Plants also feel full like humans, scientists make stunning discovery

Plants may not have brains or stomachs, but scientists have discovered they know when they have had enough to eat.

Researchers at New York University (NYU) have identified a molecular mechanism that allows plants to “feel full” after absorbing sufficient nitrogen from the soil, a breakthrough that could pave the way for crops requiring far less fertiliser.

The study, published in The Plant Cell, identifies a protein called HHO5 as the key regulator responsible for signalling “nitrogen satiety” in plants. Once enough usable nitrogen has been converted into organic compounds, HHO5 effectively tells the plant to stop taking in more from the soil.

“By identifying gene regulators that are sensitive to different levels and types of nitrogen, we uncovered a regulatory factor controlling nitrogen use,” said Gloria Coruzzi, professor of biology at NYU and co-senior author of the study.

Nitrogen is one of the most important nutrients for plant growth and is widely supplied through fertilisers. However, plants absorb only about 50% of the fertiliser applied to fields.

The remainder contaminates rivers and lakes, fuels harmful algal blooms, and contributes to emissions of nitrous oxide, a greenhouse gas nearly 273 times more potent than carbon dioxide over a 100-year period.

The researchers found that as organic nitrogen accumulates inside the plant, production of HHO5 increases. The protein then performs two critical functions simultaneously: it activates genes involved in processing and storing organic nitrogen while shutting down genes responsible for absorbing additional inorganic nitrogen from the soil.

“It’s essentially the plant saying, ‘I’m full,'” explained lead author Will Hinckley.

To test the discovery, scientists engineered plants lacking the HHO5 protein. These modified plants absorbed nearly three times more nitrogen than normal plants under certain conditions, confirming HHO5’s role as the plant’s nitrogen “off switch.”

The findings could help scientists develop crops that make much more efficient use of fertilisers. Researchers suggest future “gluttonous” crop varieties could absorb more available nitrogen, reducing fertiliser use, lowering farming costs and cutting pollution.

With global food demand rising and fertiliser production becoming increasingly expensive due to geopolitical and environmental challenges, the discovery could have significant implications for sustainable agriculture.

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