Hormone physiology of pea mutants prevented from flowering by mutations gior veg1

The veg1 (vegetative) mutant in pea (Pisum sativum L.) does not flower unde r any circumstances and gi (gigas) mutants remain vegetative under certain conditions. gi plants are deficient in production of floral stimulus, where as veg1 plants lack a response to floral stimulus. During long days in part icular, these non-flowering mutant plants eventually enter a stable compact phase characterised by a large reduction in internode length, small leaves and growth of lateral shoots from the upper-stem (aerial) nodes. The first -order laterals in turn produce second-order laterals and so on in a reiter ative pattern. The apical bud is reduced in size but continues active growt h. Endogenous hormone measurements and gibberellin application studies with gi-1, gi-2 and veg1 plants indicate that a reduction in gibberellin and pe rhaps indole-3-acetic acid level may account, at least partially, for the c ompact aerial shoot phenotype. In the gi-1 mutant, the compact phenotype is rescued by transfer from a 24- to an 8-h photoperiod. We propose that in p lants where flowering is prevented by a lack of floral stimulus or an inabi lity to respond, the large reduction in photoperiod gene activity during lo ng days may lead to a reduction in apical sink strength that is manifest in an altered hormone profile and weak apical dominance.