Bellaterra (Barcelona), February 18, 2026 - Plants don't just respond to light and water, they also run on an internal daily timekeeper known as the circadian clock. Researchers have now discovered that the plant circadian clock can regulate electrochemical signals in specific cells that help determine whether growth is invested above ground or below ground.
In a study led by Paloma Mas , CSIC Research Professor at the Centre for Research in Agricultural Genomics (CRAG), and published in the leading scientific journal Cell, scientists show that a key clock component functions as an electric flow controller, fine-tuning tiny changes in electrical charge across different tissues. These signals influence how young stems grow and how strongly roots develop, effectively helping the plant to coordinate its growth where it is needed most.
"Plants are constantly balancing priorities," says Paloma Mas. "We found that the circadian clock does more than keep time, it also coordinates growth by controlling an electrochemical 'language' that different tissues use to communicate."
A daily "push–pull" signal inside the plant
To grow, plants must move energy produced by photosynthesis from source tissues, such as leaves, to sink tissues, such as roots. The team tracked acidity changes in living plants using fluorescent sensors and uncovered a striking pattern: the rhythms of acidity in epidermal cells run almost opposite to the rhythms in the vasculature.
This matters because electrical gradients are not just side effects but rather help drive growth and transport. In the the young stem, increased acidity helps loosen cell walls, allowing cells to expand and the stem to lengthen. In the transport tissues, however, electrical charge helps power the loading of sugars into the plant's long-distance distribution network, the phloem. If that electrochemical "battery" is weakened, less sugar is loaded and transported, and roots receive less fuel for growth.
One clock factor, two opposite outcomes
The researchers pinpointed a clock factor called CCA1 as a key controller of this process. When CCA1 activity is higher, it promotes stem elongation while restricting root growth. It does this in two ways: (i) in the shoot, it boosts growth-promoting hormone signaling and shifts electrochemical conditions toward stem expansion; and (ii) in the vasculature, it turns down a critical component, a proton pump, that energizes sugar export, that helps generate the electrical and pH force needed to move sugar efficiently.
"At certain times of day, the plant prioritizes shoot growth over root growth," explains first author of the study Lu Xiong . "CCA1 helps fine‑tune this trade‑off by controlling where sugars are delivered".
Why this matters for agriculture
The discovery offers a new way to think about plant productivity: not only as a response to the environment, but as a clock-driven management system that matches energy availability with growth demand across the day.
Understanding, and eventually tuning, these electrochemical signals could help develop crops that allocate resources more efficiently in challenging conditions such as shade, drought or nutrient-poor soils, where the balance between shoot and root growth can determine survival and yield.
