CHARACTERISTICS OF CITRUS CELL-CULTURES DURING UNDIFFERENTIATED GROWTH ON SUCROSE AND SOMATIC EMBRYOGENESIS ON GALACTOSE

Growth of willow-leaf mandarin (Citrus deliciosa Ten.) nucellar callus cultures without embryo formation was supported on sucrose as the sol e carbon source. Somatic embryogenesis was obtained by substituting ga lactose for sucrose at the same concentration (0.15 M). A histocytolog ical study revealed proliferation of young globular embryos during the first half of the 18-day culture cycle, irrespective of the carbon so urce. However, during the second half of the cycle, further embryo dev elopment failed in cell cultures on sucrose-containing medium. The rat e of cell growth and the carbohydrate depletion of the medium were 3-f old higher on sucrose than on galactose-containing medium. Cell suspen sions on sucrose differed by an increase in calcium, phosphorus, magne sium and potassium utilization soon after subculturing, followed by a sharp decrease. Finally, the phosphorus utilization rate per g dry wei ght formed was 2-fold higher in cell cultures on galactose during the second half of the culture cycle, coinciding with further embryo ontog enesis.