How to know the water distribution of a leaf? Nanoscale sensors do it

Posted by Ilsa Miller on July 2nd, 2021

The water regulation in the leaves is essential to the health of the plant, affecting its growth and yield, susceptibility and drought resistance. The surface of the leaves is the most active part of the plant for water management.

A breakthrough technology developed by researchers at Cornell University uses nanoscale sensors and optical fibers to measure the water status of leaf surfaces.

This engineering feat provides a minimally invasive research tool that will greatly advance the understanding of basic plant biology and open the door to breeding more drought-resistant crops. This technology may eventually be applied to agronomic tools that measure crop moisture status in real time.

Abraham Stroock, a professor and senior author at the Smith School of Chemical and Biomolecular Engineering at the School of Engineering, said: “One of our goals is to use tools to express internal biology to the world by capture and digitization.”

Co-first author Piyush Jain, a PhD student in mechanical engineering, said: “Current technologies to measure water energy require destructive sampling of leaves, or disruption of leaf function.” This new approach, he says, “provides minimal disruption and addresses measurements of leaf water potential in intact plants in space and time.”

Outside the transport tissue known as the xylem (vein), there is an internal region called the mesophyll, where most of the photosynthesis and water stress of plants occur. Biologists suspect the signal was sent from here to the rest of the plant to manage the water. In addition, on the surface of leaves and stems, stomatal opening and closing controls the rate of gas exchange, mainly water vapor and carbon dioxide.

This new technique applies to this microscopic region.

Stroock said: “We can sense water at that terminal now. We have shown that with this local measurement, we can dissect the hydrodynamics in the tissue in a minimally invasive manner.”

This technique involves injecting nanoparticles formed by a soft synthetic hydrogel called AquaDust to measure the water potential of the leaves. The hydrogel that occupies the space between the mesophyll cells has water absorption and expands and contracts according to the water utilization rate of the leaves.

The dyes contained in AquaDust interact with each other to enable them to fluoresce at different wavelengths according to the distance between the dye molecules. By using optical fibers, researchers can illuminate a beam of light and obtain a spectrum, which provides a measurement of the water potential inside the blade.

In this study, the researchers injected AquaDust at multiple places along a few meter-long maize leaf and then measured the moisture gradient along the length of the leaf and through the mesophyll. These measurement data allowed them to build a model of tissue response to water stress and accurately predict the dynamics observed in the field.

This technology may be used commercially in crop research, production agriculture, and manufacturing, but researchers currently focus on invaluable measurements of the physiology of very local plant water management. As a research tool, it can allow plant biologists to better understand extreme water stress, which may lead to the cultivation of more water-saving crops.

Collected by Lifeasible, a biotechnology company that is specialized in agricultural science, offering a wide variety of agro-related services and products.