Farmers and garden enthusiasts often face a dilemma: how do you know if their plants are suffering from drought before the physical signs are obvious? This question raises questions about water management in agriculture, an area where precision is essential to avoid yield losses. A new detection method could be a game-changer.
The question of whether a plant lacks water or not has always been a major challenge for farmers. Thanks to research carried out by the Singapore-MIT Alliance for Research and Technology (SMART), an innovative solution presents itself.
For a decade, researchers have been working on developing sensors capable of detecting various chemical compounds. However, adapting these sensors for use in living biological systems like plants has proven difficult. New advances brought by SMART allow can now detect pH variations in living plants, an early indication of water stress.
Pioneering technology: COF sensors
Researchers from SMART's interdisciplinary DiSTAP group, in collaboration with Temasek Life Sciences Laboratory and MIT, have developed the first covalent organic framework (COF) sensors integrated into silk fibroin (SF) microneedles. These sensors provide in-planta detection of physiological pH changes. They make it possible to identify a decrease in acidity in the xylem tissues of plants, thus alerting up to 48 hours before traditional methods of the onset of water stress.
Lack of water seriously affects plant metabolism, reducing leaf size, stem growth and root proliferation, leading to lower yield. If this condition persists, plants may yellow, wilt and ultimately die.
The impact on agriculture
With the growing challenges of climate change, increasing costs and lack of space, farmers are finding it difficult to proactively intervene or diagnose problems before symptoms are visible. Integrating sensors like these into agricultural practices becomes a necessity for in-vivo assessments and timely interventions.
« This type of sensor can be easily attached to the plant and interrogated with simple instrumentation. It thus brings powerful analyses, like the tools we develop within DiSTAP, directly into the hands of farmers and researchers. said Professor Michael Strano, co-corresponding author, Co-Principal Lead of DiSTAP and Carbon P. Dubbs Professor of Chemical Engineering at MIT.
The development and operation of COF sensors
COF sensors represent a significant breakthrough because they were previously unable to interact with biological tissues. These organic frameworks are made of networks of organic molecules or polymers, containing carbon atoms bonded to elements like hydrogen, oxygen or nitrogen, forming crystal structures that change color depending on pH. This property allow early detection of water stress by real-time measurement of pH levels in xylem tissues.
« COF-silk sensors offer an example of new tools needed to make agriculture more precise in the face of the need to increase global food security under the constraints imposed by climate change, limited resources and the need to reduce carbon footprint. Seamless integration between nanosensors and biomaterials enables effortless measurement of key plant fluid parameters, such as pH, enabling monitoring of plant health explained Professor Benedetto Marelli, co-corresponding author, principal investigator at DiSTAP and associate professor of civil and environmental engineering at MIT.
Future applications
In an open access article entitled “ Chromatic Covalent Organic Frameworks Enabling In-Vivo Chemical Tomography », published recently in Nature Communications, DiSTAP researchers document their innovative work. They show how this method enables in-vivo 3D mapping of pH levels in plant tissues with only a smartphone camera, providing a minimally invasive approach compared to traditional optical methods.
Four COF compounds were designed and synthesized to exhibit tunable acid chromism—color changes associated with pH variations—with SF microneedles coated with a layer of COF film. The transparency of microneedles and COF film allow in-vivo observation and visualization of spatial pH distributions through pH-sensitive color changes.
« Building on our previous work with biodegradable COF-SF films capable of detecting food spoilage, we developed a method to detect pH changes in plant tissues. When used on plants, COF compounds change from dark red to red as pH increases in xylem tissues, indicating that plants are experiencing water stress and require early intervention to avoid yield loss said Song Wang, research scientist at SMART DiSTAP and co-first author.
« SF microneedles are robust and can be designed to remain stable even when interfacing with biological tissues. They are also transparent, allowing multidimensional mapping in a minimally invasive manner. Combined with COF films, farmers now have a precision tool to monitor plant health in real time and better respond to challenges like drought and improve crop resilience added Yangyang Han, senior postdoctoral fellow at SMART DiSTAP and co-first author.
This study lays the foundation for future developments in COF-SF microneedle-based tomographic chemical imaging of plants with COF sensors. DiSTAP researchers plan to expand this technology beyond pH sensing, focusing on the detection of a broad range of biologically relevant analytes like plant hormones and metabolites.
Illustration caption: PH-sensitive chromic sensor powders, based on a covalent organic framework (COF), developed by SMART DiSTAP researchers, exhibit visual color changes upon early detection of heat stress. drought. Credit: Smart
Article : « Chromatic covalent organic frameworks enabling in-vivo chemical tomography » – DOI: s41467-024-53532-7
Source: MIT
