Further studies on the photosynthesis of carrot tissue cultures.

The influence of kinetin and sucrose on the photosynthetic activity of carrot (Daucus carota) tissue cultures in relation to growth was investigated. The results showed that light contributes heavily to the growth of tissue cultures measured in terms of fresh and dry weight and cell division activity. In light, the fresh weight, dry weight, and number of cells per explant were about or more than doubled. This indicated that after the development of chloroplasts, carrot tissue cultures can grow autotrophically at least as far as energy and carbon are concerned. Kinetin was shown to have an important role in developing the photosynthetic apparatus and photosynthetic activity of tissue cultures as manifested by the increase of chlorophyll content (60%), Hill activity (about 3-fold), and (14)C-fixation from NaH(14)CO(3) (about 20%). On the other hand, the presence of sucrose in the medium reduced the chlorophyll content by about 30% and (14)C-fixation from NaH(14)CO(3) in the soluble fraction by about 60%. A possible correlation between the influence of kinetin on sugar uptake and the effect of kinetin on (14)C-fixation from NaH(14)CO(3) was discussed.