29 August 1986
Vol 233, Issue 4767

About The Cover

Cover image expansion

Emerging alfalfa root nodule, resulting from Rhizobium meliloti infection. The bacteria stimulate plant cortical mitoses, cause deformation of epidermal root hairs, and invade the root through an infection thread (blue-staining cell, upper right). The R. meliloti nodABC genes, required for all these events, are transcriptionally controlled by a plant-synthesized flavonoid, luteolin. See page 977. [Photograph by Mark Dudley and Sharon Long, Department of Biological Sciences, Stanford University, Stanford, CA 94305]