Untersuchungen zur Charakterisierung des Ernährungssystems von Karottengewebekulturen: Photosynthese, Kohlenstoff‐ und Stickstoffernährung, Mineralstoffverbrauch

Abstract

Characterization of the nutritional system of carrot tissue cultures: Photosynthesis, carbon and nitrogen nutrition, uptake of mineral nutrients During a culture period of 28 days qualitative and quantitative changes in the nutritional system of carrot tissue cultures can be observed. Investigations on sugar uptake, CO2 fixation, and uptake of amino acids and nitrate indicate a succession of 3 periods, i.e. a heterotrophic period at the beginning of the culture period (up to 10 days), a mixotrophic period (till about the 20th day) followed by an autotrophic period. The transition into the autotrophic period could be only observed in treatments supplemented with kinetin. Uptake of potassium, phosphorus, calcium and magnesium was closely correlated to cell division activity of the explants as induced by m‐inositol, IAA and kinetin.

Ultrastructural and biochemical development of the photosynthetic apparatus during callus induction in carrot root explants

“…These data agreed with data on Hill activity as measured earlier by ferricyanide reduction [13]. During mixotrophic growth large amounts of sugar from the medium were taken up by the ceils [14] and this sugar apparently reduced the photosynthetic activity of the chloroplasts [13]. Still CO2-fixation contributes to a considerable extent to carbon nutrition of cultured carrot explants (Table 1, see also ref.…”

“…As reported earlier [14,6], during a culture period of four weeks in a nutrient medium containing 2% sucrose at to and with IAA, inositol and kinetin, freshly isolated carrot root explants (secondary phloem) passed through a sequence of nutritional regimes, i.e. heterotrophic nutrition up to about 7-10 days after the beginning of the experiment followed by mixotrophic nutrition, and after about 3 weeks of culture autotrophic nutrition was attained.…”

Growth regulation, plastid differentiation and the development of a photosynthetic system in cultured carrot root explants as influenced by exogenous sucrose and various phytohormones

“…The higher sucrose tolerance limit of the plus kinetin treatment with respect to chlorophyll formation may be due to an elevated sucrose utilisation under the influence of this hormone combination, which not only stimulates growth [18] but also chlorophyll synthesis. Since these intensified processes cause an increased sucrose assimilation by the explants, this higher sucrose tolerance should be considered as a [18]. After about three weeks of culture most of the sucrose supplemented to the medium at to is used up and the explants aquire autotrophic nutrition in respect to carbon and energy [18,13].…”

“…Since these intensified processes cause an increased sucrose assimilation by the explants, this higher sucrose tolerance should be considered as a [18]. After about three weeks of culture most of the sucrose supplemented to the medium at to is used up and the explants aquire autotrophic nutrition in respect to carbon and energy [18,13]. Concurrently almost all plastics reached stage 5 of chloroplast development and the low temperature spectra of such explants are even more like those of leaves with more intensified absorption of chlorophyll 'a' and 'b'.…”

“…The most important factors are light, nutritional status and hormonal supply. Although several autotrophic cultures of green cells have been reported (22), a sugar supplement is usually needed in the medium for maximal growth of cells [6,[11][12][13][16][17][18]. However, a sucrose supplement to the nutrient solution usually decreases chlorophyll content and activity in CO2-fixation [16,17].…”