CYTOHISTOLOGICAL ANALYSIS OF SOMATIC EMBRYOGENESIS IN CUCUMBER (CUCUMIS-SATIVUS L) .1. COMPARISON OF CELL-SUSPENSION CONTAINING AND LACKINGNATURAL FLUORESCENCE WITH IN-VIVO DEVELOPING EMBRYOS

Under in vivo conditions early-globular embryos occur in cucumber on t he 9th day after pollination, heart-shaped ones on the 14th, and morph ologically 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 morphologica lly mature embryo only the precambium is free from starch. Somatic emb ryogenesis (SE) in suspension occurs similarly as in vivo, even though the starch localization is somewhat different and torpedo-like embryo s occur, which are not observed in vivo. The histological structure of in vitro embryos is similar to in vivo ones, and the greatest morphol ogical difference are the poorly developed cotyledons and their variab le number (1 to 3). Aggregates showing fluorescence were found to be c omposed of cells which differ in morphology from cells not showing flu orescence and appear to be more capable of attaining the mature stages .