Aside from sunshine, carbon dioxide and nutrition, the one thing that plants need is water. So it is safe to assume that they love rain, right? But a new study found that plants actually have a surprisingly complex and tortured reaction to rainfall.
A multinational team of scientists from the University of Western Australia (UWA) and Lund University in Sweden has found that plants react to rainfall with a complex chain of chemical signals, which they compare to "panic". The study was published in the journal Proceedings of the National Academy of Sciences.
This panic process involves thousands of genes, hundreds of proteins, and many growth hormones that are affected within just 10 minutes of water hitting the leaf. This reaction continues to rise for around 25 minutes. For this study, the researchers sprayed the Arabidopsis plant, a genus of small flowering plants related to cabbage and mustard, with a light shower of water and observed the chain reaction in the plant sparked by a protein called Myc2. After Myc2 is activated, the plant loads up its defenses to protect itself, which includes a delay in flowering and stunted growth.
During this panic response, plants also produce chemicals such as jasmonic acid which acts as a "warning signal" to other leaves and even other plants.
The question is, why would plants go into panic in the presence of rain? Isn't water good for them?
The answer is, although water is a fundamental need for plants to survive, it can also harbor bacteria, viruses, and fungal spores that could harm the plant.
"Strange as it sounds, rain is actually the leading cause of disease spreading between plants," study author Professor Harvey Millar, plant energy biologist from UWA, said in a statement.
"When a raindrop splashes across a leaf, tiny droplets of water ricochet in all directions," said Millar, adding that "a single droplet can spread these up to 10 meters [~33 feet] to surrounding plants."
"If a plant's neighbors have their defense 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," he continued.