Genetic control of leaf development in pea (Pisum sativum)

Three well-defined genes affect the morphological and anatomical features of the pea (Pisum sativum) compound leaf. Either singly or in combination, they specify five distinct pinna types. Using simple genetics, classical criteria for establishing homology, SEM of leaf development, and pinna histology, the phenotypes of the afila (af), tendril-less (tl), and tendrilled acacia (uni-tac)/unifoliata (uni) mutants are compared with that of wild-type plants, and the roles of the Af, Tl, and Uni genes are deduced. Marx's concept of inherent regions within the pea leaf is upheld. The leaf blade consists of three genetically/developmentally determined regions: proximal, distal, and terminal. All three genes modify leaf blade form by altering the timing of events during leaf development. In addition, these genes affect most aspects of leaf morphology (pinna pair number, pinna, petiole and leaf lengths, pinna branching) and histology (cell arrangement and size) as well as characteristics of shoot ontogeny (number of leaves, first node to flower, leaf heteroblasty).