CAM photosynthesis in orchids: unravelling the regulation of PEPC and developing a method for measuring mesophyll conductance

Phalaenopsis, like 7% of all vascular plants among which several important crop species for food,  ornament and  bioenergy production, has CAM photosynthesis. Different from C3 and C4 , CAM-plants close their stomatal during a large part of the day but open them in dark to allow CO2 uptake at a much lower water loss. Not surprisingly there is increasing interest in CAM photosynthesis as it might contribute to mitigating the problems with plant production due to global climate change. CAM-photosynthesis is also of interest to Horticulture. About 70% of the global production of the ornamental orchid Phalaenopsis occurs in Dutch Greenhouses, under well controlled environments with ample water available, but at the expense of a lot of energy as a full production cycle lasts more than 2 years.

We investigate possibilities for a more sustainable approach through increasing the fraction environmental CO2 fixated by Rubisco at the start and end of the photoperiod when stomata are still open or re-open again. This requires a more mechanistic understanding of activity of PEPC, the key-enzyme for environmental CO2-fixation in C4 (in light) and in CAM (in dark) in relation to photoperiod length supplied by LED-light. We investigate this by simultaneous advanced photosynthesis and C12/C13 isotope fractionation measurements in the HPP/CSA Photosynthesis-lab.

We currently have space for two students (MSc-theses or Research Practice) who are scientifically interested in the physiology of CAM-photosynthesis, and share a practical skillset (not afraid to learn new measuring techniques and some programming for data-analysis) with a theoretical mindset to interpreting measured results in relation to CAM physiology in literature.

Projects:
Photoperiod length and daily photosynthesis in Phalaenopsis: is diurnal
PEPC-activity in mature Phalaenopsis leaves photoperiod dependent?

Mesophyll conductance in CAM species: Development of a technique to measure diurnal variations in mesophyll conductance for CO2 diffusion in CAM-plants using stable C12/C13 isotope fractionation. Literature and practice

Interested in doing a BSc or MSc thesis at HPP? Please contact Katharina Hanika or Kim Vanderwolk via the HPP office (office.hpp@wur.nl).