Closed stoma. Coloured scanning electron micrograph (SEM) of a closed stoma (centre) on the leaf surface of the succulent Kalanchoe (Kalanchoe blossfeldiana). Stomata are pores in the leaf surface that regulate gaseous exhange with the environment. Succulent plants are adapted to hot, dry conditions and open their stomata at night to minimise water loss. The stomata absorb carbon dioxide and convert it to an organic acid. When they close during the day, they continue the process of photosynthesis, using the carbon dioxide collected the night before. The flecks on the surface are wax. Magnification: X 520 at 10 centimetres wide.