4) photosynthesis responses to water stress and elevated CO(2).
Purpose of the Study:
- To review the current understanding of C(4) photosynthesis response to water stress.
- To investigate the interaction between water stress and elevated CO(2) in C(4) plants.
- To identify knowledge gaps and suggest future research directions.
Main Methods:
- Literature review of studies on C(4) photosynthesis under water stress.
- Analysis of physiological and biochemical responses to declining leaf water status.
- Examination of the impact of elevated CO(2) on C(4) plant productivity during drought.
Main Results:
- C(4) photosynthesis shows high sensitivity to water stress, with rapid declines in CO(2) assimilation and stomatal conductance.
- Photosynthesis reduction occurs in three phases: initial stomatal, mixed stomatal-non-stomatal, and mainly non-stomatal.
- Non-stomatal factors include reduced enzyme activity, inhibited nitrate assimilation, and anatomical changes.
- Elevated CO(2) can mitigate water stress impacts by improving plant water status through reduced transpiration.
Conclusions:
- C(4) photosynthesis has limited capacity for alternative electron sinks (photorespiration, Mehler reaction) under water stress.
- This limitation may explain C(4) photosynthesis's high sensitivity to water stress, comparable to or exceeding C(3) photosynthesis.
- Despite higher water-use efficiency, C(4) plants can be very vulnerable to drought.
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