NEW TECH FOODS

Researchers in Japan have developed a needle-type multi-enzyme biosensor that can monitor sucrose levels in living plants in real time.

Developed by a team from Waseda University and collaborating institutions, the sensor tracks sucrose – a key product of photosynthesis and a vital energy source and signaling molecule in plants – without the need for destructive sampling. The technology enables continuous, in vivo monitoring of sugar transport under natural and controlled conditions.

Led by professor Takeo Miyake of Waseda University, the team designed a multi-enzyme biosensor that can be inserted into plant tissues with minimal damage. It breaks down sucrose into glucose and detects it electrochemically. The device demonstrated high sensitivity, a 100 µM detection limit, a response time of 90 seconds and stable operation over 72 hours.

In trials, the sensor revealed daily sugar transport cycles in strawberry guava, with sucrose levels peaking at night, likely reflecting internal redistribution of sugars produced during the day. In Japanese cedar, researchers found that sucrose was absorbed through stomata – microscopic pores on leaves – only when exposed to light. This indicates that, under certain conditions, plants can take up sugars directly through their leaves, a previously unconfirmed mechanism.

To verify that water carrying sucrose entered via stomata, the team used oxygen-18-labeled water and detected elevated isotope levels in light-exposed leaves. Sucrose began appearing in the stem around 45 minutes later, aligning with known transport speeds in the plant's vascular system.

The current version of the sensor is best suited for short-term lab use, but future versions may offer wireless data transmission and less invasive designs for long-term field studies. The researchers plan to expand its use to monitor sugar dynamics in other plant parts such as roots and seeds, potentially improving crop management and stress detection.

“We designed the sensor specifically to capture sucrose uptake through stomata, which is a largely unexplored pathway,” said Miyake. “The performance metrics were important, but what excites us most is the new biology it helped uncover.”

“This is the first time we’ve been able to directly track soluble sugar uptake through stomata in real-time. It challenges long-standing assumptions about how plants acquire water and nutrients.”