Water regulation in leaves is vital to a plant’s health, affecting its growth and yield, disease susceptibility, and drought resistance.

Fluorescent dyes in this maize plant leaf show epidermal cell walls (blue), chloroplasts (green) and hydrogel nanoreporters (AquaDust) that reveal water potential (red). (Photo: Piyush Jain)

A new technology uses nanoscale sensors and fiber optics to measure water status just inside a leaf’s surface, where water in plants is most actively managed.

This provides a minimally invasive research tool to advance the understanding of basic plant biology. It could lead to breeding more drought-resistant crops.

The technology could eventually be adapted as an agronomic tool for measuring water status in crops in real time.

The technique involves injecting nanoparticles formed of a soft synthetic hydrogel, called AquaDust, for measuring a leaf’s water potential. The hydrogel, which occupies the interstitial spaces between cells in the mesophyll, is water-absorbent, swelling and shrinking based on water availability in the leaf.

The AquaDust contains dyes whose interactions allow it to fluoresce at different wavelengths depending on how close the dye molecules are to each other. By using fiber optics, the researchers can shine a light and get a spectrum back, which provides a measurement of water potential inside the leaf.

In the study, the researchers injected the AquaDust in multiple places along meters-long maize leaves and then measured the water gradients both along the length of the leaves and through the mesophyll. These measurements allowed them to develop a model of the tissue response to water stress and accurately predict the dynamics observed in the field.

This technology may have commercial applications for crop research, production agriculture, and manufacturing industries, but for now the researchers’ focus is on the measurements of the very local physiology of water management in plants.

As a research tool, it allows plant biologists to better understand extremes of water stress, which could lead to breeding more water-efficient crops.