The sooner a farmer knows that their crops are suffering, the faster they can take action to prevent major crop failure. A new plant-leaf-poking sensor could soon help them do so, by sending an alert as soon as the plant gets stressed. Plants of all types continuously produce hydrogen peroxide (H2O2) as part of natural processes such as photosynthesis and respiration. They produce higher amounts of the chemical when they're stressed, however, as a means of sending signals between cells to activate their defense mechanisms. Stressors causing this reaction can include drought, pest damage, and infections. Researchers at Iowa State University developed a flat, flexible polymer patch with array of tiny gold-coated microneedles along its underside.
When the sensor is pressed onto a plant's leaf, the microneedles harmlessly pierce the very top layer of tissue, encountering the sap contained within. The greater the amount of hydrogen peroxide that is present in that liquid, the greater the number of electrons produced, and thus the stronger the measured electrical signal. If that signal is strong enough to indicate that trouble is brewing, a hardwired battery/electronics module will send an alert to the farmer's mobile device via Bluetooth, or to their home computer via Wi-Fi or existing wireless networks. In tests performed on soybean and tobacco plants, the sensor differentiated between healthy plants and those that had recently been infected with the bacterial.
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