Computer model helps simulate photosynthesis in plants, improve their leaves

Washington, November 11 : Researchers at the University of Illinois have devised a new method to successfully simulate photosynthesis in plants, and improve their productivity of leaves and fruit without needing extra fertilizer.

The researchers used a computer model, which mimics the process of evolution, for the purpose.

They have described their model, the first to simulate every step of the process of photosynthesis, in the journal Plant Physiology. They will also present their work at the BIO-Asia 2007 Conference in Bangkok, Thailand.

Photosynthesis converts light energy into chemical energy in plants, algae, phytoplankton and some species of bacteria and archaea. In plants, this process involves an elaborate array of chemical reactions requiring dozens of protein enzymes and other chemical components. Most part of the process takes place in plants’ leaves.

“The question we wanted to ask, was, ‘Can we do better than the plant, in terms of productivity?’” said principal investigator Steve Long, a professor of plant biology and crop sciences at the University of Illinois.

Long said that it was not feasible to experiment with actual plants directly because more than 100 proteins are involved in photosynthesis, and testing one protein at a time would require an enormous investment of time and money.

“But now that we have the photosynthetic process ‘in silico’, we can test all possible permutations on the supercomputer,” he said.

The researchers first created a reliable computer model that would accurately mimic the photosynthetic response to changes in the environment, with the help of the computational resources available at the National Center for Supercomputing Applications.

They then determined the relative abundance of each of the protein involved in photosynthesis, and created a series of linked differential equations, each mimicking a single photosynthetic step.

The researchers kept adjusting the model until it successfully predicted the outcome of experiments conducted on real leaves, including their dynamic response to environmental variation. After that, the model was programmed to randomly alter levels of individual enzymes in the photosynthetic process.

Long revealed that using “evolutionary algorithms” that mimic evolution by selecting for desirable traits, the model hunted for enzymes that would enhance plant productivity when increased.

Long said that the research team was well aware that before a crop plant like wheat produces grain, most of the nitrogen it takes in goes into the photosynthetic proteins of its leaves. The process revealed several proteins that, if present in higher concentrations relative to others, could greatly enhance the productivity of the plant.

The new findings are consistent with results from other researchers, who found that increases in one of these proteins in transgenic plants increased productivity.

“By rearranging the investment of nitrogen, we could almost double efficiency,” Long said.

He also had a suggestion as to why, right from the beginning, plants had not evolved as productive as their process made them.

“The answer may lie in the fact that evolution selects for survival and fecundity, while we were selecting for increased productivity,” he said.

He said that the changes suggested in the model might undermine the survival of a plant living in the wild, adding: “But our analyses suggest they will be viable in the farmer’s field.” (ANI)