No abstract

SUMMARYA culture of Phaeodactylum tricornutum was suspended in nitrogen-free growth medium under conditions which favoured photosynthesis. Nitrogen deprivation was continued for 60 h and, over this period, samples were removed for measurement of rates of uptake of arginine, guanine, nitrate, nitrite, lysine, methylammonium and urea. In another experiment, the effect of nitrogen deprivation on the ability to take up methylammonium and ammonium was compared. Cells developed, or increased, their abilities to take up all of these nitrogen compounds during nitrogen deprivation but ability to take up the two amino acids increased only slowly whereas the ability to take up the other compounds increased markedly during the first few hours of deprivation. The maximum rates of uptake developed were some 50-100 x higher for methylammonium and ammonium than they were for the other compounds. The rates of uptake are compared with those necessary to sustain growth.

No abstract

Three unselected cell lines of C. roseus maintained on a growth-associated alkaloid production medium were studied over a period of 2 to 5.5 years for the stability of alkaloid production (serpentine and ajmalicine). Large fluctuations in the total alkaloid content of 20-day-old cells were found for all three cell lines at each subculture over a two-year period. Growth rates increased during prolonged subculture and one cell line became unproductive after five years culture. By selection of small autofluorescent aggregates, high alkaloid production was restored in this cell line, while the parent line was found to be unresponsive to alkaloid induction treatments. The instability in both alkaloid production and spectrum and the loss of alkaloid productivity are discussed in relation to the selection pressures present during long-term maintenance of cell suspension cultures.Abbreviations: 2,4-D-2A-dichlorophenoxyacetic acid, nHS-n-heptane sulphonate

No abstract