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Just how much does enhancing photosynthesis improve crop yield?


Wouldn’t it be nice to have a crystal ball, of sorts, to help us determine what are the best crop-yield strategies for the long-term? A team of scientists out of Australia have gotten closer to just that kind of idea: a dynamic model that predicts which photosynthetic manipulations to plants will boost the yields of wheat and sorghum crops.

It wasn’t long ago — only a couple of months — that researchers released breakthrough data on improving photosynthesis in tobacco crops. Plants convert sunlight, carbon dioxide, and water into food through photosynthesis, and several studies have shown that this vital process can be engineered to be more efficient.

In January, one AGDAILY columnist wrote: “Just when we thought we’ve maxed out plant productivity, physiologists tell us otherwise. Turns out we have a medley of [photosynthesis] enhancements in the pipeline.”

And that’s where the latest from The University of Queensland comes into play.

“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, from the ARC Centre of Excellence for Translational Photosynthesis (CoETP). “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, the lead author of the paper published this week in the journal Nature Plants, said that this modelling tool has the capacity to link across biological scales from biochemistry in the leaf to the whole field crop over a growing season, by integrating photosynthesis and crop models.

Dr. Alex Wu (Image courtesy of ARC Centre of Excellence for Translational Photosynthesis)

Centre Deputy Director Professor Susanne von Caemmerer said one of the study’s most innovative aspects was using a cross-scale modelling approach to look at the interactions between photosynthesis and the pores of the leaf that allow the exchange of CO2 and water vapor.

“We know that it is not as simple as saying that improving photosynthesis will increase yield. The answer depends on the situation,” said von Caemmerer, a researcher at The Australian National University who is a co-author of the study.

“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.”

Co-author and Centre Chief Investigator Professor Graeme Hammer from UQ said this study fosters the type of transdisciplinary research needed for future crop improvement. “It links research across the whole Centre, which has a main focus to increase the yield of major staple crops such as wheat, rice, sorghum and maize by enhancing photosynthesis.”

“Now that we have developed and tested this predictive model, our next step is to work closely with collaborators at the CoETP to design simulation scenarios that test the effects of other bioengineering and breeding trait targets,” Hammer said.

The team 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 carbon dioxide (CO2) through the internal layers of the leaf.

The team found crop yield changes ranged from a reduction of one percent to a 12 percent increase, depending on the combination of photosynthetic targets, the crop, and environmental conditions such as water availability.

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