首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The weatherloach, Misgurnus anguillicaudatus, is a freshwater, facultative air-breathing fish that lives in streams and rice paddy fields, where it may experience drought and/or high environmental ammonia (HEA) conditions. The aim of this study was to determine what roles branchial Na+/K+-ATPase, H+-ATPase, and Rhcg have in ammonia tolerance and how the weatherloach copes with ammonia loading conditions. The loach's high ammonia tolerance was confirmed as was evident from its high 96 h LC50 value and high tissue tolerance to ammonia. The weatherloach does not appear to make use of Na+/NH4+-ATPase facilitated transport to excrete ammonia when exposed to HEA or to high environmental pH since no changes in activity were observed. Using immunofluorescence microscopy, distinct populations of vacuolar (V)-type H+-ATPase and Na+/K+-ATPase immunoreactive cells were identified in branchial epithelia, with apical and basolateral staining patterns, respectively. Rhesus C glycoprotein (Rhcg1), an ammonia transport protein, immunoreactivity was also found in a similar pattern as H+-ATPase. Rhcg1 (Slc42a3) mRNA expression also increased significantly during aerial exposure, although not significantly under ammonia loading conditions. The colocalization of H+-ATPase and Rhcg1 to the similar non-Na+/K+-ATPase immunoreactive cell type would support a role for H+-ATPase in ammonia excretion via Rhcg by NH4+ trapping. The importance of gill boundary layer acidification in net ammonia excretion was confirmed in this fish; however, it was not associated with an increase in H+-ATPase expression, since tissue activity and protein levels did not increase with high environmental pH and/or HEA. However the V-ATPase inhibitor, bafilomycin, did decrease net ammonia flux whereas other ion transport inhibitors (amiloride, SITS) had no effect. H+-ATPase inhibition also resulted in a consequent elevation in plasma ammonia levels and a decrease in the net acid flux. In gill, aerial exposure was also associated with a significant increase in membrane fluidity (or increase in permeability) which would presumably enhance NH3 permeation through the plasma membrane. Taken together, these results indicate the gill of the weatherloach is responsive to aerial conditions that would aid ammonia excretion.  相似文献   

2.
3.
Isolated perfused gills of stenohaline crabs Cancer pagurus adapted to seawater, brackish water-adapted euryhaline shore crabs Carcinus maenas and freshwater-adapted extremely euryhaline Chinese crabs Eriocheir sinensis were tested for their capacity to excrete ammonia. Gills were perfused with haemolymph-like salines and bathed with salines equal in adaptation osmolality. Applying 100 μmol · l−1 NH4Cl in the perfusion saline and concentrations of NH4Cl in the bath that were stepwise increased from 0 to 4000 μmol · l−1 allowed us to measure transbranchial fluxes of ammonia along an outwardly as well as various inwardly directed gradients. The gills of all three crab species were capable – to different extents – of active excretion of ammonia against an inwardly directed gradient. Of the three crab species, the gills of Cancer pagurus revealed the highest capacity for active excretion of ammonia, being able to excrete it from the haemolymph (100 μmol · l−1 NH+ 4) through the gill epithelium against ambient concentrations of up to 800 μmol · l−1, i.e. against an eightfold gradient. Carcinus maenas and E. sinensis were able to actively excrete ammonia against approximately fourfold gradients. Within the three crab species, the gills of E. sinensis exhibited the greatest capacity to resist influx at very high external concentrations of up to 4000 μmol · l−1. We consider the observed capacities for excretion of ammonia against the gradient as ecologically meaningful. These benthic crustaceans protect themselves by burying themselves in the sediment, where, in contrast to the water column, concentrations of ammonia have previously been reported that greatly increase haemolymph levels. Electrophysiological results indicate that the permeabilities of the gill epithelia are a clue to understanding the species-specific differences in active excretion of ammonia. During the invasion of brackish water and freshwater, the permeabilities of the body surfaces greatly decreased. The gills of marine Cancer pagurus exibited the greatest permeability (ca. 250 mS cm−2), thus representing practically no influx barrier for ions including NH+ 4. We therefore assume that C. pagurus had to develop the strongest mechanism of active excretion of ammonia to counteract influx. On the other hand, freshwater-adapted E. sinensis exhibited the lowest ion permeability (ca. 4 mS cm−2) which may reduce passive NH+ 4 influxes at high ambient levels. Accepted: 14 October 1998  相似文献   

4.
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 NH3 and NH 4 + . NH3 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 NH3 or through an energy-driven NH 4 + pump balancing a leak of NH3 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 CH3NH2 has been compared to systems where CH3NH 3 + is taken up through channels, driven by the membrane potential (ΔU i,o) or the electrochemical potential for Na+μNa i,o + ). No model can be reconciled with experimental data unless the permeability of CH3NH2 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 + /CH3NH 3 + in co-porter driven by ΔμNa 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   

5.
The swamp eel, Monopterus albus, can survive in high concentrations of ammonia (>75 mmol l−1) and accumulate ammonia to high concentrations in its brain (∼4.5 µmol g−1). Na+/K+-ATPase (Nka) is an essential transporter in brain cells, and since NH4 + can substitute for K+ to activate Nka, we hypothesized that the brain of M. albus expressed multiple forms of Nka α-subunits, some of which might have high K+ specificity. Thus, this study aimed to clone and sequence the nka α-subunits from the brain of M. albus, and to determine the effects of ammonia exposure on their mRNA expression and overall protein abundance. The effectiveness of NH4 + to activate brain Nka from M. albus and Mus musculus was also examined by comparing their Na+/K+-ATPase and Na+/NH4 +-ATPase activities over a range of K+/NH4 + concentrations. The full length cDNA coding sequences of three nkaα (nkaα1, nkaα3a and nkaα3b) were identified in the brain of M. albus, but nkaα2 expression was undetectable. Exposure to 50 mmol l−1 NH4Cl for 1 day or 6 days resulted in significant decreases in the mRNA expression of nkaα1, nkaα3a and nkaα3b. The overall Nka protein abundance also decreased significantly after 6 days of ammonia exposure. For M. albus, brain Na+/NH4 +-ATPase activities were significantly lower than the Na+/K+-ATPase activities assayed at various NH4 +/K+ concentrations. Furthermore, the effectiveness of NH4 + to activate Nka from the brain of M. albus was significantly lower than that from the brain of M. musculus, which is ammonia-sensitive. Hence, the (1) lack of nkaα2 expression, (2) high K+ specificity of K+ binding sites of Nkaα1, Nkaα3a and Nkaα3b, and (3) down-regulation of mRNA expression of all three nkaα isoforms and the overall Nka protein abundance in response to ammonia exposure might be some of the contributing factors to the high brain ammonia tolerance in M. albus.  相似文献   

6.
All the glutamate dehydrogenase activity in developing castor bean endosperm is shown to be located in the mitochondria. The enzyme can not be detected in the plastids, and this is probably not due to the inactivation of an unstable enzyme, since a stable enzyme can be isolated from castor bean leaf chloroplasts. The endosperm mitochondrial glutamate dehydrogenase consists of a series of differently charged forms which stain on polyacrylamide gel electrophoresis with both NAD+ and NADP+. The chloroplast and root enzymes differ from the endosperm enzyme on polyacrylamide gel electrophoresis. The amination reaction of all the enzymes is affected by high salt concentrations. For the endosperm enzyme, the ratio of activity with NADH to that with NADPH is 6.3 at 250 millimolar NH4Cl and 1.5 at 12.5 millimolar NH4Cl. Km values for NH4+ and NAD(P)H are reduced at low salt concentrations. The low Km values for the nucleotides may favor a role for glutamate dehydrogenase in ammonia assimilation in some situations.  相似文献   

7.
Surface and subsurface litter fulfil many functions in the biogeochemical cycling of C and N in terrestrial ecosystems. These were explored using a microcosm study by monitoring dissolved inorganic nitrogen (DIN) (NH4 +–N?+?NO3 ?–N), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and fluxes in drainage water under ambient outdoor temperatures. Subsurface litter remarkably reduced the DIN concentrations in winter, probably by microbial N uptake associated with higher C:N ratio of added litter compared with soil at 10–25?cm depth. Fluxes of DIN were generally dominated by NO3 ?–N; but NH4 +–N strongly dominated DIN fluxes during freeze–thaw events. Appreciable concentrations of NH4 +–N were observed in the drainage from the acid grassland soils throughout the experiment, indicating NH4 +–N mobility and export in drainage water especially during freeze–thaw. Litter contributed substantially to DOC and DON production and they were correlated positively (p?<?0.01) for all treatments. DOC and DON concentrations correlated with temperature for the control (p?<?0.01) and surface litter (p?<?0.001) treatments and they were higher in late summer. The subsurface litter treatment, however, moderated the effect of temperature on DOC and DON dynamics. Cumulative N species fluxes confirmed the dominance of litter as the source of DON and DOC in the drainage water. DON constituted 42, 46 and 62% of cumulative TDN flux for control, surface litter and subsurface litter treatments respectively.  相似文献   

8.
Many plants develop toxicity symptoms and have reduced growth rates when supplied with ammonium (NH4+) as the only source of inorganic nitrogen. In the present study, the growth, morphology, NH4+ uptake kinetics and mineral concentrations in the tissues of the free-floating aquatic plant Salvinia natans (water fern) supplied exclusively with NH4+–N at concentrations of 0.25–15 mM were investigated. S. natans grew well, with relative growth rates of c. 0.25 g g?1 d?1 at external NH4+ concentrations up to 5 mM, but at higher levels growth was suppressed and the plants had small leaves and short roots with stunted growth. The high-affinity transport system (HATS) that mediate NH4+ uptake at dilute NH4+ levels was downregulated at high NH4+ concentrations with lower velocities of maximum uptake (Vmax) and higher half-saturation constants (K1/2). High NH4+ levels also barely affected the concentrations of mineral cations and anions in the plant tissue. It is concluded that S. natans can be characterized as NH4+-tolerant in line with a number of other species of wetland plants as growth was unaffected at NH4+ concentrations as high as 5 mM and as symptoms of toxicity at higher concentrations were relatively mild. Depolarization of the plasma membrane to the equilibrium potential for NH4+ at high external concentrations may be a mechanism used by the plant to avoid excessive futile transmembrane cycling. S. natans is tolerant to the high NH4+ levels that prevail in domestic and agricultural wastewaters, and the inherent high growth rate and the ease of biomass harvesting make S. natans a primary candidate for use in constructed wetland systems for the treatment of various types of nitrogen-rich wastewaters.  相似文献   

9.
The increase in concentration of ammonia in lake water during the degradation of algal blooms may last for several weeks and thus cause chronic toxicity to aquatic organisms. The purpose of this study was to assess the chronic toxicity of ammonia on the selected hematological parameters and gill Na+/K+ ATPase activity of juvenile crucian carp Carassius auratus during elevated ammonia exposure and the post-exposure recovery. Juvenile crucian carp were exposed in different ammonia solutions for 45 days and then immediately transferred to pristine freshwater to initiate a 15-day recovery period. Results showed sub-lethal ammonia significantly deters growth and a 15-day recovery period was not sufficient for the fish to compensate for the loss of growth. The fish exhibited a continuous decrease in red blood cell (RBC), the total hemoglobin (Hb), and gill Na+/K+ ATPase activity as the concentration of NH3-N increased. After the 15-day recovery period, RBC, Hb, and gill Na+/K+ ATPase activity had recovered to similar levels as the controls.  相似文献   

10.
Poplar plants are cultivated as woody crops, which are often fertilized by addition of ammonium (NH4 +) and/or nitrate (NO3 ?) to improve yields. However, little is known about net NH4 +/NO3 ? fluxes and their relation with H+ fluxes in poplar roots. In this study, net NH4 +/NO3 ? fluxes in association with H+ fluxes were measured non-invasively using scanning ion-selective electrode technique in fine roots of Populus popularis. Spatial variability of NH4 + and NO3 ? fluxes was found along root tips of P. popularis. The maximal net uptake of NH4 + and NO3 ? occurred, respectively, at 10 and 15 mm from poplar root tips. Net NH4 + uptake was induced by ca. 48 % with provision of NO3 ? together, but net NO3 ? uptake was inhibited by ca. 39 % with the presence of NH4 + in poplar roots. Furthermore, inactivation of plasma membrane (PM) H+-ATPases by orthovanadate markedly inhibited net NH4 +/NO3 ? uptake and even led to net NH4 + release with NO3 ? co-provision. Linear correlations were observed between net NH4 +/NO3 ? and H+ fluxes in poplar roots except that no correlation was found between net NH4 + and H+ fluxes in roots exposed to NH4Cl and 0 mM vanadate. These results indicate that root tips play a key role in NH4 +/NO3 ? uptake and that net NH4 +/NO3 ? fluxes and the interaction of net fluxes of both ions are tightly associated with H+ fluxes in poplar roots.  相似文献   

11.
This work aimed to study the regulation of K+/Na+ homeostasis and the physiological responses of salt-treated sorghum plants [Sorghum bicolor (L.) Moench] grown with different inorganic nitrogen (N) sources. Four days after sowing (DAS), the plants were transferred to complete nutrient solutions containing 0.75 mM K+ and 5 mM N, supplied as either NO3 ? or NH4 +. Twelve DAS, the plants were subjected to salt stress with 75 mM NaCl, which was applied in two doses of 37.5 mM. The plants were harvested on the third and seventh days after the exposure to NaCl. Under the salt stress conditions, the reduction of K+ concentrations in the shoot and roots was higher in the culture with NO3 ? than with NH4 +. However, the more conspicuous effect of N was on the Na+ accumulation, which was severely limited in the presence of NH4 +. This ionic regulation had a positive influence on the K+/Na+ ratio and the selective absorption and transport of K+ in the plants grown with NH4 +. Under control and salt stress conditions, higher accumulation of free amino acids and soluble proteins was promoted in NH4 + grown roots than NO3 ? grown roots at both harvesting time, whereas higher accumulation of soluble sugars was observed only at 7 days of salt stress exposure. Unlike the NH4 + grown plants, the gas exchanges of the NO3 ? grown plants were reduced after 7 days of salt stress. These results suggest that external NH4 + may limit Na+ accumulation in sorghum, which could contribute to improving its physiological and metabolic responses to salt stress.  相似文献   

12.
13.
14.
In order to reveal the character of ammonia emission in senescent tobacco (Nicotiana tabacum), the content of NH4+, total nitrogen, and soluble protein, and the activities of nitrogen metabolism-related enzymes were measured in leaves of a quick-leaf-senescence phenotype ZY90 and a slow-leaf-senescence phenotype NC89. Compared with NC89, ZY90 had a higher NH4+ accumulation, a lower glutamine synthetase activity, and a significantly higher stomatal ammonia compensation point, and ammonia emission during 40 to 60 d after leaf emergence. During senescence, the quick-leafsenescence phenotype was characterized by nitrogen re-transfer by ammonia emmission, whereas the slow-leafsenescence phenotype by nitrogen re-assimilation. The ammonia emission was primarily regulated by glutamine synthetase activity, apoplastic pH, and NH4+ content.  相似文献   

15.
Synopsis Adult rainbow trout, Oncorhynchus mykiss, were acutely exposed for 4 hours to low pH (4.4) and elevated Al-concentrations (300 µgI–1) in soft water (Ca2+ + Mg2+ = 25 µmolI–1). Comparison of branchial and renal ion fluxes (Na+, Cl, Mg2+, Ca2+ and NH4 +) gave evidence that pH and Al effects were primarily localized at the gill site. The negative whole body ion balance seemed to be caused by stimulatory effects on Na and Cl efflux especially under Al stress and to a lesser extent by inhibition of influx. Measurements of gill potentials indicated positive shifts, which were similar in response to increasing levels of H+ ions and Al. It is suggested that Al-induced changes of branchial potentials causes high diffusable loss of ions through interference with membrane-bound Ca2+ at the gill site.  相似文献   

16.
SLC4A11 has been proposed to be an electrogenic membrane transporter, permeable to Na+, H+ (OH), bicarbonate, borate, and NH4+. Recent studies indicate, however, that neither bicarbonate or borate is a substrate. Here, we examined potential NH4+, Na+, and H+ contributions to electrogenic ion transport through SLC4A11 stably expressed in Na+/H+ exchanger-deficient PS120 fibroblasts. Inward currents observed during exposure to NH4Cl were determined by the [NH3]o, not [NH4+]o, and current amplitudes varied with the [H+] gradient. These currents were relatively unaffected by removal of Na+, K+, or Cl from the bath but could be reduced by inclusion of NH4Cl in the pipette solution. Bath pH changes alone did not generate significant currents through SLC4A11, except immediately following exposure to NH4Cl. Reversal potential shifts in response to changing [NH3]o and pHo suggested an NH3/H+-coupled transport mode for SLC4A11. Proton flux through SLC4A11 in the absence of ammonia was relatively small, suggesting that ammonia transport is of more physiological relevance. Methylammonia produced currents similar to NH3 but with reduced amplitude. Estimated stoichiometry of SLC4A11 transport was 1:2 (NH3/H+). NH3-dependent currents were insensitive to 10 μm ethyl-isopropyl amiloride or 100 μm 4,4′- diisothiocyanatostilbene-2,2′-disulfonic acid. We propose that SLC4A11 is an NH3/2H+ co-transporter exhibiting unique characteristics.  相似文献   

17.
Ammonia (NH3) fluxes between beech leaves (Fagus sylvatica) and the atmosphere were investigated in a 90-year-old forest canopy and related to leaf nitrogen (N) pools and glutamine synthetase (GS) activities. The stomatal ammonia compensation point, ?? NH3, was measured by both a twig cuvette and bioassay techniques involving measurements of pH and ammonium (NH 4 + ) concentration in the leaf apoplastic solution. The ?? NH3 determined on the basis of the gas exchange measurements followed a seasonal variation with early-season peaks during leaf expansion (9.6 nmol NH3 mol?1 air) and late-season peaks during leaf senescence (7.3 nmol NH3 mol?1 air). In the mid-season, the ?? NH3 of mature green leaves was much lower (around 3 nmol NH3 mol?1 air) and dropped below the NH3 concentration in the ambient atmosphere. For comparison, ?? NH3 obtained by the apoplastic bioassay were 7.0, 3.7 and 6.4 nmol NH3 mol?1 air in early-, mid-, and late -season, thus agreeing reasonably well with ?? NH3 values derived from the gas exchange measurements. Potential NH3 emission fluxes during early and late season were 1.31 and 0.51 nmol m?2 leaf surface area s?1, respectively, while leaves were a sink for NH3 during mid-season. During leaf establishment and senescence, both apoplastic and bulk tissue NH 4 + concentrations were relatively high coinciding with low activities of glutamine synthetase, which is a key enzyme in leaf N metabolism. In conclusion, the exchange of NH3 between beech leaves and the atmosphere followed a seasonal variation with NH3 emission peaks being related to N mobilization during early leaf establishment and remobilization during late leaf senescence.  相似文献   

18.
Recently, a “Na+/NH4 + exchange complex” model has been proposed for ammonia excretion in freshwater fish. The model suggests that ammonia transport occurs via Rhesus (Rh) glycoproteins and is facilitated by gill boundary layer acidification attributable to the hydration of CO2 and H+ efflux by Na+/H+ exchanger (NHE-2) and H+-ATPase. The latter two mechanisms of boundary layer acidification would occur in conjunction with Na+ influx (through a Na+ channel energized by H+-ATPase and directly via NHE-2). Here, we show that natural ammonia loading via feeding increases branchial mRNA expression of Rh genes, NHE-2, and H+-ATPase, as well as H+-ATPase activity in juvenile trout, similar to previous findings with ammonium salt infusions and high environmental ammonia (HEA) exposure. The associated increase in ammonia excretion occurs in conjunction with a fourfold increase in Na+ influx after a meal. When exposed to HEA (1.5 mmol/l NH4HCO3 at pH 8.0), both unfed and fed trout showed differential increases in mRNA expression of Rhcg2, NHE-2, and H+-ATPase, but H+-ATPase activity remained at control levels. Unfed fish exposed to HEA displayed a characteristic reversal of ammonia excretion, initially uptaking ammonia, whereas fed fish (4 h after the meal) did not show this reversal, being able to immediately excrete ammonia against the gradient imposed by HEA. Exposure to HEA also led to a depression of Na+ influx, demonstrating that ammonia excretion can be uncoupled from Na+ influx. We suggest that the efflux of H+, rather than Na+ influx itself, is critical to the facilitation of ammonia excretion.  相似文献   

19.
Physiological regulation of plant-atmosphere ammonia exchange   总被引:10,自引:0,他引:10  
Plants have a compensation point for NH3 which ranges from 0.1 to 20 nmol mol-1, and may be several-fold higher or lower than naturally occurring atmospheric NH3 concentrations. This implies that NH3 fluxes over vegetated surfaces are bi-directional and that ammonia exchange with the atmosphere in many cases contributes significantly to the nitrogen economy of vegetation. Physiological regulation of plant–atmosphere NH3 fluxes is mediated via processes involved in nitrogen uptake, transport and metabolism. A rapid turnover of NH3 + in plant leaves leads to the establishment of a finite NH3 + concentration in the leaf apoplastic solution. This concentration determines, together with that of H+, the size of the NH3 compensation point. Barley and oilseed rape plants with access to NH3 + in the root medium have higher apoplastic NH3 + concentrations than plants absorbing NO3 -. Furthermore, the apoplastic NH3 + concentration increases with the external NH3 + concentration. Inhibition of GS leads to a rapid and substantial increase in apoplastic NH3 + and barley mutants with reduced GS activity have higher apoplastic NH3 + than wild-type plants. Increasing rates of photorespiration do not affect the steady-state NH3 + or H+ concentration in tissue or apoplast of oilseed rape, indicating that the NH3 + produced is assimilated efficiently. Nevertheless, NH3 emission increases due to a temperature-mediated displacement of the chemical equilibrium between gaseous and aqueous NH3 in the apoplast. Sugarbeet plants grown with NO3 - seem to be temporarily C-limited in the light due to a repression of respiration. As a consequence, the activity of chloroplastic GS declines during the day causing a major part of NH3 + liberated in photorespiration to be assimilated during darkness when 2-oxoglutarate is supplied in high rates by respiration. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

20.
The widespread use of NO3 fertilization has had a major ecological impact. NH4+ nutrition may help to reduce this impact, although high NH4+ concentrations are toxic for most plants. The underlying tolerance mechanisms are not yet fully understood, although they are thought to include the limitation of C, the disruption of ion homeostasis, and a wasteful NH4+ influx/efflux cycle that carries an extra energetic cost for root cells.In this study, high irradiance (HI) was found to induce a notable tolerance to NH4+ in the range 2.5-10 mM in pea plants by inducing higher C availability, as shown by carbohydrate content. This capacity was accompanied by a general lower relative N content, indicating that tolerance is not achieved through higher net N assimilation on C-skeletons, and it was also not attributable to increased GS content or activity in roots or leaves. Moreover, HI plants showed higher ATP content and respiration rates. This extra energy availability is related to the internal NH4+ content regulation (probably NH4+ influx/efflux) and to an improvement of the cell ionic balance.The limited C availability at lower irradiance (LI) and high NH4+ resulted in a series of metabolic imbalances, as reflected in a much higher organic acid content, thereby suggesting that the origin of the toxicity in plants cultured at high NH4+ and LI is related to their inability to avoid large-scale accumulation of the NH4+ ion.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号