Fungi Release Smell Molecules That Can Hurt or Help Little Plants

A group of scientists studied how the tiny, airborne chemicals that some fungi put out affect a small flowering plant called Arabidopsis thaliana. They looked at two very different fungi: one that is known to give off these chemicals, Trichoderma harzianum, and another, Mucor mucedo, that had never been checked before. The researchers collected the “volatilome, ” or full list of volatile organic compounds, from each fungus. They found that alcohols, ketones and esters were the main players for both species, but each fungus also produced different amounts of terpenes.Next, the team exposed Arabidopsis plants to these fumes for long periods and noticed that the plants grew slower and their photosynthesis dropped. Shorter exposures, however, triggered the plant’s defense system. The plants showed higher levels of genes that protect against attack and were better at fighting off the bacterial pathogen Pseudomonas syringae. This stronger defense did not come from the usual hydrogen‑peroxide signal but seemed to involve a chain reaction that reprograms plant metabolism, including the creation of protective chemicals called glucosinolates. These results show that fungal smells can have big impacts on plant health, sometimes harming growth and other times boosting defense. Understanding these interactions could help farmers manage crops more effectively.