Nitrogen (N) availability is a critical factor affecting photosynthetic acclimation of C3 plants under elevated atmospheric CO2 concentration ([CO2]e). However, current understanding of N effects on photosynthetic electron transport rate and partitioning, as well as its impact on photosynthesis under [CO2]e, is inadequate. Using controlled environment open-top chambers, wheat (Triticum aestivum L.) was grown at two N levels (0 and 200 mg(N) kg-1 soil) and two atmospheric CO2 concentrations of 400 ([CO2]a) and 760 μmol mol-1([CO2]e) during 2009 and 2010. Under [CO2]e high N availability increased stomatal conductance and transpiration rate, reduced limitations on the activity of triose phosphate isomerase, a Calvin cycle enzyme, and increased the rate of net photosynthesis (PN). Considering photosynthetic electron transport rate and partitioning aspects, we suggest that greater N availability increased PN under [CO2]e due to four following reasons: (1) higher N availability enhanced foliar N and chlorophyll concentrations, and the actual photochemical efficiency of photosystem (PS) II reaction centers under irradiance increased, (2) increase of total electron transport rate and proportion of open PSII reaction centers, (3) enhancement of the electron transport rate of the photochemical and carboxylation processes, and (4) reduced limitations of the Calvin cycle enzymes on the photosynthetic electron transport rate. Consequently, sufficient N improved light energy utilization in wheat flag leaves under [CO2]e, thus benefiting to photosynthetic assimilation. and X. C. Zhang, X. F. Yu, Y. F. Ma.
Effects of nitrogen (N)-deficiency on midday photoinhibition in flag leaves were compared between two contrastive Japanese rice cultivars, a traditional japonica cultivar with low yield, cv. Shirobeniya (SRB), and a japonica-indica intermediate type with high yield, cv. Akenohoshi (AKN). Both cultivars were grown under high-N and low-N conditions. At midday, low-N supply resulted in more intensive reductions in net photosynthetic rate, stomatal conductance, maximal quantum yield of photosystem II (PSII) and quantum yield of PSII electron transport in SRB than in AKN, indicating that SRB was more strongly photoinhibited than AKN under low-N condition. At midday, the low-N plants of two cultivars showed higher superoxide dismutase (SOD) activities than the high-N plants. However, ascorbate peroxidase (APX) activity was maintained in AKN but significantly decreased in SRB under low-N condition (N-deficiency). In contrast, hydrogen peroxide (H2O2) content in SRB significantly increased under low-N condition, indicating that the susceptibility to midday photoinhibition in the low-N plants of SRB is related to the increased H2O2 accumulation. It is suggested that the midday depression in photosynthesis may be a result of oxidative stress occurring in the low-N plants in which antioxidant capacity is not enough to cope with the generation of H2O2. Therefore, H2O2-scavenging capacity could be an important factor in determining the cultivar difference of midday photoinhibition in flag leaves of rice under low-N condition. and E. Kumagai, T. Araki, O. Ueno.
To examine the role of sink size on photosynthetic acclimation under elevated atmospheric CO2 concentrations ([CO2]), we tested the effects of panicle-removal (PR) treatment on photosynthesis in rice (Oryza sativa L.). Rice was grown at two [CO2] levels (ambient and ambient + 200 μmol mol-1) throughout the growing season, and at full-heading stage, at half the plants, a sink-limitation treatment was imposed by the removal of the panicles. The PR treatment alleviated the reduction of green leaf area, the contents of chlorophyll (Chl) and Rubisco after the full-heading stage, suggesting delay of senescence. Nonetheless, elevated [CO2] decreased photosynthesis (measured at current [CO2]) of plants exposed to the PR treatment. No significant [CO2] × PR interaction on photosynthesis was observed. The decrease of photosynthesis by elevated [CO2] of plants was associated with decreased leaf Rubisco content and N content. Leaf glucose content was increased by the PR treatment and also by elevated [CO2]. In conclusion, a sink-limitation in rice improved N status in the leaves, but this did not prevent the photosynthetic down-regulation under elevated [CO2]. and H. Shimono ... [et al.].
The partial shading effect on the photosynthetic apparatus of the sunflower (Helianthus annuus L.) was examined by monitoring oxygen evolution, maximum quantum yield of PSII photochemistry in dark-adapted leaves (Fv/Fm), the chlorophyll (Chl) concentrations and the Rubisco contents, and leaf mass per area (LMA) at the leaf level and by determining the concentrations of cytochrome (Cyt) f and the reaction centres of photosystem (PS) I and PSII at the thylakoid level. In this experiment, partial shading was defined as the shading of 2nd leaves with shade cloths, and the whole treatment was defined as the covering of the whole individuals with shade cloths. In the leaf level responses, oxygen evolution, LMA, Chl concentrations and Rubisco contents decreased in all shade treatments administered for six days. Fv/Fm remained constant irrespective of the shade treatments. On the other hand, in the thylakoid-level responses, the concentrations of the thylakoid components per unit Chl and the stoichiometry of the two photosystems showed no statistical difference among the shade treatments. The data obtained from the present study indicate that the partial shading affected the leaf-level responses rather than the thylakoid-level responses. The light received at the lower leaves might serve as a factor in the regulation of the leaf properties of the upper leaves due to the whole plant photosynthesis, while this factor did not have an effect at the thylakoid level., J. Ymazaki, Y. Shinomiya., and Obsahuje bibliografii
a1_Two experiments were performed to compare the effect of pectin and its hydrophobic derivatives on homeostasis of cholesterol and cecal metabolism in male young rats. Control rats were fed a diet supplemented with palm fat and cholesterol (50 and 10 g/kg, respectively). Rats of other gro ups were fed the same diet containing citrus pectin or octadecylpectinamide (60 g/kg). Diets were fed for 4 weeks. In experiment I, pectinamide of lower degree of amidation (30 %) increased serum HDL cholesterol from 1.20 to 1.43 μmol/ml (p>0.05) at the expense of other cholesterol fractions. In experiment II, pectinamide of a higher degree of amidation (53 %) significantly decreased total serum cholesterol from 2.08 to 1.67 μmol/ml. Amidated pectins at both levels of substitution significantly decreased hepatic concentrations of cholesterol and fat. In both experiments the relative weight of cecum in the pectinamide group was significantly lower than in pectin group. The highest cecal concentrations of short-chain fatty acids (SCFA) were found in rats fed a diet with pectin (133.2 and 129.3 μmol/g in experiment I and II, respectively). In other groups, cecal SCFA was significantly (pectinamide groups) or non-significantly (controls) lower. In wet feces, SCFA concentrations were higher and butyrate molar proportions lower than in corresponding cecal contents., a2_Pectinamide of a lower or higher degree of substitution significantly increased fecal content of cholesterol from 18.5 and 17.3 μmol/g in controls to 31.8 and 28.0 μmol/g, respectively. Corresponding concentrations of coprostanol were decreased. Effects of pectin on cholesterol homeostasis were absent or marginal. Histological examination revealed that hepatic tissue of control and pectin-fed rats was infiltrated with lipids. The Sudan black-positive material was absent in the liver of rats fed pectinamides. No pathological changes of liver tissue were apparent. In summary, hydrophobic amidated pectins significantly altered cholesterol homeostasis in rats and might be considered as a clinically effective hypocholesterolemic agent. Low cecal SCFA concentrations in rats fed pectinamides suggest that amidation of pectin had decreased its fermentability., M. Marounek, Z. Volek, A. Synytsya, J. Čopíková., and Obsahuje bibliografii a bibliografické odkazy
a_1 In this study, we have determined power output reached at maximal oxygen uptake during incremental cycling exercise (PI,max) performed at low and at high pedaling rates in nineteen untrained men with various myosin heavy chain composition (MyHC) in the vastus lateralis muscle. On separate days, subjects performed two incremental exercise tests until exhaustion at 60 rev . min-1 and at 120 rev . min-1. In the studied group of subjects PI,max reached during cycling at 60 rev . min-1 was significantly higher (p=0.0001) than that at 120 rev . min-1 (287±29 vs. 215±42 W, respectively for 60 and 120 rev . min-1). For further comparisons, two groups of subjects (n=6, each) were selected according to MyHC composition in the vastus lateralis muscle: group H with higher MyHC II content (56.8±2.79 %) and group L with lower MyHC II content in this muscle (28.6±5.8 %). PI,max reached during cycling performed at 60 rev . min-1 in group H was significantly lower than in group L (p=0.03). However, during cycling at 120 rev . min-1, there was no significant difference in PI,max reached by both groups of subjects (p=0.38). Moreover, oxygen uptake (VO2), blood hydrogen ion [H+], plasma lactate [La-] and ammonia [NH3] concentrations determined at the four highest power outputs completed during the incremental cycling performed at 60 as well as 120 rev . min-1, in the group H were significantly higher than in group L. We have concluded that during an incremental exercise performed at low pedaling rates the subjects with lower content of MyHC II in the vastus lateralis muscle possess greater power generating capabilities than the subjects with higher content of MyHC II. Surprisingly, at high pedaling rate, power generating capabilities in the subjects with higher MyHC II content in the vastus lateralis muscle did not differ from those found in the subjects with lower content of MyHC II in this muscle., a_2 We have concluded that during an incremental exercise performed at low pedaling rates the subjects with lower content of MyHC II in the vastus lateralis muscle possess greater power generating capabilities than the subjects with higher content of MyHC II. Surprisingly, at high pedaling rate, power generating capabilities in the subjects with higher MyHC II content in the vastus lateralis muscle did not differ from those found in the subjects with lower content of MyHC II in this muscle, despite higher blood [H+], [La-] and [NH3] concentrations. This indicates that at high pedaling rates the subjects with higher percentage of MyHC II in the vastus lateralis muscle perform relatively better than the subjects with lower percentage of MyHC II in this muscle., J. Majerczak, Z. Szkutnik, K. Duda, M. Komorowska, I. Kolodziejski, J. Karasinski, J. A. Zoladz., and Obsahuje bibliografii a bibliografické odkazy
A series of experiments have been undertaken to determine the effect of water extracts from pine bark (Pinus radiata) on the inhibition of the sporulation of oocysts of three species of avian coccidia. Tubes containing coccidian oocysts isolated from droppings of coccidia-infected chickens were randomly assigned to 0, 250, 500 and 1000 µg/ml pine bark extract (PBE). The tubes were incubated at 25-29 oC for 48 h depending on the species of Eimeria. Sporulation inhibition bioassay was used to evaluate the activity of PBE on the sporulation of coccidian oocysts. The oocysts were gently aerated with an air pump away from sun light. The results show for the first time that water-soluble extracts from pine bark containing 35% condensed tannins have anticoccidial activity as evidenced by their ability to decrease significantly the sporulation of the oocysts of three species of Eimeria, namely Eimeria tenella (Railliet et Lucet, 1891), E. maxima Tyzzer, 1929 and E. acervulina Tyzzer, 1929, under laboratory conditions. Incubation of unsporulated oocysts of these parasites in water containing 500 µg PBE per ml resulted in inhibition of sporulation of these oocysts by about 28-84% relative to the oocysts in the control incubations. In addition, up to 12% of E. maxima oocysts exposed to 500-1000 µg pine bark/ml were containing abnormal sporocysts in terms of size, number and shape.
Soil salinity is one of the most severe factors limiting growth and physiological response in Raphanus sativus. In this study, the possible role of plant growth promoting bacteria (PGPB) in alleviating soil salinity stress during plant growth under greenhouse conditions was investigated. Increasing salinity in the soil decreased plant growth, photosynthetic pigments content, phytohormones contents (indole-3-acetic acid, IAA and gibberellic acid, GA3) and mineral uptake compared to soil without salinity. Seeds inoculated with Bacillus subtilis and Pseudomonas fluorescens caused significantly increase in fresh and dry masses of roots and leaves, photosynthetic pigments, proline, total free amino acids and crude protein contents compared to noninoculated ones under salinity. The bacteria also increased phytohormones contents (IAA and GA3) and the contents of N, P, K+, Ca2+, and Mg2+ but decreased ABA contents and Na+ and Cl- content which may contribute in part to activation of processes involved in the alleviation of the effect of salt., H. I. Mohamed, E. Z. Gomaa., and Obsahuje bibliografii
In the present work the surfaces of the polyacrylonitrile (PAN)-based carbon fibers were physically treated using cold plasma in argon and oxygen atmospheres, in order to modify and improve the fine mechanical properties of the carbon fibers used in the fiber reinforced polymer composites. The physical and morphological changes of the surfaces were investigated by tensile strength tests and scanning electron microscopy (SEM). It was found that the oxygen plasma treatments caused ablation of the carbon fiber surface, removing carbon atoms such as CO and CO2 molecules. In addition, the argon plasma treatment eliminated defects on the fiber surface, reducing the size of critical flaws and thus increasing the fiber’s tensile strength. A comparison of the methods applied provides a largely consistent image of the effect of plasma treatment on the fine mechanical properties. and V této práci jsou fyzikálně zkoušeny povrchy polyakrylonitrilových (PAN) vláken pomocí chladného plazmatu v argonové a kyslíkové atmosféře s cílem modifikovat a zdokonalit mechanické vlastnosti uhlíkových vláken používaných ve zpevněných polymerových kompozitech- Fyzikální a morfologické změny povrchů byly zkoušeny na pevnost v tahu a pomocí rastrovací elektronové mikroskopie (SEM). Bylo zjištěno, že obrábění kyslíkovým plazmatem způsobilo ablaci povrchu uhlíkového vlákna odstraněním uhlíkových atomů v molekulách CO a CO2. Argonové plazma kromě toho eliminovalo defekty na povrchu vlákna snížením velikosti kritických vad a tím způsobilo zvýšení pevnosti v tahu. Srovnání použitých metod poskytuje široce konzistentní obraz vlivu plazmového obrábění na mechanické vlastnosti.
Thiazolidinediones are insulin-sensitizing drugs acting through peroxisome proliferator- activated receptor (PPAR)-γ. The aim of our study was to evaluate the effect of 5-month treatment with PPAR-γ agonist – rosiglitazone (4 mg/day), on the circulating markers of endothelial dysfunction and to evaluate the role of changes in endocrine function of adipose tissue in this process. Biochemical and metabolic parameters, circulating adiponectin, resistin, ICAM-1, VCAM-1, E-selectin, P-selectin, PAI-1, myeloperoxidase (MPO), and matrix metalloproteinase-9 (MMP-9) concentrations were assessed in 10 women with type 2 DM before and after rosiglitazone treatment and in a control group of healthy women. At baseline, diabetic group had significantly higher serum concentrations of glucose, glycated hemoglobin, V-CAM and PAI-1 compared to control group. Adiponectin levels tended to be lower in diabetic group, while resistin concentrations did not differ from control group. Rosiglitazone treatment improved diabetes compensation, significantly reduced VCAM-1, PAI-1 and E-selectin concentrations and increased adiponectin levels, while it did not affect serum resistin concentrations. Adiponectin concentrations at baseline were inversely related to E-selectin and MPO levels, this correlation disappeared after rosiglitazone treatment. We conclude that 5-month rosiglitazone treatment significantly reduced several markers of endothelial dysfunction. This effect could be at least in part attributable to marked increase of circulating adiponectin levels., R. Doležalová, M. M. Haluzík, L. Bošanská, Z. Lacinová, Z. Kasalová, T. Štulc, M. Haluzík., and Obsahuje bibliografii a bibliografické odkazy