Why plants panic when it rains: https://phys.org/news/2019-10-panic.html
UWA Professor Harvey Millar said after spraying plants with water and observing the effect, the researchers noticed a chain reaction in the plant caused by a protein called Myc2: "When Myc2 is activated, thousands of genes spring into action preparing the plant's defences. These warning signals travel from leaf to leaf and induce a range of protective effects. When a raindrop splashes across a leaf, tiny droplets of water ricochet in all directions. These droplets can contain bacteria, viruses, or fungal spores. A single droplet can spread these up to 10 metres to surrounding plants."