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The concentration of kinetin and kinetinriboside plays an essential role in the induction of amaranthin accumulation in cotyledons of Amaranthus tricolor during germination. The dose/effect ratio shows that kinetin induced 3- to 3.5-fold more amaranthin than kinetinriboside at the same molecular concentration. Various concentrations of exogenous Ca did not influence the effects of kinetin on the betacyanin synthesis. However, when Ca was applied together with kinetinriboside, the amaranthin production was stimulated. Time-course experiments show a lag phase of 16 h starting from the incubation with kinetin and a distinct increase of amaranthin thereafter. If the seedlings were treated simultaneously with kinetin and Ca, the increase of amaranthin started after 12 h. At 16 h of incubation in kinetin/Ca, the amount of amaranthin increased significantly compared to controls incubated with kinetin alone. If Ca ions (16 h kinetin/Ca incubation) were removed from the medium after 2 h, 4 h, and up to 14 h, the amaranthin content was enhanced compared to controls without Ca. The stimulating effect was highest in the presence of Ca for 8 h. These data show that exogenous Ca stimulated the amaranthin synthesis mainly during the first 12 h of incubation. The Ca antagonists EGTA, chlorotetracycline, and CoCl reduced the amaranthin content up to 80%. The calmodulin antagonists chloropromazine and trifluoperazine inhibited the betacyanin accumulation up to 97% when applied at the beginning of the incubation. Neither Co nor trifluoperazine after 12 h of preincubation in kinetin had inhibiting effects on the amaranthin production. Therefore, we presume that a specific period of competence is required for calmodulin-mediated Ca effects on the accumulation of amaranthin induced by cytokinins in the seedlings of Amaranthus tricolor. [ABSTRACT FROM AUTHOR]

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From different plant tissues such as tobacco (Nicotiana rustica), potato (Solanum tuberosum), and mung bean (Phaseolus radiatus), ring- or cylinder-shaped particles called prosomes were isolated by either sucrose gradient centrifugation or fast protein liquid chromatography (FPLC). These particles have a diameter of 12 to 14 nm and a length of 16 to 18 nm. They migrate under conditions of nondenaturing gel electrophoresis as one distinct band. Sedimentation coefficient and buoyant density in Cs2SO4 of the plant prosomes were determined by analytical ultracentrifugation to be approximately 23S and 1.23 g/cm3, respectively. The total molecular mass was estimated by gel filtration to be 650 kDa. Plant prosomes are composed of 12 to 15 proteins with molecular masses in the range of 24 to 35 kDa with isoelectric points of pH 5 to 7 as revealed by two-dimensional gel electrophoresis. The protein patterns of prosomes from the three different plant species are very similar. Polyclonal antisera against potato prosomes reacted in Western blots with prosomal proteins of all three plant species. They also bind to some prosomal proteins of animal species. Antisera against animal prosomes react with some proteins of plant prosomes. As shown by lectin blotting, plant prosomes are glycosylated carrying glucosyl- or mannosyl, and N-acetylgalactosaminyl residues. Prosomal preparations contain non-stoichiometric amounts of small RNA of about 80 kDa. These results suggest that plant prosomes are structurally and functionally homologous to prosomes of other eukaryotic cells.

A 19S particle was purified from tobacco (Nicotiana rustica) leaf cells. Its density was determined as 1296 g/cm3 in Cs2SO4-DMSO gradients, indicating the presence of RNA and protein. Polyacrylamide gel electrophoresis (PAGE) revealed eight distinct proteins in the range of 20-30 kD and RNA in the range of 70-80 nucleotides. Electron microscopic examination showed the same raspberry-shaped structure with a central depression as described for prosomes. We conclude that tobacco 19S particles represent small cytoplasmic complexes, possessing biochemical and structural characteristics similar to the hither-to known prosomes of animal cells.

Plants of Bryophyllum tubiflorum were held 12 days, plants of Sempervivum tectorum 11 and 23 days without water. Then, the contents of sugars and starch were determined. In Bryophyllum the quantity of monosaccharides decreased, that of oligosaccharides and of starch increased. In Sempervivum the total contents of sugars were higher after 11 days, but the amount of starch had decreased. After 23 days of dryness the contents of sugars and of starch had decreased very much, and a somewhat exceptional behaviour of raffinose was observed.

Isocitric, citric, malic, and succinic acids are found in S. tectorum. Their contents, measured at various times during the year, show remarkable changes. Isocitric acid always dominates and reaches distinct maxima in December and June. During the winter and in the course of summer the quantity decreases, and in February and August there are minima of the amounts of this acid. The contents of citric and malic acids show a maximum during the winter months. The quantity of succinic acid increases in winter, too, but the highest values are found in the beginning of spring. The variations in the quantity of total acids are, as a result of the very high percentage of isocitric acid, essentially in accordance with the variations of the latter. The amount of total acids is highest in June and smallest in August.The factors temperature, photoperiodism, and endogenous annual rhythm are suggested to be responsible for the fluctuations in contents of the acids. A comparison with the behaviour of soluble carbohydrates suggests that acids take part in the regulation of storage of carbohydrates. Definite statements cannot be made, because the distribution of acids in the compartments of the cell is not known.