The genetic basis of plant form

Abstract

Plant architecture is relevant to a number of questions in population biology because it affects the number, size, and fecundity of individuals. Architectural differences in wild plants have frequently been described and are presumed to have a genetic basis because the differences are maintained when the plants are grown in uniform gardens, but little genetic research has been done. Studies in crop plants, however, provide substantial information about how plant form can be genetically manipulated. They show that the architecture of many crops has been successfully modified by making a small number of genetic substitutions that affect shoot length, flowering node, branch presence and orientation, habit, and growth determinacy. The changes occur at the level of metamers (leaf-axillary bud-internode) and become multiplied by iteration into the characteristic architecture of the plant. Metamer growth and iteration are tightly coordinated by genetic factors that operate at the level of the whole plant. Evidence supporting this hypothesis includes single gene control of coordinated changes among successive internodes, genetic control of production of metabolites or signals that move from mature tissues to shoot growing points, and allometries connecting organs arising from the same meristem. Since different plant architectures are associated with differences in fitness, information on the genetic basis of the morphological and physiological characters that cause the architectural differences will elucidate how fitness characters evolve.