Gibberellic Acid and the Physiological Genetics of Flowering in Peas

Abstract

IN peas (Pisum sativum) Barber¹ has shown that the Sn gene which is dominant for a delay in flowering to a higher node has at least four other pleiotropic effects. The gene induces competence to respond to photoperiod and vernalization ; it delays the formation of the first leaf with more than two leaflets ; and it causes a small reduction in internode length. The reduction in length is only about 10 per cent of that caused by segregation at the Le locus. These effects were investigated by appropriate crosses among the four commercial varieties : Telephone (late flowering, tall : Sn Le), Greenfeast (late, dwarf : Sn le), Alaska (early, tall: sn Le) and Massey (early, dwarf: sn le). The crosses have also given some evidence that segregation at the Le locus may modify the action of Sn, Le Sn plants flowering about 0.5 node later than le Sn plants in appropriate F ₂ s. The modifying effect of Le is 5–10 per cent of the effect of Sn. Segregation at the Le locus appears to have no effect on an sn background.