Comprehensive hormone profiling of the developing seeds of four grain legumes.

KEY MESSAGE: Developmental context and species-specific hormone requirements are of key importance in the advancement of in vitro protocols and manipulation of seed development. Improvement of in vitro tissue and cell culture protocols in grain legumes such as embryo rescue, interspecific hybridization, and androgenesis requires an understanding of the types, activity, and balance of hormones within developing seeds. Towards this goal, the concentration of auxin, cytokinin, gibberellin, and abscisic acid (ABA) and their precursors and derivatives were measured in the developing seeds of field pea (Pisum sativum L.), chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.), and faba bean (Vicia faba L.) from 4 days after anthesis until 8 days after reaching maximum fresh weight. The importance of developmental context (developmental time and space) is demonstrated in both the differences and similarities between species for hormone profiles, especially with regard to cytokinin and ABA biosynthesis during the embryo formation. Auxin and its conjugates are significant during the pattern formation stage of all legumes; however, IAA-Asparagine appears important in the Vicieae species and its concentrations are greater than IAA from the globular stage of embryo development on in multi-seed fruits. Finally, the significance of non-polar gibberellins during lentil seed development is highlighted.