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31.
Nitrate reduction in roots and shoots and exchange of reduced N between organs were quantitatively estimated in intact 13-d-old seedlings of two-row barley (Hordeum vulgare L. cv. Daisengold) using the 15N-incorporation model (A. Gojon et al. (1986) Plant Physiol. 82, 254–260), except that NH
+
4
was replaced by NO
-
2
. N-depleted seedlings were exposed to media containing both nitrate (1.8 mM) and nitrite (0.2 mM) under a light-dark cycle of 12:12 h at 20°C; the media contained different amounts of 15N labeling. Experiments were started either immediately after the beginning (expt. 1) or immediately prior to the end (expt. 2) of the light period, and plants were sampled subsequently at each light-dark transition throughout 36 h. The plants effectively utilized 15NO
-
3
and accumulated it as reduced 15N, predominantly in the shoots. Accumulation of reduced 15N in both experiments was nearly the same at the end of the experiment but the accumulation pattern in roots and shoots during each 12-h period differed greatly depending on time and the light conditions. In expt. 1, the roots accounted for 31% (light), 58% (dark), and 9% (light) of nitrate reduction by the whole plants, while in expt. 2 the contributions of the root were 82% (dark), 20% (light), and 29% (dark), during each of the three 12-h periods. Xylem transport of nitrate drastically decreased in the dark, but that of reduced N rather increased. The downward translocation of reduced 15N increased while nitrate reduction in the root decreased, whereas upward translocation decreased while nitrate reduction in the shoot increased. We conclude that the cycling of reduced N through the plant is important for N feeding of each organ, and that the transport system of reduced N by way of xylem and phloem, as well as nitrate reduction by root and shoot, can be modulated in response to the relative magnitude of reduced-N demands by the root and shoot, with the one or the other predominating under different circumstances.Symbols Anl
accumulation of reduced 15N from 15NO
-
3
in 14NO
-
3
-fed roots of divided root system
- Ar
accumulation in root of reduced 15N from 15NO
-
3
- As
accumulation in shoot of reduced 15N from 15NO
-
3
- Rr
15NO
-
3
reduction in root
- Rs
15NO
-
3
reduction in shoot
- Tp
translocation to root of shoot-reduced 15N from 15NO
-
3
in phloem
- Tx
translocation to shoot of root-reduced 15N from 15NO
-
3
in xylem 相似文献
32.
In vivo effect of abscisic acid (ABA) on photosynthetic oxygen evolution was investigated in barley chloroplasts. The most important kinetic parameters of O2-producing reactions were changed. The results show inhibition of the O2-flash yields at ABA concentrations of 10 mol/l and 100 mol/l and an increase in the degree of damping of the oscillations. ABA has a marked effect on the distribution of the oxygenevolving centers in S0 and S1 states and on sum of the centers (S0+S1) estimated according to the Kok model. In addition, the amplitude and the shape of the initial oxygen burst under continuous illumination are also significantly altered. At a concentration of 100 mol/l, ABA strongly inhibits Hill reaction activity measured by DCPIP reduction. The results cannot be explained by the hypothesis of socalled stomata effect. On the other hand, no effects were observed on the investigated parameters in experiments involving ABA applied in vitro to isolated chloroplasts. It is hypothesized that ABA disrupts the granal chloroplasts structure and raises the degree of participation of the cooperative mechanism of O2-evolution connected with the functioning of PS II centers in the stroma situated thylakoids.Abbreviations DCPIP
2,6-Dichlorophenolindophenol
- DCMU
3-(3,4-dichlorophenil)-1,1-dimethylurea
- HEPES
N-2-Hydroxyethylpiperazine-N-2-ethane sulfonic acid
- PSII
photosystem II
- RubisCO
Ribulose-1,5-bis-phosphate carboxylase-oxygenase 相似文献
33.
Izumi Tabata Yoriko Atomi Hiroaki Kanehisa Mitsumasa Miyashita 《European journal of applied physiology and occupational physiology》1990,60(4):254-258
The purpose of this study was to determine the effects of high-intensity endurance training on isokinetic muscle power. Six male students majoring in physical-education participated in high intensity endurance training on a cycle ergometer at 90% of maximal oxygen uptake (VO2max) for 7 weeks. The duration of the daily exercise session was set so that the energy expenditure equalled 42 kJ.kg-1 of lean body mass. Peak knee extension power was measured at six different speeds (30 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees.s-1) with an isokinetic dynamometer. After training, VO2max increased significantly from mean values of 51.2 ml.kg-1.min-1, SD 6.5 to 56.3 ml.kg-1.min-1, SD 5.3 (P less than 0.05). Isokinetic peak power at the lower test speeds (30 degrees, 60 degrees and 120 degrees.s-1) increased significantly (P less than 0.05). However, no significant differences in muscle peak power were found at the faster velocities of 180 degrees, 240 degrees, and 300 degrees.s-1. The percentage improvement was dependent on the initial muscle peak power of each subject and the training stimulus (intensity of cycle ergometer exercise). 相似文献
34.
H. S. Bachelard R. S. Badar-Goffer K. J. Brooks S. J. Dolin P. G. Morris 《Journal of neurochemistry》1988,51(4):1311-1313
We report the first measurement of the free intracellular calcium level in an actively metabolising intact cerebral tissue preparation. To this end, we applied the recently developed 19F-nuclear magnetic resonance calcium chelator, 5,5'-F2-1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), in superfused cerebral cortical slices to give values for the intracellular Ca2+ concentration of 350 and 480 nM, at external calcium concentrations of 1.2 and 2.4 mM, respectively. Under both conditions, the intracellular Ca2+ concentration was increased by depolarisation using a high external K+ concentration. Interleaved 31P spectra showed that the presence of the 5FBAPTA had a deleterious effect on the metabolic state of the tissue with an external Ca2+ concentration of 1.2 mM, but normal viability was maintained using 2.4 mM. 相似文献
35.
36.
Maize (Zea mays L.) and ricebean (Vigna umbellata [Thumb.] Ohwi and Ohashi) were grown in intercrop and monoculture on Tropaqualf soils under rainfed conditions in Northern
Thailand yearly from 1983 to 1986. De Wit's replacement design was used to compare intercrops and monocultures with a constant
plant density equivalent to 80 000 maize or 160 000 ricebean plants ha−1. Combined nitrogen was applied at varying levels to 200 kg N ha−1. In the final two seasons the intercrop ratio of maize: ricebean was also varied. At the time of maize maturity intercrops
yielded upt 49 kg ha−1 more N in the above ground plant parts than the best monoculture. Dry matter, grain and nitrogen yield of maize and ricebean
in intercrop relative to their monoculture yields (RY, relative yield) were significantly greater than their respective share
of the plant population. Relative yield totals (RYT) for grain, dry matter and nitrogen were always greater than 1.
Nitrogen uptake per maize plant increased with progressive replacement of maize by ricebean plants. This increase was similar
to that obtained by applying combined N. Available soil nitrogen tended to decrease with increasing maize:ricebean ratio.
Increasing the maize:ricebean ratio increased the % of nitrogen derived from fixation in ricebean, the increase being equivalent
to that obtained by decreasing combined nitrogen application. Approximately the same amount of fertilizer and soil nitrogen
was taken up by maize plus ricebean in intercrop as the maize monoculture. The results suggest that the improved nitrogen
economy of the intercrop resulted from the strong competitiveness of maize in the use of mineral nitrogen and the enhancement
of nitrogen fixation in intercropped ricebean which made it less dependent on the depleted pool of soil nitrogen. 相似文献
37.
Laboratory incubation and field experiments were conducted to evaluate thiourea, ATC (4-amino-1, 2, 4 triazole hydrochloride)
and N-Serve 24 E (2-chloro-6-trichloromethyl-pyridine) as inhibitors of nitrification of fertilizer N. In the incubation experiment,
most of the added aqueous NH3 or urea was nitrified at 14 days on both soils, but addition of the inhibitors to fertilizer N decreased the conversion of
NH4−N to NO3−N markedly. There was less nitrification for ATC and thiourea but not for N-Serve 24 E when the fertilizers and the inhibitors
were placed at a point as opposed to when mixed into soil. After 28 days, ATC and N-Serve 24 E were more effective in inhibiting
nitrification than thiourea. ATC and N-Serve 24 E also inhibited release of mineral N (NH4−N+NO3−N) from native soil N. In the uncropped field experiment, which received N fertilizers in the fall, nitrification of fall-applied
N placed in the 15-cm bands was almost complete by early May in the Malmo soil, but not in the Breton soil. When ATC or thiourea
had been applied with urea, nitrification of fall-applied N was depressed by May and the recovery of applied N as NH4−N was greater with increasing band spacing to 60 cm or placing N fertilizer in nests (a method of application where urea
prills were placed at a point in the soil in the center of 60×60 cm area). In late June, the percentage recovery of fall-applied
N in soil as NH4−N or mineral N increased with wide band spacing, or nest placement, or by adding ATC to fertilizer N on both soils. These
results indicate that placing ammonium-based N fertilizers in widely-spaced bands or in nests with low rates of inhibitors
slows nitrification enough to prevent much of the losses from fall-applied N.
Scientific Paper No. 552, Lacombe Research Station, Research Branch, Agric, Can. 相似文献
38.
The15N abundance of plants usually closely reflects the15N abundance of their major immediate N source(s); plant-available soil N in the case of non-N2-fixing plants and atmospheric N2 in the case of N2 fixing plants. The15N abundance values of these sources are usually sufficiently different from each other that a significant and systematic difference in the15N abundance between the two kinds of plants can be detected. This difference provides the basis for the natural15N abundance method of estimating the relative contribution of atmospheric N2 to N2-fixing plants growing in natural and agricultural settings. The natural15N abundance method has certain advantages over more conventional methods, particularly in natural ecosystems, since disturbance of the system is not required and the measurements may be made on samples dried in the field. This method has been tested mainly with legumes in agricultural settings. The tests have demonstrated the validity of this method of arriving at semi-quantitative estimates of biological N2-fixation in these settings. More limited tests and applications have been made for legumes in natural ecosystems. An understanding of the limits and utility of this method in these systems is beginning to emerge. Examples of systematic measurements of differences in15N abundance between non-legume N2-fixing systems and neighbouring non-fixing systems are more unusual. In principle, application of the method to estimate N2-fixation by nodulated non-legumes, using the natural15N abundance method, is as feasible as estimating N2-fixation by legumes. Most of the studies involving N2-fixing non-legumes are with this type of system (e.g., Ceanothus, Chamabatia, Eleagnus, Alnus, Myrica, and so forth). Resuls of these studies are described. Applicability for associative N2-fixation is an empirical question, the answer to which probably depends upon the degree to which fixed N goes predominantly to the plant rather than to the soil N pool. The natural15N abundance method is probably not well suited to assessing the contribution of N2-fixation by free-living microorganisms in their natural habitat, particularly soil microorganisms.This work was supported in part by subcontracts under grants from the US National Science Foundation (DEB79-21971 and BSR821618) 相似文献
39.
Kucey R. M. N. Snitwongse P. Chaiwanakupt P. Wadisirisuk P. Siripaibool C. Arayangkool T. Boonkerd N. Rennie R. J. 《Plant and Soil》1988,108(1):33-41
Controlled environment and field studies were conducted to determine relationships between various measurements of N2 fixation using soybeans and to use these measures to evaluate a number ofBradyrhizobium japonicum strains for effectiveness in N2 fixation in Thai soils.15N dilution measurements of N2 fixation showed levels of fixation ranging from 32 to 161 kg N ha−1 depending on bacterial strain, host cultivar and location. Midseason measures of N2 fixation were correlated with each other, but not related measures taken at maturity. Ranking ofB. japonicum strains based on performance under controlled conditions in N-free media were highly correlated with rankings based on soybean
seed yields and N2 fixation under field conditions. This study showed that inoculation of soybeans with effectiveB. japonicum strains can result in significant increases in yield and uptake of N through fixation. The most effective strains tested
for use in Thai conditions were those isolated from Thai soils; however, effective strains from other locations were also
of benefit. 相似文献
40.
Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge,NE Bavaria 总被引:4,自引:0,他引:4
Summary Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The 13C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (13C between-25.3 and-27.8) were significantly less depleted in 13C than needles (13C between-27.3 and-29.1), and 13C in twigs increased consistently with age. The 15N values of needles ranged between-2.5 and-4.1 and varied according to stand and age. In young needles 15N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in 15N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. 15N values in twigs were more negative than in needles (-3.5 to-5.2) and showed age- and stand-dependent trends that were similar to the needles. 15N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4 in the mineral soil. The 15N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed. 相似文献