Scientists have identified a new technique to help plants grow with less water.

Crop irrigation is estimated to account for around 70% of freshwater use on the planet.

A team at the University of Glasgow has developed a way of speeding up the opening and closing of the stomata – pores in the leaves of plants – through which carbon dioxide (CO2) enters for photosynthesis.

Researchers used a synthetic, light-activated ion channel engineered from plant and algal virus proteins.

Plants lose most of their water through stomata and previous attempts to reduce water usage by manipulating these pores has generally come at a cost in CO2 uptake, the team said.

But the plants engineered at Glasgow showed improved growth while conserving water use.

The modified plants grew as normal, and substantially better, under typical field conditions, fixing more CO2 while losing less water to the atmosphere.

The study’s lead author Dr Maria Papanatsiou, of the university’s Institute of Molecular, Cell and Systems Biology, said: “Plants must optimise the trade-off between photosynthesis and water loss to ensure plant growth and yield.

“We adopted a well-established approach used in neuroscience, called optogenetics, to better equip stomata that are essential in balancing CO2 uptake and water loss.

“We used a genetic tool that acts as a switch allowing stomata to better synchronise with light conditions and therefore enhance plant performance under light conditions often met in agricultural settings.”

Professor Mike Blatt, of the institute, said: “Previous efforts to improve plant water use efficiency have focused on reducing stomatal density, despite the implicit penalty in CO2 uptake for photosynthesis.

“Alternative approaches, like the one we have used, circumvent the carbon-water trade-off and could be used to improve crop yield, particularly under water limiting conditions.”

The paper, Optogenetic manipulation of stomatal kinetics improves carbon assimilation, water use, and growth, is published in Science.

The work was funded by grants from the Biotechnology and Biological Sciences Research Council.