Leaf and Flower Development in Pea (Pisum sativum L.): Mutants cochleata and unifoliata

The stipule mutant cochleata (coch) and the simple-leaf mutant unifoliata (uni) are utilized to increase understanding of the control of compound leaf and flower development in pea. The phenotype of the coch mutant, which affects the basal stipules of the pea leaf, is described in detail. Mutant coch flowers have supernumerary organs, abnormal fusing of flower parts, mosaic organs and partial male and female sterility. The wild-type Coch gene is shown to have a role in inflorescence development, floral organ identity and in the positioning of leaf parts. Changes in meristem size may be related to changes in leaf morphology. In the coch mutant, stipule primordia are small and their development is retarded in comparison with that of the first leaflet primordia. The diameter of the shoot apical meristem of the uni mutant is approx. 25 % less than that of its wild-type siblings. This is the first time that a significant difference in apical meristem size has been observed in a pea leaf mutant. Genetic controls in the basal part of the leaf are illustrated by interactions between coch and other mutants. The mutant coch gene is shown to change stipules into a more 'compound leaf-like' identity which is not affected by the stipules reduced mutation. The interaction of coch and tendril-less (tl) genes reveals that the expression of the wild-type Tl gene is reduced at the base of the leaf, supporting the theories of gradients of gene action.