DNA, RNA and protein content of tissue during growth and embryogenesis in wild-carrot suspension cultures.

A highly selected population of cells (clumps from 63 to 125 micron in diameter), obtained by screening 14-day-old stock suspension cultures of wild carrot (Daucus carota L.), was used to initiate cultures in this study. Time-course changes in DNA, RNA and protein were followed when these cultures were grown in the presence or absence of 2.25 muM 2,4-dichlorophenoxyacetic acid (2,4-D). The data show that growth of these cultures, particularly in the early part of the growth curve, is different from that in most other studies reported on suspension cultures initiated without screening. The gross compositional analysis shows that this difference stems from the very high RNA:DNA and protein: DNA ratios of the cellular material used as the inoculum in this study. The presence of 2,4-D in the medium promoted total RNA and protein levels. Correlations were sought between the appearance of embryos in the absence of exogenous 2,4-D and gross compositional differences developing in cultures grown in the presence and absence of 2,4-D. The handling of cultures during inoculation appeared to have led to a substantial loss of DNA. This had, however, little effect on dry weight or protein content of the tissue.