Pruinescence in succulents
Have you eaten grapes and noticed the whitish, powdery coating on the skins? That is called the pruina. Studies on its purpose appear to be few or lacking altogether, but because it is prevalent on plants that receive high amounts of solar exposure, the pruina then can be construed as an adaptation for the purpose of bouncing off elevated light levels and heat, thus preventing the occurrence of sunburn. Additionally, the pruina may help in the regulation of transpiration. An interesting adaptation seen in a number of plants from different families with known representatives inhabiting very dry localities is the so-called Crassulacean Acid Metabolism (CAM). Most plants transpire, or breath, day and night which allows them to release unwanted gasses and also moisture. However, in dry habitats, moisture is a valuable resource and releasing it during the heat of the day can expose the plants to risk of dehydration. And so in plants that have resorted to the CAM, transpiration is only don...