Chinese Dunce Cap (Orostachys spinosa) is a slow-growing succulent (fleshy-leafed) plant in the family Crassulaceae. It is found in arid areas in Mongolia, Russia, China, and Kazakhstan, and is remarkably hardy, thriving in temperatures as low as -40 degrees C (-40 F) and able to photosynthesize under a thin layer of snow. A fully-grown Chinese Dunce Cap resembles a sunflower head 10 cm (4 inches) across, with a flattened dome of spiral, tightly closed leaves surrounded by a ring of upright leaves. When the plant is mature, which takes about five years, it produces the conical flower stalk responsible for its common name and dies afterwards. Like other members of the Crassulaceae, O. spinosa copes with arid conditions by fixing carbon using the CAM (Crassulacean acid metabolism) pathway: it keeps stomata on the leaves closed during the day to minimize evaporative water loss, but opens them at night to absorb carbon dioxide and store it for photosynthesis during the day. It is the most cold-tolerant CAM plant known. O. spinosa is used in Mongolian herbal medicine, as forage for livestock in winter, and in decorative rock gardens.
- Oyungerel, Shagjjav. A Study To Detect The CAM Photosynthesis in Succulent Plants. Dissertation, National University of Mongolia. 2008. (Online at: http://old.num.edu.mn/Portals/0/Oyungerel_ABstract_Eng_Feb_18_08.pdf )