Roles of the Af and Tl genes in pea leaf morphogenesis: Shoot ontogeny and leaf development in the heterozygotes

Abstract

The wildtype leaf blade of Pisum sativum possesses proximal leaflets and distal tendrils, which may be altered by two recessive mutations that affect pinna morphology, afila (afaf) and tendrilless (tltl). Using morphological observations and SEM, the variation in leaf forms along the plant axis and leaf development were characterized for plants heterozygous at the Af and/or T/loci. The Af and Tl genes interacted to affect many characteristics of shoot ontogeny, including rate changes in leaf blade length and complexity increases, as well as time to flowering. The Af gene retarded early vegetative development and accelerated the time to flowering. The leaf phenotypes of these heterozygous genotypes were specified mainly by changes in the timing of major developmental events. The data support the hypotheses that both genes are heterochronic in nature and that the pea leaf blade consists of three genetically- and developmentally- determined regions: proximal, distal and terminal.