The social lives of plants

Just like humans, plants need social contact and fare better when they can communicate with each other.

Many plants are very good companions and support each other by improving growth, fixing nitrogen, controlling pests or attracting beneficial organisms such as insects or mycorrhizae. Current explanations for these sociable interactions have focused on the effects of light (and shade), chemical signalling or physical proximity and contact.

Recent work by Drs Monica Gagliano and Michael Renton from the University of Western Australia has shown that chilli plants grow better when grown with basil plants, even when other known means of communication, such as physical contact, chemical and light-mediated signals, were blocked.

The researchers attempted to grow chilli seeds (Capsicum annuum) in the presence or absence of other chilli plants, or basil (Ocimum basilicum). In the absence of a neighbouring plant, germination rates were very low, but when the basil plants were able to openly communicate with the chilli seeds more seedlings grew.

However, when chilli seeds were separated from basil plants with black plastic, so that they were not influenced by light or chemical signals, they germinated as though they could still communicate with the basil. A partial response was seen for fully grown chilli plants blocked from known communication with the seeds.

The researchers suggest that plants communicate via nanomechanical vibrations.

“Our results show that plants are able to positively influence growth of seeds by some as-yet-unknown mechanism,” explained Gagliano. “Bad neighbours, such as fennel, prevent chilli seed germination in the same way. We believe that the answer may involve acoustic signals generated using nanomechanical oscillations from inside the cell, which allow rapid communication between nearby plants.”

This work was published in BioMed Central’s open access journal BMC Ecology.