Innovative Biosensor Enables Real-Time Monitoring of Plant Sugar Uptake

Researchers at Waseda University have developed an advanced non-invasive biosensor capable of monitoring real-time sucrose levels in plants, providing unprecedented insights into the mechanisms of light-driven sugar uptake through stomata. This innovation, detailed in a recent study published in the journal *Biosensors and Bioelectronics*, marks a significant advancement in plant physiological research, allowing for dynamic analysis of sucrose transport without disrupting the plant's internal environment.

Sucrose is a critical component in plant physiology, serving as both a primary energy source and a signaling molecule that influences growth, development, and responses to environmental stressors. Historically, studies on sucrose transport have relied on destructive sampling methods, such as biochemical assays, which inhibit continuous monitoring. The new biosensor addresses these limitations by employing a minimally invasive approach that enables in vivo measurements of sucrose concentration within living plant tissues.

The biosensor operates through a gel interface embedded with a trio of enzymes: invertase, mutarotase, and glucose oxidase. Invertase hydrolyzes sucrose into glucose and fructose, while mutarotase converts glucose into a form that glucose oxidase can efficiently process. The electrochemical reaction generated at the sensor's electrode allows for precise measurement of sucrose concentrations, detecting as low as 100 micromolar and reaching up to 60 millimolar, which are typical physiological levels in plant tissues.

In laboratory tests, the device demonstrated a response time of approximately 90 seconds and was successfully inserted into the stems of *Psidium cattleianum* (strawberry guava) and leaves of *Cryptomeria japonica* (Japanese cedar). These real-world applications revealed fluctuations in sucrose concentration that correlated with environmental cues, such as light and darkness, highlighting the sensor's capacity for continuous tracking over 24-hour cycles.

To further explore how sucrose enters plant tissues, researchers used water enriched with the stable isotope oxygen-18, confirming that water and dissolved sucrose were absorbed through stomatal openings. This finding provides in vivo confirmation of the hypothesis that stomata, traditionally understood as regulators of gas and water exchange, may also facilitate sucrose uptake under certain conditions.

The data from the biosensor indicated that sucrose levels in strawberry guava peaked during the night, suggesting a translocation of sugars produced during daylight to growing tissues after dark. Conversely, in Japanese cedar, sucrose concentrations increased during light exposure and decreased in darkness, directly linking sucrose uptake to stomatal activity influenced by light.

This innovative biosensor offers a new tool for researchers aiming to study sucrose dynamics in plants. Its ability to provide real-time, sensitive measurements across a broad concentration range opens up possibilities for deeper understanding of carbohydrate transport mechanisms in plants. The findings challenge traditional views that carbohydrate transport is a strictly internal and passive process, suggesting instead that it is responsive to external environmental factors.

The implications of this research extend beyond plant physiology, potentially impacting agricultural practices and resource management in crop production. By elucidating the relationship between environmental cues and sucrose uptake, this technology could inform strategies for optimizing plant growth and productivity in changing climates.

In conclusion, the development of this biosensor represents a pivotal step forward in plant research, providing critical insights that could reshape our understanding of plant physiology and enhance agricultural practices worldwide. Future studies will likely explore the broader applications of this technology and its potential to improve crop resilience and productivity in response to environmental challenges.

**Key Findings:** - The biosensor detects sucrose concentrations from 100 micromolar to 60 millimolar. - Real-time monitoring revealed fluctuations in sucrose levels linked to light exposure and stomatal activity. - The study suggests stomata have a dual role in gas exchange and sucrose uptake. - Findings may influence agricultural practices by optimizing plant resource management.

For further details, refer to the full study: Wu, S. et al. (2025). A plant-insertable multi-enzyme biosensor for the real-time monitoring of stomatal sucrose uptake. *Biosensors and Bioelectronics*. DOI: [10.1016/j.bios.2025.117674](https://doi.org/10.1016/j.bios.2025.117674).