Applicable to Pleistocene but is highly age-dependent. Bias introduced when utilizing only a single taxon as a basis for paleoenvironmental interpretations. These solutions are taxon-independent. Paleobotanical record is that of the solutions to environmental problems in a variety of spatial and temporal scales. Gas exchange important component, although earliest cuticularized plants do not possess exchange mechanisms.
Gas exchange is facilitated by the presence of stomates.
Cuticle thickness is related to water stress. Stomatal size NOT a good indicator, related to ploidy level of organism, but the relationship between stomata and epidermal cells has been shown to be a reliable climate proxy . Assemblages must be evaluated taphonomically before utilization of this technique. Factors include light intensity, day length, temperature change, nutrient flux, water stress, physical damage, infection all affect abscission. Synchroneity of abscission related to seasonal fluctuations in light, temperature and water.