Production of somatic embryos from carrot tissues in hormone-free medium

Abstract

Carrot “seed” after the germination of their zygotic embryos, contain cells which can develop in aseptic culture into somatic embros in a reliable and predictable manner without the use of exogenously added growth regulators. In the course of further development beyond the cotyledonary stage, somatic embryos form secondary embryos along their axes. If continually subcultured, they do so in a cyclical manner yielding loosely attached aggregates of embryos and plantlets. Subcellular embryogenesis stops and normal plantlets are recoverable if the medium is allowed to become stale. Excised zygotic embryos of carrot in vitro are also able to form somatic embryos in the same way, but only when broken in half, and at a much lower response level. Component(s) of the basal medium responsible for inducing somatic embryogenesis remain to be elucidated, but a lowered sucrose concentration prevents secondary somatic embryogenesis. Cytological and histological examinations show that the somatic embryos are diploid and are most likely derived both from cells of the fruit wall and the endosperm.