Embryogenesis

Plants offer intriguing developmental contrasts to animals, not only with respect to their diverse forms, but also in how those forms arise. A sequoia tree, for example, may grow for thousands of years before reaching a size big enough for an automobile to drive through its trunk. In contrast, an Arabidopsis plant can complete its life cycle in little more than a month, making hardly more than a handful of leaves (Figure 17.1). Dissimilar as they may be, both species employ growth mechanisms common to all multicellular plants, in which form is elaborated gradually through adaptive postembryonic growth processes. Animals, by contrast, typically have a more predictable pattern of development in which the basic body plan is largely determined during embryogenesis.