Getting around the legume nodule: I. The structure of the peripheral zone in four nodule types

Nodules in the family Leguminosae come in many different shapes and forms, depending partly on the host that bears them. This review focuses on the peripheral tissues that surround the infected tissues of four anatomically distinct classes of nodules: nodules with indeterminate meristems (from the Trifolieae and Fabeae tribes); desmodioid nodules with determinate meristems (from the Phaseoleae and Loteae tribes); aeschynomenoid nodules ( Arachis hypogaea L., peanut); and lupinoid nodules ( Lupinus sp. L., lupine). I have especially stressed the importance of the three-dimensionality of the organ, because not all nodules display a radial symmetry as it is often assumed. The goal of this review is to provide a strong base of nodule structure so that forthcoming molecular studies can integrate this information into their approach.