Extreme weather events such as heatwaves, heavy rainfall, and droughts have heightened the need for advanced tools to monitor plant responses to environmental stress. While drones and aircraft offer broad aerial perspectives, their data lacks the detail necessary for tracking individual plant health. Other existing sensors capable of close monitoring require manual handling and maintenance, making them impractical for large-scale use.
"The traditional methods may work well for some purposes, but they are difficult to operate and quite expensive," said Kaori Kohzuma, a lead researcher. "In order to continuously monitor small changes, we needed a new solution."
To meet this demand, the research team designed a wireless sensor that attaches to the underside of plant leaves. Equipped with a spectroscopic sensor and light source, the device measures leaf color changes without obstructing sunlight. This waterproof sensor is powered by a battery, features Wi-Fi connectivity, and can operate outdoors for over a month, making it an effective tool for extended monitoring.
"Smart agriculture is a huge time-saver," noted Ko-ichiro Miyamoto. "Farmers don't have time to manually check every single plant. This sensor is able to provide fine-tuned readings for what's going on in real time. Then, they can react accordingly to areas where plants are experiencing high levels of stress."
The sensor demonstrated accuracy comparable to commercial spectrometers in tests conducted on 90 leaves from 30 plant species. It effectively detected changes across seven of its eight wavelengths, with strong performance at 620 nm - consistent with commercial chlorophyll meters. Additional trials using a stress-sensitive Arabidopsis thaliana mutant revealed that its readings at 550 nm aligned with the commonly used Photochemical Reflectance Index (PRI), further confirming its reliability.
In an outdoor trial, the device tracked changes in birch leaf color during autumn over a two-week period, capturing chlorophyll decreases and sunlight-related fluctuations. These results highlight the sensor's potential to provide detailed, continuous insights into plant health under natural conditions.
"This affordable sensor is a promising tool for accurately monitoring plant health and stress through leaf color and light reflection data," Kohzuma concluded. "Its low cost makes it possible to place multiple sensors across various locations, creating a network for simultaneous monitoring in many spots."
The new sensor technology is poised to play a significant role in smart farming, forestry, and other sectors requiring detailed plant health tracking, enabling targeted interventions where they are most needed.
Research Report:Analysis of plant physiological responses based on leaf color changes through the development and application of a wireless plant sensor
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