The study appears in the journal Microorganisms.
Bacteria stimulate root hair growth in all plants that form root hairs, so the researchers examined the chemical interactions between bacteria inside root cells and the root cell.
They found that bacteria are carried in seeds and absorbed from soils, then taken into root cells where the bacteria produce ethylene, a plant growth hormone that makes root cells grow root hairs. When the root hair grows, it ejects some of the bacteria back into the soil, then the remaining bacteria in the root hairs replicate and trigger a growth spurt every 15 minutes until the hairs are fully developed.
Ethylene is also a stress hormone that causes plants to adapt and become more resistant to oxidative stresses, including heat, soil salt, heavy metals and stresses potentially caused by climate change.
The researchers found that ethylene triggers root cells to secrete superoxide onto bacteria in root cells, causing bacteria to produce nitric oxide that detoxifies the superoxide. Nitric oxide combines with superoxide to form nitrate that is absorbed by root cells. In this process, bacteria in root cells make root hairs grow and supply root cells with nitrogen and other nutrients.
