Sensors printed on leaves could tell farmers when to water crops

The advance from engineers at MIT is claimed to be the earliest indicator of drought for agricultural applications.

“You can put sensors into the soil, or you can do satellite imaging and mapping, but you never really know what a particular plant is detecting as the water potential," said Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and senior author of the new study.

The MIT sensor takes advantage of plants' stomata, which are small pores in the surface of a leaf that allow water to evaporate. As water evaporates from the leaf, water pressure in the plant falls, allowing it to draw water up from the soil.

According to MIT, plant biologists know that stomata open when exposed to light and close in darkness, but the dynamics of this opening and closing have been little studied because there hasn't been a good way to directly measure them in real time.