n-Alkanes are an important part of epicuticular leaf lipids, which are principally used to keep water balance of plant leaf surface. Their average carbon chain length (ACL), as the physiological response of plants to environmental water stress, is proposed to be related to the evolution of plants. The ACL of higher plant-derived n-alkanes is longer than that of lower plants and aquatic algae, so are those of gymnosperm than angiosperm and C₄ than C₃ plants, suggesting the implications of n-alkanes for rough classification of plants. Therefore, the ACL of n-alkanes has been applied intensively in paleoenvironment research to investigate the relative contributions of aquatic vs. land plants in sediments and of herbaceous vs. woody plants in paleosols. Hydrogen of higher plant-derived n-alkanes is initially taken from water during photosynthesis and its isotopic composition is mainly affected by environmental conditions and biochemical processes. However, the influences from environmental change have been found to be largely compensated by those from the concurrent vegetation shift, making higher plant-derived n-alkane δD have the potential to record meteoric water δD, and hence useful for paleogydrology studies.