Selaginella lepidophylla

Selaginella lepidophylla (syn. Lycopodium lepidophyllum) is a species of desert plant in the spikemoss family (Selaginellaceae). Known as a 'resurrection plant', S. lepidophylla is renowned for its ability to survive almost complete desiccation. During dry weather in its native habitat, its stems curl into a tight ball, uncurling only when exposed to moisture. The outer stems of the plant bend into circular rings after a relatively short period without water. The inner stems instead curl slowly into spirals in response to dessication, due to the action of the strain gradient along their length. Selaginella lepidophylla reaches a maximum height of 5 cm, and is native to the Chihuahuan Desert. Common names for this plant include flower of stone, false rose of Jericho, rose of Jericho, resurrection plant, resurrection moss, dinosaur plant, siempre viva, stone flower, and doradilla. Selaginella lepidophylla is not to be confused with Anastatica. Both species are resurrection plants and form tumbleweeds. They share the common name 'rose of Jericho', in reference to the biblical city of Jericho, constantly reborn from its ashes. Similarly, the capacity of S. lepidophylla for revival on rehydration allows it to resurrect and resume growth after long periods of drought. The striking feature of Selaginella lepidophylla is its adaptation to conditions of prolonged drought in its natural environment. It deploys the physiological strategy of drying up and rolling inwards in the absence of water to form a ball, and can survive for up to several years, and lose up to 95% of its moisture content, without suffering damage. When ground and air humidity begin to rise again, even a considerable time after it has wilted, the plant 'resuscitates'. If rehydrated, it continues its life cycle, fully recovering its photosynthesis and growth abilities. When desiccated, its rooted leaves become leathery at the base, appearing dark brown or light to reddish brown. The dry ball opens a few hours after being placed in contact with water, the parched leaves gradually resuming their green colour. If the roots are not too damaged, the plant may survive in pozzolanic ash. No matter how dried or damaged it becomes, because of the particular biological structure of its leaves the plant retains the ability to imbibe water and unfold itself, even many years after its death. The plant enters a dormant state in the absence of water, avoiding tissue and cell damage during drying by synthesizing trehalose, a crystallized sugar that acts as a compatible solute. Dissolved salts become concentrated in the plant tissues as water evaporates. The trehalose produced by the plant acts in place of the evaporating water, so preventing the salts from causing damage and protecting against death due to an excess of salinity. S. lepidophylla also uses betaines, substances which have the same function as trehalose.