This is a species of water lily whose leaves float on the surface of a pond or lake. If it were like an ordinary leaf, it would have the majority of its stomata in the lower epidermis, pressed against the water’s surface – they would be unable to absorb any carbon dioxide from the atmosphere. This arrangement – having all the stomata in the upper epidermis – permits the leaves to absorb carbon dioxide. It also causes them to lose much more water, but that is not much of a problem for water lilies. This unusual anatomy would not be adaptive for most terrestrial species, but it is functional in this particular habitat. |