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1.
Mixed gels of κ-carrageenan (κ-car) from Hypnea musciformis and galactomannans (Gal) from Cassia javanica (CJ) and locust bean gum (LBG) were compared using dynamic viscoelastic measurements and compression tests. Mixed gels at 5 g/l of total polymer concentration in 0.1 M KCl showed a synergistic maximum in viscoelastic measurements for κ-car/CJ and κ-car/LBG at 2:1 and 4:1 ratios, respectively. The synergistic maximum obtained from compression tests carried out for mixed gels at 10 g/l of total polymer concentration in 0.25 M KCl was the same for both κ-car/CJ and κ-car/LBG gels. An enhancement in the storage modulus (G′) and the loss modulus (G″) was observed in the mechanical spectra for the mixtures in relation to κ-car. The proportionally higher increase in G″ compared with G′, as indicated by the values of the loss tangent (tan δ), suggests that the Gal adhere non-specifically to the κ-car network.  相似文献   

2.
The natural occurrence of the lichen Cladonia verticillaris as sunny and shaded populations implies changes in the pigment content. Shade specimens contain more chlorophyll a and b as well as more - and β-carotene than those found in unshaded lichens. However, lichens growing in sunny locations contain more methyl β-orcinol carboxylate, orcinol and fumarprotocetraric acid than those found in lichens growing under low light intensities. No structural differences in the chloroplasts of the two species bave been detected.  相似文献   

3.
In higher plants, mannans are found as dominant reserve material in the endosperm of Arecaceae seeds and also in some species from Apiaceae, Rubiaceae and Asteraceae. A linear β(1 → 4)-d-mannan was now isolated from the endosperm of Schizolobium parahybae, family Caesalpiniaceae, a native of Southern Brazil. Its seeds were germinated and the consumption of polysaccharides from the endosperm, namely galactomannans and β(1 → 4)-d-mannan, was analysed at differents stages of germination. At the 6th day after germination no residual 3:1 Man:Gal galactomannan was found, indicating that complete degradation of galactomannan had been reached. However, after 12 days of germination, the mannan was recovered from the remaining endosperm. Its presence in the endosperm after germination demonstrated that it is not a reserve material as described for seeds of other species.  相似文献   

4.
The viscosity in the low shear rate Newtonian domain of three biopolymers, locust bean gum, guar gum and xanthan gum was studied as a function of temperature and of polymer concentration in various aqueous solvents. The intrinsic viscosities [η]o of both galactomannans are not modified in the presence of 10 or 40% sucrose. In this case, a master curve relating the Newtonian specific viscosity (ηsp)o, to the reduced concentration c[η]o is obtained and allows (in good agreement with theoretical conjectures), two critical concentrations C* and C** to be defined, from which the value of the expansion coefficient may be estimated. For xanthan, as expected for a polyelectrolyte, [η]o depends strongly on salt concentration and on added sucrose and the results did not obey the above-mentioned master curve. However, it is shown that (ηsp)o depends only on xanthan concentration whenC > C**, and then it is assumed that chain dimensions have attained their unperturbed values whatever the solvent. Considering that both types of chains, random coils (galactomannans) and semi-rigid (xanthan) should give the same (ηsp)o-C[η]o master curve for C > C** when [η]o is replaced by its unperturbed counterpart [η]θ, a method for estimating [η]θ for the xanthan sample is proposed. In conclusion, the numerous exceptions to the widely accepted (ηsp)o vs C[η]o “universal” behaviour are mainly ascribed to significant differences in expansion coefficient values which depend on both the polymer and the solvent.  相似文献   

5.
HPLC-analysis was used to determine the concentrations of the lichen compounds alectoronic acid (depsidon), -collatolic acid (depsidon) and atranorin (depsid) in the lichenized ascomycete Tephromela atra (syn. Lecanon atra) (Hudson) Hafeliner from limestone walls on the Baltic island of Öland, Sweden. In 24 individuals of T. atra sampled on a stone wall, the pre-reproductive and reproductive tissue did not differ in the concentrations of alectoronic acid, collatolic acid and atranorin. The concentrations of the three lichen compounds were inter-correlated in the reproductive tissue, but not in the pre-reproductive tissue. Single individuals of T. atra ranged in area covered from 10.1 to 147.4 cm2 (mean: 38.5 cm2; N=24); 38.6% of this area was pre-reproductive tissue. However, the concentrations of the three lichen compounds were correlated neither with the total area covered by the lichen nor with the percentage of pre-reproductive tissue. This suggests that the concentrations of the lichen compounds do not change with increasing size (age) of the lichen. Analysis of specimens of T. atra from eight localities revealed a significant variation in lichen compounds (range between localities: alectoronic acid 0.60–3.26 μg/mg lichen dry weight (DW); collatolic acid 2.14–11.59 μg/mg lichen DW; atranorin 0.58–4.16 μg/mg lichen DW). The level of grazing observed in the lichens differed significantly among localities. However, no correlations between the concentrations of the three lichen compounds and the grazing damage to the lichens were found.  相似文献   

6.
Biological soil crusts are an integral part of dryland ecosystems. We monitored the cover of lichens and mosses, cyanobacterial biomass, concentrations of UV-protective pigments in both free-living and lichenized cyanobacteria, and quantum yield in the soil lichen species Collema in an undisturbed Mojave Desert shrubland. During our sampling time, the site received historically high and low levels of precipitation, whereas temperatures were close to normal. Lichen cover, dominated by Collema tenax and C. coccophorum, and moss cover, dominated by Syntrichia caninervis, responded to both increases and decreases in precipitation. This finding for Collema spp. at a hot Mojave Desert site is in contrast to a similar study conducted at a cool desert site on the Colorado Plateau in SE Utah, USA, where Collema spp. cover dropped in response to elevated temperatures, but did not respond to changes in rainfall. The concentrations of UV-protective pigments in free-living cyanobacteria at the Mojave Desert site were also strongly and positively related to rainfall received between sampling times (R2 values ranged from 0.78 to 0.99). However, pigment levels in the lichenized cyanobacteria showed little correlation with rainfall. Quantum yield in Collema spp. was closely correlated with rainfall. Climate models in this region predict a 3.5–4.0 °C rise in temperature and a 15–20% decline in winter precipitation by 2099. Based on our data, this rise in temperature is unlikely to have a strong effect on the dominant species of the soil crusts. However, the predicted drop in precipitation will likely lead to a decrease in soil lichen and moss cover, and high stress or mortality in soil cyanobacteria as levels of UV-protective pigments decline. In addition, surface-disturbing activities (e.g., recreation, military activities, fire) are rapidly increasing in the Mojave Desert, and these disturbances quickly remove soil lichens and mosses. These stresses combined are likely to lead to shifts in species composition and the local extirpation of some lichen or moss species. As these organisms are critical components of nutrient cycling, soil fertility, and soil stability, such changes are likely to reverberate throughout these ecosystems.  相似文献   

7.
Galactomannans were isolated from ripe seeds of Annona muricata (Annonaceae), Convolvulus tricolor (Convolvulaceae), Sophora japonica (Leguminosae), and from immature seeds of Arenga saccharifera and Cocos nucifera (both Palmae). Their sugar compositions were determined and their structures studied by the methylation and periodate-oxidation techniques. All the galactomannans studied are of the leguminous type, the molecules having main chains consisting of (1→4)-linked β- -mannose residues, with differing proportions of side chains consisting of single - -galactose residues linked to the main chains by (1→6)-bonds. The molecular weights were found to vary from 6,000 (Sophora) to 17,000 (Arenga). The isolation of the galactomannan of Annona is the first recorded occurrence of this type of polysaccharide in the family Annonaceae, whereas there has been a previous report of the occurrence of a galactomannan in the Convolvulaceae; the study of the structure of the Sophora galactomannan is the first one in the tribe Sophoreae of the Leguminosae.  相似文献   

8.
A reliable and reproducible method for plant regeneration in vitro of two important temperate eucalypts, Eucalyptus nitens and E. globulus, has been developed which utilises seedling explants. Highly regenerative callus was obtained from individual cotyledon and hypocotyledon explants of both species following cultivation on Murashige and Skoog’s (MS) basal nutrient medium supplemented with 30 g l−1 sucrose, 5–10% (v/v) coconut water, 0.8% agar, 1 mg l−1 -naphthalene-acetic acid (NAA) and 0.5 mg l−1 N6 benzylaminopurine (BAP). Shoot differentiation was observed 7–8 weeks after transfer of callus onto regeneration medium containing 0.5 mg l−1 NAA and 1 mg l−1 BAP. In a few instances, direct shoot regeneration occurred without an intervening callus phase in both species. The frequency of plant regeneration was higher for callus derived from hypocotyl segments (30–35%) compared to cotyledonary explants (20–25%) though the average number of shoots per cotyledonary explant was generally higher than for hypocotyl explants. Somatic embryos were observed occasionally in E. nitens, arising from the surface of organogenic callus. Organised structures closely resembling somatic embryos were also observed in E. globulus. Regenerated shoots (30–40%) of both species could be rooted in modified MS media containing indole-3-butyric acid (IBA) and plantlets were successfully transferred to soil.  相似文献   

9.
The crystal and the molecular structure of 4,1′,6′-trichloro-4,1′,6′-trideoxy-galacto-sucrose (TGS) was determined by X-ray analysis at 294 K. Crystals of TGS are orthorhombic, space group P212121, with a = 7.318(3), b = 12.027(4), c = 18.136(5) Å, V = 1596(1) Å3, Z = 4; Dx = 1.655 g.cm-3, λ(MoK) = 0.71073 Å, μ(MoK) = 5.44 cm-1, F(000) = 816. The X-ray intensities of 2649 reflections with I 2.5σ(I) were measured with Zr-filtered MoK-radiation. The structure was solved by the Patterson procedure and refined by full-matrix least-squares to a final R-value of 0.0298. Large conformational differences between TGS and sucrose were observed, particularly in the conformation of the glycosidic linkage. These differences originate from chlorine substitution, which affects intramolecular hydrogen bonding and sweet-taste glucophores.  相似文献   

10.
崇明东滩南部滩面高程、土壤盐度在空间上呈明显的梯度变化规律。高程整体西高东低、北高南低, 盐度东北高、西南低, 两者共同限制着盐沼植物在空间上的分布。该文围绕崇明东滩南部主要植被类群及其空间分布, 探讨了土壤盐度、潮滩高程两大环境因子与植物种群分布的对应关系。基于2013年夏、秋季植被空间网格采样和空间插值, 分析了东滩南部植物的空间分布现状, 发现不同植物类群在高程和土壤盐度上存在极显著的差异(p < 0.01)。高程差异: 莎草科类群主要分布于高程区间2.93-4.07 m的低潮滩, 禾本科主要集中分布在高程3.13-4.31 m的中、高潮滩; 盐度差异: 海三棱藨草(Scirpus mariqueter)和互花米草(Spartina alterniflora)优势种群植被覆盖区表层30 cm的平均土壤盐度为(3.2 ± 0.6) g·kg-1, 显著高于其他类群植物分布区的平均土壤盐度(2.0 ± 0.3) g·kg-1 (p < 0.01)。崇明东滩湿地生态系统的关键种兼先锋种——海三棱藨草, 分布高程介于2.53-3.97 m, 而互花米草能适应海三棱藨草80%的高程区间, 两者在高程上存在竞争关系。统计数据显示, 研究区域中近90%的海三棱藨草分布在研究区东北部, 土壤盐度范围为1.6-4.5 g·kg-1, 海三棱藨草、互花米草能较好地适应该空间内的盐度胁迫, 两种植物在此交替出现。但是在高程和土壤盐度的综合作用下, 互花米草的生长状况更好, 因此该区的海三棱藨草很可能会被互花米草逐步取代。对各类群植被分布和优势面积的研究发现, 海三棱藨草总分布面积为294 hm2, 优势群落面积120 hm2, 海三棱藨草仅占莎草科植物总优势面积的15.7%, 占研究区总面积的6.9%, 在6种主要植物(芦苇(Phragmites australis)、白茅(Imperata cylindrica)、互花米草、糙叶薹草(Carex scabrifolia)、藨草(Scirpus triqueter)、海三棱藨草)中比重最小, 这给保护区内海三棱藨草种群的恢复和保护带来极大的挑战。  相似文献   

11.
The braided rivers with their ever-changing water channels are recognized as one of New Zealand's most distinctive and important ecosystem. We made a survey of the vegetation on the shingle plains in the upper reaches of the braided rivers of South Island. A well-defined colonizing vegetation type was recognized. It consists of lichens, mosses, low herbs, low cushion plants and tufted grasses, and mat-forming plants. Because of the close mechanical connection between the thalli of the lichens of the genus Placopsis (Agyraceae: Ascomycota) with moss cushions and spreading mats of vascular plants, we see this Placopsis trachyderma – Raoulia – community as a special type of biological soil crusts.  相似文献   

12.
The reaction of dilithiated o-carborane (closo-1,2-Li2-1,2-C2B10H10) with CuCl2 gives 1,1′-bis(o-carborane) (1), 1,3′-bis(o-carborane) (2) and 1,4′-bis(o-carborane) (3). Compound 2 (C4B20H22) crystallizes in the monoclinic space group P21/n with A = 6.9275(6), B = 9.7655(8), C = 12.356(1) Å, β = 90.028(2)° and Z = 2. The structure was solved by direct methods and refined to R = 0.048 and Rw = 0.074. Compound 3 (C4B20H22) crystallizes in the orthorhombic space group P212121 with A = 6.8854(5), B = 12.523(1), C = 19.847(1) Å and Z = 4. The structure was solved by direct methods and refined to R = 0.078 and Rw = 0.091. The coupling reaction of dilithiated m-carborane (closo-1,7-Li2-1,7-C2B10H10) with CuCl2 results in the formation of 1,1′-bis(m-carborane) (4) and tetra(m-carborane) (5).  相似文献   

13.
Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO)5+BF4 in CH2Cl2 yields the corresponding [(steroid)Mn(CO)3]BF4 salts 1 and 2 as mixtures of and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO)3]BF4 · CH2Cl2 (1) having the Mn(CO)3 moiety on the side of the steroid is reported: space group P21 with a=10.3958(9), b=10.9020(6), c=12.6848(9) Å, β=111.857(6)°, Z=2, V=1334.3(2) Å3, calc=.481 cm−3, R=0.0508, and wR=0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear Mn---C---O linkages. The nucleophiles NaBH4 and LiCH2C(O)CMe3 add to [(β-estradiol 3,17-dimethyl ether)Mn(CO)3]BF4 (2) in high yield to give the corresponding - and β-cyclohexadienyl manganese tricarbonyl complexes (3). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo-CH2C(O)CMe3 substituent is reported (complex 4): space group P212121 with a=7.5154(8), b=15.160(2), c=25.230(3) Å, Z=4, V=2874.4(5) Å3, calc=1.244 g cm−3, R=0.0529 and wR2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 Å out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths.  相似文献   

14.

1. 1.Preferred temperature ranges were determined for workers of 5 species of Myrmecocystus in a temperature gradient on wet sand.

2. 2.Workers of the diurnally foraging species, M. mendax Wheeler, M romainei Cole, M. depilis Forel, and M. mimicus Wheeler, were distributed between 7 and 45°C, and workers of one nocturnal species, M. mexicanus Wesmael, were distributed between 5 and 35°C.

3. 3.Mean preferred temperatures of the 5 species increased as follows: mexicanus < mendax < romainei < depilis < mimicus.

4. 4.Preferred temperatures of M. romainei and M. mexicanus were higher in the summer than in the fall.

5. 5.After 2 h in the gradient on dry sand, workers of M. romainei were distributed similarly to those on wet sand, but after 8 h on dry sand, most workers were below 12°C where the air was saturated.

Author Keywords: Myrmecocystus romainei; Myrmecocystus depilis; Myrmecocystus mimicus; Myrmecocystus mendax; Myrmecocystus mexicanus; honey ants: preferred temperatures; temperature limits; desert adaptations: humidity responses  相似文献   


15.
Chromium and salt tolerance in five indigenous cyanobacterial strains isolated from contaminated sites was investigated along with their metal bioaccumulative potential. All the five species showed significantly better growth when the medium was spiked with salt or chromium. As compared to single metal or salt treatment, the binary metal–salt (MS) treatments had more favorable effect on cyanobacterial growth as indicated by significantly higher concentration of the primary photosynthetic pigment chlorophyll at M20S2000 (9.9–25.3 μg/mL) as compared to that at M0S0 (4.0–12.3 μg/mL). Similarly biomass was much higher at M20S1000 and M20S2000 (41.8–86.2 mg/10 mL) as compared to that at control, M0S0 (21.5–36.3 mg/10 mL). Accessory pigments like carotenoids and phycobilinproteins too tended to increase significantly in response to both metal and salts in the two species of Lyngbya (L. putealis and L. ceylanica var. constricta) and Gloeocapsa. These species also showed greater potential of chromium bioaccumulation, which increased further as both salt and metal concentration increased. In the two species of Nostoc however, bioaccumulative potential improve at higher metal concentration, but not affected significantly by salt concentration.  相似文献   

16.
Morimura N  Inoue T  Katayama K  Aruga J 《Gene》2006,380(2):72-83
Leucine-rich repeat and fibronectin III domain-containing (Lrfn) has five members in mouse and human (Lrfn1, Lrfn2, Lrfn3, Lrfn4, Lrfn5), and homologues in other vertebrates. Lrfn proteins share leucine-rich repeat (LRR)–immunoglobulin-like (Ig)–fibronectin type III (Fn)–transmembrane domain structure, which is also found in LRR–Ig–Fn superfamily proteins. Mouse Lrfn genes were expressed at adult stage predominantly in the brain. In the course of development, expression of Lrfn1, Lrfn3, and Lrfn4 started from immature neural cells, whereas that of Lrfn2 and Lrfn5 was limited to mature ones. Lrfn1–5 commonly encode glycoproteins spanning the plasma membrane, with their N-terminus located on the extracellular side. C-termini of Lrfn1, Lrfn2 and Lrfn4 were bound by PDZ domains of postsynaptic protein PSD95, re-distributing PSD95 to cell periphery where the Lrfn proteins were detected. These results suggest that Lrfn proteins are neuronal components with a role in the developing or mature vertebrate nervous system.  相似文献   

17.
为了解黄渤海甲壳类的分类多样性特征, 我们统计了2010-2015年中国水产科学研究院黄海水产研究所调查捕获的黄渤海甲壳类(软甲纲: 十足目与口足目)物种名录。结合历史文献, 进一步系统整理得到黄渤海甲壳类物种总名录。基于这2个名录, 应用分类阶元包含指数(the inclusion index at taxonomic level, TINCLi)、平均分类差异指数(average taxonomic distinctness index, Δ+)和分类差异变异指数(variation in taxonomic distinctness index, Λ+)研究了其分类多样性特征。结果显示: 2010-2015年调查名录中, 甲壳类共93种, 隶属于2目39科66属, 其中10种为新分布种; 对虾科、藻虾科、长臂虾科、梭子蟹科和弓蟹科的物种数最多, 合计占总物种数的38.71%; TINCLi分别为1.41种/属和2.38种/科; Δ+和Λ+分别为50.25和35.20。总名录中, 甲壳类共228种, 隶属于2目53科123属, 其中藻虾科、豆蟹科、对虾科、弓蟹科和鼓虾科的物种数最多, 合计占总物种数的30.70%; TINCLi分别为1.85种/属和4.30种/科, Δ+和Λ+分别为50.18和30.87。对虾科的相对丰富度指数(the relative richness index, Rr)最高(100), 其次是梭子蟹科(71.43)和长臂虾科(62.50), 豆蟹科最低(6.25)。黄渤海甲壳类的平均分类差异指数(Δ+)明显小于鱼类(P < 0.05)。2010-2015年调查的Δ+计算值高于理论值, 且在理论值的95%置信区间内, 说明黄渤海甲壳类群落正处在中等程度的干扰中。  相似文献   

18.
Complexes of type A4[VO(tart)]2·nH2O, where A = Rb or Cs and tart =d,l-tartrate(4−) (n = 2) or d,d-tartrate(4−) (n = 2 for Rb and n = 3 for Cs), were prepared from an aqueous mixture of V2O5, AOH and H4tart. These complexes were studied by single-crystal X-ray diffraction methods: Rb4[VO(d,l-tart)]2·2H2O, space group P1 with a = 8.156(1),b = 8.246(1),c = 8.719(1)Å, = 66.09(1)°, β = 65.07(1)°, γ = 82.40(1)°,Z = 2, 1917 observed reflections, and final Rw = 0.035; Cs4[VO(d,l-tart)]2·2H2O, space group P21/c with a = 9.350(1),b = 13.728(2),c = 8.479(1)Å, β = 106.77(1)°,Z = 4, 2235 observed reflections, and final Rw = 0.054; Rb4[VO(d,d-tart)]2·2H2O, space group P4122 with a = 8.072(1),c = 32.006(3)Å,Z = 8, 1014 observed reflections and final Rw = 0.038; Cs4[VO(d,d-tart)]2·3H2O, space group P122 with a = 8.184(1),c = 33.680(5)Å,Z = 8, 1310 observed reflections, and final Rw = 0.063. Bulk magnetic susceptibility data (1.5–300 K) for these compounds and A4[VOl,l-tart)]2·nH2O (A = Rb, Cs) were obtained on polycrystalline samples. These data were analyzed in terms of a Van Vleck exchange coupled S = 1/2 model which was modified to include an interdimer exchange parameters Θ. Analysis of the low-temperature (1.5–20 K) susceptibility data gave 2J = +1.30 cm−1 and Θ = −1.86 K for Rb4[VO(d,l-tart)]2·2H2O, 2J = +1.16 cm−1 and Θ = −1.69 K for Cs4[VO(d,l-tart)]2·2H2O, 2J = +1.90 cm−1 and Θ = −0.82 K for Rb4[VO(d,d-tart)]2·2H2O, 2J = +2.04 cm−1 and Θ = −0.80 K for Rb4[VO(l,l-tart)]2·2H2O, 2J = +1.52 cm−1 and Θ = −0.25 K for Cs4[VO(d,d-tart)]2·3H2O, and 2J = +1.64 cm−1 and Θ = −0.31 K for Cs4[VO(l,l-tart)]2·3H2O. These results suggest the magnitudes of intradimer (ferromagnetic and interdimer (antiferromagnetic) exchange interactions are similar in these complexes, as observed for the analogous Na salts.  相似文献   

19.
Two molecular species of bovine P450(11β), P450(11β)-2 and P450(11β)-3 have been identified, in which the amino acid differences were found at the 6th, 36th and 82nd positions from the NH2-termini of the mature proteins. They catalyzed the 11β-, 18- and 19-hydroxylation and aldosterone formation from 11-deoxycorticosterone, and the rate of production of 18-hydroxycorticosterone and aldosterone by P450(11β)-3 was greater than that by P450(11β)-2 [Morohashi et al., J. Biochem. 107 (1990) 635–640].

In this study, chimeric clones were constructed whose 6th, 36th and 82nd amino acid residues were exchanged with each other. Two original clones and six chimeric clones were expressed in COS-7 cells, and their steroidogenic activities studied. The ratio of aldosterone or 18-hydroxycorticosterone production to corticosterone production by one clone was compared with that of the other. The ratios for the four clones having Gly36 [P450(11β)-3 type] were 0.08–0.22, whereas those for the clones having Ser36 [P450(11β)-2 type] were 0.03–0.05, suggesting that the Gly36 structure is important for aldosterone production.  相似文献   


20.
《植物生态学报》2017,41(4):450
Aims Stoichiometric homeostasis is an important mechanism in maintaining ecosystem structure, function, and stability. The invasion of exotic species, Spartina alterniflora, has largely threatened the structure and function of native ecosystems in the Minjiang River estuarine wetland. However, how S. alterniflora invasion affect plant stoichiometric homeostasis is largely unknown. This could enhance our understanding on wetland ecosystem stability and expand the applications of ecological stoichiometry theory.
Methods Nitrogen (N) and phosphorus (P) contents of plant organs and soils in the S. alterniflora, Cyperus malaccensis var. brevifolius, and S. alterniflora-C. malaccensis var. brevifolius mixture were measured, and the homeostatic index (H) was calculated according to the stoichiometric homeostasis theory.
Important findings Our results showed that the invasion of S. alterniflora significantly increased soil N:P ratio (p < 0.05), but did not affect soil N or P contents. The N and P contents of leaf and stem were the highest for S. alterniflora, and those of the stem were the highest for C. malaccensis var. brevifolius. At the ecosystem level, the average of homeostatic index (H) of N (HN, 25.31) was larger than those of P (HP, 10.33) and N:P (HN:P, 2.50). At the organ level, root HN was significantly larger than stem HN (p < 0.05) and sheath HN:P was greater than root HN:P (p < 0.05), while there was no significant difference for HP among root, stem, leaf, and sheath (p > 0.05). As for species, root HN of S. alterniflora was significantly larger than that of C. malaccensis var. brevifolius in the mixture community (p < 0.05). In the monoculture, stem HN:P of S. alterniflora was significantly higher than that of C. malaccensis var. brevifolius (p < 0.05). Furthermore, root HN, leaf HN and sheath HN of S. alterniflora in the mixed community was significantly larger than that of S. alterniflora in the monoculture (p < 0.05), suggesting that S. alterniflora invasions increased their stoichiometric homeostasis. Meanwhile, the stoichiometric homeostasis of invasive and native plants were influenced by multiple factors, such as nutrients, organs, vegetation, and invasion. However, larger homeostasis was found in S. alterniflora than in C. malaccensis var. brevifolius in some particular organs either in mixture or monoculture communities. Therefore, the successful invasion of S. alterniflora may result from higher homeostatic index than the native species, C. malaccensis var. brevifolius.  相似文献   

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