Effects of endogenous auxin on citrus somatic embryogenesis

This study investigated the changes in endogenous auxin concentration durin g embryogenesis of citrus (Citrus sinensis Osb.) in tissue culture. Embryog enic callus (EC) was induced from ovules of 'Trovita orange' and 'Oomishima navel'. In both varieties, the EC having greater capacity for embryogenesi s had a correspondingly higher endogenous indole-3-acetic acid (IAA) concen tration. When the EC in 'Washington navel' and 'Oomishima navel' were cultu red on hormone-free media which can induce embryogenesis, the IAA concentra tion increased for 2 days, then rapidly decreased and stabilized 14 days la ter. These results suggest that the decrease in IAA concentration is closel y related to citrus embryogenesis.