heteroblastic development

A progressive change in the form and size of successive organs. In many grasses, for example, successive leaf blades are progressively longer and only after a maximum length is achieved will the plant begin to flower. In many plants with compound leaves it may be seen that the younger leaves are simpler than the later leaves. For example, in hemp (Cannabis sativa) successive leaves have a greater number of lobes and the margins become more serrated (see diagram). This trend to greater complexity is often reversed after flowering.