Cytohistological analysis of somatic embryogenesis in cucumber (Cucumis sativus L). I. Comparison of cell suspension containing and lacking natural fluorescence with in vivo developing embryos

Abstract

Under in vivo conditions early-globular embryos occur in cucumber on the 9th day after pollination, heart-shaped ones on the 14th, and morphologically mature embryos appear on the 19th day. Single starch grains already appear in the cells of the globular embryo, and in the heart-shaped one they occur within the forming root cap. In the morphologically mature embryo only the precambium is free from starch. Somatic embryogenesis (SE) in suspension occurs similarly as in vivo, even though the starch localization is somewhat different and torpedo-like embryos occur, which are not observed in vivo. The histological structure of in vitro embryos is similar to in vivo ones, and the greatest morphological difference are the poorly developed cotyledons and their variable number (1 to 3). Aggregates showing fluorescence were found to be composed of cells which differ in morphology from cells not showing fluorescence and appear to be more capable of attaining the mature stages.