Somatic embryogenesis from stamen filaments of Aesculus flava Sol. and peroxidase activity during the transition from friable to embryogenic callus

•Somatic embryos (SEs) were efficiently induced from stamen filaments of yellow buckeye.•Darkness, 2,4-D and Kin were indispensable for SE initiation.•SE number considerably increased by recurrent somatic embryogenesis.•SEs exhibited high germination and embryo-to-plantlet conversion rates.•Peroxidase activity decreased during the course of friable to embryogenic callus transition.