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1.
Summary Pure and mixed cultures of the dicotyledons Atriplex hortensis L. (C3 plant) and Amaranthus retroflexus L. (C4 plant) were maintained under open air conditions in standard soil at low and high nitrogen supply levels.A comparison of shoot dry weight and shoot length in the various series shows that the growth of the aboveground parts of both species was severely reduced under low N conditions. In both pure and mixed cultures the differences resulting from low N vs. high N conditions was less pronounced with Atriplex (C3 plant) than with Amaranthus (C4 plant). The root dry weight of the two species was not reduced so much under low N conditions as was the shoot dry weight. The low N plants were found to contain a larger proportion of their biomass in the roots than did the high N plants. In general the root proportion of Atriplex was greater than that of Amaranthus. The contents of organic nitrogen and nitrate and the nitrate reductase activity (NRA) per g dry weight of both species decreased continually throughout the experiments. With the exception of young plants, the low N plants always had tower contents of organic nitrogen and nitrate and nitrate reductase activities than did the high N plants. The highest values of NRA were measured in the leaf laminae. The eaves also exhibited the highest concentrations of organic nitrogen. The highest nitrate concentrations, however, were observed in the shoot axis, and in most cases the lowest nitrate values were found in the laminae. At the end of ne growing season this pattern was found to have been reversed with Atriplex, but not with Amaranthus. Thus Atriplex was able to maintain a higher NRA in the laminae than Amaranthus under low N conditions.The transpiration per leaf area of the C4 plant Amaranthus during the course of a day was substantially lower than that of the C3 plant Atriplex. There were no significant differences in transpiration between the low N and high N series of Amaranthus. The low N plants of Atriplex, however, clearly showed in most cases higher transpiration rates than the corresponding high N plants. These different transpiration rates of the high N and the low N Atriplex plants were also reflected in a distinct 13C discrimination.The sum of these results points to the conclusion that the C3 plant Atriplex hortensis can maintain a better internal inorganic nitrogen supply than the C4 plant Amaranthus retroflexus under low N conditions and an ample water supply, due to the larger root proportion and the more pronounced and flexible transpiration of the C3 plant.Dedicated to Prof. Dr. Karl Mägdefrau, Deisenhofen, on the ocasion of his 80th birthday 相似文献
2.
Summary The purpose of this study was to investigate the phytotoxicity of nitrapyrin 2-chloro-6-(trichloromethyl)pyridine to sunflower
(Helianthus annuus L.) under different N regimes and to see if N forms affect the phytotoxicity of nitrapyrin. Sunflower was grown in pot culture
for 21 days and was fertilized with (NH4)2SO4, NH4NO3 and NaNO3 to provide 0, 100 and 200 ppm N and with nitrapyrin application of 0 and 20 ppm. All N-treated sunflower plants in all N
regimes and regardless of titrapyrin treatment produced more root and shoot dry weights and contained a significantly higher
N than untreated check. Nitrapyrin toxicity appeared as a curling of leaf margin and a tendril type of stem growth, the visible
toxicity symptoms decreased in the order: (NH4)2SO4>NH4NO3>NaNO3. Furthermore nitrapyrin addition suppressed sunflower growth in each N regime, the suppressing effect being greater with
(NH4)2SO4 and NH4NO3 than as with NaNO3. Although, shoot growth from plants receiving nitrapyrin was not significantly affected by any N regime, root growth of nitrapyrin-treated
plants was somewhat restricted by NH4
+−N nutrition relative to NO3
−−N nutrition. 相似文献
3.
Two phospholipases A2 (PLA2) fromNaja naja atra andNaja nigricollis snake venoms were subjected to tyrosine modification withp-nitrobenzenesulfonyl fluoride (NBSF) atpH 8.0. Three major NBS derivatives from each PLA2 were separated by high-performance liquid chromatography. The results of amino acid analysis showed that only two Tyr residues out of nine were modified, and the modified residues were identified to be Tyr-3 and Tyr-63 (or Tyr-62) in the sequence. Spectrophotometric titration indicated that the phenolic group of Tyr-3 and Tyr-63 (or Tyr-62) had apK of 10.1 and 11.0, respectively. The reactivity of Tyr-3 toward NBSF was not affected in the presence or absence of Ca
2+; however, the reactivity of Tyr-63 (or Tyr-62) toward NBSF was greatly enhanced by Ca2+. Modification of Tyr-63 (or Tyr-62) resulted in a marked decrease in both lethality and enzymatic activity. Conversely, modification of Tyr-3 inN. naja atra PLA2 could cause more than a sixfold increase in lethal potency, in sharp contrast to the loss of enzymatic activity.Tyrosine-63-modifiedN. naja atra PLA2 exhibited the same Ca2+-induced difference spectra as that of native PLA2, indicating that the Ca2+-binding ability of Tyr-63-modifiedN. naja atra PLA2 was not impaired. However, Tyr-3-modified PLA2 and all Tyr-modifiedN. nigricollis CMS-9 were not perturbed by Ca2+, revealing that the Ca2+-binding ability have been lost after tyrosine modification. These results suggest that Tyr-62 inN. nigricollis CMS-9 and Tyr-3 in both enzymes are involved in Ca2+ binding. AtpH 8.0, both native PLA2 enzymes enhance the emission intensity of 8-anilinonaphthalene sulfonate (ANS) dramatically, while all of the Tyr-modified derivatives did not enhance the emission intensity at all either in the presence or absence of Ca2+, suggesting that the hydrophobic pocket that interacts with ANS might be the substrate binding site, in which Tyr-3 and Tyr-63 (or Tyr-62) are involved. 相似文献
4.
An increasing amount of evidence indicates that N can be transferred between plants. Nonetheless, a number of fundamental
questions remain. A series of experiments was initiated in the field to examine N transfer between N2-fixing soybean (Glycine max [L.] Merr.) varieties and a non-nodulating soybean, and between N2-fixing peanut (Arachis hypogaea L.) or soybean and neighboring weed species. The experiments were conducted in soils with low N fertilities and used differences
in N accumulation and/or 15N natural abundance to estimate N transfer. Mixtures of N2-fixing and non-nod soybean indicated that substantial inter-plant N transfer occurred. Amounts were variable, ranging from
negligible levels to 48% of the N found in the non-nod at maturity. Transfer did not appear to strongly penalize the N2-fixing donor plants. But, in cases where high amounts of N were transferred, N content of donors was noticeably lowered.
Differences were evident in the amount of N transferred from different N2-fixing donor genotypes. Results of experiments with N2-fixing crops and the weed species prickly sida (Sida spinosa L.) and sicklepod (Senna obtusifolia [L.] Irwin & Barneby) also indicated substantial N transfer occurred over a 60-day period, with amounts accounting for 30–80%
of the N present in the weeds. Transfer of N, however, was generally very low in weed species that are known to be non-hosts
for arbuscular mycorrhizae (yellow nutsedge, Cyperus esculentus L. and Palmer amaranth, Amaranthus palmeri [S.] Watson). The results are consistent with the view that N transfer occurs primarily through mycorrhizal hyphal networks,
and they reveal that N transfer may be a contributing factor to weed problems in N2-fixing crops in low N fertility conditions. 相似文献
5.
The influence of growth rate, the presence of acetate and variation in the dissolved oxygen concentration on the kinetics
of nitrite oxidation was studied in suspensions of intact cells of Nitrobacter winogradskyi and Nitrobacter hamburgensis. The cells were grown in nitrite-limited chemostats at different dilution rates under chemolithotrophic and mixotrophic conditions.
Growth of N. hamburgensis in continuous culture was dependent on the presence of acetate. Acetate hardly affected the maximal nitrite oxidation rate
per cell (V
max), but displayed a distinctly negative effect on the saturation constants for nitrite oxidation (K
m
) of both Nitrobacter species. This effect was reversible; when acetate was removed from the suspensions the K
m
-values for nitrite oxidation returned to their original values.
A reduction of the dissolved oxygen concentration from 100% to 18% air saturation slightly decreased the V
max of chemolithotrophically grown N. winogradskyi cells, whereas a 2.3 fold increase was observed with mixotrophically grown cells of N. hamburgensis. It is suggested that the large variation in K
m
encountered in field samples could be due to this observed phenotypic variability. The V
max per cell is not a constant, but apparently is dependent on growth rate and environmental conditions. This implies that potential
nitrite oxidation activity and numbers of cells are not necessarily related. Considering their kinetic characteristics, it
is unlikely that N. hamburgensis is able to compete succesfully with N. winogradskyi for limiting amounts of nitrite under mixotrophic conditions. However, at reduced partial oxygen tensions, N. hamburgensis may become the better competitor. 相似文献
6.
El Amin Yousif Raddad Ahmed Ali Salih Mohamed Ahmed El Fadl Vesa Kaarakka Olavi Luukkanen 《Plant and Soil》2005,275(1-2):261-269
The symbiotic biological N2fixation by Acacia senegal was estimated using the 15N natural abundance (δ
15N) procedure on eight provenances collected from different environments and soil types grown in a clay soil in the Blue Nile
region, Sudan. Balanites aegyptiaca (a non-legume) was used as a non-N2-fixing reference plant to allow 15N-based estimates of the proportion of the Acacia N derived from atmospheric N2 (Ndfa) to be calculated. Results show variation in leaf δ
15N between A. senegal and the reference plant and among years. The relative δ
15N values (‰) were higher in B. aegyptiaca than in the N2-fixing acacia provenances. Provenances originally collected from clay soils fixed little N in the first year, but the amount
fixed increased as the trees aged. All provenances showed a decrease in δ
15N with age. The Ndfa varied between 24% (Mazmoom provenance) and 61% (Rahad provenance) 4 years after planting. There was no significant difference
in δ
15N between provenance groups based on soil type or rainfall at original growing site. The amount of Ndfa increased significantly with age in all provenances. The above-ground contribution of fixed N to foliage growth in a 4-year-old
A. senegal was highest in the Rahad sand–soil provenance (46.7 kg N ha−1) and lowest in the Mazmoom clay-soil provenance (28.7 kg N ha−1). Our study represents the first use of the δ
15N method for estimating the N input by A. senegal to the clay plain soils of the gum belt in the Sudan. 相似文献
7.
A homodimer of b subunits constitutes the peripheral stalk linking the F1 and F0 sectors of the Escherichia coli ATP synthase. Each b subunit has a single-membrane domain. The constraints on the membrane domain have been studied by systematic mutagenesis. Replacement of a segment proximal to the cytoplasmic side of the membrane had minimal impact on F1F0 ATP synthase. However, multiple substitutions on the periplasmic side resulted in defects in assembly of the enzyme complex. These mutants had insufficient oxidative phosphorylation to support growth, and biochemical studies showed little F1F0 ATPase and no detectable ATP-driven proton pumping activity. Expression of the b
N2A,T6A,Q10A
subunit was also oxidative phosphorylation deficient, but the b
N2A,T6A,Q10A
protein was incorporated into an F1F0 complex. Single amino acid substitutions had minimal reductions in F1F0 ATP synthase function. The evidence suggests that the b subunit membrane domain has several sites of interaction contributing to assembly of F0, and that these interactions are strongest on the periplasmic side of the bilayer. 相似文献
8.
With the ability to symbiotically fix atmospheric N2, legumes may lack the N-limitations thought to constrain plant response to elevated concentrations of atmospheric CO2. The growth and photosynthetic responses of two perennial grassland species were compared to test the hypotheses that (1) the CO2 response of wild species is limited at low N availability, (2) legumes respond to a greater extent than non-fixing forbs to elevated CO2, and (3) elevated CO2 stimulates symbiotic N2 fixation, resulting in an increased amount of N derived from the atmosphere. This study investigated the effects of atmospheric CO2 concentration (365 and 700 mol mol–1) and N addition on whole plant growth and C and N acquisition in an N2-fixing legume (Lupinus perennis) and a non-fixing forb (Achillea millefolium) in controlled-chamber environments. To evaluate the effects of a wide range of N availability on the CO2 response, we incorporated six levels of soil N addition starting with native field soil inherently low in N (field soil + 0, 4, 8, 12, 16, or 20 g N m–2 yr–1). Whole plant growth, leaf net photosynthetic rates (A), and the proportion of N derived from N2 fixation were determined in plants grown from seed over one growing season. Both species increased growth with CO2enrichment, but this response was mediated by N supply only for the non-fixer, Achillea. Its response depended on mineral N supply as growth enhancements under elevated CO2 increased from 0% in low N soil to +25% at the higher levels of N addition. In contrast, Lupinus plants had 80% greater biomass under elevated CO2 regardless of N treatment. Although partial photosynthetic acclimation to CO2 enrichment occurred, both species maintained comparably higher A in elevated compared to ambient CO2 (+38%). N addition facilitated increased A in Achillea, however, in neither species did additional N availability affect the acclimation response of A to CO2. Elevated CO2 increased plant total N yield by 57% in Lupinus but had no effect on Achillea. The increased N in Lupinus came from symbiotic N2 fixation, which resulted in a 47% greater proportion of N derived from fixation relative to other sources of N. These results suggest that compared to non-fixing forbs, N2-fixers exhibit positive photosynthetic and growth responses to increased atmospheric CO2 that are independent of soil N supply. The enhanced amount of N derived from N2 fixation under elevated CO2 presumably helps meet the increased N demand in N2-fixing species. This response may lead to modified roles of N2-fixers and N2-fixer/non-fixer species interactions in grassland communities, especially those that are inherently N-poor, under projected rising atmospheric CO2. 相似文献
9.
Dan Gibson Yonit Kasherman Dina Kowarski Inna Freikman 《Journal of biological inorganic chemistry》2006,11(2):179-188
In order to monitor the trans labilization of cisplatin at physiological pH we have prepared the complex cis-[PtCl2(13CH3NH2)2] and studied its interactions with excess glutathione in aqueous solution at neutral pH by two-dimensional [1H,13C] heteronuclear
single-quantum correlation (HSQC) NMR spectroscopy. [1H,13C] HSQC spectroscopy is a good method for following the release
of 13CH3NH2 but is not so good for characterizing the Pt species in solution. In the reaction of cisplatin with glutathione, Pt–S bonds
are formed and Pt–NH3 bonds are broken. The best technique for following the formation of Pt–S bonds of cisplatin is by UV spectroscopy. [1H,13C]
HSQC spectroscopy is the best method for following the breaking of the Pt–N bonds. [1H,15N] HSQC spectroscopy is the best
method for characterizing the different species in solution. However, the intensity of the peaks in the 15NH3–Pt–S region, in [1H,15N] HSQC, reflects a balance between the formation of Pt–S bonds, which increases the signal intensity,
and the trans labilization, which decreases the signal intensity. [1H,15N] HSQC spectroscopy and [1H,13C] HSQC spectroscopy are complementary
techniques that should be used in conjunction in order to obtain the most accurate information on the interaction of platinum
complexes with sulfur-containing ligands. 相似文献
10.
Two plant species, Medicago truncatula (legume) and Avena sativa (non-legume), were grown in low-or high-N soils under two CO2 concentrations to test the hypothesis whether C allocation within plant-soil system is interactively or additively controlled
by soil N and atmospheric CO2 is dependent upon plant species. The results showed the interaction between plant species and soil N had a significant impact
on microbial activity and plant growth. The interaction between CO2 and soil N had a significant impact on soil soluble C and soil microbial biomass C under Madicago but not under Avena. Although both CO2 and soil N affected plant growth significantly, there was no interaction between CO2 and soil N on plant growth. In other words, the effects of CO2 and soil N on plant growth were additive. We considered that the interaction between N2 fixation trait of legume plant and elevated CO2 might have obscured the interaction between soil N and elevated CO2 on the growth of legume plant. In low-N soil, the shoot-to-root ratio of Avena dropped from 2.63±0.20 in the early growth stage to 1.47±0.03 in the late growth stage, indicating that Avena plant allocated more energy to roots to optimize nutrient uptake (i.e. N) when soil N was limiting. In high-N soil, the shoot-to-root
ratio of Medicago increased significantly over time (from 2.45±0.30 to 5.43±0.10), suggesting that Medicago plants allocated more energy to shoots to optimize photosynthesis when N was not limiting. The shoot-to-root ratios were
not significantly different between two CO2 levels. 相似文献
11.
Lupins, canola, ryegrass and wheat fertilized with Na2
35SO4 and either 15NH4Cl or K15NO3(N:S=10:1), were grown in the field in unconfined microplots, and the sources of N and S (fertilizer, soil, atmosphere, seed)
in plant tops during crop development were estimated. Modelled estimates of the proportion of lupin N derived from the atmosphere,
which were obtained independently of reference plants, were used to calculate the proportion of lupin N derived from the soil.
Total uptake of N and S and uptake of labelled N and S increased during crop development. Total uptake of S by canola was
higher than lupins, but labelled S uptake by lupins exceeded uptake by canola. The form of N applied had no effect on uptake
of labelled and unlabelled forms of N or S. Ratios of labelled to unlabelled S and ratios of labelled to unlabelled N derived
from soil sources decreased during growth, and were less for S than for N for each crop at each sampling time. Although ratios
of labelled to unlabelled soil-derived N were similar between crops at 155, 176 and 190 days after sowing, ratios of labelled
to unlabelled S for lupins were higher than for the reference crops and declined during this period. The ratios of labelled
to unlabelled S in lupins and the reference plants therefore bore no relationship either to ratios of labelled to unlabelled
soil-derived N in the plants, or to total S uptake by the plants. Therefore the hypothesis that equal ratios of labelled N
to unlabelled soil-derived N in legumes (Rleg) and reference plants (Rref) would be indicated by equal ratios of labelled to unlabelled S was not supported by the data. The results therefore show
that the accuracy of reference plant-derived values of Rleg cannot be evaluated by labelling with 35S. 相似文献
12.
The kinetics of NH4
+ and NO3
− uptake in young Douglas fir trees (Pseudotsuga menziesii [Mirb.] Franco) were studied in solutions, containing either one or both N species. Using solutions containing a single N
species, the Vmax of NH4
+ uptake was higher than that of NO3
− uptake. The Km of NH4
+ uptake and Km of NO3
− uptake differed not significantly. When both NH4
+ and NO3
− were present, the Vmax for NH4
+ uptake became slightly higher, and the Km for NH4
+ uptake remained in the same order. Under these conditions the NO3
− uptake was almost totally inhibited over the whole range of concentrations used (10–1000 μM total N). This inhibition by NH4
+ occurred during the first two hours after addition. ei]{gnA C}{fnBorstlap} 相似文献
13.
Soil N availability may play an important role in regulating the long-term responses of plants to rising atmospheric CO2 partial pressure. To further examine the linkage between above- and belowground C and N cycles at elevated CO2, we grew clonally propagated cuttings of Populus grandidentata in the field at ambient and twice ambient CO2 in open bottom root boxes filled with organic matter poor native soil. Nitrogen was added to all root boxes at a rate equivalent
to net N mineralization in local dry oak forests. Nitrogen added during August was enriched with 15N to trace the flux of N within the plant-soil system. Above-and belowground growth, CO2 assimilation, and leaf N content were measured non-destructively over 142 d. After final destructive harvest, roots, stems,
and leaves were analyzed for total N and 15N.
There was no CO2 treatment effect on leaf area, root length, or net assimilation prior to the completion of N addition. Following the N addition,
leaf N content increased in both CO2 treatments, but net assimilation showed a sustained increase only in elevated CO2 grown plants. Root relative extension rate was greater at elevated CO2, both before and after the N addition. Although final root biomass was greater at elevated CO2, there was no CO2 effect on plant N uptake or allocation. While low soil N availability severely inhibited CO2 responses, high CO2 grown plants were more responsive to N. This differential behavior must be considered in light of the temporal and spatial
heterogeneity of soil resources, particularly N which often limits plant growth in temperate forests. 相似文献
14.
Nodulated seedlings of Acacia auriculiformis Cunn. ex Benth and Acacia mangium Willd were grown with different phosphorus (P) regimes for 90 days, and half of them were exposed to elevated CO2 (800 μl l−1) during the last 30 days. Under ambient CO2, plant growth and the amount of N fixed symbiotically in N2-fixing seedlings decreased with the decrease of supplied P; this relationship did not occur under elevated CO2. The increase in plant biomass by elevated CO2 at low P was accompanied by the increase in internal P use efficiency, the amount of N fixed symbiotically and N use efficiency. Elevated CO2 recovered the low P-induced reduction in leaf dry matter per unit area or unit fresh weight, but it had no effect on the low P-induced increase in partitioning dry matter to roots. These results suggest that elevated CO2 alleviates the low P effect mainly by increasing the use efficiency of internal P for plant growth and symbiotic N2 fixation, and the source-sink relationship is possibly an important driving force for this effect of elevated CO2 in A. auriculiformis and A. mangium. 相似文献
15.
The effects of planted fallows of Sesbania sesban (L.) Merr. and Calliandra calothyrsus (Meissner) on soil inorganic nitrogen dynamics and two subsequent maize crops were evaluated under field conditions in the highlands of eastern Kenya. Continuous unfertilised maize, maize/bean rotation and natural regrowth of vegetation (weed fallow) were used as control treatments. The proportion of symbiotic N2-fixation was estimated by measuring both leaf 15N enrichment and whole-plant 15N enrichment by the 15N dilution technique for Sesbania and Calliandra, using Eucalyptus saligna (Sm.) and Grevillea robusta (A. Cunn) as reference species. Above- and below-ground biomass and N contents were examined in Sesbania, Calliandra, Eucalyptus and Grevillea 22 months after planting. Both the content of inorganic N in the topsoil and the quantity of N mineralised during rainy seasons were higher after the Sesbania fallows than after the other treatments. Compared to the continuous unfertilised maize treatment, both residual crop yields were significantly higher when mineral N (one application of 60 kg N ha–1) was added. Furthermore, the second crop following the Sesbania fallow was significantly higher than the continuous maize crop. The above-ground biomass of the trees at final harvest were 31.5, 24.5, 32.5 and 43.5 Mg ha–1 for the Sesbania, Calliandra, Grevillea and Eucalyptus, respectively. For the total below-ground biomass the values for these same tree species were 11.1, 15.5, 17.7, and 19.1 Mg ha–1, respectively, of which coarse roots (>2 mm), including tap roots, amounted to 70–90%. About 70–90% of the N in Sesbania, and 50–70% in Calliandra, was derived from N2-fixation. Estimates based on leaf 15N enrichment and whole-plant 15N enrichment were strongly correlated. The N added by N2-fixation amounted to 280–360 kg N ha–1 for Sesbania and 120–170 kg N ha–1 for Calliandra, resulting in a positive N balance after two maize cropping seasons of 170–250 kg N ha–1 and 90–140 kg N ha–1, for Sesbania and Calliandra, respectively. All the other treatments gave negative N balances after two cropping seasons. We conclude that Sesbania sesban is a tree species well suited for short duration fallows due to its fast growth, high nutrient content, high litter quality and its ability to fix large amounts of N2 from the atmosphere. 相似文献
16.
BassiriRad Hormoz Prior Stephen A. Norby Rich J. Rogers Hugo H. 《Plant and Soil》1999,217(1-2):195-204
Models describing plant and ecosystem N cycles require an accurate assessment of root physiological uptake capacity for NH
4
+
and NO
3
-
under field conditions. Traditionally, rates of ion uptake in field-grown plants are determined by using excised root segments
incubated for a short period in an assay solution containing N either as a radioactive or stable isotope tracer (e.g., 36ClO3 as a NH
4
+
analogue, 14CH3NH3 as an NO
3
-
analogue or 15NH
4
+
and 15NO
3
-
). Although reliable, this method has several drawbacks. For example, in addition to radioactive safety issues, purchase and
analysis of radioactive and stable isotopes is relatively expensive and can be a major limitation. More importantly, because
excision effectively interrupts exchange of compounds between root and shoot (e.g., carbohydrate supply to root and N transport
to shoot), the assay must be conducted quickly to avoid such complications. Here we present a novel field method for simultaneous
measurements of NH
4
+
and NO
3
-
uptake kinetics in intact root systems. The application of this method is demonstrated using two tree species; red maple
(Acer rubrum) and sugar maple (Acer saccharum) and two crop species soybean (Glycine max) and sorghum (Sorghum bicolor). Plants
were grown in open-top chambers at either ambient or elevated levels of atmospheric CO2 at two separate US national sites involved in CO2 research. Absolute values of net uptake rates and the kinetic parameters determined by our method were found to be in agreement
with the literature reports. Roots of the crop species exhibited a greater uptake capacity for both N forms relative to tree
species. Elevated CO2 did not significantly affect kinetics of N uptake in species tested except in red maple where it increased root uptake capacity,
V, for NH
4
+
. The application, reliability, advantages and disadvantages of the method are discussed in detail.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Masahiro Yamaguchi Makoto Watanabe Mayumi Iwasaki Chikako Tabe Hideyuki Matsumura Yoshihisa Kohno Takeshi Izuta 《Trees - Structure and Function》2007,21(6):707-718
To obtain the basic data for evaluating the critical level of ozone (O3) to protect Japanese deciduous broad-leaved forest tree species, the growth and photosynthetic responses of Fagus crenata seedlings to O3 under different nitrogen (N) loads were investigated. The seedlings were grown in potted andisol supplied with N as NH4NO3 solution at 0, 20 or 50 kg ha−1 year−1 and were exposed to charcoal-filtered air or O3 at 1.0, 1.5 and 2.0 times the ambient concentration for two growing seasons. The interactive effect of O3 and N load on the whole-plant dry mass of the seedlings at the end of the second growing season was significant. The O3-induced reduction in the whole-plant dry mass of the seedlings was greater in the relatively high N treatment than that in
the low N treatment. This interactive effect was mainly due to the difference in the degree of O3-induced reduction in net photosynthesis among the N treatments. The degree of O3-induced reduction in N availability to photosynthesis was greater in the relatively high N treatment than that in the low
N treatment. In conclusion, the sensitivity of growth and photosynthetic parameters of F. crenata seedlings to O3 become high with increasing amounts of N added to the soil. Therefore, N deposition from the atmosphere should be taken into
account to evaluate the critical level of O3 to protect Japanese deciduous broad-leaved forest tree species. 相似文献
18.
Improvement of dinitrogen fixation in beans (Phaseolus vulgaris L.) will depend on the selection of superior plant genotypes and the presence of efficient rhizobial strains. This study
was conducted to evaluate diverse bean lines for N2 fixation potential using the15N-depleted dilution technique under field conditions in Wisconsin, USA. Plants of 21 bean lines and three non-nodulating isolines
of soybean received appliin Wisconsin, USA. Plants of 21 bean lines and three non-nodulating isolines of soybean received
applications of15N-depleted ammonium sulphate. Shoots harvested at the V6, R3 and R7 stages and dry seeds were analyzed for total N using the Kjeldahl procedure, and the ratio of15N to14N was determind on a MAT 250 mass spectrometer. Nodule occupancy of the applied strain ofR. leguminosarum biovarphaseoli, CIAT 899, was determined in five of the bean lines. Total shoot N content showed a pattern of accumulation similar to shoot
dry weight and fixed N2 in the shoot. Based on shoot total N, N2 fixed in the shoot and shoot dry weight Riz 30 and Preto Cariri were identified as being as good fixers as Puebla 152 and
Cargamanto appear to begin N2 fixation early. Furthermore, some bean lines that fixed considerable N2 did not translocate a large amount of N to the grains. Preto Cariri accumulated 21.2 kg N ha−1 in the seeds compared to Puebla 152 which accumulated 43.8 kg N ha−1 of the fixed N2 into the grains. At the early sampling, Puebla 152 and 22–27 had a considerable higher percentage of their crown nodules
formed by the inoculant strain CIAT 899, than did Rio Tibagi which has been considered a poor N2 fixer. 相似文献
19.
b. Rerkasem K. Rerkasem M. B. Peoples D. F. Herridge F. J. Bergersen 《Plant and Soil》1988,108(1):125-135
The yield of N in maize (Zea mays L.) and ricebean (Vigna umbellata [Thumb.] Ohwi and Ohashi) were compared on a Tropoqualf soil in North Thailand in 1984 and 1985. Both species were grown
in field plots in monoculture or as intercrops at a constant planting density equivalent to 8 maize or 16 ricebean plants
per m2. The contribution of symbiotic N2 fixation to ricebean growth was estimated from measurements of the natural abundance of15N (δ15N) in shoot nitrogen and from analysis of ureides in xylem sap vacuumextracted from detached stems.
The natural abundance of15N in the intercropped ricebean was found to be considerably less than that in monoculture in both growing seasons. Using maize
and a weed (Ageratum conyzoides L.) as non-fixing15N reference plants the proportions (P
15N) of ricebean shoot N derived from N2 fixation ranged from 0.27 to 0.36 in monoculture ricebean up to 0.86 when grown in a 75% maize: 25% ricebean intercrop. When
glasshouse-derived calibration curves were used to calculate plant proportional N2 fixation (Pur) from the relative ureide contents of field collected xylem exudates, the contribution of N2 fixation to ricebean N yields throughout the 1985 growing season were greater in intercrop than in monocrop even at the lowest
maize:legume ratio (25∶75). Seasonal patterns of sap ureide abundance indicated that N2 fixation was greatest at the time of ricebean podset. The averagePur andP
15N in ricebean during the first 90 days of growth showed identical rankings of monocrop and intercrop treatments in terms of
N2 fixation, although the two sets ofP values were different. Nonetheless, seasonal estimates of N2 fixation during the entire 147 days of legume growth determined from ureide analyses indicated that equivalent amounts of
N could be fixed by ricebean in a 75∶25 intercrop and in monoculture despite the former being planted at one-quarter the density. 相似文献
20.
Photosynthetic pathway Types (C3, C4, and CAM) and life forms of native species from Hulunbeier rangelands, north China were studied. Of the total 258 species, 216 species in 132 genera and 42 families had C3 photosynthetic pathway, including dominant herbs, e.g. Stipa baicalensis Roshev. and Leymus chinensis (Trin.) Tzvel., Filifolium sibiricum Kitam. and Arudinella hirta (Thunb.) Koidz. 38 species in 28 genera and 10 families were found with C4 photosynthesis, and 4 species in 2 genera and 1 family had CAM photosynthetic pathway. The occurrence of C4 species was common in Gramineae and Chenopodiaceae, and the two families were leading ones within C4 plants. More than 52 % of the total 258 species were in H form, 21 % in Th form, 19 % in G form; the other life form Types, e.g. Ch, M, N, and HH, formed less than 3 %. 68 % of C4 species were in Th form and 24 % in H form, indicating that these Types were the dominant life forms for C4 species in the rangeland region. The occurrence of C4 species was closely related with plant habitats, disturbed lands had the highest C4 abundance (55 % of the total C4 species), followed by grasslands and sandy soil, and forests had the lowest C4 abundance (8 %). Hence the occurrence of C4 species could be efficient indicator for rangeland dynamics in Hulunbeier rangelands. 相似文献