PRECIPITATED PROTEINS IMPROVE THE PRODUCTION OF CARROT SOMATIC EMBRYOS

Extracellular compounds isolated from embryogenic carrot cell suspensi on cultures increase, by 1.5 to 6-fold, endstage embryo production whe n added back to carrot cultures initiating embryogenesis. The causativ e factors related to the enhancement of embryo production are most lik ely to be extracellular, high molecular weight proteins found in the e mbryo-free medium (EFM) after somatic embryos have been formed. The ad dition of heat-treated EFM to fresh cultures did not result in enhanci ng effects on the production of end-stage embryos. However, the additi on of compounds precipitated from EFM, by high concentrations of salt, accelerated by four days the formation of comparable amounts of end-s tage embryos and surpassed total end-stage embryo levels by a factor o f 4-6, dependent on the precipitate dose. These results suggest that h eat-labile polypeptide molecules may be responsible for growth factor- like effects during somatic embryogenesis.