Morphology of somatic embryogenesis and plantlet formation in tissue cultures of lantern tree (Koelreuteria bipinnata var. integrifoliola)

Abstract

Somatic embryogenesis of Koelreuteria bipinnata var. integrifoliola was observed, plantlet formation in different types of somatic embryos was studied and the effect of abnormal embryos on plantlet formation was identified. Results show that somatic embryos of K. bipinnata var. integrifoliola include normal embryos, embryos with abnormal cotyledons, vitrified embryos, albino embryos, secondary embryos, linked embryos, embryos with abnormal growing points and embryos with expanding hypocotyl. After 40 d of callus culture, the response of normal somatic embryos from K. bipinnata var. integrifoliola was 26.7%, embryos with abnormal cotyledon 30.3% while other types of somatic embryos were below the 20% level. Most of normal embryos developed into plantlets and plantlet formation reached 94.9%. But the percentage of plantlet formation decreased apparently in abnormal embryos: the number of embryos with abnormal cotyledon declined to 76.1%, that of linked embryos to 47.4% and other types of abnormal embryos to below the 20% level. Albino embryos and embryos with abnormal growing point did not develop at all into plantlets. Embryos with abnormal cotyledons, linked embryos and embryos with abnormal growing points were observed during early stages of somatic embryogenesis, but vitrified, secondary and albino embryos and calli of embryos were observed at later stages. Increasing sucrose concentrations can decrease the occurrence of vitrified embryos, but the number of albino embryos decreased with an increasing in sucrose concentration.