Are there any circumstances under which water drops on leaves can cause sunburn? Yes, but only if the leaf has a dense covering of water-repellent hairs, in which case drops can be held above the leaf surface, allowing them to focus light on the surface itself. The researchers were able to demonstrate such damage on the leaves of the floating fern Salvinia natans (inset above) which has such hairs, if they were kept still in a small container of water. But terrestrial plants with similar hairs shed water drops very quickly, again making sunburn extremely unlikely in practice. In any case, most plants with densely hairy leaves are drought-tolerant, so why would you feel the need to water them anyway?