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1.
In short-term water culture experiments with different 15N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH 4
+ at a higher rate than NO 3
–. Maximum NO 3
– uptake by the whole plant occurred at 120 mg L –1 NO 3
–-N, whereas NH 4
+ absorption was saturated at 240 mg L –1 NH 4
+-N. 15NH 4
+ accumulated in roots and to a lesser degree in both leaves and stems. However, 15NO 3
– was mostly partitioned between leaves and roots.Adding increasing amounts of unlabeled NH 4
+ (15–60 mg L –1 N) to nutrient solutions containing 120 mg L –1 N as 15N labeled nitrate reduced 15NO 3
– uptake. Maximum inhibition of 15NO 3
– uptake was about 55% at 2.14 m M NH 4
+ (30 mg L –1 NH 4
+-N) and it did not increase any further at higher NH 4
+ proportions.In a long-term experiment, the effects of concentration and source of added N (NO 3
– or NH 4
+) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH 4
+ versus NO 3
– nutrition, whereas the reverse was true for Ca, K, Zn and Mn.The effects of different NO 3
–-N:NH 4
+-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L –1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO 3
– or NH 4
+ as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO 3
–-N/NH 4
+-N ratio. With increasing proportions of NH 4
+ in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH 4
+, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO 3
–-N:NH 4
+-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH 4
+ in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO 3
–:NH 4
+ ratio. 相似文献
2.
A fully automatic growth chamber system was built in order to study NH 3, exchange and NH 3, compensation points of plant canopies growing under controlled environmental conditions in which atmospheric NH 3, concentrations corresponded to those naturally occurring over terrestrial ecosystems. The system included plant cuvettes with separate root and shoot compartments constructed of coated polycarbonate. This material did not change the spectral composition of photosynthetically active light and had a low adsorption of NH 3, and water vapour. Atmospheric NH 3, concentrations in the inlet of the cuvettes were controlled by mass-flow controllers. Inlet and outlet NH 3, concentrations were measured on-line with a modified chemiluminescent NH 3, monitor. At airflow rates per unit leaf area of about 3 dm 3 m ?2 s ?1, the system allowed accurate determinations of NH 3, exchange rates down to about 0.1 nmol NH 3, m ?2 s ?1. The NH 3, compensation points at anthesis for barley cultivars Laevigatum and Golf were 4.2±2.8 and 4.6±2.9nmol mol ?1 of NH 3, in air (SE, n=4), respectively. NH 3, absorption in both cultivars increased linearly with atmospheric NH 3, concentration in the range 0–30 nmol mol ?1 of NH 3, in air. NH 3, absorption was much higher in the light than in the dark, indicating a strong stomatal and/or metabolic control of NH 3, exchange. Photosynthesis and transpiration were not affected by exposure to NH 3, concentrations in the range 0–30nmol mol ?1 for 7d. 相似文献
3.
NH 4
+ transport system of a psychrophilic marine bacterium Vibrio sp. strain ABE-1 ( Vibrio ABE-1) was examined by measuring the uptake of [ 14C]methylammonium ion ( 14CH 3NH 3
+) into the intact cells. 14CH 3NH 3
+ uptake was detected in cells grown in medium containing glutamate as the sole nitrogen source, but not in those grown in
medium containing NH 4Cl instead of glutamate. Vibrio ABE-1 did not utilize CH 3NH 3
+ as a carbon or nitrogen source. NH 4Cl and nonradiolabeled CH 3NH 3
+ completely inhibited 14CH 3NH 3
+ uptake. These results indicate that 14CH 3NH 3
+ uptake in this bacterium is mediated via an NH 4
+ transport system and not by a specific carrier for CH 3NH 3
+. The respiratory substrate succinate was required to drive 14CH 3NH 3
+ uptake and the uptake was completely inhibited by KCN, indicating that the uptake was energy dependent. The electrochemical
potentials of H + and/or Na + across membranes were suggested to be the driving forces for the transport system because the ionophores carbonylcyanide
m-chlorophenylhydrazone and monensin strongly inhibited uptake activities at pH 6.5 and 8.5, respectively. Furthermore, KCl
activated 14CH 3NH 3
+ uptake. The 14CH 3NH 3
+ uptake activity of Vibrio ABE-1 was markedly high at temperatures between 0° and 15°C, and the apparent K
m value for CH 3NH 3
+ of the uptake did not change significantly over the temperature range from 0° to 25°C. Thus, the NH 4
+ transport system of this bacterium was highly active at low temperatures.
Received: August 1, 1998 / Accepted: October 8, 1998 相似文献
4.
The exchange of ammonia between the atmosphere and the canopy of barley, wheat, oilseed rape and pea crops was studied over two growing seasons by use of a modified aerodynamic gradient technique in which passive horizontal flux samplers were applied with a wind profile in gradient configuration. The crop foliage was a net source of NH 3 to the atmosphere, with NH 3 emissions on a seasonal basis between 1 and 5 kg NH 3–N ha –1. The amount of NH 3 lost constituted between 1 and 4% of the applied nitrogen and between 1 and 4% of the actual amount of nitrogen present in the mature shoots. The volatile NH 3 losses depended on seasonal variations in climatic conditions affecting the growth and nitrogen economy of the crops and increased under conditions with excessive N absorption by roots and a high N concentration in the foliage. The accumulated NH 3 loss was positively correlated with the above-ground crop N content at anthesis, but not with that at final maturity. There were no indications that NH 3 emissions were larger under conditions unfavourable for nitrogen remobilization from vegetative plant parts (low N harvest index). Nevertheless, a distinct peak in NH 3 emission occurred during senescence. It is concluded that crops in many areas will represent a significant input of ammonia to the atmosphere and that NH 3 losses may become large enough to significantly affect crop N budgets. 相似文献
5.
Similar NH 4+ and NO 3?.uptake kinetic patterns were observed in Neoagardhiella baileyi (Harvey ex Kiitzing) Wyinne & Taylor and Gracilaria foliifera (Forssk?l) Borgesen. NO 3? was taken up in a rate-sturating fashion described by the Michaelis-Menten equation. NH 4+ uptake was multicomponent: a saturable component was accompanied by a diffusive or a high K component showing no evidence of saturation (at ≤50 μM [NH 4+]). Nitrogen starved plantsi(C/N atom ratios > ca. 10) showed higher transient rates of NH 4+ uptake at a given concentration than plants not N-Iimited. Only plants with high N content exhibited diel changes inNH 4+ uptake rates, and showed transient rates of NH 4+ accumulation which did not greatly exceed the capacity to incorporate N in steady-state growth. NH 4+ was preferred over NO 3?even in plants preconditioned on NO 3?as the sole N. source, NO 3? uptake was suppressed at 5μM [NH 4+], but simultaneous uptake occurred at unsurpressed rates at lower concentrations. Potential for N accumulation was greater via NH 4+uptake than via NO 3?uptake. Changing capacity for NH 4+ uptake with N content appears to be a mechanism whereby excessive accumulation of N was avoided by N-.satiated plants but a large accumulation was possible for N-depleted plants. 相似文献
6.
The cytoplasmic and vacuolar pH and changes thereof in the presence of ammonia (NH 4Cl) and methylamine (CH 3NH 3Cl) have been measured in rhizoid cells of Riccia fluitans by means of a pH-sensitive microelectrode. On addition of 1 micromolar NH4Cl, the cytoplasmic pH of 7.2 to 7.4 drops by 0.1 to 0.2 pH units, but shifts to pH 7.8 in the presence of 50 micromolar NH4Cl or 500 micromolar CH3NH3Cl. The pH of the vacuole increases drastically from 4.5 to 5.7 with these latter concentrations. Since a NH4+/CH3NH3+ uniporter has been demonstrated in the plasmalemma of R. fluitans previously (Felle 1983 Biochim Biophys Acta 602:181-195), the concentration-dependent shifts of cytoplasmic pH are interpreted as results of two processes: first, acidification through deprotonation of the actively transported NH4+; and second, alkalinization through protonation of NH3 which is taken up to a significant extent from high external concentrations. Furthermore, it is concluded that the determination of intracellular pH by means of methylamine distribution is not a reliable method for eucaryotic systems. 相似文献
7.
The dependence of substrate saturated uptake of 15NH 4+, 15NO 3?, 32PO 43?, and 14CO 2 on photosynthetic photon flux density (PPFD or photsynthetically active radiation, 400–700 nm) was characterized seasonally in oligotrophic Flathead Lake, Montana. PO 43? uptake was not dependent upon PPFD at any time of the year, whereas NH 4+, NO 3?, and CO 2 uptake were consistently dependent on PPFD over all seasons. Maximal rates of NH 4+, NO 3? and CO 2 uptake usually occurred near 40% of surface PPFD, which corresponded to about 5 m in the lake; inhibition was evident at PPFD levels greater than 40%. NH 4+, NO 3? and PO 43? were incorporated in the dark at measurable rates most of the year, whereas dark CO 2 uptake was always near 0 relative to light uptake. CO 2 and NO 3? uptake were more strongly influenced by PPFD than was NH 43? uptake. The PPFD dependence of PO 43?, NH 4+, NO 3? and CO 2 uptake may affect algal growth and nutrient status by influencing the balance in diel and seasonal C:N:P uptake ratios. 相似文献
8.
The impacts of various nitrogen sources, i.e. NO −
3, NH 4
+ or NH 4NO 3 in combination with gaseous NH 3, on nitrogen-, carbon- and water-use efficiency and 13C discrimination (δ 13C) by plants of the C 3 species Triticum aestivum L. (wheat) and the C 4 species Zea mays L. (maize) were studied. Triticum aestivum and Z. mays were hydroponically grown with 2 mol · m −3 of N supplied as NO −
3, NH 4
+ or NH 4NO 3 for 21 and 18 d, respectively, and thereafter exposed to gaseous NH 3 at 320 μg · m −3 or to ambient air for 7 d. In T. aestivum and Z. mays over a 7-d growth period, nitrogen-use efficiency (NUE) values were influenced by N-sources in the decreasing order NH 4NO 3-N > NO −
3-N > NH 4
+-N and NO −
3-N > NH 4NO 3-N > NH 4
+-N, respectively. Fumigation with NH 3 decreased the NUE values of plants grown with any of the N-forms. During 28- and 7-d growth periods, N-sources affected water-use
efficiency (WUE) values in the decreasing order of NH 4
+-N > NO −
3-N≈NH 4NO 3-N in non-fumigated T. aestivum, while fumigation with NH 3 increased the WUE of NO −
3-grown plants. There were insignificant effects of N-sources on WUE values of Z. mays over 25- and 7-d growth periods. Furthermore, δ 13C values in plant tissues (leaves, stubble and roots) were higher (less negative) in NH 4
+-grown plants of T. aestivum and Z. mays than in those supplied with NH 4NO 3 or NO −
3. Regardless of the N-form supplied to the roots of the plant species, exposure to NH 3 caused more-positive δ 13C values in the plant tissues. These results indicate that the variations in N-source were associated with small but significant
variations in δ 13C values in plants of T. aestivum and Z. mays. These differences in δ 13C values are in the direction expected from differences in WUE values over long or short growth periods and with differences
in the extent of non-Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase, EC 4.1.1.39) carboxylate contribution to net
C acquisition, as a function of N-source.
Received: 12 September 1997 / Accepted: 13 January 1998 相似文献
9.
Tocopheramines (TNH 2) and tocotrienamines (T 3NH 2) are analogues of tocopherols (TOH) and tocotrienols in which phenolic OH is replaced by NH 2. It was shown in previous studies that TNH 2 and T 3NH 2 act as potent antioxidants. In this study we compared the one-electron oxidation of TNH 2/T 3NH 2 by diphenyl picryl hydrazyl (DPPH ) and galvinoxyl (GOX ) radicals with the one of α-TOH as a reference compound using ESR spectroscopy, stopped flow spectrophotometry and density functional theory (DFT) calculations. ESR spectroscopy revealed the presence of tocopheramine radicals during electrochemical oxidation of α-TNH 2. Kinetic measurements demonstrated that in apolar n-hexane TNH 2/T 3NH 2 derivatives reacted two to three orders of magnitude slower than α-TOH with the model radicals. DFT calculations indicated that this correlates well with the higher bond dissociation energy (BDE) for N–H in TNH 2 than for O–H in α-TOH in pure H-atom transfer (HAT). In the more polar medium ethanol TNH 2/T 3NH 2 derivatives partially reacted faster than α-TOH depending on the reaction partner. DFT calculations suggest that this is due to reaction mechanisms alternative to HAT. According to thermochemistry data sequential proton loss and electron transfer (SPLET) is more favored for α-TOH in ethanol than for TNH 2. Therefore, for TNH 2 a contribution of the alternative mechanism of sequential electron transfer–proton transfer (SET–PT) could be a possible explanation. These data show that the antioxidant reactivity strongly depends on the structure, reaction partners and environment. According to these findings TNH 2/T 3NH 2 should be superior as antioxidants over α-TOH in polar head group regions of membranes but not in the apolar core of lipid bilayers. 相似文献
10.
C. kiangsu adults were observed visiting human urine, especially on hot summer days. The main chemicals in fresh human urine include inorganic salts and CO(NH 2) 2. When human urine was incubated, NH 4HCO 3 became the richest nitrogenous compound. The phagostimulants, repellents and attractants in urine were identified here. On the filter papers treated with fresh or incubated urine samples, the 5th instar nymphs and the adults started and continued gnawing around the edges, in contrast to the 3rd and the 4th instar nymphs. The consumed areas were dramatically greater on the filters treated with the urine samples incubated for 3-6 days. The feedings of both male and female adults were also stimulated by several urine-borne components such as NaCl, NaH 2PO 4, Na 2SO 4, KCl, NH 4Cl and NH 4HCO 3 but not by CO(NH 2) 2. Among them NaCl was the most powerful phagostimulant. The repelling, or attractive/arresting effects of CO(NH 2) 2 and NH 4HCO 3 were also evaluated by a two-choice test. When exposed to water- and CO(NH 2) 2 solution-immersed filters simultaneously, the adults prefer to stay on water-immersed filter. In contrast, when provided water- and NH 4HCO 3 solution-treated filters, the adults prefer to stay on NH 4HCO 3 solution-treated filter. This demonstrated that CO(NH 2) 2 acted as a repellent and NH 4HCO 3 as an attractant/arrestant. In the bamboo forest, similar feeding behavior was also elicited by NaCl, NH 4HCO 3 but not by CO(NH 2) 2. Comparing to NaCl solution, a mixed solution of NaCl and CO(NH 2) 2 (1:1) significantly decreased the consumed area of the treated filters whereas a mixed solution of NaCl and NH 4HCO 3 (1:1) dramatically increased the consumed area. These results demonstrated that the phagostimulatory effect by NaCl was reduced by CO(NH 2) 2 in fresh urine and was enhanced by NH 4HCO 3 in incubated urine. 相似文献
11.
Ammonia is the preferred nitrogen source for many algae including the cyanobacterium Synechococcus elongatis (Synechococcus R-2; PCC 7942). Modelling ammonia uptake by cells is not straightforward because it exists in solution as NH 3 and NH 4 + . NH 3 is readily diffusible not only via the lipid bilayer but also through aquaporins and other more specific porins. On the other hand, NH 4 + requires cationic transporters to cross a membrane. Significant intracellular ammonia pools (≈1–10 mol?m ?3) are essential for the synthesis of amino acids from ammonia. The most common model envisaged for how cells take up ammonia and use it as a nitrogen source is the “pump–leak model” where uptake occurs through a simple diffusion of NH 3 or through an energy-driven NH 4 + pump balancing a leak of NH 3 out of the cell. The flaw in such models is that cells maintain intracellular pools of ammonia much higher than predicted by such models. With caution, [ 14C]-methylamine can be used as an analogue tracer for ammonia and has been used to test various models of ammonia transport and metabolism. In this study, simple “proton trapping” accumulation by the diffusion of uncharged CH 3NH 2 has been compared to systems where CH 3NH 3 + is taken up through channels, driven by the membrane potential (Δ U i,o) or the electrochemical potential for Na + (Δ μNa i,o + ). No model can be reconciled with experimental data unless the permeability of CH 3NH 2 across the cell membrane is asymmetric: permeability into the cell is very high through gated porins, whereas permeability out of the cell is very low (≈40 nm?s ?1) and independent of the extracellular pH. The best model is a Na in + /CH 3NH 3 + in co-porter driven by Δ μNa i,o + balancing synthesis of methylglutamine and a slow leak governed by Ficks law, and so there is significant futile cycling of methylamine across the cell membrane to maintain intracellular methylamine pools high enough for fixation by glutamine synthetase. The modified pump–leak model with asymmetric permeability of the uncharged form is a viable model for understanding ammonia uptake and retention in plants, free-living microbes and organisms in symbiotic relationships. 相似文献
12.
NH 4
+-N can have inhibitory effects on plant growth. However, the mechanisms of these inhibitory effects are still poorly understood. In this study, effects of different N forms and a combination of ammonium + 6-benzylaminopurine (6-BA, a synthetic cytokinin) on growth, transpiration, uptake and flow of water and potassium in 88-days-old tobacco ( Nicotiana tabacum L. K 326) plants were studied over a period of 12 days. Plants were supplied with equal amounts of N in different forms: NO 3
–, NH 4NO 3, NH 4
+ or NH 4
++6-BA (foliar spraying every 2 days after onset of the treatments). For determining flows and partitioning upper, middle and lower strata of three leaves each were analysed. During the 12 days study period, 50% replacement of NO 3
–-N by NH 4
+-N (NH 4NO 3) did not change growth, transpiration, uptake and flow of water and K + compared with the NO 3
–-N treatment. However, NH 4
+-N as the sole N-source caused: (i) a substantial decrease in dry weight gain to 42% and 46% of the NO 3
–-N and NH 4NO 3 treatments, respectively; (ii) a marked reduction in transpiration rate, due to reduced stomatal conductance, illustrated by more negative leaf carbon-isotope discrimination ( 13C) compared with the NO 3
– treatment, especially in upper leaves; (iii) a strong reduction both in total water uptake, and in the rate of water uptake by roots, likely due to a decrease in root hydraulic conductivity; (iv) a marked reduction of K + uptake to 10%. Under NH 4
+ nutrition the middle leaves accumulated 143%, and together with upper leaves 206% and the stem 227% of the K + currently taken up, indicating massive mobilisation of K + from lower leaves and even the roots. Phloem retranslocation of K + from the shoot and cycling through the root contributed 67% to the xylem transport of K +, and this was 2.2 times more than concurrent uptake. Foliar 6-BA application could not suppress or reverse the inhibitory effects on growth, transpiration, uptake and flow of water and ions (K +) caused by NH 4
+-N treatment, although positive effects by 6-BA application were observed, even when 6-BA (10 –8
M) was supplied in nutrient solution daily with watering. Possible roles of cytokinin to regulate growth and development of NH 4
+-fed plants are discussed. 相似文献
13.
Interaction between the sodium salt of a DNA extracted from salmon sperm (41% GC) with [Pt(NH 3) 4]Cl 2, [Pt(NH 2? (CH 2) 2? NH? (CH 2) 2? NH 2Cl]Cl, cis-Pt(NH 2? (CH 2) 2? NH 2)Cl 2, cis-Pt(NH 3) 2Cl 2, trans-Pt(NH 3) 2Cl 2, K[Pt(C 2H 4)Cl 3], and K 2[PtCl 4) indicates at least three types of complexation. A correlation is found between the change of pH and the number of platinum atoms fixed per (AT + GC) unit. The first binding site is located on the G-C pairs (guanine–cytosine), most likely the N-7(G) site, as it was shown in a previous study of the guanosine-platinum salts. The fixation of the second platinum atom by the pair (AT + GC) takes place with liberation of protons. In the case of the complexes cis-Pt(NH 2? (CH 2) 2? NH 2)Cl 2, cis-Pt(NH 3) 2Cl 2, and trans-Pt(NH 3) 2Cl 2 the second interaction seems to involve simultaneously the N-7(A) and the N-1(G) and N-3(C) sites. This latter intercrosslink between guanine and cytosine obviously liberates protons and the decrease of pH is related in this case to the trans effect of the platinum compounds. The first two platinum atoms in the reaction of K 2PtCl 4] or the Zeise salt, K[Pt(C 2H 4)Cl 3] with DNA are fixed on the G-C pairs. A maximum of six platinum atoms per (AT + GC) unit were fixed in this case. Preliminary experiments with a DNA extracted from bacteria Micrococcus lysodeikticus (72% GC) give similar results. 相似文献
14.
When 0.001 M NH 4Cl is added to sea water containing Valonia macrophysa there seems to be a rapid penetration of undissociated NH 3 (or NH 4OH) which raises the pH value of the sap so that the thermodynamic potential of KOH becomes greater inside than outside and in consequence K leaves the cell: NaOH continues to go in because its thermodynamic potential is greater outside than inside. NH 4Cl accumulates, reaching a much higher concentration inside than outside. This might be explained on the ground that NH 3, after entering, combines with a weak organic acid produced in the cell whose anion is exchanged for the Cl - of the sea water, or (more probably) the organic acid is exchanged for HCl. 相似文献
15.
The ability of the macrotetrolide nactins to complex selectivity with a wide variety of cations makes these ionophorous antibiotics important model systems for the study of biologic ionic transport. We report a Raman spectroscopic investigation of the Na +, K +, Rb +, Cs +, Tl +, NH 4+, NH 3OH +, C(NH 2) 3+, and Ba ++ complexes of nonactin, monactin, and dinactin in 4:1 (v/v) CH 3OH/CHCl 3 and in the solid state. The nactins display characteristic spectral changes upon complexation, some of which are specific for a given cation. In the K +, Rb +, Cs +, NH 3OH +, and C(NH 2) 3+ complexes, which are apparently isosteric, the ester carbonyl stretch frequency is found to be linearly proportional to the cation–carbonyl electrostatic interaction energy, as calculated from a simplified model. Deviations for the Na +, NH 4+, Tl +, and Ba ++ complexes are interpreted as arising from additional nonelectrostatic interactions. Additional information is obtained from other spectral regions and from measurements of depolarization ratios. Spectra of the nactin complexes differ from each other more in the solid state than in solution, reflecting the effects of crystalline contact forces. 相似文献
16.
In N-starved (?N) fronds of Lemna gibba L. G 1, NH 4+ uptake rates were several-fold those of NO 3?-supplied (+N) fronds. NO 3?, uptake in +N-plants was slow and not inhibited by addition of NH 4+. However, in ?N-plants with higher NO 3? and still higher NH 4+ uptake rates, addition of NH 4+ immediately reduced the NO 3? uptake rates to about one third until the NH 4+ was consumed. The membrane potential (E m) decreased immediately upon addition of NH 4+ in all fronds, but whereas depolarisation was moderate and transient in +N-plants, it was strong, up to 150 mV, in N-starved plants, where E m remained at the level of the K + diffusion potential (E D) until NH 4+ was removed. In N-starved plants NH 4+ uptake and membrane depolarisation showed the same concentration dependence, except for an apparent linear component for uptake. Phosphate uptake was inhibited by NH 4+ similarly to NO 3? uptake, but only in P- and N-starved plants, not after mere P starvation. Influx of NO 3? and H 2PO 4? into the negatively charged cells of Lemna is mediated by anion/H + cotransport, but NH 4+ influx can follow the electrochemical gradient. Its saturating component may reflect a carrier-mediated NH 4+ uniport, the linear component diffusion of NH 4+ or NH 3. Inhibition of anion/H + cotransport by high NH 4+ influx rates may be due to loss of the proton-driving force, Δμ?H +, across the plasmalemma. Reversible inhibition by NH 4+ of the H + extrusion pump may contribute to the finding that Δμ?H + cannot be reconstituted in the presence of higher NH 4+ concentrations. 相似文献
17.
Growth of soybean was not altered, whatever the inorganic N-source (NO 3, NH 4 or a NO 3/NH 4 mixture); conversely, growth of Erica x darleyensis plants in vitro decreased more in. NH 4 medium than in a NO 3 medium, compared to a NO 3/NH 4 medium. The GS/GOGAT pathway (in NH 4 medium), the nitrate and nitrite reductase activities (in NO 3 medium), as the contents in free nitrogenous forms and total nitrogen (in NO 3 and NH 4 media) were not more altered in Erica than in soybean, compared to a NO 3/NH 4 medium. PEPCase activity was the highest in soybean irrespective of the N-treatments; the involvement of PEPCase in N-metabolism
could be explained by its function in ionic and osmotic balances rather than its function in supplying carboxylates as acceptors
for NH 4-assimilation. 相似文献
18.
通过大田试验,设置5种不同的施肥比例(基肥:分蘖肥:拔节肥:穗肥-2:2:3:3(R1)、3:2:2:3(R2)、4:2:2:2(R3)、4:3:1:2(R4)与0:0:0:0(CK)),研究氮肥运筹对稻田NH 3挥发和氮肥利用率的影响。结果表明,(1)相对于不施肥,施肥显著提高了稻田NH 3挥发量。氮肥施用后,NH 3挥发损失量占施氮量的6.2%-8.5%,其中,以分蘖期NH 3挥发损失量最大,齐穗期次之,苗期和拔节期最小。施肥处理间,处理R1稻田累积NH 3挥发量最小,显著低于其它施肥处理,比处理R2、R3和R4分别低9.1%( P<0.05)、10.9%( P<0.05)和17.7%( P<0.05)。(2)相关分析表明,田面水NH 4+、pH值和土壤NH 4+和pH值均与稻田土壤NH 3挥发通量呈显著或者极显著相关;(3)处理R1水稻氮肥利用率相对于处理R2、R3和R4增加了28.4%( P<0.05)、55.4%( P<0.05)和74.9%( P<0.05)。研究表明,氮肥后移能有效降低免耕稻田NH 3挥发,提高水稻的氮肥利用率。 相似文献
19.
Summary The effects of concentration and source (NH 4, NO 3, and NO 3 plus NH 4) of added N on the rate of growth, final yield, and content and rate of intake of N, P, K, Ca, Mg and S by wheat seedlings were evaluated. Rate of growth in dilute liquid cultures differed among the N sources giving yields relative to those of the all-NO 3 system of 92 per cent for the all-NH 4 system, and of 154 per cent for the NO 3 plus NH 4 system. At low rates of NH 4 intake in the all-NH 4 systems growth rates were equal to or slightly better than those of plants supplied equivalent concentrations of NO 3. Rates of NH 4 intake exceeding 100 mole g –1 h –1 resulted in reduced growth rates and incipient NH 4 toxicity. Yields at 95 per cent of maximum resulted with steady-state N concentrations of 80 M in all NO 3 systems, 30 M NH 4 in all-NH 4 systems, and in combined source systems when 200 M NO 3 plus 30 M NH 4 were supplied. The rate of N intake and plant protein content, were maximal when both NO 3 and NH 4 were supplied. Increasing rates of NO 3 intake were associated with increases in the rates of Ca, Mg, and K intake; but with increasing rates of NH 4 absorption, intake of Ca and Mg decreased. The yield and growth rate enhancement observed from the addition of low concentrations of NH 4 to cultures supplying adequate NO 3 is suggested to result from the reduced energy requirement for utilization of NH 4, as compared to NO 3 in protein synthesis and from the increased photosynthetic capacity of the higher-protein NH 4-fed plants. In the all-NH 4 systems the maximum attainable growth rate was limited by NH 4 toxicity; whereas in the all-NO 3 systems the rate of NO 3 reduction was limiting.Contribution from the Department of Soils and Plant Nutrition, University of California, Davis, California 95616. 相似文献
20.
Imino ligands have proven to be able to activate the trans geometry of platinum(II) complexes towards antitumor activity. These ligands, like aromatic N-donor heterocycles, have a planar shape but, different from the latter, have still an H atom on the coordinating nitrogen which can be involved in H-bond formation. Three classes of imino ligands have been extensively investigated: iminoethers (HN=C(R)OR′), ketimines (HN=CRR′), and amidines (HN=C(R)NR′R″). The promising efficacy of the platinum compounds with amidines (activity comparable to that of cisplatin for cis complexes and much greater than that of transplatin for trans complexes) prompted us to extend the investigation to amidine complexes with a bulkier organic residue (R = t-Bu). The tert-butyl group can confer greater affinity for lipophilic environments, thus potentiating the cellular uptake of the compound. In the present study we describe the synthesis and characterization of pivaloamidine complexes of platinum(II), ( cis and trans-[PtCl 2(NH 3){ Z-HN=C( t-Bu)NH 2}] and cis and trans-[PtCl 2{ Z-HN=C( t-Bu)NH 2} 2]), platinum(III) ([Pt 2Cl 4{HN=C( t-Bu)NH} 2(NH 3) 2]), and platinum(IV) ( trans-[PtCl 4(NH 3){ Z-HN=C( t-Bu)NH 2}] and trans-[PtCl 4{ Z-HN=C( t-Bu)NH 2} 2]). The cytotoxicity of all new Pt complexes was tested toward a panel of cultured cancer cell lines, including cisplatin and multidrug resistant variants. In addition, cellular uptake and DNA binding, perturbations of cell cycle progression, induction of apoptosis, and p53 activation were investigated for the most promising compound trans-[PtCl 2(NH 3){ Z-HN=C( t-Bu)NH 2}]. Remarkably, the latter complex was able to overcome both acquired and intrinsic cisplatin resistance. 相似文献
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