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1.
Alder and lupine enhance nitrogen cycling in a degraded forest soil in Northern Sweden 总被引:3,自引:0,他引:3
Positive effects of legumes and actinorhizal plants on N-poor soils have been observed in many studies but few have been done at high latitudes, which was the location of our study. We measured N2 fixation and several indices of soil N at a site near the Arctic Circle in northern Sweden. More than 20 years ago lupine (Lupinus nootkatensis Donn) and gray alder (Alnus incana L. Moench) were planted on this degraded forest site. We measured total soil N, net N mineralization and nitrification with a buried bag technique, and fluxes of NH+
4 and NO–
3 as collected on ion exchange membranes. We also estimated N2 fixation activity of the N2-fixing plants by the natural abundance of 15N of leaves with Betula pendula Roth. as reference species. Foliar nitrogen in the N2-fixing plants was almost totally derived from N2 fixation. Plots containing N2-fixing species generally had significantly higher soil N and N availability than a control plot without N2-fixing plants. Taken together, all measurements indicated that N2-fixing plants can be used to effectively improve soil fertility at high latitudes in northern Sweden. 相似文献
2.
Leif Klemedtsson Karin Von Arnold† Per Weslien Per Gundersen‡ 《Global Change Biology》2005,11(7):1142-1147
Forested histosols have been found in some cases to be major, and in other cases minor, sources of the greenhouse gas nitrous oxide (N2O). In order to estimate the total national or global emissions of N2O from histosols, scaling or mapping parameters that can separate low‐ and high‐emitting sites are needed, and should be included in soil databases. Based on interannual measurements of N2O emissions from drained forested histosols in Sweden, we found a strong negative relationship between N2O emissions and soil CN ratios (r2adj=0.96, mean annual N2O emission=ae(?b CN ratio)). The same equation could be used to estimate the N2O emissions from Finnish and German sites based on CN ratios in published data. We envisage that the correlation between N2O emissions and CN ratios could be used to scale N2O emissions from histosols determined at sampled sites to national levels. However, at low CN ratios (i.e. below 15–20) other parameters such as climate, pH and groundwater tables increase in importance as regulating factors affecting N2O emissions. 相似文献
3.
The characteristic ratio CN = 〈r2〉0/Nlv2 of the β-D (1 → 4′)-linked polysaccharides xylan and mannan has been computed as a function of the angle τ at the bridge oxygen atom and the degree of polymerization N. The calculated values of the characteristic ratio CN are very high relative to their free rotational dimensions. The characteristic ratio of these polysaecharides converges to the asymptotic value at low degree of polymerization at higher τ values. The low values of the calculated characteristic ratio of xylan compared to cellulose and mannan for the same τ value indicate that the former is more flexible and assumes a compact configuration. A pronounced difference in the values of the characteristic ratio CN of cellulose and mannan has also been observed lower τ angles (<120°). On the other hand, nearly the same values of CN have been obtained at higher τ angles (120°–125°), which suggests that, cellulose and mannan may have similar configuralons in certain solvents. 相似文献
4.
Nobuyuki Suetsugu Isao Fukuzawa Shunsaku Koyama Ken’ichi Takeo Takashi Kuge 《Bioscience, biotechnology, and biochemistry》2013,77(10):2109-2110
The structures of N-glycans of total glycoproteins in royal jelly have been explored to clarify whether antigenic N-glycans occur in the famous health food. The structural feature of N-glycans linked to glycoproteins in royal jelly was first characterized by immunoblotting with an antiserum against plant complex type N-glycan and lectin-blotting with Con A and WGA. For the detail structural analysis of such N-glycans, the pyridylaminated (PA-) N-glycans were prepared from hydrazinolysates of total glycoproteins in royal jelly and each PA-sugar chain was purified by reverse-phase HPLC and size-fractionation HPLC. Each structure of the PA-sugar chains purified was identified by the combination of two-dimensional PA-sugar chain mapping, ESI-MS and MS/MS analyses, sequential exoglycosidase digestions, and 500 MHz 1H-NMR spectrometry.The immunoblotting and lectinblotting analyses preliminarily suggested the absence of antigenic N-glycan bearing β1-2 xylosyl and/or α1-3 fucosyl residue(s) and occurrence of β1-4GlcNAc residue in the insect glycoproteins.The detailed structural analysis of N-glycans of total royal jelly glycoproteins revealed that the antigenic N-glycans do not occur but the typical high mannose-type structure (Man9~4GlcNAc2) occupies 71.6% of total N-glycan, biantennary-type structures (GlcNAc2Man3GlcNAc2) 8.4%, and hybrid type structure (GlcNAc1Man4GlcNAc2) 3.0%. Although the complete structures of the remaining 17% N-glycans; C4, (HexNAc3Hex3HexNAc2: 3.0%), D2 (HexNAc2Hex5HexNAc2: 4.5%), and D3 (HexNAc3Hex4HexNAc2: 9.5%) are still obscure so far, ESI-MS analysis, exoglycosidase digestions by two kinds of β-N-acetylglucosaminidase, and WGA blotting suggested that these N-glycans might bear a β1-4 linkage N-acetylglucosaminyl residue. 相似文献
5.
P. M. Chalk 《Plant and Soil》1991,132(1):29-39
During the past 10 years estimates of N2 fixation associated with sugar cane, forage grasses, cereals and actinorhizal plants grown in soil with and without addition of inoculum have been obtained using the 15N isotope dilution technique. These experiments are reviewed in this paper with the aim of determining the proportional and absolute contribution of N2 fixation to the N nutrition of non-legumes, and its role as a source of N in agriculture. The review also identifies deficiencies in both the totality of data which are currently available and the experimental approaches used to quantify N2 fixation associated with non-legumes.Field data indicate that associative N2 fixation can potentially contribute agronomically-significant amounts of N (>30–40 kg N ha-1 y-1) to the N nutrition of plants of importance in tropical agriculture, including sugar cane (Saccharum sp.) and forage grasses (Panicum maximum, Brachiaria sp. and Leptochloa fusca) when grown in uninoculated, N-deficient soils. Marked variations in proportions of plant N derived from the atmosphere have been measured between species or cultivars within species.Limited pot-culture data indicate that rice can benefit naturally from associative N2 fixation, and that inoculation responses due to N2 fixation can occur. Wheat can also respond to inoculation but responses do not appear to be due to associative N2 fixation. 15N dilution studies confirm that substantial amounts of N2 can be fixed by actinorhizal plants. 相似文献
6.
Marc Le Bret 《Biopolymers》1980,19(3):619-637
Closed random Gaussian polygonal chains of N (6 < N < 150) bonds of equal length b and thickness d have been generated on a computer. The knot type, the writhing number w, the radius of gyration, and the average of the inverse of the distance between two apices have been determined for each chain. For all the studied knot types—0, 31, 41, 51, and 52—the probability density of finding a given w is Gaussian. The Gaussian is centered about 0 for the amphichiral knots. Therefore, for long circular DNAs, the contribution to the supercoiling energy, which depends on w only, may be considered as purely entropic and may be expressed as ARTw2/N, in agreement with previous semiempirical considerations. The parameter A increases with chain thickness, it decreases as N gets larger but rapidly reaches a plateau. Comparison with experimental data from the literature would suggest that the ratio of the writhing to the constraint increases with ionic strength. The ratio of sedimentation constant of the supercoiled DNA to the sedimentation constant of the nicked DNA varies as N1/4 (w/N)2, and therefore depends on the writhing density and on the length of the DNA. 相似文献
7.
For infrared absorption measurements, the following five isotopic polyglycines have been prepared: ordinary polyglycine (—NHCH2CO—)n, N-deuterated polyglycine (—NDCH2CO—)n, C-deuterated polyglycine (—NHCD2CO—)n, completely deuterated polyglycine (—NDCD2CO—)n, and N15-substituted polyglycine (—15NHCH2CO—)n. Infrared spectra have been observed both in the I and II forms of each of these five isotopic polyglycines in the spectral region of 4000–300 cm.?1. On the basis of the comparison of these spectra with each other, a nearly complete set of assignments of the observed bands of polyglycines has been given. 相似文献
8.
Soil pH as the chief modifier for regional nitrous oxide emissions: New evidence and implications for global estimates and mitigation 总被引:4,自引:0,他引:4
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Yajing Wang Jingheng Guo Rolf David Vogt Jan Mulder Jingguo Wang Xiaoshan Zhang 《Global Change Biology》2018,24(2):e617-e626
Nitrous oxide (N2O) is a greenhouse gas that also plays the primary role in stratospheric ozone depletion. The use of nitrogen fertilizers is known as the major reason for atmospheric N2O increase. Empirical bottom‐up models therefore estimate agricultural N2O inventories using N loading as the sole predictor, disregarding the regional heterogeneities in soil inherent response to external N loading. Several environmental factors have been found to influence the response in soil N2O emission to N fertilization, but their interdependence and relative importance have not been addressed properly. Here, we show that soil pH is the chief factor explaining regional disparities in N2O emission, using a global meta‐analysis of 1,104 field measurements. The emission factor (EF) of N2O increases significantly (p < .001) with soil pH decrease. The default EF value of 1.0%, according to IPCC (Intergovernmental Panel on Climate Change) for agricultural soils, occurs at soil pH 6.76. Moreover, changes in EF with N fertilization (i.e. ΔEF) is also negatively correlated (p < .001) with soil pH. This indicates that N2O emission in acidic soils is more sensitive to changing N fertilization than that in alkaline soils. Incorporating our findings into bottom‐up models has significant consequences for regional and global N2O emission inventories and reconciling them with those from top‐down models. Moreover, our results allow region‐specific development of tailor‐made N2O mitigation measures in agriculture. 相似文献
9.
Paul V. Bernhardt Piao Chin Philip C. Sharpe Jing-Yan C. Wang Des R. Richardson 《Journal of biological inorganic chemistry》2005,10(7):761-777
The search for orally effective drugs for the treatment of iron overload disorders is an important goal in improving the health
of patients suffering diseases such as β-thalassemia major. Herein, we report the syntheses and characterization of some new
members of a series of N-aroyl-N′-picolinoyl hydrazine chelators (the H2IPH analogs). Both 1:1 and 1:2 FeIII:L complexes were isolated and the crystal structures of Fe(HPPH)Cl2, Fe(4BBPH)Cl2, Fe(HAPH)(APH) and Fe(H3BBPH)(3BBPH) were determined (H2PPH=N,N′-bis-picolinoyl hydrazine; H2APH=N-4-aminobenzoyl-N′-picolinoyl hydrazine, H23BBPH=N-3-bromobenzoyl-N′-picolinoylhydrazine and H24BBPH=N-(4-bromobenzoyl)-N′-(picolinoyl)hydrazine). In each case, a tridentate N,N,O coordination mode of each chelator with Fe was observed. The FeIII complexes of these ligands have been synthesized and their structural, spectroscopic and electrochemical characterization
are reported. Five of these new chelators, namely H2BPH (N-(benzoyl)-N′-(picolinoyl)hydrazine), H2TPH (N-(2-thienyl)-N′-(picolinoyl)-hydrazine), H2PPH, H23BBPH and H24BBPH, showed high efficacy at mobilizing 59Fe from cells and inhibiting 59Fe uptake from the serum Fe transport protein, transferrin (Tf). Indeed, their activity was much greater than that found for
the chelator in current clinical use, desferrioxamine (DFO), and similar to that observed for the orally active chelator,
pyridoxal isonicotinoyl hydrazone (H2PIH). The ability of the chelators to inhibit 59Fe uptake could not be accounted for by direct chelation of 59Fe from 59Fe–Tf. The most effective chelators also showed low antiproliferative activity which was similar to or less than that observed
with DFO, which is important in terms of their potential use as agents to treat Fe-overload disease. 相似文献
10.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2688-2696
Recently, asparagine-linked oligosaccharides (N-glycans) have been found to play a pivotal role in glycoprotein quality control in the endoplasmic reticulum (ER). In order to screen proteins interacting with N-glycans, we developed affinity chromatography by conjugating synthetic N-glycans on sepharose beads. Using the affinity beads with the dodecasaccharide Glc1Man9GlcNAc2, one structure of the N-glycans, a 75-kDa protein, was isolated from the membranous fraction including the ER in Aspergillus oryzae. By LC-MS/MS analysis using the A. oryzae genome database, the protein was identified as one (AO090009000313) sharing similarities with calnexin. Further affinity chromatographic experiments suggested that the protein specifically bound to Glc1Man9GlcNAc2, similarly to mammalian calnexins. We designated the gene AoclxA and expressed it as a fusion gene with egfp, revealing the ER localization of the AoClxA protein. Our results suggest that our affinity chromatography with synthetic N-glycans might help in biological analysis of glycoprotein quality control in the ER. 相似文献
11.
《Bioscience, biotechnology, and biochemistry》2013,77(3):562-568
Structural changes in N-linked oligosaccharides of glycoproteins during seed development of Ginkgo biloba have been explored to discover possible endogenous substrate(s) for the Ginko endo-β-N-acetylglucosaminidase (endo-GB; Kimura, Y., et al. (1998) Biosci. Biotechnol. Biochem., 62, 253-261), which should be involved in the production of high-mannose type free N-glycans.The structural analysis of the pyridylaminated oligosaccharides with a 2D sugar chain map, by ESI-MS/MS spectroscopy, showed that all N-glycans expressed on glycoproteins through the developmental stage of the Ginkgo seeds have the xylose-containing type (GlcNAc2~0Man3Xyl1Fuc1~0GlcNAc2) but no high-mannose type structure. Man3Xyl1Fuc1GlcNAc2, a typical plant complex type structure especially found in vacuolar glycoproteins, was a dominant structure through the seed development, while the amount of expression of GlcNAc2Man3Xyl1Fuc1GlcNAc2 and GlcNAc1Man3Xyl1Fuc1GlcNAc2 decreased as the seeds developed. The dominantly occurrence of xylose-containing type structures and the absence of the high-mannose type structures on Ginkgo glycoproteins were also shown by lectin-blotting and immunoblotting of SDS-soluble glycoproteins extracted from the developing seeds at various developmental stages.Concerning the endogenous substrates for plant endo-β-N-acetylglucosaminidase, these results suggested that the endogenous substrates might be the dolicol-oligosaccharide intermediates or some glycopeptides with the high-mannose type N-glycan(s) derived from misfolded glycoproteins in the quality control system for newly synthesized glycoproteins. 相似文献
12.
Trichodesmium N2 fixation has been studied for decades in situ and, recently, in controlled laboratory conditions; yet N2‐fixation rate estimates still vary widely. This variance has made it difficult to accurately estimate the input of new nitrogen (N) by Trichodesmium to the oligotrophic gyres of the world ocean. Field and culture studies demonstrate that trace metal limitation, phosphate availability, the preferential uptake of combined N, light intensity, and temperature may all affect N2 fixation, but the interactions between growth rate and N2 fixation have not been well characterized in this marine diazotroph. To determine the effects of growth rate on N2 fixation, we established phosphorus (P)–limited continuous cultures of Trichodesmium, which we maintained at nine steady‐state growth rates ranging from 0.27 to 0.67 d?1. As growth rate increased, biomass (measured as particulate N) decreased, and N2‐fixation rate increased linearly. The carbon to nitrogen ratio (C:N) varied from 5.5 to 6.2, with a mean of 5.8 ± 0.2 (mean ± SD, N = 9), and decreased significantly with growth rate. The N:P ratio varied from 23.4 to 45.9, with a mean of 30.5 ± 6.6 (mean ± SD, N = 9), and remained relatively constant over the range of growth rates studied. Relative constancy of C:N:P ratios suggests a tight coupling between the uptake of these three macronutrients and steady‐state growth across the range of growth rates. Our work demonstrates that growth rate must be considered when planning studies of the effects of environmental factors on N2 fixation and when modeling the impact of Trichodesmium as a source of new N to oligotrophic regions of the ocean. 相似文献
13.
Whether grown as pulses for grain, as green manure, as pastures or as the tree components of agro-forestry systems, the value of leguminous crops lies in their ability to fix atmospheric N2, so reducing the use of expensive fertiliser-N and enhancing soil fertility. N2 fixing legumes provide the basis for developing sustainable farming systems that incorporate integrated nutrient management. By exploiting the stable nitrogen isotope 15N, it has been possible to reliably measure rates of N2 fixation in a wide range of agro-ecological field situations involving many leguminous species. The accumulated data demonstrate that there is a wealth of genetic diversity among legumes and their Rhizobium symbionts which can be used to enhance N2 fixation. Practical agronomic and microbiological means to maximise N inputs by legumes have also been identified. 相似文献
14.
China is the world's largest producer and consumer of fertilizer N, and decades of overuse has caused nitrate leaching and possibly soil acidification. We hypothesized that this would enhance the soils' propensity to emit N2O from denitrification by reducing the expression of the enzyme N2O reductase. We investigated this by standardized oxic/anoxic incubations of soils from five long‐term fertilization experiments in different regions of China. After adjusting the nitrate concentration to 2 mM, we measured oxic respiration (R), potential denitrification (D), substrate‐induced denitrification, and the denitrification product stoichiometry (NO, N2O, N2). Soils with a history of high fertilizer N levels had high N2O/(N2O+N2) ratios, but only in those field experiments where soil pH had been lowered by N fertilization. By comparing all soils, we found a strong negative correlation between pH and the N2O/(N2O+N2) product ratio (r2 = 0.759, P < 0.001). In contrast, the potential denitrification (D) was found to be a linear function of oxic respiration (R), and the ratio D/R was largely unaffected by soil pH. The immediate effect of liming acidified soils was lowered N2O/(N2O+N2) ratios. The results provide evidence that soil pH has a marginal direct effect on potential denitrification, but that it is the master variable controlling the percentage of denitrified N emitted as N2O. It has been known for long that low pH may result in high N2O/(N2O+N2) product ratios of denitrification, but our documentation of a pervasive pH‐control of this ratio across soil types and management practices is new. The results are in good agreement with new understanding of how pH may interfere with the expression of N2O reductase. We argue that the management of soil pH should be high on the agenda for mitigating N2O emissions in the future, particularly for countries where ongoing intensification of plant production is likely to acidify the soils. 相似文献
15.
Gerald B. Wells Salvatore J. Turco Barbara A. Hanson Robert L. Lester 《Analytical biochemistry》1981,110(2):397-406
Fourteen dolichylpyrophosphoryloligosaccharides, precursors of the asparagine-linked oligosaccharides of glycoproteins, have been separated by liquid chromatography on silica gel. The dolichylpyrophosphoryl-N-acetylglucosamine and the dolichylpyrophosphoryl-(N-acetylglucosamine)2-(mannose)9(glucose)2,3 thus resolved were shown to retain their activity as substrates in enzyme catalyzed reactions. The chromatography procedure for the first time makes available many of these single intermediates for further study. 相似文献
16.
Simone Dell’Acqua Isabel Moura José J. G. Moura Sofia R. Pauleta 《Journal of biological inorganic chemistry》2011,16(8):1241-1254
Identifying redox partners and the interaction surfaces is crucial for fully understanding electron flow in a respiratory
chain. In this study, we focused on the interaction of nitrous oxide reductase (N2OR), which catalyzes the final step in bacterial denitrification, with its physiological electron donor, either a c-type cytochrome or a type 1 copper protein. The comparison between the interaction of N2OR from three different microorganisms, Pseudomonas nautica, Paracoccus denitrificans, and Achromobacter cycloclastes, with their physiological electron donors was performed through the analysis of the primary sequence alignment, electrostatic
surface, and molecular docking simulations, using the bimolecular complex generation with global evaluation and ranking algorithm.
The docking results were analyzed taking into account the experimental data, since the interaction is suggested to have either
a hydrophobic nature, in the case of P. nautica N2OR, or an electrostatic nature, in the case of P. denitrificans N2OR and A. cycloclastes N2OR. A set of well-conserved residues on the N2OR surface were identified as being part of the electron transfer pathway from the redox partner to N2OR (Ala495, Asp519, Val524, His566 and Leu568 numbered according to the P. nautica N2OR sequence). Moreover, we built a model for Wolinella succinogenes N2OR, an enzyme that has an additional c-type-heme-containing domain. The structures of the N2OR domain and the c-type-heme-containing domain were modeled and the full-length structure was obtained by molecular docking simulation of these
two domains. The orientation of the c-type-heme-containing domain relative to the N2OR domain is similar to that found in the other electron transfer complexes. 相似文献
17.
Some unicellular N2-fixing cyanobacteria have recently been found to lack a functional photosystem II of photosynthesis. Such organisms, provisionally
termed UCYN-A, of the oceanic picoplanktion are major contributors to the global marine N-input by N2-fixation. Since their photosystem II is inactive, they can perform N2-fixation during the day. UCYN-A organisms cannot be cultivated as yet. Their genomic analysis indicates that they lack genes
coding for enzymes of the Calvin cycle, the tricarboxylic acid cycle and for the biosynthesis of several amino acids. The
carbon source in the ocean that allows them to thrive in such high abundance has not been identified. Their genomic analysis
implies that they metabolize organic carbon by a new mode of life. These unicellular N2-fixing cyanobacteria of the oceanic picoplankton are evolutionarily related to spheroid bodies present in diatoms of the
family Epithemiaceae, such as Rhopalodia gibba. More recently, spheroid bodies were ultimately proven to be related to cyanobacteria and to express nitrogenase. They have
been reported to be completely inactive in all photosynthetic reactions despite the presence of thylakoids. Sequence data
show that R. gibba and its spheroid bodies are an evolutionarily young symbiosis that might serve as a model system to unravel early events
in the evolution of chloroplasts. The cell metabolism of UCYN-A and the spheroid bodies may be related to that of the acetate
photoassimilating green alga Chlamydobotrys. 相似文献
18.
F. A. Bliss 《Plant and Soil》1993,152(1):71-79
Common bean (Phaseolus vulgaris L.), which is an important food crop in the Americas, Africa and Asia, usually is thought to fix only small amounts of atmospheric nitrogen. However, field data indicate considerable genetic variability for total N2 fixation and traits associated with fixation. Studies have shown that selection to increase N2 fixation will be successful if: (1) discriminating traits (selection criteria) are measured precisely, (2) variability in germplasm is heritable, (3) selected parents are also agronomically suitable, (4) units of selection facilitate quantification of selection criteria, and (5) a breeding procedure that allows maximum genetic gain for N2 fixation and recombination with essential agronomic traits is chosen. Breeding lines capable of fixing enough atmospheric N2 to support seed yields of 1000–2000 kg ha–1 have been identified and new cultivars with high N2 fixation potential are being released. 相似文献
19.
Leonard Nunney 《Biological journal of the Linnean Society. Linnean Society of London》1996,59(4):411-425
Understanding the relationship between effective population size (Ne) and the number of adults in a population (N) is important for predicting genetic change in small populations. In general, Ne is expected to be close to N/2, i.e. in the range N/4-3N/4, provided that the powerful effect of population bottlenecks on reducing Ne is factored out (using the harmonic mean of N). However, some very low published estimates of Ne/N(< 0.1) raise the possibility that other factors acting to reduce Ne have been underestimated. Here one such factor, variation in female fecundity, is investigated. Its effect on Ne depends on the standardized variance in fecundity (per breeding season), a measure that is generally independent of mean fecundity. Empirical estimates of this standardized variance from 16 animal studies yielded an average value of 0.44, and a maximum value less than 1.5. To investigate the effect of such values, three kinds of fecundity variation were modelled: random (seasonal): individual; and age-related. Fixed individual differences among females reduce Ne the most. However, to reduce Ne to N/10, the resulting standardized variance must usually be 10 or more. Random differences need to be even larger to achieve the same reduction. One possible mechanism, the random loss of whole families, requires very high family mortality (90% or more). The third model, fecundity that increases linearly with age, is ineffective at causing a marked decrease in Ne. Given the finding that very unusual conditions are required to reduce Ne below Ne/10, low estimates of Ne/N need to be examined critically: the lowest published ratio, for a natural population of oysters, was found to be questionable because of possible immigration into the population by cultivated oysters. 相似文献
20.
Andrew G. Peterson 《Oecologia》1999,118(2):144-150
The relationship between photosynthetic carbon assimilation (A
max) and leaf nitrogen content (N
leaf) can be expressed on either a leaf area basis (A
area vs N
area) or a leaf mass basis (A
mass vs N
mass). Dimensional analysis shows that the units for the slope of this relationship are the same for both expressions (μmol [CO2] g−1 [N] s−1). Thus the slope measures the change in CO2 assimilation per gram of nitrogen, independent of leaf mass or leaf area. Although they have the same units, large differences
between the area and mass-based slopes have been observed over a broad range of taxonomically diverse species. Some authors
have claimed that regardless of these differences, the fundamental nature of the A
max-N
leaf relationship is independent of the units of expression. In contrast, other authors have claimed that the area-based A
max-N
leaf relationship is fundamentally different from the mass-based relationship because of interactions between A
max, N
leaf, and leaf mass per area (LMA, g [leaf] m−2 [leaf]). In this study we consider the mathematical relationships involved in the transformation from mass- to area-based
expressions (and vice versa), and the implications this transformation has for the slope of the A
max-N
leaf relationship. We then show that the slope of the relationship is independent of the units of expression when the effect of
LMA is controlled statistically using a multiple regression. The validity of this hypothesis is demonstrated using 13 taxonomically
and functionally diverse C3 species. This analysis shows that the slope of the A
max-N
leaf relationship is similar for the mass- and area-based expressions and that significant errors in the estimate of the slope
can arise when the effect of LMA is not controlled.
Received: 7 May 1998 / Accepted: 19 October 1998 相似文献