Nevertheless, it has been shown that physiological activity at leaf margins is greatest early in the growing season, and that toothed margins are more active with respect to transpiration — both of which are vital for growth — than are untoothed, entire margins.
Thus, toothed margins apparently help plants in temperate regions to maximize their growth and productivity at the start of the growing season.
Fossils provide us with our only direct record of prehistoric life.
Studying them can help us to reconstruct the anatomy, behaviour and evolution of long-extinct organisms.
Adaptations reflect how the plant deals with temperature, light and the availability of water and nutrients.
It also has difficulty with some types of climate or vegetation, such as rainforests.
Overall, this work shows that some living angiosperms (flowering plants) and conifers subjected to high carbon dioxide concentrations have low stomatal densities, whereas plants in very windy conditions have high stomatal densities, but the stomata are very small.
Assuming that fossil plants also show this correlation, the relationship between the number of stomata and the number of epidermal cells (the stomatal index) can be a useful palaeoclimate proxy.
It is also important for regulating temperature and water loss.
It is not a solid barrier: to live and grow, plants need efficient gas exchange, which is controlled by the stomata (pores) in the leaves (Fig. The thickness of the cuticle itself is an indicator of how much water stress the plant experiences: the more abundant water is in the environment, the less need the plant has to prevent water escaping, and the thinner the cuticle.