Manipulating the cell/air space ratio to optimize photosynthesis
MANIPULATING THE CELL/AIR SPACE RATIO TO OPTIMIZE PHOTOSYNTHESIS
Cell density and airspace patterning in the leaf can be manipulated to increase leaf photosynthetic capacity
Lehmeier C, Pajor R, Lundgren MR, Mathers A, Sloan J, Bauch M, Mitchel A, Bellasio C, Green A, Bouyer D, Schnittger A, Sturrock C, Osborne CP, Rolfe S, Mooney S, Fleming AJ (2017). The Plant Journal 92, 981-994.
http://onlinelibrary.wiley.com/doi/10.1111/tpj.13727/full
MicroCT imaging of a block of an Arabidopsis leaf. Top left: microCT scan, with cells and air spaces; Top right shape and distribution of the air spaces computationally extracted from the left image. Bottom panel: airspaces visualized as a network; each red line represents an air channel. Photo: Andrew Mathers
Improving photosynthetic efficiency has long been a focus of plant breeding and is an obvious target for plant biotechnology. Accordingly, there are many ongoing efforts towards this goal, e.g. to improve the efficiency of RubisCO, to introduce CO2-concentrating mechanisms, or to bypass photorespiration. How about an approach based on plant anatomy? The interdisciplinary study by Lehmeier et al. altered the number of cells in Arabidopsis leaves by manipulating cell cycle gene expression, then used X-ray micro-computed tomography (microCT) to measure air spaces in these leaves, and showed that they did have increased photosynthetic capacity. If so, why not have a solid brick of cells – why does a leaf bother to have air spaces? It is important to balance the surface area needed for gas and water vapour diffusion and for photosynthesis and transpiration, so there must be limits. How important are the distinct palisade and spongy mesophyll layers in a typical eudicot leaf? What would a “perfect” leaf look like? Given rising CO2 levels, what will a “perfect” leaf look like in 50 years? The authors are now working to construct a 3D model of photosynthesis in rice, to discover how leaf form informs photosynthetic function in crops.
Sheila McCormick, Research Highlights Editor.