Differences in Endogenous Levels of Gibberellin Activity in Male and Female Partners of Two Dioecious Tree Species

It was found that in two dioecious species, the carob (Ceratoniasiliqua) and the date palm (Phoenix dactylifera) growing intheir natural Mediterrancan habitat, the female partner invariablymanifested higher endogenous GN-like activity. While this trendwas consistent, marked seasonal fluctuations in both free andglycosidic bound-GN were observedhigher levels being associatedwith essentially vegetative spring growth and the converse associatedwith anthesis. It is postulated that while a clear correlationexists between female growth and high GN activity in these species,the switch from vegetative to generative growth in both themale and female may be associated with a lower relative proportionof endogenous GN in a specific multi-hormonal complex presumablyrequired for flower induction.