The Hidden Role of Sugar in Plant Growth

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TThe fortune of plants revolves around light and heat. Extreme temperatures can quickly kill many species, but even small changes can have a huge impact, stimulate rapid growth or put the plants to sleep. But exactly how plants detect and react to different combinations of light and heat have remained a mystery. Tacking these complex relationships is an increasing concern as the planet warms up.

Now, a group of researchers has discovered that sugar is a thermostat hidden in plants. The observation calls into question the previous evidence according to which the suggested plants are based exclusively on two specific proteins sensitive to light to determine when temperatures increase and increase. In fact, plants are counting on several starters throughout the day and night to detect changes in sun and climate.

Meng Chen, a cellular biologist at the University of California in Riverside, studied the way plants react to light and temperature for two decades. Chen focused mainly on the two proteins sensitive to light: Phyb, which accelerates growth, and Elf-3, which generally acts as a brake on growth. But these proteins only detect high temperatures at night, while plants mainly experience extremes of heat during the day.

To better understand what is happening in day conditions, Chen decided to experiment on Arabidopsis, a small plant in the mustard family which is commonly used in laboratory experiences. He and his team exhibited normal Arabidopsis plants at different temperatures, from 54 to 81 degrees Fahrenheit, and different intensities of red light, and followed how their stems are getting longer. When it is hot, plants grow longer stems to help keep their leaves cooler. Unlike their expectations, researchers have found that the Phyb can control growth at the same time at night and under moderately shiny light conditions similar to those of the plant during the day. But Phyb has stopped working when the light conditions have become intense.

“To meet the temperature, you need sugar.”

Chen and his colleagues also used mutant plants which had dysfunctional phyb and lacked chloroplasts, the organelles responsible for photosynthesis. These plants only grew up in lively light conditions. They could not feel higher temperatures in the dark. Scientists wondered if the sugar could make a difference. During the day, plants store energy in starch inside the chloroplasts. At night, plants usually break this starch into sugars to fuel their metabolism.

To test how sugar would have an impact on plant growth, researchers added liquid glucose to the growth environments of their mutant factories. This adjustment allowed plants to detect higher temperatures in darkness as well as light. “In one way or another, to be able to respond to the temperature, you need sugar,” explains Chen. “It was a huge surprise,” to find the involvement of sugar in temperature detection. The results could help scientists remove how to grow plants that can withstand the extreme temperature, both warm and cold, says Chen.

A new image emerges, says Chen: the one that shows several systems that overlap at the game at different times of the day and at different temperatures. While the Phyb generally ceases to work at high light intensities, Elf3 brake on growth is released at high temperatures, which also triggers the release of sucrose from chloroplasts, day and night. The three systems work together. Research was published in Nature communications.

Understanding how plants react to temperature is essential to our ability to continue to feed the world as temperatures increase. “We are not talking about the whole planet turning into a burning oven,” explains Chen. “We are talking about the greatest change in climatic areas due to a moderate temperature increase. Even a change of 7 or 8 degrees can actually induce a very dramatic change in the morphology of plants and also flowering time. ”

Philip Wigge, a researcher in vegetable adaptation at the Leibniz Institute of vegetable and ornamental crops near Berlin, Germany, said that the study did elegant work by studying how warm diurnal temperatures influence plant growth paths.

“Plants are very sensitive to hot temperature, but the underlying mechanisms by which the temperature is detected and integrated into growth and development are not fully understood,” he says. “We have known for a few years that light and temperature interact, but how it happens during the day was not clear.” Wigge, who has not been involved in the study, says it will be interesting to see if these paths are also observed in cultivated plants such as wheat and rice.

Chen plans to continue the work of understanding plant detection. He says that the following steps are to identify the sensors in chloroplasts that trigger the release of sugar and control the response to the temperature. Finally, he would like to design the internal temperature detection system itself. He hopes that a more intimate understanding of how plants manage the dance between light and heat guarantee that they can flourish in the climates of the future.

Lead image: shablovskyistock / shutterstock

• Katharine Gammon

  Published on August 22, 2025

  Katharine Gammon is an independent scientific writer based in Santa Monica, California, who writes on the environment, science and parenting. You can find it on X (formerly known as Twitter) @kategammon.