| | 1 | Author
| Judit Kissim, Á. Gnes Tantos3, Annam Ária, M. Észáros3, ErzsébetJ. Ám Bor-Benczúrb, G. Ábor Horváth3 | Requires cookie* | | | Title
| Stress Alterations in Growth Parameters, Pigment Content and Photosynthetic Functions of in vitro Cultured Plants  | | | | Abstract
| Effects of different concentrations of glucose, sucrose and the natural growth regulator, triacontanol were studied under the unfavourable stress conditions of micropropagation of two woody plants, Sorbus rotundifolia L. and Primus x davidiopersica 'Piroska'. After 4 -6 weeks of cultures, the number and length of shoots, the photosynthetic activity as well as the chlorophyll, carotenoid and anthocyanin contents were investigated. As shown by the growth parameters, the optimal carbohydrate concentration was between 1 .5 -2 .5 % , whereas in higher concentrations, a definite inhibition could be observed. A similar response was found in changes of the anthocyanin content in Prunus x davidiopersica 'Piroska', but this effect was less pronounced with the photosynthetic pigments in both species. The Fv/Fm ratio representing the quantum yield of photosynthesis was low due to the inhibitory effect of stress and altered significantly by changing the carbohydrate concentrations. In all cases, the addition of 2 -4 jig triacontanol/1 further enhanced the stimulating effect of the optimal carbohydrate concentrations, which indicated the specific importance of the appropriate hor mone balance under such stress conditions. | | | |
Reference
| Z. Naturforsch. 54c, 834—8 (1999); received November 28 1998/March 18 1999 | | | |
Published
| 1999 | | | |
Keywords
| Anthocyanin, Fluorescence, Huckberry, Peach, Triacontanol | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0834.pdf | | | | Identifier
| ZNC-1999-54c-0834 | | | | Volume
| 54 | |
| 2 | Author
| NavassardV. Karapetyanab, Ute Windhövel3 ', AlfredR. Holzwarthc, Peter Bögera | Requires cookie* | | | Title
| Physiological Significance of Overproduced Carotenoids in Transformants of the Cyanobacterium Synechococcus PCC7942 | | | | Abstract
| The functional location of carotenoids in the photosynthetic apparatus of -crtB and -pys transformants of the cyanobacterium Synechococcus PCC7942 was studied and compared with a control strain -pF P l-3. These transformants overproduce carotenoids due to the insertion of an additional foreign phytoene synthase gene. A higher carotenoid content was found for -crtB and -pys transformants both in whole cells and isolated membranes; the -crtB transformant was also enriched with chlorophyll. 77-K fluorescence emission and excita tion spectra of the phycobilin-free membranes were examined for a possible location of overproduced carotenoids in pigment-protein complexes in situ. A similar ratio of the ampli tudes of fluorescence bands at 716 and 695 nm emitted by photosystems I and II, found for the three strains, indicates that the stoichiometry between photosystems of the transformants was not changed. Overproduced carotenoids are not located in the core antenna of photosys tem I, since 77-K fluorescence excitation spectra for photosystem I of isolated membranes from the studied strains do not differ in the region of carotenoid absorption. When illumi nated with light of the same intensity but different quality, absorbed preferentially by either carotenoids, chlorophylls or phycobilins, respectively, oxygen evolution was found always higher in the transformants -crtB and -pys than in -p F P l-3 control cells. Identical kinetics of fluorescence induction of all strains under carotenoid excitation did not reveal a higher activity of photosystem II in cells enriched with carotenoids. It is suggested that overpro duced carotenoids of the transformants are not involved in photosynthetic light-harvesting; rather they may serve to protect the cells and its membranes against photodestruction. | | | |
Reference
| Z. Naturforsch. 54c, 191—198 (1999); received December 18 1998 | | | |
Published
| 1999 | | | |
Keywords
| Carotenoid, Chlorophyll, Cyanobacterium, Fluorescence, Oxygen Evolution | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0191.pdf | | | | Identifier
| ZNC-1999-54c-0191 | | | | Volume
| 54 | |
| 3 | Author
| Zoltán Takács, Zsolt Csintalan, Zoltán Tuba | Requires cookie* | | | Title
| Responses of the Lichen Cladonia convoluta to High C 0 2 Level and Heavy Metal Treatment | | | | Abstract
| Despite of the downward acclimation of photosynthesis in C. convoluta, increased net photosynthesis and carbon balance can be anticipated in response to elevated atmospheric C 0 2 level. C 0 2 exchange measurement seems to be m ore indicative when detecting heavy metal stress than fluorescence parameters. Among these, the relative fluorescence decrease ratio (R F d 690) shows damage first, suggesting that the primary attack site for heavy metal ions is C 0 2 fixation and reaction centres are harmed last. Long-term elevated C 0 2 amelio rates partly this damage by improving C-balance to a greater extent in the heavy-metal stressed lichens. | | | |
Reference
| Z. Naturforsch. 54c, 797—8 (1999); received November 15 1998/M arch 5 1999 | | | |
Published
| 1999 | | | |
Keywords
| Cadmium, Lead, Fluorescence, Respiration, Photosystem II | | | |
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| default:Reihe_C/54/ZNC-1999-54c-0797.pdf | | | | Identifier
| ZNC-1999-54c-0797 | | | | Volume
| 54 | |
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