14 DAY TRIAL // Researchers have recently been finally able to substantiate the claims that gardeners have been making for a long time, namely that you shouldn't water plants when it's hot outside. Those in the business of taking care of plants say that doing so may cause the leaves to get burnt, as the water droplets behave similarly to the magnifying glass. Intense sunlight can pass through the water drop, and be focused on the surface of the leaf below, producing sunburns. Theoretically, it has been proven that open flames can also appear, if the vegetation is dry enough, LiveScience reports.
“This is far from a trivial question. The prevailing opinion is that forest fires can be sparked by intense sunlight focused by water drops on dried-out vegetation,” Hungarian biophysicist Gabor Horvath, from the Eotvos University in Budapest, shares. Intrigued by the gardeners' claims, Horvath and his team conducted a thorough analysis of the physics behind plants, water and the Sun. The investigators used advanced computer models and direct experiments to test these hypotheses, and determined that the final result tended to be directly linked to the type of vegetation the water drops fell on.
The researchers reveal that smooth-surfaced leaves, such as the ones belonging to healthy maple trees, are in no danger of getting sunburns. On the other hand, leaves that carry wax hairs on their surfaces, such as floating fern, are at increased risk. This happens because the water does not fall directly on the leaf, but remains separated from the surface, on the top of the hairs. This allows for sunlight to be focused enough to create the sunburn effect gardeners have been warning against. Full details of the investigation appear in the latest issue of the respected journal New Phytologist.
“If the focal region of drops falls exactly on the dry plant surface intensely focused sunlight could theoretically start a fire. However, the likelihood is reduced as the water drops should evaporate before this, so these claims should be treated with a grain of salt,” Horvath adds. “In sunshine, water drops residing on smooth hairless plant leaves are unlikely to damage the leaf tissue. However water drops held by plant hairs can indeed cause sunburn and the same phenomenon can occur when water droplets are held above human skin by body hair,” he concludes.