Recognizing rice roots

In a publication in yesterday’s Proceedings of the National Academy of Sciences (PNAS), a team of researchers including Herbert Edelsbrunner, Professor at IST Austria, newly identify two forms of communication important for plant root development. Herbert Edelsbrunner’s contribution was developing the RootWork software used for reconstructing image sequences.

Plants interact with their environment, both above ground and in the soil. However, due to roots’ restricted accessibility, communication in the root system and its effect on root growth has not been studied in detail so far. In their publication, Suqin Fang and Philip N. Benfey from Duke University and their collaborators sought to determine how environmental interactions occur at the level of individual roots, in particular how planting density and the proximity of physical objects affect root growth. By growing rice plants in a transparent gel system, the scientists were able to image root growth and reconstruct and quantify root interactions in three dimensions.

Surprisingly, they found that roots systems of the same genotype overlap significantly more often than root systems of different genotypes, which tend to avoid each other. Investigating how plants recognize genotypes, the scientists removed the plant parts above ground to exclude the possibility of aerial communication. In this case, roots of different genotype continued to avoid each other, suggesting that roots directly communicate with each other. This genotype-specific signal is likely to be recognized at the root tip, however, the biochemical basis for this interaction has not yet been determined. The scientists also showed that roots are also able to recognize obstacles in the form of physical objects. This recognition also occurs at the root tip, however, it is dependent on physical contact. Thus, the researchers identified two types of communication in the root system of rice: root-root recognition mediated through direct communication, and root-object recognition mediated through contact.