Effect of copper deficiency on photosynthetic electron transport in wheat plants

Copper deficiency in wheat ( Triticum aestivum L. cv. Nazareno Stramppeli) markedly affects photosynthetic activity. Flag leaves of copper-deficient plants showed a 50% reduction of the photosynthetic rate expressed as mg CO₂ dm⁻²h⁻¹. The activities of PSI and PSII, determined for isolated chloroplasts, as well as fluorescence measurements on intact leaves of copper-deficient plants, indicated a low activity of photosynthetic electron transport. Ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity was not affected by copper deficiency but copper deficiency affected the chloroplast ultrastructure, especially at the level of grana, where a disorganization of thylakoids is evident.     

The relationship between phosphate status and cyanide-resistant respiration in bean roots

Bean ( Phaseolus vulgaris L.) seedlings were cultured on complete or phosphate-deficient nutrient medium. After 14 days of culture on phosphate-deficient medium the visible symptoms of P_i deficiency were observed only in the shoot, the fresh and dry weights of the roots were slightly higher than in control plants. The decreased P_i content in the roots had little effect on total respiration rate but had an effect on the level of inhibition of respiration by cyanide. The high resistance of respiration to cyanide observed in P_i-deficient roots was the result of the suppression of cytochrome path activity and an increased participation of the alternative, cyanide-resistant pathway. The cytochrome pathway activity increased when inorganic phosphate was supplied to P_i-deficient roots for 1 or 3.5 h. It is speculated that the suppression of cytochrome pathway in P_i-deficient roots may result from restriction of the phosphorylating capacity or a partial inhibition of cytochrome oxidase activity.     

Zn buffering capacity and Zn accumulation in Swiss chard for some sludge-amended soils

Zinc sorption by soils can greatly affect its availability to plants. This study was conducted to determine the relationship between the Zn sorption capacity and plant Zn accumulation in five sludge-amended soils using Swiss chard (Beta vulgaris L.) as an indicator plant. Zinc sorption as a function of Zn concentration and pH was determined for the soils which received no sludge amendment; also DTPA (diethylenetriaminepentaacetic acid) extractable Zn was determined in all soils. Whereas the responses of DTPA-Zn and plant Zn to pH and the quantities of Zn sorbed were similar, the logarithm of DTPA-Zn accounted for only 82% of the variability in the logarithm of Zn accumulation by the plants. The variability was better explained when pH was included with DTPA-Zn in stepwise multiple regressions. The Zn buffering capacity, defined as the ratio of the change in quantity of Zn sorbed ( Zn_s) to the change in Zn solution concentration (Zn₁) (or Zn_s/Zn₁), and the estimated quantity of Zn sorbed were used as a basis to measure Zn intensity. Zinc intensity, which reflects Zn solution concentration, was the predominant factor controlling Zn accumulation by Swiss chard, judging from the good fit of the values of both parameters to the Michaelis-Menten equation. The maximum Zn accumulation was approximately 9 mmol kg^–1.Scientific paper no. 8901-29, Department of Agronomy and Soils, College of Agriculture and Home Economics Research Center. Washington State University, Pullman, WA 99164, USA.Scientific paper no. 8901-29, Department of Agronomy and Soils, College of Agriculture and Home Economics Research Center. Washington State University, Pullman, WA 99164, USA.     

Growth, dry weight partitioning and wood properties of Pinus radiata D. Don after 2 years of CO2 enrichment

Abstract Advanced selections (families 20010 and 20062) of P. radiata D. Don were exposed to either 340 or 660 μmol CO₂ mol ¹ for 2 years to establish if growth responses to high CO₂ would persist during the development of woody tissues. The experiment was carried out in glasshouses and some of the trees at each CO₂ concentration were subjected to phosphorus deficiency and to periodic drought. CO₂ enrichment increased whole-plant dry matter production irrespective of water availability, but only when phosphorus supply was adequate. The greatest increase occurred during the exponential period of growth and appeared to be tied to increased rates of photosynthesis, which caused accelerated production of leaf area. The increase in whole-plant dry matter production was similar for both families; however, family 20010 partitioned larger amounts of dry weight to the trunks than family 20062. which favoured the roots and branches. Wood density was generally increased by elevated CO₂ and for family 20010 this increase was due to thickening of the tracheid walls. Tracheid length was similar at both CO₂ levels but differed between families. These results suggest that, as the atmospheric CO₂ concentration rises, field-grown P. radiata should produce more dry weight at sites where phosphorus is not acutely deficient, even where drought limits growth; however, increases in wood production are likely only for genotypes which continue to partition at least the same proportion of dry weight to wood in the trunk.     

Effects of metals on enzyme activity in plants

Abstract. Uptake of phytotoxic amounts of metal by higher plants or algae can result in inhibition of several enzymes, and in increase in activity (= induction) of others. Two mechanisms of enzyme inhibition predominate: (1) binding of the metal to sulphydryl groups, involved in the catalytic actionor structural integrity of enzymes, and (2) deficiency of an essential metal in metalloproteins or metal-protein complexes, eventually combined with substitution of the toxic metal for the deficient element. Metal accumulation in the cellular compartment of the enzyme is a prerequisite for enzyme inhibition in vivo. The induction of some enzymes is considered to play a significant role in the stress metabolism, induced by metal phytotoxicity. Peroxidase induction is likely to be related to oxidative reactions at the biomembrane; several enzymes of the intermediary metabolism might be stimulated to compensate for metal-sensitive photosynthetic reactions. The induction of enzymes and metal-specific changes in isoperoxidase pattern can be used as diagnostic criteria to evaluate the phytotoxicity of soils, contaminated by several metals. Lines for future research on metal phytotoxicity are proposed, involving the study of inhibition and induction of enzymes at the different cell membranes (especially the plasmamembrane) in vivo.     

Consequences of the iron-dependent formation of ferredoxin and flavodoxin on photosynthesis and nitrogen fixation on Anabaena strains

Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply.Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same K_m values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution.     

Effects of copper aspirinate and aspirin on tissue copper,zinc, and iron concentrations following chronic oral treatment in the adjuvant arthritic rat

Concentrations of copper, zinc, and iron were analyzed and compared in a number of tissues of adjuvant arthritic rats following 22 d of chronic treatment (per os) with either vehicle, aspirin or copper aspirinate, at doses of 100 mg/kg, 200 mg/kg, or 400 mg/kg. Such chronic treatment resulted in a negative balance in copper, zinc, and iron in many tissues. Among the tissues examined, liver and kidney exhibited the greatest changes in metal concentrations; brain and skeletal muscle exhibited the least. Arthritis-induced changes in the concentrations of all three metals in the liver were reversed upon treatment with aspirin. Treatment with copper aspirinate, on the other hand, resulted in an extremely high accumulation of copper in the liver. Arthritis-induced changes in copper, zinc, and iron concentrations in the pancreas and copper concentration in the plasma were generally not reversed upon treatment with either aspirin or copper aspirinate. Among the three metals examined, the degree of change observed as a result of drug treatments was greatest for iron and least for zinc. Finally, it appeared that the effects of aspirin and copper aspirinate on tissue metal concentrations were independent of the antiarthritic effects of these compounds.     

Regional Reductions of Transketolase in Thiamine-Deficient Rat Brain

Abstract: Thiamine deficiency impairs oxidative metabolism and causes metabolic encephalopathy. An early reduction in transketolase (TK) activity may be an important pathogenic event. To assess the role of TK, we have delineated the regional/cellular distribution of TK protein and mRNA in adult rat brain in pyrithiamine-induced thiamine deficiency. TK activity declined in both vulnerable and spared regions. Immunoblots showed a parallel reduction of TK protein. With a few exceptions, immunocytochemistry indicated an overall decline of TK immunoreactivity and the decrease was not specific to vulnerable areas. In contrast to the pronounced, general decline of TK protein, in situ hybridization revealed a regional decrease of 0–25% of TK mRNA in thiamine deficiency. Northern blots indicated a similar level of TK mRNA in whole brain in thiamine deficiency. These results show that the decline of TK activity results from a proportional decrease of TK protein, and the deficiency may be due to an instability of TK protein or an inhibition of TK mRNA translation. The lack of correlation of the distribution, and the absence of specific alteration, of TK in affected regions suggest that the reduced TK may not be linked directly to selective vulnerability in thiamine deficiency.     

CHANGES IN CELL COMPOSITION AND LIPID METABOLISM MEDIATED BY SODIUM AND NITROGEN AVAILABILITY IN THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1

The effects of nitrogen starvation in the presence or absence of sodium in the culture medium were monitored in batch cultures of the marine diatom Phaeodactylum tricornutum Bohlin. During nitrogen starvation in the presence of sodium, cell nitrogen and chlorophyll a decreased, mainly as a consequence of continued cell division. These decreases were accompanied by decreases in the rates of photosynthesis and respiration. There was no change in either cell volume or carbohydrate, but both carbon and lipid increased. During nitrogen starvation in the absence of sodium, cell division ceased. Cell nitrogen and chlorophyll a remained constant, and respiration did not decrease, but the changes in the photosynthetic rate and the lipid content per cell were similar to cultures that were nitrogen-starved in the presence of sodium. The carbon-to-nitrogen ratio increased in both cultures. Nitrogen, in the form of nitrate, and sodium were resupplied to cultures that had been preconditioned in nitrogen- and sodium-deficient medium for 5 d. Control cultures to which neither nitrate or sodium were added remained in a static state with respect to cell number, volume, and carbohydrate but showed slight increases in lipid. Cells in cultures to which 10 mM nitrate alone was added showed a similar response to cultures where no additions were made. Cells in cultures to which 50 mM sodium alone was added divided for 2 d, with concomitant small decreases in all measured constituents. Cell division resumed in cultures to which both sodium and nitrate were added. The lipid content fell dramatically in these cells and was correlated to metabolic oxidation via measured increases in the activity of the glyoxylate cycle enzyme, isocitrate lyase. We conclude that lipids are stored as a function of decreased growth rate and are metabolized to a small extent when cell division resumes. However, much higher rates of metabolism occur if cell division resumes in the presence of a nitrogen source.