Plants growing in deserts or high salinity habitats are all exposed to more or less constant water stress. To survive such conditions plants have developed growth strategies such as increased water use efficiency with C4- or CAM metabolism (Keeley and Rundel, 2003), succulent growth and extensive root systems (Henry et al., 2011). These strategies are good in a dry environment, but in more “favourable” conditions at least some of these plants may, due to lower growth rates, more easily be outcompeted by other less drought tolerant plants. Other adaptations to plant life in dry environments are thick cuticula and wax layers, depressed stomata and high density of trichomes. Thick cuticula and wax layers reduce extra-stomatal transpiration, and depressed stomata and trichomes create a thicker boundary layer outside the stomata, where the humidity gradient is more gradual, thereby reducing the stomatal transpiration.