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1.
Vittoria Di Martino Rigano Vincenza Vona Catello Di Martino Carmelo Rigano 《Physiologia plantarum》1986,68(1):34-38
Cyanidium caldarium (Tilden) Geitler, a non-vacuolate unicellular alga, resuspended in medium flushed with air enriched with 5% CO2 , assimilated NH4 + at high rates both in the light and in the dark. The assimilation of NO3 − , by contrast, was inhibited by 63% in the dark. In cell suspensions flushed with CO2 -free air, NH4 + assimilation decreased with time both in the light and in the dark and ceased almost completely after 90 min. The addition of CO2 completely restored the capacity of the alga to assimilate NH4 + . NO3 − assimilation, by contrast, was 33% higher in the absence of CO2 and was linear with time. It is suggested that NO3 − and NH4 + metabolism in C. caldarium are differently controlled in response to the light and carbon conditions of the cell. 相似文献
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The possibility to induce nitrate reductase (NR; EC 1.6.6.2) in needles of Scots pine ( Pinus sylvestris L.) seedlings was studied. The NR activity was measured by an in vivo assay. Although increased NR activities were found in the roots after application of NO3 − , no such increase could be detected in the needles. Detached seedlings placed in NO3 − solution showed increasing NR activities with increasing NO3 − concentrations. Exposure of seedlings to NOx (70–80 ppb NO2 and 8–12ppb NO) resulted in an increase of the NR activity from 10–20 nmol NO2 − (g fresh weight)−1 h−1 to about 400 nmol NO2 − (g fresh weight)−1 h−1 . This level was reached after 2–4 days of exposure, thereafter the NR activity decreased to about 200 nmol NO2 − (g fresh weight)−1 h−1 . Analyses of free amino acids showed low concentrations of arginine and glutamine in NOx -fumigated seedlings compared to corresponding controls. 相似文献
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Leif Skøt 《Physiologia plantarum》1983,59(4):581-584
The quantitative relationship between C2 H2 reduction, H2 evolution and 15 N2 fixation was investigated in excised root nodules from pea plants ( Pisum sativum L. cv. Bodil) grown under controlled conditions. The C2 H2 /N2 conversion factor varied from 3.31 to 5.12 between the 32nd and the 67th day after planting. After correction for H2 evolution in air, the factor (C2 H2 -H2 )/N2 decreased to values near the theoretical value 3, or in one case to a value significantly ( P < 0.05) below 3. The proportion of the total electron flow through nitrogenase, which is not wasted in H2 production but used for N2 reduction, is often stated as the relative efficiency (1-H2 /C2 H2 ). This factor varied significantly ( P < 0.05) during the growth period. The actual allocation of electrons to H2 and N2 , expressed as the H2 /N2 ratio, was independent of plant age, however. This discrepancy and the observation that the (C2 H2 -H2 )/N2 conversion factor tended to be lower than 3, suggests that the C2 H2 reduction assay underestimates the total electron flow through nitrogenase. 相似文献
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P. J. APARICIO F. G. WITT J. M. RAMÍREZ M. A. QUIÑONES T. BALANDÍN 《Plant, cell & environment》1994,17(12):1323-1330
In M. braunii, the uptake of NO3− and NO2− is blue-light-dependent and is associated with alkalinization of the medium. In unbuffered cell suspensions irradiated with red light under a CO2-free atmosphere, the pH started to rise 10s after the exposure to blue light. When the cellular NO3− and NO2− reductases were active, the pH increased to values of around 10, since the NH4+ generated was released to the medium. When the blue light was switched off, the pH stopped increasing within 60 to 90s and remained unchanged under background red illumination. Titration with H2SO4 of NO3− or NO2− uptake and reduction showed that two protons were consumed for every one NH4+ released. The uptake of Cl− was also triggered by blue light with a similar 10 s time response. However, the Cl− -dependent alkalinization ceased after about 3 min of blue light irradiation. When the blue light was turned off, the pH immediately (15 to 30 s) started to decline to the pre-adjusted value, indicating that the protons (and presumably the Cl−) taken up by the cells were released to the medium. When the cells lacked NO3− and NO2− reductases, the shape of the alkalinization traces in the presence of NO3− and NO2− was similar to that in the presence of Cl−, suggesting that NO3− or NO2− was also released to the medium. Both the NO3− and Cl−-dependent rates of alkalinization were independent of mono- and divalent cations. 相似文献
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Abstract The utilization of NO− 3 , NO− 2 and NH+ 4 was studied in whole filaments and isolated heterocysts of Anabaena 7120 (ATCC27893). NO− 3 - and NO− 2 -uptake were detectable in whole filaments but not in heterocysts, whereas NH+ 4 -uptake was detectable in both. Activity of NO− 3 -reductase was present in cell-free extracts of whole filaments but not of heterocysts, whereas activities of NO− 2 -reductase and glutamine synthetase were present in both. NO− 3 -uptake and reductase activities could not be induced in heterocysts even after prolonged incubation in NO− 3 medium. It is suggested that NO− 3 -metabolism in heterocysts is impaired due to a selective and irreversible loss of NO− 3 -uptake and reductase systems resulting in the abolition of competition for molybdenum cofactor (Mo-Co) and reductant between nitrogenase and NO− 3 -reductase, and an increase in glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase levels. 相似文献
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Abstract A mutant strain of Rhizobium japonicum (CJ9) unable to assimilate ammonium (Asm− ) was isolated following mutagenesis with N -methyl N -nitro-nitrosoguanidine (NTG). Glutamate synthase activity was not detectable in cell-free extracts of the mutant strain in contrast to the wild type and revertant strains. Although mutant CJ9 induced nitrogenase activity in an 'in vitro' assay system under microaerobic conditions, it failed to fix nitrogen (acetylene reduction) in soybean root nodules. These properties of mutant CJ9 constitute a new Asm− mutant class in Rhizobium spp. 相似文献
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The atmospheric CO2 concentration has risen from the preindustrial level of approximately 290 μl l−1 to more than 350 μl l−1 in 1993. The current rate of rise is such that concentrations of 420 μl l−1 are expected in the next 20 years. For C3 plants, higher CO2 levels favour the photosynthetic carbon reduction cycle over the photorespiratory cycle, resulting in higher rates of carbohydrate production and plant productivity. The change in balance between the two photosynthetic cycles appears to alter nitrogen and carbon metabolism in the leaf, possibly causing decreases in nitrogen concentrations in the leaf. This may result from increases in the concentration of storage carbohydrates of high molecular weight (soluble or insoluble) and/or changes in distribution of protein or other nitrogen containing compounds. Uptake of nitrogen may also be reduced at high CO2 due to lower transpiration rates. Decreases in foliar nitrogen levels have important implications for production of crops such as wheat, because fertilizer management is often based on leaf chemical analysis, using standards estimated when the CO2 levels were considerably lower. These standards will need to be re-evaluated as the CO2 concentration continues to rise. Lower levels of leaf nitrogen will also have implications for the quality of wheat grain produced, because it is likely that less nitrogen would be retranslocated during grain filling. 相似文献
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Folivorous insect responses to elevated CO2-grown tree species may be complicated by phytochemical changes as leaves age. For example, young expanding leaves in tree species may be less affected by enriched CO2-alterations in leaf phytochemistry than older mature leaves due to shorter exposure times to elevated CO2 atmospheres. This, in turn, could result in different effects on early vs. late instar larvae of herbivorous insects. To address this, seedlings of white oak (Quercus alba L.), grown in open-top chambers under ambient and elevated CO2, were fed to two important early spring feeding herbivores; gypsy moth (Lymantria dispar L.), and forest tent caterpillar (Malacosoma disstria Hübner). Young, expanding leaves were presented to early instar larvae, and older fully expanded or mature leaves to late instar larvae. Young leaves had significantly lower leaf nitrogen content and significantly higher total nonstructural carbohydrate:nitrogen ratio as plant CO2 concentration rose, while nonstructural carbohydrates and total carbon-based phenolics were unaffected by plant CO2 treatment. These phytochemical changes contributed to a significant reduction in the growth rate of early instar gypsy moth larvae, while growth rates of forest tent caterpillar were unaffected. The differences in insect responses were attributed to an increase in the nitrogen utilization efficiency (NUE) of early instar forest tent caterpillar larvae feeding on elevated CO2-grown leaves, while early instar gypsy moth larval NUE remained unchanged among the treatments. Later instar larvae of both insect species experienced larger reductions in foliage quality on elevated CO2-grown leaves than earlier instars, as the carbohydrate:nitrogen ratio of leaves substantially increased. Despite this, neither insect species exhibited changes in growth or consumption rates between CO2 treatments in the later instar. An increase in NUE was apparently responsible for offsetting reduced foliar nitrogen for the late instar larvae of both species. 相似文献
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R. J. Swap J. N. Aranibar P. R. Dowty W. P. Gilhooly III S. A. Macko 《Global Change Biology》2004,10(3):350-358
The mean annual rainfall in southern Africa is found to explain over half of the observed variance in the stable nitrogen (N) isotopic signatures of C3 vegetation in southern Africa (r2=0.54, P<0.01). The inverse relationship between the stable N isotopic signatures of foliar samples from C3 vegetation and long‐term southern African rainfall is found on a scale larger than previously observed. A modest relationship is found between stable carbon (C) isotopic signatures of C3 vegetation and rainfall across the region (r2=0.20, P<0.01). No such relationship is found between stable C and N isotopic signatures of C4 vegetation and rainfall. The explanation of the relationship between 15N in C3 vegetation and the mean annual rainfall presented here is that nutrient availability varies inversely with water availability. This suggests that water‐limited systems in southern Africa are more open in terms of nutrient cycling and therefore the resulting natural abundance of foliar 15N in these systems is enriched. The use of this relationship may be of value to those researchers modeling both the dynamics of vegetation and biogeochemistry across this region. The use of the isotopic enrichment in C3 vegetation as a function of rainfall may provide an insight into nutrient cycling across the semi‐arid and arid regions of southern Africa. This finding has implications for the study of global change, especially as it relates to vegetation responses to changing regional rainfall regimes over time. 相似文献
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M. Schortemeyer O. K. Atkin N. McFarlane & J. R. Evans 《Plant, cell & environment》2002,25(4):567-579
In the present study the effect of elevated CO2 on growth and nitrogen fixation of seven Australian Acacia species was investigated. Two species from semi‐arid environments in central Australia (Acacia aneura and A. tetragonophylla) and five species from temperate south‐eastern Australia (Acacia irrorata, A. mearnsii, A. dealbata, A. implexa and A. melanoxylon) were grown for up to 148 d in controlled greenhouse conditions at either ambient (350 µmol mol?1) or elevated (700 µmol mol?1) CO2 concentrations. After establishment of nodules, the plants were completely dependent on symbiotic nitrogen fixation. Six out of seven species had greater relative growth rates and lower whole plant nitrogen concentrations under elevated versus normal CO2. Enhanced growth resulted in an increase in the amount of nitrogen fixed symbiotically for five of the species. In general, this was the consequence of lower whole‐plant nitrogen concentrations, which equate to a larger plant and greater nodule mass for a given amount of nitrogen. Since the average amount of nitrogen fixed per unit nodule mass was unaltered by atmospheric CO2, more nitrogen could be fixed for a given amount of plant nitrogen. For three of the species, elevated CO2 increased the rate of nitrogen fixation per unit nodule mass and time, but this was completely offset by a reduction in nodule mass per unit plant mass. 相似文献
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δ, C isotope composition relative to Pee Dee BelemniteWSC, water-soluble carbohydratesN, nitrogenC, carboncv, cultivarME, efficiency of mobilized pre-anthesis C utilization in grain filling (g C g–1C)Significant mobilization of protein and carbohydrates in vegetative plant parts of wheat regularly occurs during grain filling. While this suggests a contribution of reserves to grain filling, the actual efficiency of mobilized assimilate conversion into grain mass (ME) is unknown. In the present study the contribution of pre-anthesis C (C fixed prior to anthesis) to grain filling in main stem ears of two spring wheat (Triticum aestivum L.) cultivars was determined by 13C/12C steady-state labelling. Mobilization of pre-anthesis C in vegetative plant parts between anthesis and maturity, and the contributions of water-soluble carbohydrates (WSC) and protein to pre-anthesis C mobilization were also assessed. Experiments were performed with two levels of N fertilizer supply in each of 2 years. Pre-anthesis reserves contributed 11–29% to the total mass of C in grains at maturity. Pre-anthesis C accumulation in grains was dependent on both the mass of pre-anthesis C mobilized in above-ground vegetative plant parts (r2 = 0·87) and ME (defined as g pre-anthesis C deposited in grains per g pre-anthesis C mobilized in above-ground vegetative plant parts; r2 = 0·40). ME varied between 0·48 and 0·75. The effects of years, N fertilizer treatments and cultivars on ME were all related to differences in the fractional contribution of WSC to pre-anthesis C mobilization. Multiple regression analysis indicated that C from mobilized pre-anthesis WSC may be used more efficiently in grain filling than C present in proteins at anthesis and mobilized during grain filling. Possible causes for variability of ME are discussed. 相似文献
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John D. Tjepkema 《Physiologia plantarum》1997,99(4):648-652
Preliminary studies have indicated that after addition of C2 H2 there is a rapid decline in nitrogenase activity in the nodules of Datisca glomerata . The present work was undertaken to determine whether (1) there is also a decline in respiration and (2) the decline is associated with the cessation of ammonia production. The rates of C2 H4 and CO2 evolution by nodulated root systems of Datisca were measured as a function of time after exposure to C2 H2 . The peak rate of C2 H4 evolution occurred at 30 s after C2 H2 exposure, while the rate of CO2 evolution started to decline at 60 s after exposure to C2 H2 . Incubation of nodules in a gas mixture containing Ar also caused a decline in CO2 evolution. Further, pretreatment with Ar eliminated most of the C2 H2 -induced decline in nitrogenase activity and CO2 evolution. These C2 H2 - and Ar-induced declines in Datisca nodules are more rapid than those reported in any other nodules. They are evidence that continued ammonia formation is essential for maintenance of normal nitrogenase activity in Datisca nodules. 相似文献
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Fitzgerald L. Booker † Stephen A. Prior‡ H. Allen Torbert‡ Edwin L. Fiscus † Walter A. Pursley † Shuijin Hu§ 《Global Change Biology》2005,11(4):685-698
A critical global climate change issue is how increasing concentrations of atmospheric CO2 and ground‐level O3 will affect agricultural productivity. This includes effects on decomposition of residues left in the field and availability of mineral nutrients to subsequent crops. To address questions about decomposition processes, a 2‐year experiment was conducted to determine the chemistry and decomposition rate of aboveground residues of soybean (Glycine max (L.) Merr.) grown under reciprocal combinations of low and high concentrations of CO2 and O3 in open‐top field chambers. The CO2 treatments were ambient (370 μmol mol?1) and elevated (714 μmol mol?1) levels (daytime 12 h averages). Ozone treatments were charcoal‐filtered air (21 nmol mol?1) and nonfiltered air plus 1.5 times ambient O3 (74 nmol mol?1) 12 h day?1. Elevated CO2 increased aboveground postharvest residue production by 28–56% while elevated O3 suppressed it by 15–46%. In combination, inhibitory effects of added O3 on biomass production were largely negated by elevated CO2. Plant residue chemistry was generally unaffected by elevated CO2, except for an increase in leaf residue lignin concentration. Leaf residues from the elevated O3 treatments had lower concentrations of nonstructural carbohydrates, but higher N, fiber, and lignin levels. Chemical composition of petiole, stem, and pod husk residues was only marginally affected by the elevated gas treatments. Treatment effects on plant biomass production, however, influenced the content of chemical constituents on an areal basis. Elevated CO2 increased the mass per square meter of nonstructural carbohydrates, phenolics, N, cellulose, and lignin by 24–46%. Elevated O3 decreased the mass per square meter of these constituents by 30–48%, while elevated CO2 largely ameliorated the added O3 effect. Carbon mineralization rates of component residues from the elevated gas treatments were not significantly different from the control. However, N immobilization increased in soils containing petiole and stem residues from the elevated CO2, O3, and combined gas treatments. Mass loss of decomposing leaf residue from the added O3 and combined gas treatments was 48% less than the control treatment after 20 weeks, while differences in decomposition of petiole, stem, and husk residues among treatments were minor. Decreased decomposition of leaf residues was correlated with lower starch and higher lignin levels. However, leaf residues only comprised about 20% of the total residue biomass assayed so treatment effects on mass loss of total aboveground residues were relatively small. The primary influence of elevated atmospheric CO2 and O3 concentrations on decomposition processes is apt to arise from effects on residue mass input, which is increased by elevated CO2 and suppressed by O3. 相似文献
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The long-term effects of different nitrogen sources on the endogenous IAA and cytokinin levels in two bromeliad species were investigated. In nature, Vriesea philippocoburgii is a tank-forming epiphytic bromeliad which uses the tank water reservoir as a substitute for soil, whereas Tillandsia pohliana is a tankless atmospheric epiphytic species. A culture was established from seeds germinated in aseptic condictions, and the plantlets were grown for 6 months in a modified Knudson medium to which was added 8 mol m−3 of nitrogen in the form of NO3−, NH4+ or urea. The hormonal contents of the bromeliad shoots were determined by means of high-performance liquid chromatography (HPLC), coupled to an enzyme-linked immunosorbent assay (ELISA) for indole-3-acetic acid (IAA), isopentenyladenine (iP), isopentenyladenosine ([9R]iP), zeatin (Z) and zeatin riboside ([9R]Z). Nitrogen supplied in the form of urea gave the highest values of fresh and dry weights for both species, and this was positively correlated to IAA levels. The cytokinin patterns showed that isopentenyladenosine was the predominant form for both species in all samples. However, urea induced the highest level of this riboside form and also the highest level of total cytokinins for V. philippocoburgii, while NH4+ had the same effect on the atmospheric species. These results are discussed in terms of the different growth habits of these two species in nature. It is suggested that urea may be an important source of nitrogen often found inside the tank of V. philippocoburgii. NO3− treatment increased the IAA/Cks balance, mainly for V. philippocoburgii, while urea and NH4+ shifted this ratio in favour of cytokinins, thus apparently inhibiting root development in both species. 相似文献
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We grew a non-bicarbonate using red seaweed, Lomentaria articulata (Huds.) Lyngb., in media aerated with four O2 concentrations between 10 and 200% of current ambient [O2] and four CO2 concentrations between 67 and 500% of current ambient [CO2], in a factorial design, to determine the effects of gas composition on growth and physiology. The relative growth rate of L. articulata increased with increasing [CO2] up to 200% of current ambient [CO2] but was unaffected by [O2]. The relative growth enhancement, on a carbon basis, was 52% with a doubling of [CO2] but fell to 23% under 5× ambient [CO2]. Plants collected in winter responded more extremely to [CO2] than did plants collected in the summer, although the overall pattern was the same. Discrimination between stable carbon isotopes (Δ13C) increased with increasing [CO2] as would be expected for diffusive CO2 acquisition. Tissue C and N were inversely related to [CO2]. Growth in terms of biomass appeared to be limited by conversion of photosynthate to new biomass rather than simply by diffusion of CO2, suggesting that non-bicarbonate-using macroalgae, such as L. articulata, may not be directly analogous to C3 higher plants in terms of their responses to changing gas composition. 相似文献