Dissertation
Biochemical and diffusional limitations of C4 photosynthesis
Doctor of Philosophy (PhD), Washington State University
01/2020
Handle:
https://hdl.handle.net/2376/111285
Abstract
For increasing yield and productivity of C4 food and biofuel crops there is a need to identify biochemical and diffusional limitations of C4 photosynthesis under different environmental conditions. It is hypothesized that diffusion and biochemical processes limit the CO2 concentrating mechanism (CCM) of C4 plants in response to different environmental conditions. Changes in activities of different enzymes of the CCM, such as Rubisco, PEPC, and PPDK, and diffusion rates such as stomatal (gs), mesophyll (gm), and bundle-sheath (gbs) conductance influenced the rates and efficiency of C4 photosynthesis in response to temperature, CO2 and water availability. In the first chapter, we examined the temperature response and cold acclimation of the CCM in the C4 chilling-tolerant Miscanthus for investigating potential biochemical and diffusion limitations. We found that gm and gbs did not change between cold- and warm grown plants, and the CCM was able to maintain and acclimate to cold through increased activity of PPDK and Rubisco. In the second chapter, we examined the role of PEPC in limiting C4 photosynthesis at high temperatures. We generated RNAi lines to reduce the C4 isoform of PEPC in the C4 model grass Setaria viridis. We found that in the PEPC knockdowns, photosynthesis was not limited by gm or CA but by low PEPC activity under low pCO2 availability and high temperatures. In turn the limitation of C4 photosynthesis by PEPC decreased the WUEi of PEPC knockdown plants. In the third chapter, we examined the coordination between C4 photosynthesis and gs in response to light, CO2, and ABA concentration. We genereated RNAi lines with reduced photosynthesis by reducing Rubisco and the C4 isoform of PEPC in the model C4 grass S. viridis. We found that PEPC and Rubisco knockdowns were able to maintain the coordination between photosynthesis and gs in response to light, but PEPC knockdowns were not able to maintain this coordination in response to CO2. This observation suggests that the responses to light and CO2 are distinct and that the CO2 response requires WT levels of PEPC activity in the mesophyll and guard cells to coordinate photosynthesis and gs.
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Details
- Title
- Biochemical and diffusional limitations of C4 photosynthesis
- Creators
- Erika Adriana Serrano Romero
- Contributors
- Asaph B Cousins (Advisor)R.Dave Evans (Committee Member)Hanjo Hellmann (Committee Member)Mechthild Tegeder (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Program in Molecular Plant Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 191
- Identifiers
- 99900581807601842
- Language
- English
- Resource Type
- Dissertation