Heterophylly

the presence of differently shaped leaves on the same shoot or on different shoots of the same plant. Heterophylly occurs in many aquatic plants (for example, arrowhead, water crowfoot, water starwort, and some species of pondweed), in which the underwater leaves often differ sharply in form from those growing above the water.

In aquatic plants, heterophylly has an adaptive significance; the more finely divided underwater leaves are better able to absorb the carbon dioxide dissolved in the water. Heterophylly also occurs in land plants (for instance, in mulberry, some species of eucalyptus, and ivy) and is linked with developmental changes. (For example, in mulberry the leaves of the young shoots of non-fruit-bearing trees are often divided into lobes, while the leaves of older shoots are broad ovals or ovate.) Heterophylly in land plants is also associated with varying functions. In the epiphytic tropical fern Platycerium the first leaves are cup-shaped. When rotting leaves and branches fall into these cups, a layer of soil is formed and the air roots settle in. Subsequently formed leaves are long and serve to assimilate nutrients.