Interaction between lateral branch growth and pod set in primary inflorescences of lupin

Abstract

In Lupinus angustifolius, L. luteus and L. mutabilis, flower formation and pod set were largely independent of the basal lateral branches. Partial or complete removal of lateral branches near the primary inflorescence increased the number of flowers formed and pods set. Flower formation was unaffected by most of the experimental treatments and was most closely correlated with the main-stem leaf area in L. angustifolius and L, mutabilis. Loss of leaf area from the main stem reduced flower formation and pod set more in L. mutabilis than in L. angustifolius. Leaves on lateral branches did not contribute significantly to flower formation or pod set in the presence of main-stem leaves, but could compensate for losses of main-stem leaves in L. mutabilis, especially when the upper lateral branches were intact and actively growing. Removal of all growing points from the upper lateral branches enhanced pod set. These findings suggest that crop management can increase pod set on primary inflorescences in lupin crops that have limited water in early summer, by bringing about a temporary restriction in upper lateral branch growth during the pod-setting process. It is concluded that the effect of lateral branch growth is more significant in the control of pod set in lupin species than the autonomous control by abscisic acid.