<P> A. miersiana has thick cuticle as expected to be found on xerophytes, but H. disermifolia and G. africana have thin cuticles . Since resources are scarce in arid regions, there is selection for plants having thin and efficient cuticles to limit the nutritional and energy costs for the cuticle construction . </P> <P> In periods of severe water stress and stomata closure, the cuticle's low water permeability is considered as one of the most vital factor in ensuring the survival of the plant . The rate of transpiration of the cuticles of xerophytes is 25 times lower than that of stomatal transpiration . To give an idea of how low this is, the rate of transpiration of the cuticles of mesophytes is only 2 to 5 times lower than stomatal transpiration . </P> <P> There are many changes that happen on the molecular level when a plant experiences stress . When in heat shock, for example, their protein molecule structures become unstable, unfold, or reconfigure to become less efficient . Membrane stability will decrease in plastids, which is why photosynthesis is the first process to be affected by heat stress . Despite the many stresses, xerophytes have the ability to survive and thrive in drought conditions due to their physiological and biochemical specialties . </P> <P> Some plants can store water in their root structures, trunk structures, stems, and leaves . Water storage in swollen parts of the plant is known as succulence . A swollen trunk or root at the ground level of a plant is called a caudex and plants with swollen bases are called caudiciforms . </P>

Twisted trunk and thick barn in xerophytes are adaptation for