Nitrogen uptake and allocation in <Emphasis Type="Italic">Populus simonii</Emphasis> in different seasons supplied with isotopically labeled ammonium or nitrate

Key message

The total uptake of ¹⁵ NO ₃ -N was twofold higher than that of ¹⁵ NH ₄ -N when supplied with ammonium and/or nitrate in different seasons; the seedlings fertilized with NO ₃ -N had good growth with high photosynthetic rate and total biomass.

Abstract

Appropriate fertilization is crucial for maximum plant growth and improving nitrogen use efficiency. Poplar is an important fast-growing tree species for biomass production, however, little is known about fertilizer management of poplar plantations growing on barren soil in different seasons. To understand nitrogen uptake and allocation of Populus simonii supplied with different forms of nitrogen in different seasons, we determined nitrogen uptake and allocation of P. simonii potted seedlings after a 4-day supply of ¹⁵NH₄-N, ¹⁵NO₃-N, ¹⁵NH₄NO₃, and NH ₄ ¹⁵ NO₃ in May, July, and September. The total ¹⁵N uptake was twofold higher when supplied with sole ¹⁵NO₃-N compared to sole ¹⁵NH₄-N in all the investigated seasons. In the presence of ammonium nitrate (¹⁵NH₄NO₃ and NH ₄ ¹⁵ NO₃), the total ¹⁵N uptake was two times higher when supplied with NH ₄ ¹⁵ NO₃ compared to ¹⁵NH₄NO₃. Per unit biomass, the ¹⁵N-uptake ability of fine roots was higher in May and July compared to that in September. ¹⁵N was present mainly in leaves in May and July, and was mainly stored in roots and stems in autumn. The effect of nitrogen on the growth of P. simonii seedlings was studied by fertilizing with NH₄-N, NO₃-N, and NH₄NO₃ for 8 weeks. The seedlings fertilized with NO₃-N had good growth with high photosynthetic rate and total biomass indicating that NO₃-N is crucial for P. simonii growth. These data contribute to understand the nitrogen uptake in different seasons in trees supplied with different forms of nitrogen. This provides important theoretical bases for fertilizer management of poplar plantations.

     

Human erythrocyte ammonium transport is mediated by functional interaction of ammonium (RhAG) and anion (AE1) transporters

The ammonia/ammonium (NH₃/NH ₄ ⁺ ) influx into red blood cells (RBCs) is mediated by surface glycoprotein RhAG that forms a structural complex with anion exchanger 1 (AE1, band 3). Owing to the activity of this complex, RBCs exposed to the isosmotic ammonium buffer swell and finally lyse. Isoosmotic NH ₄ ⁺ -containing media alters the pH gradient in RBCs (intracellular alkalosis in response to NH₃/NH ₄ ⁺ influx) and triggers the AE1 activity resulting in redundant chloride and water influx and finally in cell swelling. Here we demonstrate that the ammonia/ammonium transport in human RBCs depends on the pH (pH optimum 7.4 ± 0.1), temperature (Q₁₀ 2.6 ± 0.3), HCO ₃ ^? concentration (EC₅₀ 4.7 ± 0.3 mM), and AE1 function. The data confirm functional interactions between AE1 and RhAG. The initial velocity of cell swelling increased almost 50-fold in the isosmotic ammonium buffer containing 25 mM HCO ₃ ^? (37°C) in comparison to the reaction in the same buffer without HCO ₃ ^? . This indicates that the reaction is facilitated mostly by the carrier proteins, not just owing to the simple diffusion of NH₃ across the erythrocyte membrane. We demonstrate that pH_i reaches its maximum value much faster than the volume increase does. These data suggest that there is no direct correlation between pH_i changes and the influx of NH₃/NH ₄ ⁺ . Taken together, our data show that the RhAG and AE1 complex activity enables erythrocytes to be ammonia/ammonium storage sites in order to maintain the physiological blood ammonia/ammonium equilibrium.     

Seasonal and within-event dynamics of rainfall and throughfall chemistry in an open tropical rainforest in Rondônia,Brazil

Prolonged dry periods, and increasingly the generation of smoke and dust in partially-deforested regions, can influence the chemistry of rainfall and throughfall in moist tropical forests. We investigated rainfall and throughfall chemistry in a palm-rich open tropical rainforest in the southwestern Brazilian Amazon state of Rondônia, where precipitation averages 2300 mm year^?1 with a marked seasonal pattern, and where the fragmentation of remaining forest is severe. Covering the transition from dry to wet season (TDWS) and the wet season (WS) of 2004–2005, we sampled 42 rainfall events on event basis as well as 35 events on a within-event basis, and measured concentrations of DOC, Na⁺, K⁺, Ca²⁺, Mg²⁺, NH ₄ ⁺ , Cl^?, SO ₄ ^2? , NO ₃ ^? and pH in rainfall and throughfall. We found strong evidence of both seasonal and within-event solute rainfall concentration dynamics. Seasonal volume-weighted mean (VWM_S) concentrations in rainfall of DOC, K⁺, Ca²⁺, Mg²⁺, NH ₄ ⁺ , SO ₄ ^2? and NO ₃ ^? were significantly higher in the TDWS than the WS, while VWM_S concentrations in throughfall were significantly higher for all solutes except DOC. Patterns were generally similar within rain events, with solute concentrations declining sharply during the first few millimeters of rainfall. Rainfall and throughfall chemistry dynamics appeared to be strongly influenced by forest and pasture burning and a regional atmosphere rich in aerosols at the end of the dry season. These seasonal and within-event patterns of rainfall and throughfall chemistry were stronger than those recorded in central Amazônia, where the dry season is less pronounced and where regional deforestation is less severe. Fragmentation and fire in Rondônia now appear to be altering the patterns in which solutes are delivered to remaining moist tropical forests.     

The effect of total inorganic nitrogen and the balance between its ionic forms on adventitious bud formation and callus growth of ‘Węgierka Zwykła’ plum (<Emphasis Type="Italic">Prunus domestica</Emphasis> L.)

The effect of different ammonium NH ₄ ⁺ and nitrate NO ₃ ^? ratios (4:1, 2:1, 1:1, 1:2, 1:4, 1:6) on organogenesis of ‘W?gierka Zwyk?a’ leaf explants cultivated on media with nitrogen levels equalling full- or half-MS was investigated. On media with total nitrogen equal to ½ MS, explant regeneration increased significantly and was highest on media with 1:2 or 1:4 NH ₄ ⁺ :NO ₃ ^? ratio. An excess of ammonium versus nitrate ions had a negative effect on both regeneration and biomass. Addition of potassium to the medium increased the fresh weight of explants and the number of adventitious buds.     

Involvement of phosphoenolpyruvate carboxylase and antioxydants enzymes in nitrogen nutrition tolerance in <Emphasis Type="Italic">Sorghum bicolor</Emphasis> plants

Plants of Sorghum bicolor (C₄ species) were grown at different nitrate or ammonium concentrations (0.5, 5, 20 and 50 mM) in order to examine the effect of nitrogen nutrition on growth, phosphoenolpyruvate carboxylase (PEPC) and antioxidant enzymes activities in both roots and leaves of 30-day-old plants. At high NO₃^? levels (20 and 50 mM) the fresh weight was significantly higher. When the nitrogen source was in ammonium form, the leaf and root mass increased drastically at low concentration 5 mM and significantly at 20 mM, however similar fresh weight was found at high level of ammonium (50 mM). The leaves catalase (CAT), guaiacol peroxidase (POD), glutathione reductase (GR), and glutathione S-transferase (GST) activities and the roots glutathione reductase and glutathione S-transferase activities were significantly higher in the NH₄⁺-fed plants than those grown in the nitrate medium. Activity and proteins levels of phosphoenolpyruvate carboxylase in both leaves and roots of sorghum plants were increased progressively with increasing external nitrogen concentration. This increase was more pronounced at high level of ammonium (50 mM), being 2-fold at 50 mM of NO₃^? and 3-fold at 50 mM of NH₄⁺. Our results suggested that antioxidant enzymes activities and PEPC play a key role in ammonium detoxification and tolerance in sorghum plants.     

Decrease of phosphate concentration in the medium by <Emphasis Type="Italic">Brevibacterium casei</Emphasis> cells

Brevibacteria able to decrease phosphate concentration in the medium are of interest for the study of the role of bacteria in the phosphorus cycle and for development of biotechnology of phosphate removal from waste. Brevibacterium casei, Brevibacterium linens, and Brevibacterium epidermidis grown in media with initial phosphorus concentrations of 1–11 mM were shown to decrease its concentration by 90%. The composition of the incubation medium required for B. casei to carry out this process was established. This process occurs in the absence of glucose but requires the presence of Mg²⁺, NH ₄ ⁺ , and α-ketoglutarate. The latter two components may be replaced by amino acids metabolized to NH ₄ ⁺ and α-ketoglutarate: histidine, arginine, glutamine, proline, or glutamic acid. No formation of insoluble phosphate salts was observed when the media were incubated under the same conditions with heat-inactivated cells or without cells at pH 7–8.5.     

Effects of exogenous polyamines on nitrate tolerance in cucumber

Putrescine (Put), spermidine (Spd), and spermine (Spm) are the major polyamines (PAs) in plant, which are not only involved in the regulation of plant developmental and physiological processes, but also play key roles in modulating the defense response of plants to diverse environmental stresses. In this study, Cucumis sativus L. seedlings were cultivated in nutrient solution and sprayed with three kinds of PAs (Put, Spd, and Spm). The effects of PAs were investigated on excess nitrate stress tolerance of C. sativus by measuring growth and nitrogen (N) metabolism parameters. The contents of NO_3-^?N, NH_4-⁺N, proline and soluble protein in leaves were increased; while plant height, leaf area, shoot fresh and dry weight, root fresh weight were decreased under 140 mM NO₃^? treatment for 7 d. In addition, the activities of nitrate reductase (NR), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) were significantly inhibited under 140 mM NO₃^? treatment for 7 d. With foliar treatment by 1 mM Spd or Spm under stress treatment, the contents of Spm, Put, and Spd in leaves increased significantly, except that Spm content decreased under Spd treatment. The activities of NR, glutamine synthetase (GS), GOGAT and GDH and plant height, leaf area, shoot fresh and dry weights were significantly increased. The contents of proline and soluble protein in leaves were significantly enhanced. In contrast, the accumulation of NO_3-^?N and NH_4-⁺N were significantly decreased. However, there were minor differences in activities of N metabolism enzymes and the content of osmotic adjustment substances under 1 mM Put treatment. These findings suggest that 1 mM exogenous Spm or Spd could enhance the capacity of N metabolism, promote growth and increase resistance to high concentrations of NO₃^?. The ameliorating effect of Spd was the best, and that of Put the worst.     

New insights into the photochemistry of carotenoid spheroidenone in light-harvesting complex 2 from the purple bacterium <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis>

Light-harvesting complex 2 (LH2) from the semi-aerobically grown purple phototrophic bacterium Rhodobacter sphaeroides was studied using optical (static and time-resolved) and resonance Raman spectroscopies. This antenna complex comprises bacteriochlorophyll (BChl) a and the carotenoid spheroidenone, a ketolated derivative of spheroidene. The results indicate that the spheroidenone-LH2 complex contains two spectral forms of the carotenoid: (1) a minor, “blue” form with an S₂ (1¹B _u ⁺ ) spectral origin band at 522 nm, shifted from the position in organic media simply by the high polarizability of the binding site, and (2) the major, “red” form with the origin band at 562 nm that is associated with a pool of pigments that more strongly interact with protein residues, most likely via hydrogen bonding. Application of targeted modeling of excited-state decay pathways after carotenoid excitation suggests that the high (92%) carotenoid-to-BChl energy transfer efficiency in this LH2 system, relative to LH2 complexes binding carotenoids with comparable double-bond conjugation lengths, derives mainly from resonance energy transfer from spheroidenone S₂ (1¹B _u ⁺ ) state to BChl a via the Q_x state of the latter, accounting for 60% of the total transfer. The elevated S₂ (1¹B _u ⁺ ) → Q_x transfer efficiency is apparently associated with substantially decreased energy gap (increased spectral overlap) between the virtual S₂ (1¹B _u ⁺ ) → S₀ (1¹A _g ^? ) carotenoid emission and Q_x absorption of BChl a. This reduced energetic gap is the ultimate consequence of strong carotenoid–protein interactions, including the inferred hydrogen bonding.     

Effect of ammonium and other ions on the glucose-dependent active transport of l-histidine in slices of rat-brain cortex

1. The influence of cations on the active transport into cells of rat-brain-cortex slices of l-histidine, an amino acid that is not metabolized by this tissue, has been studied. 2. Like other amino acids, l-histidine accumulated in the cells in the presence of glucose in concentrations up to over double that in the incubation medium. 3. The active transport of l-histidine was highest in a medium containing Ca²⁺ (3mm). The addition of K⁺ (27mm) led to a marked decrease in the intracellular concentration of l-histidine, though the oxygen uptake of the slices was higher. 4. The active l-histidine transport was inhibited by NH₄⁺. The inhibitory effect increased with the NH₄⁺ concentration, being about 25% at 8mm, 65% at 20mm, and 90% at 27 and 50mm. The oxygen uptake of the brain slices was depressed by only 25% by the highest NH₄⁺ concentration used, and less by lower concentrations.     

Element fluxes in watershed-lake ecosystems recovering from acidification: Plešné Lake,the Bohemian Forest, 2001–2005

Fluxes of major ions and nutrients were measured in the watershed-lake ecosystem of a strongly acidified lake, Ple?né jezero (Ple?né Lake), in the Czech Republic in hydrological years from 2001 through 2005. The lake is situated in a Norway spruce forest and has a steep watershed between elevations of 1090 and 1378 m. The average water input and output from the ecosystem was 1372 mm and 1157 mm (37 L km^?2 s^?1), respectively, and the water residence time averaged 306 days. Despite ecosystem recovery from acidification occurring since the late 1980s, the Ple?né watershed was an average net source of 25 mmol SO ₄ ^2? m^?2 yr^?1. Nitrogen saturation of the watershed caused low retention of the deposited inorganic N (< 44% on average) before 2004. Then, the watershed became a net source of 28–32 mmol m^?2 yr^?1 of inorganic N in the form of NO ₃ ^? due to climatic effects (a dry summer in 2003 and a cold winter in 2004) and forest dieback caused by a bark beetle attack in 2004. Nitrogen transformations and SO ₄ ^2? release were the dominant terrestrial sources of H⁺ (72 and 49 mmol m^?2 yr^?1, respectively) and the watershed was a net source of 24 mmol H⁺ m^?2 yr^?1. Ionic composition of surface inlets showed seasonal variations, with the most pronounced changes in NO ₃ ^? , ionic Al (Al_i), and DOC concentrations, while the composition of subsurface inlets was more stable. The in-lake biogeochemical processes reduced on average 59% of the incoming H⁺ (251 mmol H⁺ m^?2 yr^?1 on a lake-area basis). NO ₃ ^? assimilation and denitrification, photochemical and microbial decomposition of allochthonous organic acids, and SO ₄ ^2? reduction in the sediments were the most important aquatic H⁺ consuming processes (358, 121, and 59 mmol H⁺ m^?2 yr^?1, respectively), while hydrolysis of Al_i was the dominant in-lake H⁺ generating process (233 mmol H⁺ m^?2 yr^?1). Photochemical liberation from organic complexes was an additional in-lake source of Al_i. The net in-lake retention or removal of total phosphorus, total nitrogen, and silica were on average 50%, 27%, and 23%, respectively. The lake was a net source of NH ₄ ⁺ due to a cease in nitrification (pH < 5) and from NH ₄ ⁺ production by dissimilation exceeding its removal by assimilation.     

Characterization of ammonium and nitrate uptake and assimilation in roots of tea plants

It has been pointed out that tea (Camellia sinensis (L.) O. Kuntze) prefers ammonium (NH ₄ ⁺ ) over nitrate (NO ₃ ^? ) as an inorganic nitrogen (N) source. ¹⁵N studies were conducted using hydroponically grown tea plants to clarify the characteristics of uptake and assimilation of NH ₄ ⁺ and NO ₃ ^? by tea roots. The total ¹⁵N was detected, and kinetic parameters were calculated after feeding ¹⁵NH ₄ ⁺ or ¹⁵NO ₃ ^? to tea plants. The process of N assimilation was studied by monitoring the dynamic ¹⁵N abundance in the free amino acids of tea plant roots by GC-MS. Tea plants supplied with ¹⁵NH ₄ ⁺ absorbed significantly more ¹⁵N than those supplied with ¹⁵NO ₃ ^? . The kinetics of ¹⁵NH ₄ ⁺ and ¹⁵NO ₃ ^? influx into tea plants followed a classic biphasic pattern, demonstrating the action of a high affinity transport system (HATS) and a low affinity transport system (LATS). The V _max value for NH ₄ ⁺ uptake was 54.5 nmol/(g dry wt min), which was higher than that observed for NO ₃ ^? (39.3 nmol/(g dry wt min)). K_M estimates were approximately 0.06 mM for NH ₄ ⁺ and 0.16 mM for NO ₃ ^? , indicating a higher rate of NH ₄ ⁺ absorption by tea plant roots. Tea plants fed with ¹⁵NH ₄ ⁺ accumulated larger amounts of assimilated N, especially glutamine (Gln), compared with those fed with ¹⁵NO ₃ ^? . Gln, Glu, theanine (Thea), Ser, and Asp were the main free amino acids that were labeled with ¹⁵N under both conditions. The rate of N assimilation into Thea in the roots of NO ₃ ^? -supplied tea plants was quicker than in NH ₄ ⁺ -supplied tea plants. NO ₃ ^? uptake by roots, rather than reduction or transport within the plant, seems to be the main factor limiting the growth of tea plants supplied with NO ₃ ^? as the sole N source. The NH ₄ ⁺ absorbed by tea plants directly, as well as that produced by NO ₃ ^? reduction, was assimilated through the glutamine synthetase-glutamine oxoglutarate aminotransferase pathway in tea plant roots. The ¹⁵N labeling experiments showed that there was no direct relationship between the Thea synthesis and the preference of tea plants for NH ₄ ⁺ .     

Ammonium nutrition increases water absorption in rice seedlings (Oryza sativa L.) under water stress

Water stress is a primary limitation on plant growth. In previous studies, it has been found that ammonium enhances the tolerance of rice plants to water stress, but how water is related to nitrogen form and water stress remains unknown. To study the effects of nitrogen form (NH ₄ ⁺ , NO ₃ ^? , and a mixture of NH ₄ ⁺ and NO ₃ ^? ) on the growth and water absorption of rice (Oryza sativa L.) seedlings, a hydroponic experiment with water stress, simulated by the addition of polyethylene glycol (PEG, 10% w/v, MW 6000), was conducted in a greenhouse. The results showed that, compared with non-water stress, under water stress, the fresh weight of rice seedlings increased by 14% with NH ₄ ⁺ nutrition, whereas it had decreased by about 20% with either NO ₃ ^? or mixed nitrogen nutrition. No significant difference was found in the transpiration rate of excised shoots or in xylem exudation of excised roots in NH ₄ ⁺ supply between the two water situations, whereas xylem flow decreased by 57% and 24% under water stress in NO ₃ ^? and mixed nutrition, and root hydraulic conductivity decreased by 29% and 54% in plants in NH ₄ ⁺ and NO ₃ ^? nutrition conditions, respectively. Although water absorption ability decreased in both NH ₄ ⁺ and NO ₃ ^? nutrition, aquaporin activity was higher in NH ₄ ⁺ than in NO ₃ ^? nutrition, regardless of water stress. We conclude that NH ₄ ⁺ nutrition can improve water handling in rice seedlings and subsequently enhance their resistance to drought.     

Distorted tetrahedral nickel-nitrosyl complexes: spectroscopic characterization and electronic structure

The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitrogen-based ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3), was prepared by the reaction of the potassium salt of the ligand with the nickel-nitrosyl precursor [Ni(NO)(Br)(PPh ₃ ) ₂ ]. The obtained nitrosyl complexes as well as the corresponding chlorido complexes [Ni(NO)(Cl)(PPh ₃ ) ₂ ] and [Ni(Cl)(L3)] were characterized by X-ray crystallography and different spectroscopic methods including IR/far-IR, UV–Vis, NMR, and multi-edge X-ray absorption spectroscopy at the Ni K-, Ni L-, Cl K-, and P K-edges. For comparative electronic structure analysis we also performed DFT calculations to further elucidate the electronic structure of [Ni(NO)(L3)]. These results provide the nickel oxidation state and the character of the Ni-NO bond. The complex [Ni(NO)(L3)] is best described as [Ni ^II (NO ^– )(L3)], and the spectroscopic results indicate that the phosphane complexes have a similar [Ni ^II (NO ^– )(X)(PPh ₃ ) ₂ ] ground state.     

Carbon and nitrogen in the ground waters of the Tellerman forest (European southern forest steppe)

Under the upland forests growing on the Dnieper loamy soils at 150–160 m above sea level, sandy aquifers are found at ~120 and ~140 m above sea level. The general mineralization of groundwaters (GWs) and the concentration of SO ₄ ^-2 increase upon approaching the foundation of fluvial glacial sediments. The concentration of C supplied to the local GWs is 10–12 mg L^–1 per year^–1. The concentration of C(CO ₃ ^-2 ; HCO ₃ ^-1 ; NO ₃ ^-1 ; NO ₂ ^-1 ) in the DSW is consistent with the C balance of upper biogeocenoses and the rate of groundwater migration. The concentrations of N(nh ₄ ⁺¹ ) are unrelated to the filtration of biogeocenosis moisture. They are identical both under sodic grassy glades and highly productive tree stands. The main part of N-containing ions in situ is synthesized and destroyed by anaerobic microorganisms living in the GW.     

The mechanisms for N-heterocyclic olefin-catalyzed formation of cyclic carbonate from CO<Subscript>2</Subscript> and propargylic alcohols

The mechanistic details of N-heterocyclic olefin-catalyzed formation of cyclic carbonate from CO₂ and propargylic alcohols were investigated by DFT calculations. Six mechanisms, four for the formation of five-membered cyclic carbonate (M-A, M-B, M-B’ and M-C), and two for six-membered cyclic carbonate (M-D and M-E), were fully investigated. The energy profiles in dichloromethane showed that M-B is the predominant reaction with the lowest barrier of 31.99 kcal mol^?1, while M-C and M-D may be kinetically competitive to M-B. The very high activation energy of 45.37 kcal mol^-1, 57.07 kcal mol^-1 and 59.61 kcal mol^?1 for M-A, M-B’ and M-E, respectively, suggest that they are of lesser importance in the overall mechanism.

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Graphical abstract Formations of five-membered ring product and six-membered ring product are kinetically competitive, but five-membered ring product is thermodynamically more preferable.

     

Positive feedback between acidification and organic phosphate mineralization in the rhizosphere of maize (Zea mays L.)

To test the hypothesis that rhizosphere acidification would enhance the hydrolyzation of organic phosphates by increasing phosphatase activity. A Petri dish experiment with sterile agar and a pot experiment with a low P soil were used. In the Petri dish experiment, roots of each plant were cultured in two compartments, each of which contained agar with one of three nitrogen combinations: NH ₄ ⁺ /N0 (N0 = nitrogen free), NH ₄ ⁺ /NO ₃ ^- , and NO ₃ ^- /N0. Phytin was supplied as the sole phosphorus (P) source to all compartments. In the pot experiment, the soil in each pot was treated with N0, KNO₃, or (NH₄)₂SO₄) together with 0 or 75 mg kg^?1 phytin-P. Dry weight, P concentration, and P content of roots were highest in the NH ₄ ⁺ compartments in the Petri dish experiment. In the pot experiment, dry weight, P concentration, and P content of both shoots and roots were higher with NH ₄ ⁺ than with NO ₃ ^- . NH ₄ ⁺ treatments reduced rhizosphere pH, promoted the hydrolization of phytin, enhanced acid phosphatase activity in the rhizosphere, and increased phytin-P utilization relative to N0 and NO ₃ ^- treatments. Phosphatase activity was negatively correlated with rhizosphere pH but was positively correlated with plant P content in both experiments. Rhizosphere acidification optimized the activity of acid phosphatase excreted by maize roots and promoted phytin mineralization. NH ₄ ⁺ -induced acidification in the maize rhizosphere improved the growth of maize roots by improving P uptake from phytin; the improved growth, in turn, increased NH ₄ ⁺ uptake and acidification.     

Karyotypic study of five Lutjanid species using conventional and Ag-NORs banding techniques

The first cytogenetic comparisons of five snapper species from Thailand were presented here. Renal cell samples were taken from blacktail snapper (Lutjanus fulvus), five lined snapper (L. quinquelineatus), dory snapper (L. fulviflamma), brownstripe red snapper (L. vitta), and mangrove red snapper (L. argentimaculatus). The mitotic chromosome preparation was prepared directly from kidney cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results exhibited that all five snapper species have the diploid chromosome numbers of 2n = 48 and the fundamental numbers (NF) of 48. The presences of large, medium, and small telocentric chromosomes were 22-24-2, 24-20-4, 36-10-2, 28-16-4 and 36-10-2, respectively. The Ag- NORs banding technique provides the pair of nucleolar organizer regions (NORs) at subcentromeric region of the long arm of the respective telocentric chromosome pairs 9, 1, 3, 4 and 9. Their karyotype formulas is as follows: L. fulvus (2n = 48): L ₂₂ ^t + M ₂₄ ^t + S ₂ ^t , L. quinquelineatus (2n = 48): L ₂₄ ^t + M ₂₀ ^t + S ₄ ^t , L. fulviflamma (2n = 48): Lt36 + Mt10 + St2, L. vitta (2n = 48): L ₂₈ ^t + M ₁₆ ^t + S ₄ ^t , and L. argentimaculatus (2n = 48): L ₃₆ ^t + M ₁₀ ^t + S ₂ ^t .     

Role of organic acids in the formation of the ionic composition in developing glycophyte leaves

The ionic composition in the leaves of some glycophyte plants (Phaseolus vulgaris L., Lycopersicon esculentum L., and Amaranthus cruentus L.) was studied during leaf development. Plants were grown in a stationary hydroponic culture; a growth medium contained equimolar concentrations of inorganic ions (NO ₃ ^? , Cl^?, SO ₄ ^2? , H₂PO ₄ ^? , K⁺, Ca²⁺, Mg²⁺, and Na⁺) equal to 5 mg-equiv./l for each ion. In the juvenile leaf, the main ions were K⁺ and water-soluble anions of organic acids represented mainly by di-and tricarboxylic acids in kidney bean and tomato and oxalic acid in amaranth. An increase in the total amount of organic anions, coinciding with the accumulation of bivalent cations, was registered in leaves of glycophytes during their development. Mature and senescing leaves of tomato and kidney bean accumulated mainly di-and tricarboxylic acid salts with the prevalence of Ca²⁺ ions. In amaranth leaves, the formation of water-insoluble (acid-soluble) oxalate pool containing Ca²⁺ ions (mature leaves) or Ca²⁺ and Mg²⁺ ions (senescing leaves) was registered. The priority role of the metabolism of organic acids in the formation of the ionic composition of glycophyte leaves during their development is discussed. It is supposed that the species-specific ionic composition of glycophyte leaves at different developmental stages is due mainly to the pattern of carbon metabolism causing the accumulation either of di-and tricarboxylic acids or oxalic acid.     

Influence of different mineral nitrogen sources (NO 3 − -N vs. NH 4 + -N) on arbuscular mycorrhiza development and N transfer in a Glomus intraradices–cowpea symbiosis

Labeled nitrogen (¹⁵?N) was applied to a soil-based substrate in order to study the uptake of N by Glomus intraradices extraradical mycelium (ERM) from different mineral N (NO ₃ ^? vs. NH ₄ ⁺ ) sources and the subsequent transfer to cowpea plants. Fungal compartments (FCs) were placed within the plant growth substrate to simulate soil patches containing root-inaccessible, but mycorrhiza-accessible, N. The fungus was able to take up both N-forms, NO ₃ ^? and NH ₄ ⁺ . However, the amount of N transferred from the FC to the plant was higher when NO ₃ ^? was applied to the FC. In contrast, analysis of ERM harvested from the FC showed a higher ¹⁵?N enrichment when the FC was supplied with ¹⁵NH ₄ ⁺ compared with ¹⁵NO ₃ ^? . The ¹⁵?N shoot/root ratio of plants supplied with ¹⁵NO ₃ ^? was much higher than that of plants supplied with ¹⁵NH ₄ ⁺ , indicative of a faster transfer of ¹⁵NO ₃ ^? from the root to the shoot and a higher accumulation of ¹⁵NH ₄ ⁺ in the root and/or intraradical mycelium. It is concluded that hyphae of the arbuscular mycorrhizal fungus may absorb NH ₄ ⁺ preferentially over NO ₃ ^? but that export of N from the hyphae to the root and shoot may be greater following NO ₃ ^? uptake. The need for NH ₄ ⁺ to be assimilated into organically bound N prior to transport into the plant is discussed.