CO2 is a key constituent of the plant growth-promoting volatiles generated by bacteria in a sealed system

Key message Plant growth is greatly inhibited in tightly sealed Petri dishes for lack of CO 2 . Bacteria which co-cultured with plant can produce CO 2 to promote plant growth in sealed systems. Bacteria produce a wide variety of volatiles, some of which can support and others can damage plant growth. It is a controversial issue whether CO 2 or other bacterial volatile compounds promote plant growth in sealed systems. CO 2 is critical for photosynthesis. Here, we show that CO 2 is a key constituent of the plant growth-promoting volatiles generated by bacteria in a sealed system. We revealed that the growth of Arabidopsis seedlings in an airtight container was retarded due to insufficient supply of the CO 2 . When either CO 2 was introduced into the container, or the seedlings were co-cultured along with certain bacterial species, the plants’ growth was restored. Conclusion: The benefit of co-culturing was largely due to the CO 2 generated by respiration of the bacteria.