Reproductive allocation of an annual,<Emphasis Type="Italic"> Xanthium canadense</Emphasis>, at an elevated carbon dioxide concentration

Stimulation of vegetative growth by an elevated CO₂ concentration does not always lead to an increase in reproductive yield. This is because reproductive yield is determined by the fraction of biomass allocated to the reproductive part as well as biomass production. We grew Xanthium canadense at low N (LN) and high N levels (HN) under an ambient (360 mol mol^-1) and elevated (700 mol mol^-1) CO₂ concentration ([CO₂]) in open-top chambers. Reproductive yield was analysed as the product of: (1) the duration of the reproductive period, (2) the rate of dry mass acquisition in the reproductive period, and (3) the fraction of acquired biomass allocated to the reproductive part. Elevated [CO₂] increased the total amount of biomass that was allocated to reproductive structures, but this increase was caused by increased capsule mass without a significant increase in seed production. The increase in total reproductive mass was due mainly to an increase in the rate of dry mass acquisition in the reproductive period with a delay in leaf senescence. This positive effect was partly offset by a reduction in biomass allocation to the reproductive part at elevated [CO₂] and HN. The duration of the reproductive period was not affected by elevated [CO₂] but increased by HN. Seed production was strongly constrained by the availability of N for seed growth. The seed [N] was very high in X. canadense and did not decrease significantly at elevated [CO₂]. HN increased seed [N] without a significant increase in seed biomass production. Limited seed growth caused a reduction in biomass allocation to the reproductive part even though dry mass production was increased due to increased [CO₂] and N availability.     

Interspecific variation in the growth response of plants to an elevated ambient CO2 concentration

The effect of a doubling in the atmospheric CO₂ concentration on the growth of vegetative whole plants was investigated. In a compilation of literature sources, the growth stimulation of 156 plant species was found to be on average 37%. This enhancement is small compared to what could be expected on the basis of CO₂-response curves of photosynthesis. The causes for this stimulation being so modest were investigated, partly on the basis of an experiment with 10 wild plant species. Both the source-sink relationship and size constraints on growth can cause the growth-stimulating effect to be transient.Data on the 156 plant species were used to explore interspecific variation in the response of plants to high CO₂. The growth stimulation was larger for C₃ species than for C₄ plants. However the difference in growth stimulation is not as large as expected as C₄ plants also significantly increased in weight (41% for C₃ vs. 22% for C₄). The few investigated CAM species were stimulated less in growth (15%) than the average C₄ species. Within the group of C₃ species, herbaceous crop plants responded more strongly than herbaceous wild species (58%vs. 35%) and potentially fast-growing wild species increased more in weight than slow-growing species (54%vs. 23%). C₃ species capable of symbiosis with N₂-fixing organisms had higher growth stimulations compared to other C₃ species. A common denominator in these 3 groups of more responsive C₃ plants might be their large sink strength. Finally, there was some tendency for herbaceous dicots to show a larger response than monocots. Thus, on the basis of this literature compilation, it is concluded that also within the group of C₃ species differences exist in the growth response to high CO₂.Abbreviations LAR leaf area ratio - LWR leaf weight ratio - NAR net assimilation rate - PS_a rate of photosynthesis per unit leaf area - RGR relative growth rate - RWR root weight ratio - SLA specific leaf area     

Carbon balance in a monospecific stand of an annual herb <Emphasis Type="Italic">Chenopodium album</Emphasis> at an elevated CO<Subscript>2</Subscript> concentration

Elevated CO₂ enhances carbon uptake of a plant stand, but the magnitude of the increase varies among growth stages. We studied the relative contribution of structural and physiological factors to the CO₂ effect on the carbon balance during stand development. Stands of an annual herb Chenopodium album were established in open-top chambers at ambient and elevated CO₂ concentrations (370 and 700 μmol mol⁻¹). Plant biomass growth, canopy structural traits (leaf area, leaf nitrogen distribution, and light gradient in the canopy), and physiological characteristics (leaf photosynthesis and respiration of organs) were studied through the growing season. CO₂ exchange of the stand was estimated with a canopy photosynthesis model. Rates of light-saturated photosynthesis and dark respiration of leaves as related with nitrogen content per unit leaf area and time-dependent reduction in specific respiration rates of stems and roots were incorporated into the model. Daily canopy carbon balance, calculated as an integration of leaf photosynthesis minus stem and root respiration, well explained biomass growth determined by harvests (r ² = 0.98). The increase of canopy photosynthesis with elevated CO₂ was 80% at an early stage and decreased to 55% at flowering. Sensitivity analyses suggested that an alteration in leaf photosynthetic traits enhanced canopy photosynthesis by 40–60% throughout the experiment period, whereas altered canopy structure contributed to the increase at the early stage only. Thus, both physiological and structural factors are involved in the increase of carbon balance and growth rate of C. album stands at elevated CO₂. However, their contributions were not constant, but changed with stand development.     

Light, temperature and nutrients as factors in photosynthetic adjustment to an elevated concentration of carbon dioxide

The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated concentrations of CO₂ usually observed in C₃ plants sometimes does not persist. Experiments were conducted to test whether the patterns of response to the environment during growth were consistent with the hypotheses that photosynthetic adjustment to elevated CO₂ concentration is due to (1) feedback inhibition or (2) nutrient stress. Soybean [Glycine max (L.) Merr. cv. Williams] and sugar beet (Best vulgaris L. cv. Mono Hye-4) were grown from seed at 350 and 700 μl^? CO₂, at 20 and 25°C, at a photon flux density of 0.5 and 1.0 mmol m^?2 S^?1 and with three nutrient regimes until the third trifoliolate leaf of soybean or the sixth leaf of sugar beet had finished expanding. Net rates of CO₂ exchange of the most recently expanded leaves were then measured at both 350 and 700 μl 1^?1 CO₂. Plants grown at the elevated CO₂ concentration had net rates of leaf CO₂ exchange which were reduced by 33% in sugar beet and 23% in soybean when measured at 350 μl 1^?1 CO₂ and when averaged over all treatments. Negative photosynthetic adjustment to elevated CO₂ concentration was not greater at 20 than at 25°C, was not greater at a photon flux density of 1.0 than at 0.5 mmol m^?2 S^?1 and was not greater with limiting nutrients. Furthermore, in soybean, negative photosynthetic adjustment could be induced by a single night at elevated CO₂ concentration, with net rates of CO₂ exchange the next day equal to those of leaves of plants grown from seed at the elevated concentration of CO₂. These patterns do not support either the feedback-inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations of CO₂.     

Detoxification of the cruciferous phytoalexin brassinin in Sclerotinia sclerotiorum requires an inducible glucosyltransferase

The phytoalexins, brassinin, 1-methoxybrassinin and cyclobrassinin, were metabolized by the stem rot fungus Sclerotinia sclerotiorum into their corresponding glucosyl derivatives displaying no detectable antifungal activity. Importantly, co-incubation of S. sclerotiorum with camalexins, various phytoalexin analogs, and brassinin indicated that a synthetic camalexin derivative could slow down substantially the rate of brassinin detoxification. Furthermore, inducible brassinin glucosyltransferase (BGT) activity was detected in crude cell-free extracts of S. sclerotiorum. BGT activity was induced by the phytoalexin camalexin, and the brassinin analogs methyl tryptamine dithiocarbamate and methyl 1-methyltryptamine dithiocarbamate. The overall results suggest that the fungus S. sclerotiorum in its continuous adaptation and co-evolution with brassinin producing plants, has acquired efficient glucosyltransferase(s) that can disarm some of the most active plant chemical defenses.     

Protective effect of quercetin and rutin on photosensitized lysis of human erythrocytes in the presence of hematoporphyrin

Photosensitized hemolysis of human erythrocytes by hematoporphyrin was suppressed by flavonols such as quercetin and rutin at submillimolar concentrations. The suppression of photohemolysis was accompanied by inhibition of lipid peroxidation by the reagents. Quercetin and rutin were photooxidized in the presence of hematoporphyrin and the photooxidation was partially suppressed by 1 mM NaN3, a quencher of singlet molecular oxygen. Flavonols were also oxidized by radicals formed during degradation of lauroyl peroxide. These results indicate that flavonols can function as antioxidants in biological systems by terminating radical chain reactions and removing singlet molecular oxygen. A pharmacological function of flavonols, decrease of the increased permeability and fragility of capillary, was discussed in relation to their antioxidative functions.     

臭氧浓度升高对昆虫影响的研究进展

臭氧(O3)是最具危害性的空气污染物之一。目前流层中的臭氧水平从100多年前的10ppb到今天的40ppb,预计到2050年将达到68ppb左右。臭氧通过改变植物"质量"而影响植食性昆虫的取食偏嗜性、行为、生长和发育,进而影响天敌昆虫的适合度。臭氧还通过改变化学信息物质而影响昆虫的行为。本文根据国内外研究进展,结合作者的研究,论述了大气臭氧浓度升高对刺吸式昆虫、咀嚼式昆虫和天敌昆虫的影响,展望了未来研究的前景。     

The evaluation of the reactogenicity and immunological activity of an inactivated 3-component influenza vaccine with an elevated hemagglutinin concentration in the inoculation dosage

In this work the reactogenic properties and antigenic potency of inactivated trivalent influenza vaccine, obtained by elution and centrifugation and containing up to 9-11 micrograms of hemagglutinin for influenza viruses A(H1N1) and A(H3N2) and up to 14 micrograms for influenza virus B, were studied. The reactogenicity of the preparation was found to correspond to the regulations. The immunogenic potency characteristics of individual batches of this trivaccine were higher than the immunogenicity of divaccines, but did not meet the requirements of technical specifications.     

A new viewpoint to understand the response of leaf dark respiration to elevated CO<Subscript>2</Subscript> concentration

By investigating the R _D-C _a (dark respiration rate-atmospheric CO₂ concentration) and P _N (net photosynthetic rate)-C _a curves of bamboo (Fargesia denudata) and poplar (Populus cathayanna), we found that: (1) the minimal R _D was close to ambient CO₂ concentration, and the elevated or decreased atmospheric CO₂ concentration enhanced the R _D of both species; (2) the response curves of R _D-C _a were simulated well by quadratic function. This phenomenon might be an inherent property of leaf R _D of F. denudata and P. cathayanna. If this was true, it implies that effect of CO₂ on R _D could be interpreted with the relationship of R _D-C _a curves and the quadratic function.     

Differential responses in two varieties of winter wheat to elevated ozone concentration under fully open‐air field conditions

Two modern cultivars [Yangmai16 (Y16) and Yangfumai 2 (Y2)] of winter wheat (Triticum aestivum L.) with almost identical phenology were investigated to determine the impacts of elevated ozone concentration (E‐O₃) on physiological characters related to photosynthesis under fully open‐air field conditions in China. The plants were exposed from the initiation of tillering to final harvest, with E‐O₃ of 127% of the ambient ozone concentration (A‐O₃). Measurements of pigments, gas exchange rates, chlorophyll a fluorescence and lipid oxidation were made in three replicated plots throughout flag leaf development. In cultivar Y2, E‐O₃ significantly accelerated leaf senescence, as indicated by increased lipid oxidation as well as faster declines in pigment amounts and photosynthetic rates. The lower photosynthetic rates were mainly due to nonstomatal factors, e.g. lower maximum carboxylation capacity, electron transport rates and light energy distribution. In cultivar Y16, by contrast, the effects of E‐O₃ were observed only at the very last stage of flag leaf ageing. Since the two cultivars had almost identical phenology and very similar leaf stomatal conductance before senescence, the greater impacts of E‐O₃ on cultivars Y2 than Y16 cannot be explained by differential ozone uptake. Our findings will be useful for scientists to select O₃‐tolerant wheat cultivars against the rising surface [O₃] in East and South Asia.     

Stimulation of monoclonal antibody production by human-human hybridoma cells with an elevated concentration of potassium or sodium phosphate in serum-free medium

Potassium or sodium phosphate was found to stimulate the production of human monoclonal antibody by human-human hybridoma HB4C5. The addition of 15 mM Na-phosphate (pH 7.4) into serum-free culture medium increased the antibody production up to 4-fold, when seeded at cell density of 1×10⁵ cells/ml in dishes. At the higher cell density of 5×10⁵ cells/ml, K-phosphate was more effective than Na-phosphate, at the same concentration. In large-scale continuous culture, the addition of 10 mM Na-phosphate into serum-free culture medium stimulated antibody production by HB4C5 cells 6-fold.     

Comparative biochemistry of eumelanogenesis and the protective roles of phenoloxidase and melanin in insects

The phenolic biopolymer eumelanin is an important skin pigment found throughout the animal kingdom. The enzyme, tyrosinase, initiates melanogenesis in mammals. The biogenesis is assisted by a number of mammalian protein factors including dopachrome tautomerase and 5,6-dihydroxyindole-2-carboxylate oxidase. Invertebrates, such as insects, employ phenoloxidase and dopachrome (decarboxylating) isomerase for melanin biosynthesis. Recently generated molecular biological and biochemical data indicate that tyrosinase and phenoloxidase are distinctly different enzymes in spite of possessing both monophenol monooxygenase activity as well as o-diphenoloxidase activity. Similarly, insect dopachrome isomerase also differs significantly from its mammalian counterpart in several of its properties including the nature of the enzymatic reaction. In addition, there are considerable differences in the eumelanogenic pathways of these two animal groups that include the utility of substrates, use of dihydroxyindoles and the nature of eumelanin pigment. Thus, the biochemistry and molecular biology of melanogenesis in mammals and insects are significantly different. The advantages of generating different eumelanin pigments and intermediates by the insects are discussed.     

Comparative immuno-removal: a novel method for estimating the concentration of an unknown immunoreactive compound

We describe a method for estimating the molar concentration of an unknown immunoreactive compound. The amount of antibody required to bind half of a standard is compared to the amount required to bind half of an equal number of immunoreactive equivalents of the unknown. We demonstrate the utility of the method using a morphine antibody affinity resin and compounds structurally related to morphine.     

Effects of initial sucrose concentration on excretion of anthocyanin pigments in suspended cultures of Perilla frutescens cells

Cell cultures of Perilla frutescens, growing on Linsmaier and Skoog medium, released more anthocyanin with 40 to 50 g sucrose/l compared with the control of 30 g sucrose/l of medium. More proteins were also released into the medium with the higher sucrose concentration and the cell volume was smaller, suggesting that the higher osmotic pressure, caused by the high sucrose concentration, may cause these releases. The capacitance of the cultured cells indicated a difference in membrane structure between the cells cultivated with different sucrose concentrations, supporting the hypothesis that cell permeabilization is increased at higher sucrose concentrations.J.-J. Zhong is with the Research Institute of Biochemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China, G.-R. Xu is with the Department of Fermentation Technology, Wuxi Institue of Light Industry, Jiangsu 214036, China. T. Yoshida is with the International Center of Cooperative Research in Biotechnology, Faculty of Engineering. Osaka University, Osaka 565, Japan.