Plants Panic When It Rains

Plants need water to survive as much as we do. However, in a surprising turn of events, study has revealed that plants exhibit a form of reaction that is close to that of panic when it rains.

In the paper, published in Proceedings of the National Academy of Sciences (PNAS), researchers noted that when a raindrop splatters across a leaf, the plant sends out complex chemical signals in preparation to fend off dangers posed by rain.  

Simulating rain with a spray bottle and observing the effect, the team noticed a swift knock-on effect in the plant triggered by a potent protein called Myc2. When the protein is active, thousands of genes swung into action inducing a range of protective effects from each individual leaf.  

As strange as it might sound, the reason as to why plants panic when it rains is – moisture is the primary driver of diseases among plants. So if the leaves are wet for an extended period of time, there’s a good chance that a pathogen would find its way there.

“When a raindrop splashes across a leaf, tiny droplets of water ricochet in all directions,” explains Harvey Millar of the University of Western Australia’s School of Molecular Sciences. “These droplets can contain bacteria, viruses, or fungal spores. A single droplet can spread these up to 10 metres to surrounding plants.”

The study also found that the same wake-up calls sent across leaves are transmitted to neighbouring plants through the air. One of the chemicals produced in response to rain, the researchers say, is a hormone called jasmonic acid, which is involved in plants development, interaction and stress response.

“If a plant’s neighbours have their defence mechanisms turned on, they are less likely to spread disease, so it’s in their best interest for plants to spread the warning to nearby plants,” Millar says.

“When danger occurs, plants are not able to move out of the way so instead they rely on complex signalling systems to protect themselves.”

And in another study, researchers found that when plants are under attack, they warn the others through a universal language that come in the form of chemicals called volatile organic compounds (VOCs). These chemicals are transmitted in air, and when neighboring plants pick up they stay prepared for the perceived threat.

Plants may not have the reflexes of the animal kingdom, but the complex signaling systems they evolve are not something to sneeze at.