Which crops can survive drought? Nanosensors may offer clues

For the current study, the researchers injected the solution into corn husks, which they chose, in part because cultivation is essential to the global food supply. The nanosensors covered the outside of the leaf cells, swelling or shrinking depending on the amount of water available.

The dye molecules in AquaDust fluoresce at different wavelengths, depending on their proximity to each other, and these wavelengths can be measured with an instrument called a spectrometer. When water is readily available, the nanoparticles swell, pushing aside the dyes and creating a peak in the green wavelength emitted by the dyes. When there is not a lot of water, the nanoparticles shrink and the dyes come together, resulting in a spike in the yellow wavelength. Then, researchers can convert the emission spectrum readings into measurements of water potential, all without harming the plant.

The technique can be applied in different places along the leaf to track water flow, says Piyush Jain, co-author of the study and a PhD student in mechanical engineering at Cornell. “What this allows us to do is basically model the flow of water through different tissues, from the stem to different parts of the leaf,” he says.

The researchers focused their AquaDust measurements on the area just below the leaf surface, where plants perform important functions such as uptake of CO.2, releasing water vapor into the atmosphere and packing the sugars created by photosynthesis. To select crops that manage water better, a better understanding of the biology and behavior of water at these critical points will be very helpful, the researchers say.

Ultimately, the technology could be used in real life situations, such as for workers in fields or greenhouses. It might even be possible one day to spray AquaDust on a field and then use a multispectral camera to quickly measure the water potential of hundreds of plants.

A researcher using AquaDust in a cornfield.Photograph: Siyu Zhu / Cornell University

And although it’s still a distant development, AquaDust appears to be a useful technology, says Irwin Goldman, professor of horticulture at the University of Wisconsin, Madison, who was not involved in the study. “The use of any sort of remote sensing technology – in this case, they’re using nanosensors – is a huge step forward,” he says. “My feeling about this technology is that it’s the future, really.”

Breeders have focused on developing drought tolerant crops for some time, Goldman says. “For at least 15 years, the plant breeder community has felt that we need to incorporate breeding for greater resilience into our crops as part of our breeding programs, that it is not enough to just produce products. for higher yield or better quality, or for disease resistance, ”he says. But, he points out, it will be a long process to identify which plants are most resistant to water loss and which genes are linked to that resilience, before pairing them with other desirable traits like good nutrition. and good flavor. “Once we identify the genes, it’s very helpful, but that doesn’t necessarily bring us to the end of the project,” he says. “We still have to find useful combinations.

Right now, AquaDust is primarily a research tool, not something that’s ready to be rolled out on a large scale that farmers or breeders could use to, say, assess 1,000 plants in an hour. On the one hand, the injected solution itself contains water, which must evaporate before anyone can take a measurement. “We wait about a day for the leaf to return to its natural state,” Jain explains.

AquaDust’s application and reading methods should be fine-tuned before it is ready for such high throughput measurements or for commercial products. But in the meantime, being able to accurately target the flow of water in plants could help researchers solve some mysteries. One of them, says Stroock, is whether plants ever allow the innermost layers of their leaves, called mesophylls, to dry out. For years, the conventional wisdom was that they avoided it, but indirect measures by other laboratories now suggest that this is a possibility. Being able to test this directly with AquaDust could fundamentally change our understanding of how plants manage their water and how they deal with stress caused by dry internal tissues, he says.

“We think there are some very interesting questions to answer in the lab that take precedence over commercialization,” says Stroock. “Right now, farmers in Iowa aren’t calling us and saying, can we cover our field with AquaDust? “

These farmers are probably just hoping for rain. But, one day, technology like nanosensors could help them when those hopes run out.

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