Manipulating photosynthesis to improve crop yield

Scientists have developed a model that predicts which photosynthetic manipulations to plants will boost the yields of wheat and sorghum crops, which will help feed the growing global population.

“We have developed a reliable, biologically rigorous prediction tool that can quantify the yield gains associated with manipulating photosynthesis in realistic crop environments,” said Dr Alex Wu, lead author and researcher from the Australian Research Council (ARC) Centre of Excellence for Translational Photosynthesis (CoETP) and the University of Queensland (UQ).

Plants convert sunlight, carbon dioxide and water into food through photosynthesis, and several studies suggest this process can be made more efficient.

“Until now, it has been difficult to assess the impacts of these manipulations on crop yield. This prediction tool will help us to find new ways to improve the yields of food crops around the world,” Wu said.

The study used a cross-scale modelling approach to look at the interactions between photosynthesis and the pores of the leaf that allow the exchange of carbon dioxide (CO₂) and water vapour.

“We know that it is not as simple as saying that improving photosynthesis will increase yield. The answer depends on the situation,” explained Professor Susanne von Caemmerer, Centre Deputy Director, co-author of the study and a researcher at The Australian National University (ANU). “For example, we found that in crops like sorghum, more photosynthesis can actually decrease yield in water-limited cropping situations. The modelling predicts that we can manage this ‘yield penalty’ if we can also maintain a stable rate of carbon dioxide entering, or water vapour exiting, the pores of a leaf.”

The researchers investigated three main photosynthesis manipulation targets: enhancing the activity of the main photosynthetic enzyme, Rubisco; improving the capacity of the leaves to transport electrons; and improving the flow of CO₂ through the internal layers of the leaf. Crop yield changes ranged from a 1% decrease to a 12% increase, depending on the combination of photosynthetic targets, the crop and environmental conditions such as water availability.

“In this study we are scaling up to the whole crop growth season and incorporating the feedback effects on photosynthesis of resources for the crop, such as water, which is critical in predicting consequences on crop productivity in future Australian crop environments,” said co-author and Centre Chief Investigator Professor Farquhar from ANU.

The research is published in the journal Nature Plants and was funded by the ARC CoETP at ANU and UQ.

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