Scientists have made a key breakthrough in understanding the nitrogen-fixation process in legumes, which could ultimately lead to nitrogen-fixing in wheat and other crops.

Researchers at the John Innes Centre (JIC) have discovered that plants themselves let nitrogen-fixing bacteria in by allowing it to breach the cell walls.

Once inside the right cells, these bacteria take nitrogen from the air and supply it to legumes in a form they can use, ammonia.

The debate over whether the bacteria breach the cell walls by producing enzymes that degrade it, or the plant does the work for them, has been contested since an 1887 paper in which the importance of the breach was first recognised.

“Our results are so clear we can unequivocally say that the plant supplies enzymes to break down its own cell walls and allow bacteria access,” said Professor Allan Downie, lead author at the JIC in Norwich, which is funded by BBSRC.

The findings are part of research at JIC to understand the symbiosis that enables legumes to be the largest producers of natural nitrogen fertiliser in agriculture.

The ultimate aim is to enable non-legumes, and possibly even cereals such as wheat and rice, to develop the symbiosis and source their own nitrogen from the air like legumes.

“The fact that legumes themselves call the shots is a great finding but it also shows the complexity of the challenge to try to transfer the process to non-legumes,” said Prof Downie.

“There will be many more hurdles to overcome, but our findings reveal a key step in the development of nitrogen fixation symbioses.”