Plants get wearables to track their health
With new sensors, farmers could use real-time information to manage crop conditions before visible signs of plant stress appear
image:
“The leaf sensor is more of an early warning system showing how the plant is responding in the moment, before visible signs appear,” said Nafize Hossain.
view moreCredit: Nafize Hossain
A smartwatch can tell us the level of oxygen in our blood, when our sleep is restless, or the number of steps we take in a day. Now imagine that kind of tracking ability for plants.
By the time farmers see curling leaves or stunted growth in their fields, their crops may already have spent days under stress. A new innovation in plant “wearable” sensors aims to catch those distress signals earlier—before the plant visibly suffers, allowing farmers to respond and help their crops thrive.
In a recent study from Tufts University, researchers created tiny tattoo-like sensors that adhere to leaf surfaces and a stretchable band that wraps around stems. Together, they track two vital signs of plant life—the temperature and humidity beneath the leaf’s surface, and whether the stem is still growing. Even more striking, the system runs without an external battery, scavenging power from moisture evaporating from the plant itself.
“The larger promise is not merely that one plant can wear one sensor,” said Sameer Sonkusale, professor of electrical and computer engineering at Tufts and senior researcher in the project. “It is that fields could one day contain networks of plant-level monitors, each reporting early signs of thirst, salt stress, disease or nutrient imbalance. Satellites and drones already give farmers a bird’s-eye view. Plant wearables could provide something more intimate: the plant’s-eye view.”
Current methods in monitoring crops use satellite imagery and drones to get visible, infrared, and microwave data that map out greenness, uneven growth, temperature, pest damage, soil moisture, and other big picture measurements of crop stress. Soil sensors can measure moisture, temperature, pH, and some nutrient levels. And weather stations provide information on air temperature, humidity, rainfall, wind, and sun exposure.
While those measurements are useful, they focus on conditions that may affect the crops in the future or an assessment of damage already done. “The leaf sensor is more of an early warning system showing how the plant is responding in the moment, before visible signs appear,” said Nafize Hossain, a graduate student at Tufts who led the research in the Sonkusale lab.
The sensors can also be extended to track other important indicators of plant health, such as levels of important nutrients and plant hormones that are early signals of root, leaf, stem, and fruit growth, as well as response to pathogens.
Stress Trackers
Resembling a temporary tattoo, the leaf sensor is thin, flexible, and can sit on uneven surfaces, allowing the plant to breathe and bend in the wind without damaging it. “Other plant sensors exist, but their ability to track multiple stressors and growth-related parameters is limited,” said Hossain, “and the technology often relies on external batteries, which complicate field deployment.”
The sensor first developed by the researchers provides information on the “vapor pressure deficit,” or VPD. It’s a technical term, but it describes something very intuitive—how likely the air is to pull water from the plant. When VPD is high, the air is dry and pulls moisture from leaves more aggressively. Plants respond by closing their stomata, the tiny pores that regulate gas exchange and water loss. That can protect them from dehydration, but it also slows photosynthesis and growth.
The Tufts leaf moisture sensor uses vanadium pentoxide crystals separated into extremely thin “nanosheets.” The nanosheets are stacked into layers and arranged in a membrane. Another layer of graphene (made of carbon atoms) forms a sieve to let moisture through from the plant to the nanosheets. When that happens, the water forms ions, which sweep through sheets creating a current—and voila, it’s not only a sensor, but also a battery. The level of the current is directly proportional to the amount of moisture exchange with the air.
The power is tiny—microwatts—but enough, with low-power electronics and energy storage to support periodic sensing.
The stem-based device borrows from kirigami, the Japanese art of cutting paper so it can stretch and deform in controlled ways. The sensor is coated with a eutectogel, a soft, ion-conducting gel that changes electrical resistance as the stem expands or contracts. In healthy growth, the stem diameter tends to increase. Under stress, growth may slow or the stem may even shrink.
Pairing the two types of sensors is important, because plants can show stress on more than one time scale. Leaf sensors, for example, can show if the plant is facing immediate conditions that drive water loss, while stem growth captures a slower biological process.
In tests on bell pepper plants, the system distinguished healthy plants from plants facing water deficit and salinity stress. Healthy plants showed rhythmic VPD changes over time, following normal daily cycles of air moisture.
Water-stressed plants showed a rising VPD trend. Salinity-stressed plants showed a different pattern, with reduced VPD compared with controls, likely linked to altered water uptake and stomatal behavior. Meanwhile, the stem sensor tracked growth in healthy plants and shrinking or reduced diameter in stressed plants.
The sensors are built with field conditions in mind. The leaf sensor is designed to tolerate bending and stretching, while ethe stem sensor’s kirigami pattern helps distribute strain and reduces the effects of abrupt disturbances like strong winds.
The team is currently working on a fully functional wireless communication platform for the sensors using LoRa (long range) or Bluetooth-based communication standards.
Journal
ACS Applied Materials & Interfaces
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
In-Planta Tattoo and Kirigami Sensors for Moisture-Powered Monitoring of Vapor Pressure Deficit and Growth Dynamics
Roots steer clear of plant rot
Newly identified ‘saprotropism’ helps roots avoid decaying plant matter—but not animal decay
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The roots of plants bend away from decaying plant material (in the center). This process—newly identified by researchers at the Institute of Science and Technology Austria (ISTA) and Northwest A&F University in China—is called saprotropism, derived from the Greek term “sapro” for “rotten”.
view moreCredit: © Bao et al. / Science
Decaying matter shapes life in soil, but it can also create hostile zones for growing roots. Professor Jiří Friml of the Institute of Science and Technology Austria (ISTA) and international collaborators have now identified “saprotropism,” a root response that guides plants away from decaying plant-derived matter—but not animal-derived decay. The study, led by Yuzhou Zhang, Professor at Northwest A&F University in China and published in Science, reveals how roots adapt their growth direction by sensing local pH gradients around rot.
Plants cannot run away from danger or toward something they desire. Instead, they adjust the direction in which they grow. Shoots bend toward light (a well-known phenomenon called phototropism), roots and shoots use gravity to grow downward and upward, respectively (gravitropism), and roots can also bend toward water (hydrotropism). These directional growth responses, known as plant tropisms, help plants navigate changing environments. Now, researchers from China and Austria describe a new member of this family: saprotropism, from “sapro”, meaning rotten or decaying.
“Going beyond the classic tropisms such as gravitropism, phototropism, and hydrotropism was Yuzhou’s idea,” says co-author Jiří Friml, professor at the Institute of Science and Technology Austria (ISTA). “As an alum of my group at ISTA, he took this question further and identified saprotropism, as well as the mechanisms behind it.”
Saprotropism: Don’t touch dead plants, it’s yucky!
The researchers first showed that direct contact with decaying plant tissue strongly inhibited root growth and activated defense pathways linked to immunity and pathogens. In other words, roots treated these decay zones as biologically threatening environments.
“Animals instinctively avoid rotten food because it often harbors harmful microbes,” says corresponding author Yuzhou Zhang, Professor at Northwest A&F University in China and an alum of the Friml group at ISTA. “We wondered whether plants, although immobile, might have evolved a comparable strategy below ground.”
And, in fact, they do: The newly identified tropism enables roots to actively bend away from decaying plant matter. In experiments, roots avoided decay zones made from ‘fleshy’ matter such as apples or leaves, and—contrary to initial assumptions—also from woody material such as sawdust.
Dead animals don’t bother plants
However, when the researchers tested animal-derived decay, such as small pieces of chicken meat, the roots showed no directional growth response.
“One of the striking findings was therefore that the roots did not simply avoid anything rotten,” says Friml. “They responded specifically to decomposing plant material. This tells us that saprotropism is not a general reaction to rot, but a dedicated response to plant-derived decay.”
The response was observed not only in the model plant Arabidopsis thaliana, but also in crop species including rapeseed, tomato, and wheat—suggesting that saprotropism is widespread among plants.
Watching the effects of a tiny ‘plant graveyard’
The team found that a key signal comes from microorganisms, especially fungi, as they break down dead plant material. During decomposition, fungi release acidic metabolites, including organic and phenolic acids. These compounds diffuse into the surrounding soil and create stable local pH gradients around the decaying material. Roots can detect this acidity pattern even before direct contact and use it as directional information, bending away from the more acidic side.
However, the ‘plant graveyard’ does not send a permanent warning signal—it stops automatically after the matter has turned into soil. “Once the plant material had almost fully broken down, the acidic warning signal faded—and the roots stopped bending away,” explains Zhang.
To study the process under controlled conditions, the researchers used a vertical split-agar system—a flat, upright plate in which different agar media create a defined chemical gradient. As roots grow downward along the plate, scientists can observe whether they bend toward or away from a specific cue, such as acidity connected with decay.
“At ISTA, we have used similar systems for many years to study how roots grow toward water,” says Friml. A specialized vertical microscope had been constructed at the Institute for that specific purpose. “Now, that same setup helped reveal the opposite response—roots growing away from a potentially harmful cue. Unlike other tropisms, the key player here isn’t the plant hormone auxin.”
Roots dance to the sound of ABA
Within the root, an external signal is transformed into a growth decision: Cells on the root surface detect that one side of the root is exposed to stronger acidity than the other. This uneven signal changes the distribution of the plant hormone abscisic acid, or ABA, across the root tip. As a result, the internal framework of root cells is rearranged, causing one side of the root to grow differently than the other. The root then bends away from the decaying plant material.
“Our research shows that decaying plant matter is not just a passive source of nutrients,” Zhang states. “It creates a chemical landscape that roots can read. Saprotropism shows how plants interpret microbial activity in the soil and make growth decisions accordingly.”
Fundamental science with relevance for agriculture and food security
The discovery of saprotropism—a term coined by the study authors—opens up new research avenues, such as how roots interpret microbial activity in soil. In the long term, a better understanding of such root behaviors could help inform approaches in agriculture, soil management, and crop resilience.
“Crop culture practices that involve excessive incorporation of undecomposed crop residues can create large decay zones that exceed the root's capacity to navigate around them, potentially increasing exposure to harmful microbes and promoting root diseases,” explains Zhang. Understanding the molecular basis of saprotropism opens new opportunities to develop crops with enhanced ability to detect and avoid pathogen-rich environments. “In the future, breeding or engineering varieties with stronger ‘decay-avoidance’ capacity could complement conventional disease resistance strategies by preventing root-pathogen encounters before infection occurs,” he sums up.
Journal
Science
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Roots navigate around decay regions by sensing local pH gradients
Article Publication Date
9-Jul-2026
Fungi and other microbes break down dead plant material in the soil. By doing so, they release acidic chemicals that spread outward like a warning signal. Nearby roots sense this acidic zone before touching the decay and bend away from it.
The process in detail: A molecular framework for root saprotropism guiding navigation around microbial decay. Microbial decay establishes a soil microenvironment characterized by stable acidic pH gradients. This pH asymmetry is sensed by the epidermal pH sensor, RGF-RGFR peptide-receptor module, which converts it into asymmetric abscisic acid (ABA) distribution. ABA asymmetry drives microtubule-dependent anisotropic cell expansion and handed root twisting, ultimately steering roots away from hostile decay zones.
Plants bend their roots away from a rotten apple, leaf, and even sawdust. The response was observed not only in the model plant Arabidopsis thaliana, but also in crop species including rapeseed, tomato, and wheat—suggesting that saprotropism is widespread among plants.
When the researchers tested animal-derived decay, in this case rotten chicken, the roots showed no directional growth response.
ISTA Professor Jiří Friml with the mouse-ear cress (A. thaliana) — his research group’s main model organism.
Credit
© FWF/Luiza Puiu
© FWF/Luiza Puiu
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