Plants adjust their growth by detecting nearby volatiles

Barley plants are able to detect the growth rate of their neighbors through volatile organic compounds. Exposure to these signals alters biomass accumulation and gene expression in the recipient plants. The result indicates a still poorly understood function of these volatiles in environments with plant competition.

Research evaluated barley cultivars, Vulgar hordeum. The scientists used Fairytale, a slow-growing plant; Luhkas, an intermediate-growing plant; and Salome, a fast-growing plant, with distinct growth strategies. The recipient plants received only volatiles from the aerial parts of the emitting plants. The system prevented contact between roots and other underground compounds.

Dependent response

The results showed a response dependent on the origin of the volatiles. Fairytale accumulated more biomass when it received compounds emitted by Salome. Salome reduced biomass when it received volatiles from Fairytale. Exposure to plants with similar growth rates produced small or no significant difference in effects.

According to a statement from the scientists, the recipient plants adjusted their growth according to the competitive pressure indicated by the "smell" of their neighbor. The response occurred in leaves, stems, and roots. The effect indicated not only a redistribution of resources between organs.

Gene expression analysis reinforced this interpretation. Fairytale exposed to Salome showed more genes with reduced expression. These genes were related to protein maintenance processes, stress response, and defense. Salome exposed to Fairytale showed a large increase in genes linked to RNA processing, DNA replication, cellular transport, and protein metabolism.

Growth and defense

Scientists interpret the data as evidence of a balance between growth and defense. Plants exposed to signals from rapidly growing neighbors tended to prioritize growth. Plants exposed to signals from slowly growing neighbors tended to reduce growth and amplify responses linked to induced defense.

Chemical profile

The study also analyzed the chemical profile of volatiles. The three cultivars emitted distinct mixtures. Classification by random forest model achieved 93,1 percent accuracy in separating the profiles of intact plants. Salome and Fairytale showed the greatest chemical separation.

Among the compounds that contributed most to this separation were benzyl nitrile, linalool, octanal, 1-octen-3-ol, benzothiazole, tetradecane, dodecane, and nonanal. Benzyl nitrile and an unidentified compound, with a retention index of 1160, showed the highest emission in Fairytale. 1-octen-3-ol characterized Salome. Tetradecane, octanal, and linalool varied between Fairytale and Salome.

This work expands the understanding of the role of volatile organic compounds in plant communication. Previous studies focused on signals released after damage, such as herbivore attacks. In this research, undamaged plants emitted signals capable of altering growth and gene expression in neighboring plants.

The experiments were conducted in a laboratory, with plants grown under controlled conditions. Evaluations included dry biomass, morphological characteristics, RNA sequencing, and gas chromatography coupled with mass spectrometry.

More information at doi.org/10.1101/2025.08.15.670058