Karl-Hermann Neumann

The influence of sucrose and an elevated CO2 concentration on photosynthesis of photoautotrophic peanut (Arachis hypogaea L.) cell cultures

Using photoautotrophic cells ofArachis hypogaea (L.) growing at ambient CO2, it was shown that exogenous sucrose supplied to the liquid medium reduced14CO2 fixation (supplied as NaH14CO3). This was mostly due to a reduced labelling in P-esters, and to a lesser extent, in the serine/glycine moiety. However, radioactivity in the neutral sugar fraction was increased upon supplement of exogenous sucrose. The reduced labelling of P-esters and serine/glycine agrees with a lower concentration and specific activity of Rubisco in the sucrose supplied treatments as compared to the control. Following a transfer into a sugar free nutrient medium the concentration and activity of Rubisco is increased. The concentration of PEPCase was not influenced by sucrose application, although its specific activity was increased.At elevated CO2 concentration (2.34% v/v) the Rubisco concentration and specific activity was at the same level as in the control (0.03% v/v CO2). However, the concentration and the specific activity of PEPCase was increased and dry weight increase was about 8–9-fold higher than at ambient CO2.

Qualitative Differences in the DNA of Some Higher Plants, and Aspects of Selective DNA Replication During Differentiation

The kinetic complexity of the genome of Daucus carota was studied by reassociation experiments and compared with that of Petroselinum and Datura innoxia, and about 20% homology were found by cross-hybridization studies. Small differences in cot fractions occur between certain varieties of carrot. Renaturation experiments and density gradient studies indicated that carrot tissues display various fractions of repetitive DNA and satellite DNA, respectively, at differing developmental stages and after application of gibberellic acid. While these results indicate the selective replication of certain DNA sequences during development, microfluorometric DNA measurements do not. Therefore, we have obtained some evidence, but no direct proof, for differential DNA replication in carrot tissue cultures.

Embryogenesis of photoautotrophic cell cultures of Daucus carota L.

In this paper photoautotrophic carrot (Daucus carota L.) suspension cultures are described which are able to produce somatic embryos. The development of somatic embryos, however, requires a sucrose supplement. Although an elevation of the CO2 concentration up to 2.3% results in the same level of dry weight production as with sucrose in the medium, somatic embryos could not be observed.