CHANGES IN SOLUBLE-PROTEINS AND PHYTOHORMONE CONCENTRATIONS OF CULTURED CARROT PETIOLE EXPLANTS DURING INDUCTION OF SOMATIC EMBRYOGENESIS (DAUCUS-CAROTA L.)

A supplement of an auxin (indol-3-acetic acid or 2,4 dichlorophenoxyac etic acid) to the nutrient medium initiated a differentiation program including rhizogenesis followed by somatic embryogenesis in cultured c arrot petiole explants during a cultural cycle of 30 days. The evaluat ion of the occurrence and the synthesis of 282 soluble proteins extrac ted from cultured petiole explants during the induction of embryogenes is during the first two weeks of the cultural cycle indicated the swit ching on and off of protein synthesis sub-programs with a characterist ic protein pattern. The concentration of abscisic acid continually dec reased during a culture period of 20 days from a high level in the ini tial explants. The concentration of indol-3-acetic acid reached the hi ghest level at day 6 of the cultural cycle concurrently with the appea rance of root primordia, then a decrease followed. Using transgenic pl ant material (MAS-promoter coupled to GUS-reporter gene) the distribut ion of IAA was followed by histochemistry. Total cytokinin concentrati on increased from a low level in the original petiole explants up to d ay 10, which coincides with the development of embryogenic cells in th e sub-epidermis which was followed by lower concentrations during furt her embryo development. Of the 6 cytokinins determined (2-isopentenyla denine, zeatin and dihydrozeatin and their ribosides), 2-isopentenylad enine and its riboside clearly dominate at all stages of the cultural cycle analyzed.