A Conserved microRNA Signal Specifies Leaf Polarity

Abstract

. Leaf primordia arise on the flank of the shoot apical meristem (SAM) and become patterned along the adaxial/abaxial axis in response to signals from the SAM. (a) Scanning electron micrograph of a maize shoot apex. The meristem (M) contains a population of stem cells that allows the continued initiation of leaf primordia. The youngest leaf primordium is indicated as P1, the second youngest as P2, etc. (b) 14-day-old maize seedling. The red box marks the approximate position of the SAM within the surrounding older leaves that have distinct adaxial/upper and abaxial/lower surfaces.