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15 May 2007
A fluorescence-based sensor could soon be used to optimize crop growth by monitoring levels of polyphenolics in crops.
FORCE-A, a spin-off company of the French National Research Centre (CNRS), has secured USD 3 million in funding to develop optical sensors that measure the health status of crops.
"Our technology gives a real-time, in-vivo and precise diagnosis," Jean-Luc Ayral CEO of FORCE-A, told optics.org. "It opens up new applications in maturity level sensing, plant protection against pathogens and the fight against weed infestation."
The optical sensor uses the entire UV-VIS-IR spectrum to detect the plant's intrinsic fluorescence. This allows the team to assess the plant's constituents including both chlorophyll and polyphenolics.
"Current devices use chlorophyll fluorescence to assess the nutrition status of plants," explained Ayral. "This is the first time that optical sensors have used the entire UV-VIS-IR spectrum for quantitative assessment of plant constituents, including polyphenolics in addition to chlorophyll."
According to Ayral, fluorescence measurements are up to one hundred times more sensitive than reflectance. "Our fluorescence-based portable or mounted sensors offer the association of real-time and high spatial resolution sensing with high sensitivity and high specificity measurements," he said.
Selecting the appropriate excitation and emission wavelengths allows FORCE-A to target the optical signatures for specific crops. "We are able to define optical indicators of the crop quality, for example the phenolic maturity of grapes," said Ayral. "Polyphenolics indicate the health status of a plant. A large part of these polyphenolics, such as flavonols, are UV-absorbers. Others, such as anthocyanins absorb in the visible."
One of the main benefits of this optical sensing device is that it alleviates the problem of crop sampling. "Crops are often very heterogeneous and obtaining a representative sample is very difficult. Our rapid and non-destructive technology allows a very large number of measurements to be made, up to the assessment of the whole crop," explained Ayral.
FORCE-A technology will be deployed in fields as a monitoring tool but also as the basis of a decision support system. It will allow the right amount of nutrients and pesticides to be delivered at the right time and only where the crop really needs them. The optical sensing device should also help to harvest crops at the optimum time by measuring their maturity.
The next challenge is to enlarge the applications of multiparameter sensors and to apply the technique to a wider range of crops. The researchers also plan to mount their sensor on a moving platform, for high-resolution mapping.
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