Postdoctoral research associate University of Illinois Urbana-Champaign Urbana, Illinois
Body of Abstract: The importance of leaf structure on C4 photosynthetic efficiency is thought to be critical, but it has not previously been analyzed in 3D reconstructions. Even subcellular structures like plasmodesmata with a known role in C4 photosynthesis metabolite transport are lacking basic measurements, like surface area between cells. These are critical knowledge gaps that constrain in silico modeling of C4 photosynthesis and thereby limit our ability to design potential strategies to optimize the photosynthetic efficiency of C4 bioenergy feedstocks. We have measured the volume and surface area of chloroplasts, cells, and plasmodesmata and made 3D reconstruction of two C4 species, maize and sugarcane. We identified the volume and surface area of chloroplasts and surface area of plasmodesmata for maize and sugarcane. Our findings enabled the 3D visualization of chloroplast and plasmodesmata inside of bundle sheath and mesophyll cell types in maize and sugarcane. Also, mesophyll cells were lobed and randomly protruded where chloroplasts are positioned, while bundle sheath cells were cylindrical with chloroplasts aligned centrifugally. Chloroplasts accounted for approximately 30-50% of mesophyll cell volume, and 60-70% of the volume of bundle sheath cells in maize and sugarcane. Approximately 2-3% of each cell surface area was occupied by plasmodesmata pit fields for both bundle sheath and mesophyll cells. Going forward, we plan to couple future microscopy measurements with leaf gas exchange to better link cell structure to photosynthetic performance.