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| 2. |
- Krupa, Z, et al.
(författare)
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Cadmium-affected level of inorganic phosphate in rye leaves influences Rubisco subunits
- 1999
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Ingår i: Acta Physiologiae Plantarum. - : Springer Science and Business Media LLC. - 0137-5881 .- 1861-1664. ; 21:3, s. 257-261
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Tidskriftsartikel (refereegranskat)abstract
- Heavy metals, like Cd, decrease intracellular levels of essential mineral nutrient elements. Here we show the effects of the interaction between Cd and inorganic phosphate and its effects on some aspects of the photosynthetic competence of first rye leaves. The decrease in the level of small and large Rubisco subunits in the leaves of Cd-treated seedlings is discussed both in terms of the recovering effect of an additional Pi supply to the leaves, as well as of direct and indirect mechanisms of Cd-toxicity towards photosynthesis.
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| 4. |
- KRUPA, Z, et al.
(författare)
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PHOTOINHIBITION OF PHOTOSYNTHESIS AND GROWTH-RESPONSES AT DIFFERENT LIGHT LEVELS IN PSBA GENE MUTANTS OF THE CYANOBACTERIUM SYNECHOCOCCUS
- 1991
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 82:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Photoinhibition of photosynthesis and growth responses at different light levels (10, 120 and 250-mu-mol m-2 s-1) were studied in psbA gene mutants R2S2C3 (psbAI gene present) and R2K1 (psbAII/psbAIII genes present) of the cyanobacterium Synechococcus sp. PCC 7942 (Anacystis nidulans R2). Mutant R2K1 (possessing form II of the D1 protein of photosystem II) was much more resistant to photoinhibition than the mutant R2S2C3 (possessing form I of the D1 protein). At moderate inhibitory light levels (100 to 300-mu-mol m-2 s-1) this was largely ascribed to an increased resistance of the photosystem II reaction centres possessing form II of the D1 protein. However, at higher light levels the higher resistance of mutant R2K1 was assigned to a higher rate of photosystem II repair, i.e. turnover of the D1 protein. Moreover, our results support the hypothesis that photoinhibition of photosystem II and photoinhibitory induced quenching are due to separate processes. Results from growth experiments show that the R2K1 mutant has a slower growth rate than the R2S2C3 mutant but shows an increased survival under high light stress conditions. It is hypothesized that high resistance to photoinhibition, though allowing a better survival under high light, is not advantageous for optimal growth.
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| 5. |
- KRUPA, Z, et al.
(författare)
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THE EFFECTS OF CADMIUM ON PHOTOSYNTHESIS OF PHASEOLUS-VULGARIS - A FLUORESCENCE ANALYSIS
- 1993
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 88:4, s. 626-630
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Tidskriftsartikel (refereegranskat)abstract
- Bean plants (Phaseolus vulgaris L. cv. Scarlett), germinated in darkness for 1 week, were transferred to light (200 mumol m-2 s-1) and cultivated for 1 week in a complete nutrient solution. After this period, cadmium ions in the form of CdSO4 were added at the concentrations of 0, 10, 20 and 50 muM. The effects of this metal on the properties of photosystem II photochemistry were studied by means of modulated fluorescence analysis. Steady state photochemical quenching, non-photochemical quenching and terminal fluorescence were determined in control and cadmium-treated plants. We postulate that, during short term exposure of plants to cadmium in the early stages of growth, the Calvin cycle reactions are more likely than photosystem II to be the primary target of the toxic influence of cadmium. The reduced demand for ATP and NADPH upon Calvin cycle inhibition causes a down-regulation of photosystem II photochemistry and of the yield of linear electron transport.
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| 6. |
- Siedlecka, A, et al.
(författare)
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A relationship between carbonic anhydrase and rubisco in response to moderate cadmium stress during light activation of photosynthesis
- 1999
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Ingår i: Zeitschrift für Naturforschung C - A Journal of Biosciences. - 0939-5075 .- 1865-7125. ; 54:9-10, s. 759-763
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Tidskriftsartikel (refereegranskat)abstract
- In our previous research, we showed that low Cd concentration increases the effectiveness of the process es leading to activation of ribulose-1,5-bisphosphate carboxylase/oxygen ase (Rubisco). This stimulation was dependent on carbonic anhydrase (CA) activity and resulted in protecting Rubisco activity against Cd toxicity. The aim of the present paper was to test whether this mechanism has any influence on light activation of photosynthesis during the first 2 h of illumination. Both the "activation mechanism" of plant response to Cd-stress conditions and its full efficiency at low Cd concentration were confirmed. The CA-dependent light activation of Rubisco at low Cd level was correlated with accelerated attaining of the maximum Rubisco activity by these plants. The amount of Rubisco was also Cd- and time-dependent and varied from continuous accumulation in control plants till reaching the maximum level within 30 minutes for the high Cd concentration. An increase in CA activity that was found to be parallel to the decrease of the amount of CA suggested activation of the enzyme by low Cd concentration.
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| 7. |
- Siedlecka, A, et al.
(författare)
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Primary carbon metabolism in Phaseolus vulgaris plants under Cd/Fe interaction
- 1997
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Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 35:12, s. 951-957
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the Cd/Fe interaction on primary carbon metabolism in Phaseolus vulgaris L. cv. Slowianka plants was investigated. It was documented earlier that Cd induced a decrease in the leaf Fe content, and increased levels of Fe may reduce Cd toxicity. The aim of the present study was to check whether Cd is toxic to Calvin cycle enzymes and especially if different Fe levels can modify the Cd effect. Bush-bean seedlings were cultivated in the presence of different Cd concentrations (0, 10, 20, 50 mu M) and at different Fe doses (deficient: 0 mmol, normal: 0.25 mmol, excessive: 0.5 mmol). Leaf content of ATP, ADP, Calvin cycle metabolites, activity of RUBISCO and carbonic anhydrase were measured. The influence of Cd/Fe interaction on the content of Calvin cycle metabolites seemed to be of both direct and indirect nature. The Cd-induced increase in ATP content, and in the ATP/ADP ratio, resulted from a decreased ATP consumption. At a higher Fe dose, the Cd/Fe interaction resulted in a revitalisation of the adenylate pool and Calvin cycle metabolites. The inhibition of RUBISCO carboxylase activity may be considered as the primary plant response to Cd-stress. The mechanisms of RUBISCO activation operate to overcome this limitation, although their efficiency was decreased by high Cd concentrations, resulting in decreased RUBISCO activity. At a low Cd concentration, the increase in RUBISCO activity was correlated with increased carbonic anhydrase activity.
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