On the Photosynthetic System and Assimilate Metabolism of Daucus and Arachis Cell Cultures

Abstract

Most cell and tissue culture systems are set up to be nourished by heterotrophic nutrition drawing energy and carbon from sugar and reduced nitrogen from amino acids, both supplemented to the nutrient medium. In the light many cultured cells turn green and mixotrophic conditions may be established, as reported by some authors in recent years (Hanson and Edelman 1972; Neumann and Raafat 1973; Nato et al. 1977; Neumann et al. 1978; Kumar et al. 1983a,b, 1984). Eventually even some reports appeared describing photoautotrophic cultures of cells of some plant species (Hüsemann and Barz 1977, Yamada et al. 1978; Hüsemann 1981; Bender et al. 1981). In mixotrophic cultures, illumination contributes considerably to growth of cultured cells. Possibly, such tissue cultures could serve as model systems to study the nutrition of young differentiating leaf cells before their photosynthetic system is sufficiently developed. Here organic nutrition depends on organic solutes derived either from the seed during germination or from older leaves during ontogenesis. As will be shown, such model systems are probably better suited to follow the development of the photosynthetic apparatus than the hitherto employed etiolated seedlings upon illumination. As pointed out earlier (Kumar et al. 1983a,b), in cultured cells as well as in the cells of the growing shoot apex etioplasts characteristic of shoot cells of dark-grown seedlings are absent. Finally it remains to be seen to what extent fully autotrophic cell cultures may some day find application in biotechnology.