Scientists from the Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP) interdisciplinary research team affiliated with the Singapore-MIT Alliance for Research and Technology have created the world’s initial near-infrared fluorescent nanosensor capable of real-time, non-invasive, and species-independent identification of indole-3-acetic acid (IAA) — the principal bioactive auxin hormone that dictates how plants grow, develop, and react to stress.
Auxins, especially IAA, are crucial in controlling essential plant processes such as cell division, elongation, root and shoot development, and responses to environmental stimuli like light, temperature, and drought. External conditions, including light, influence auxin distribution within the plant, temperature affects its production levels, and insufficient water can disturb hormone equilibrium. When plants struggle to manage auxins properly, they may fail to thrive, adapt to shifting environments, or yield sufficient produce.
Current methods for detecting IAA, including liquid chromatography, necessitate taking samples from the plant — thereby harming or removing portions of it. Traditional approaches usually assess the outcomes of IAA rather than detecting it outright, and they’re often not adaptable across various plant species. Furthermore, since IAA is a small molecule that cannot be easily monitored in real time, biosensors incorporating fluorescent proteins must be inserted into the plant’s genome to measure auxin, which would cause it to emit a fluorescent signal for live imaging.
The newly developed nanosensor from SMART allows direct, real-time monitoring of auxin concentrations in living plants with exceptional accuracy. The sensor employs near-infrared imaging to track IAA variations non-invasively across tissues such as leaves, roots, and cotyledons, and is adept at overcoming chlorophyll interference to ensure reliably accurate readings, even in richly pigmented tissues. This technology does not necessitate genetic modification and can seamlessly integrate with existing agricultural frameworks — providing a scalable precision tool to enhance both crop management and fundamental plant physiology research.
By delivering real-time, accurate auxin measurements, the sensor equips farmers with timely and precise insights into plant health. With these insights and extensive data, farmers can make more informed, data-driven decisions regarding irrigation, nutrient supply, and pruning, tailored to the specific needs of the plants — ultimately enhancing growth, increasing resilience to stress, and improving yields.
“We require innovative technologies to tackle global issues of food insecurity and climate change. Auxin is a fundamental growth signal within living plants, and this work provides a means to leverage it to provide new insights for farmers and researchers,” states Michael Strano, co-lead principal investigator at DiSTAP, Carbon P. Dubbs Professor of Chemical Engineering at MIT, and co-corresponding author of the paper. “The applications are numerous, including the early identification of plant stress, enabling timely interventions to protect crops. For urban and indoor farms, where light, water, and nutrients are already meticulously managed, this sensor can serve as an invaluable tool for precisely fine-tuning growth conditions, optimizing yield and sustainability.”
The research team detailed the nanosensor’s development in a publication titled, “A Near-Infrared Fluorescent Nanosensor for Direct and Real-Time Measurement of Indole-3-Acetic Acid in Plants,” published in the journal ACS Nano. The sensor consists of single-walled carbon nanotubes encased in a specially formulated polymer, allowing it to detect IAA by observing changes in near-infrared fluorescence intensity. Successfully tested across diverse species, including Arabidopsis, Nicotiana benthamiana, choy sum, and spinach, the nanosensor can map IAA responses under various environmental contexts such as shade, low light, and heat stress.
“This sensor builds upon DiSTAP’s continuing work in nanotechnology and the CoPhMoRe technique, which has previously facilitated the development of other sensors that can identify significant plant compounds such as gibberellins and hydrogen peroxide. By modifying this approach for IAA, we are expanding our repertoire of innovative, precise, and non-invasive tools for monitoring plant health. Ultimately, these sensors could be multiplexed or combined to monitor a range of plant growth indicators for comprehensive insights into plant physiology,” observes Duc Thinh Khong, research scientist at DiSTAP and co-first author of the paper.
“This compact yet powerful nanosensor addresses a long-standing challenge in agriculture: the necessity for a universal, real-time, and non-invasive tool to assess plant health across different species. Our collaborative breakthrough not only empowers researchers and farmers to enhance growth conditions and boost crop yield and resilience, but also advances our scientific comprehension of hormone pathways and plant-environment dynamics,” remarks In-Cheol Jang, senior principal investigator at TLL, principal investigator at DiSTAP, and co-corresponding author of the paper.
Looking forward, the research team aims to integrate multiple sensing platforms to concurrently detect IAA and its associated metabolites to create a comprehensive hormone signaling profile, offering more profound insights into plant stress reactions and advancing precision agriculture. They are also exploring the use of microneedles for highly targeted, tissue-specific sensing, and collaborating with urban farming partners to translate the technology into practical, field-ready implementations.
The research was conducted by SMART, supported by the National Research Foundation of Singapore under its Campus for Research Excellence And Technological Enterprise program.