ABSTRACT
This chapter summarizes key findings on sex determination, endogenous phytohormones linked to sex expression, and the results of molecular studies leading to cloning of genes that are differentially expressed in male and female flowers and appear to be the targets of cytokinins. Cytokinins also had feminizing effects on monoecious mercuries, resulting in entirely female inflorescences. The balance between cytokinin and auxin in sex development was determined with a medium containing both hormones. The mascu-linization effect of auxin on female nodes can be prevented at very low concentrations of cytokinins. Endogenous cytokinin-auxin balances are probably involved in sex differentiation of entirely male and female plants. Precise measurements and characterizations, in genotypes selected for their different sensitivities to feminizing agents, are necessary to confirm these results. Cytokinin contents in apices of isogenic lines were determined by gas chromatography-mass spectrometry after high-performance liquid chromatography.
