The af gene regulates timing and direction of major developmental events during leaf morphogenesis in garden pea (Pisum sativum)

The wildtype leaf of the garden pea possesses proximal pairs of leaflets and distal pairs of tendrils in the blade region. The afila (af) mutation causes leaflets to be replaced by compound (branched) tendrils. We characterized the morphological variation in leaf form along the plant axis and leaf development in early and late postembryonic leaves on afila plants to infer the role of the Af gene. Leaf forms are more diverse early in shoot ontogeny on afila plants. Af influences pinna length and pinna branching in addition to pinna type. Pinna initiation in the proximal region of afila leaf primordia is basipetal and delayed compared to wildtype plants. In addition, pinna development in the proximal region of afila leaves occurs for a longer period of time than on wildtype leaf primordia. Therefore, Af regulates the timing and direction of leaf developmental processes in the proximal region of the leaf, but has little effect on the distal region. These data support the heterochronic model of pea leaf morphogenesis proposed by Lu ct al. . (C) 1999 Annals of Botany Company.