If you want to know how much water a plant is taking up, one of the best places to look is in its leaves. A new material known as AquaDust could help scientists more easily do so, without harming the plant.
Leaves contain vein-like conduits called xylem, which transport water up from a plant's roots. That water is in turn dispersed into leaf material between the xylem, known as the mesophyll. It is in this area where most of the plant's photosynthesis is carried out, and where a lack of water is likely to cause the most stress. For this reason, scientists believe that signals produced by the mesophyll are chiefly responsible for controlling the plant's uptake and distribution of water.
Previously, the main methods of measuring the water potential of the material involved either removing leaves for analysis, or altering the manner in which they functioned. Not only are these techniques somewhat labor-intensive, but by stressing the plant, they can also skew the data.
Seeking an easier, more accurate alternative, scientists at New York's Cornell University developed the AquaDust. It's made of nanoparticles of a soft, synthetic hydrogel dye, which are injected into the mesophyll of a live leaf. Those particles end up sitting in the interstitial spaces between the mesophyll cells, where they absorb water. The more that they absorb, the larger they swell, and the smaller the spaces between them become.
When a fiber optic probe is subsequently used to illuminate the mesophyll, the hydrogel dye molecules respond by fluorescing. Importantly, though, the wavelength at which they fluoresce varies with how close they are to one another. Therefore, by measuring that wavelength, it's possible to know how swollen the gel particles have become, and thus how much water is available within the mesophyll.
The technology has already been used to accurately measure water gradients in various locations along the length of meters-long maize leaves. It is hoped that once commercialized, AquaDust could be utilized by both crop researchers and farmers alike.
A paper on the research was recently published in the journal Proceedings of the National Academy of Sciences.
Source: Cornell University