<Emphasis Type="Italic">Trichoderma</Emphasis> improves the growth of <Emphasis Type="Italic">Leymus chinensis</Emphasis>

Bio-fertilizer application has been proposed as a strategy for enhancing soil fertility, regulating soil microflora composition, and improving crop yields, and it has been widely applied in the agricultural yields. However, the application of bio-fertilizer in grassland has been poorly studied. We conducted in situ and pot experiments to investigate the practical effects of different fertilization regimes on Leymus chinensis growth, with a focus on the potential microecological mechanisms underlying the responses of soil microbial composition. L. chinensis biomass was significantly (P?<?0.05) increased by treatment with 6000 kg ha^?1 of Trichoderma bio-fertilizer compared with other treatments. We found a positive (R² =?0.6274, P <?0.001) correlation between bacterial alpha diversity and L. chinensis biomass. Hierarchical cluster analysis and nonmetric multidimensional scaling (NMDS) revealed that soil bacterial and fungal community compositions were all separated according to the fertilization regime used. The relative abundance of the most beneficial genera in bio-fertilizer (BOF) (6000 kg ha^?1Trichoderma bio-fertilizer) was significantly higher than in organic fertilizer (OF) (6000 kg ha^?1 organic fertilizer) or in CK (non-amend fertilizer), there the potential pathogenic genera were reduced. There were significant negative (P?<?0.05) correlations between L. chinensis biomass and the relative abundance of several potential pathogenic genera. However, the relative abundance of most beneficial genera were significantly (P?<?0.05) positively correlated with L. chinensis biomass. Soil properties had different effects on these beneficial and on these pathogenic genera, further influencing L. chinensis biomass.     

A Comparative Study on Removal Efficiency of Cr(VI) in Aqueous Solution by <Emphasis Type="Italic">Fusarium</Emphasis> sp. and <Emphasis Type="Italic">Myrothecium</Emphasis> sp.

Environmental pollution with chromium is due to residues of several industrial processes. Bioremediation is an alternative actually considered to remove Cr (VI) from the environment, using adapted organisms that grow in contaminated places. Have been conducted studies with fungi mechanisms of interaction with chromium, most of which have focused on processes biosorption, characterized it by passive binding of metal components of the cell surface, and bioaccumulation, wherein the metal entry to cells occurs with energy expenditure. The paper presents the results of studies carried out on sorption of chromium (VI) ions from aqueous solutions by Fusarium sp. and Myrothecium sp. Both biomasses have the ability to take up hexavalent chromium during the stationary phase of growth and as well inactive conditions. Fusarium sp. showed 26% of biosorption with active biomass and 64% in inactive biomass; meanwhile, Myrothecium sp. obtained 97 and 82%, respectively. Both fungi showed adjust to pseudo-second-order model in active (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.96) and inactive biomass assay (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.99). The data of the active biomass test also confirmed to the intraparticle diffusion model (Fusarium sp. R ² = 0.98; Myrothecium sp. R ² = 0.93). The results obtained through this investigation indicate the possibility of treating waste effluents containing hexavalent chromium using Fusarium sp. and Myrothecium sp.     

Catalase and Phosphatase Activities During Hydrocarbon Removal from Oil-Contaminated Soil Amended with Agro-Industrial By-products and Macronutrients

Microbiological activities are essential in the bioremediation of polluted soils. The enzymatic activities of microorganisms are usually used as a biological indicator of soil health. The aim of this work was to observe the catalase, acid phosphatase (AcP), and alkaline phosphatase (AlP) activities in soil that was amended with agro-industrial by-products and macronutrients during the process of total petroleum hydrocarbon (TPH) removal. To this end, microcosm tests were performed with soil and agro-industrial by-products ratios of 100:2:2, for soil:sugarcane bagasse pith:filter cake mud (SSF); 100:2, for both soil:sugarcane bagasse pith (SS); and for soil filter cake mud (SF). The macronutrients—carbon, nitrogen, and phosphorus—in the experimental treatments were adjusted to 100:10:1 with a solution of NH₄NO₃ and K₂HPO₄. The best TPH removal (51.4%) was obtained with SSF at 15 days. In addition, a significant correlation was observed between TPH removal and AlP as well as AcP (r = 0.74, p < 0.0001; r = 0.70, p < 0.0107, respectively). Fungi growth was also correlated with both AlP (r = 0.97, p < 0.0001) and AcP (r = 0.95, p < 0.0001) activities. Besides, bacterial and fungi growth showed a correlation with TPH (r = 0.86, p < 0.001; r = 0.77, p < 0.0034, respectively). It could be said that the agro-industrial by-products and macronutrients contributed to pollutant removal from the oil-polluted soil at relatively short amount of time. In addition, the enzymatic activities were increased after the treatment; in this study, the high sensitivity enzyme was AlP, and it could be used as an indirect indicator of oil pollutant removal.     

Morphological and genetic diversity of shea tree (<Emphasis Type="Italic">Vitellaria paradoxa</Emphasis>) in the savannah regions of Ghana

Vitellaria paradoxa C. F. Gaertn., commonly known as shea tree or Vitellaria, is ranked the most important tree species of the savannah regions in the most African countries due to its ecological and economic importance for livelihoods and national economies. However, the savannah regions are the most vulnerable areas to the global climate change. Moreover, the Vitellaria populations on farmlands are threatened by the dominance of old trees with low or lack of regeneration. In this study both morphological and genetic diversity were assessed using several phenotypic traits and 10 microsatellite markers, respectively, to assess the impact of land use and agro-ecozone types on Vitellaria in Ghana. The land use types were forests and farmlands, and the agro-ecozone types included the Transitional, Guinea, and Sudan savannah zones. The mean values of morphological traits, such as diameter at breast height (DBH) and canopy diameter (CD), were statistically different between forest (DBH = 22.20, CD = 5.37) and farmland (DBH = 39.85 CD = 7.49) populations (P < 0.00001). The Sudan savannah zone with mean petiole length of 4.96 cm showed significant difference from the other zones, likely as a result of adaptation to drier climate conditions. Genetic data analysis was based on 10 microsatellite markers and revealed high genetic diversity of Vitellaria in Ghana: mean expected heterozygosity, H _e was 0.667, and allelic richness, measured as number of effective alleles A _e , was 4.066. Both farmlands and forests were very diverse indicating lack of negative influence of farmer’s selection on genetic diversity. Fixation index was positive for all populations (mean F _IS = 0.136) with farmlands recording relatively higher values than forests in all ecological zone types studied, probably indicating less gene flow in the farmlands. Moderate differentiation (F′ _ST = 0.113) was comparable to other similar tree species. Both land use and ecological zone types influenced genetic differentiation of Vitellaria at varying levels. The species was spatially structured across three ecozones and following climatic gradient. The forest reserves are used in situ conservation for Vitellaria in Ghana. High diversity observed in the most arid zones provides opportunity to find and use appropriate plant materials for breeding climate change resilient trees.     

Dominant Characteristics Between <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> and <Emphasis Type="Italic">Cyclotella</Emphasis> Sp. Accompanying Dilution Process in Eutrophic Lake

Although dilution of lake water has been used for improvement of water quality and algal blooms control, it has not necessarily succeeded to suppress the blooms. We hypothesized that the disappearance of algal blooms by dilution could be explained by flow regime, nutrient concentrations, and their interaction. This study investigated the effects of daily renewal rate (d), nitrogen (N) and phosphorus (P) concentration, and their interaction on the domination between Microcystis aeruginosa and Cyclotella sp. through a monoxenic culture experiment. The simulation model as functions of the N:P mass ratio and dilution rate (D) (calculated from d) was constructed, and the dominant characteristics of both species were predicted based on the model using parameters obtained in a monoculture experiment and our previous study. Results of monoxenic culture experiment revealed that M. aeruginosa dominated in all conditions (d = 5 or 15%; N = 1.0 or 2.5 or 5.0 mg-N L^?1; P = 0.1 or 0.5 mg-P L^?1) and the predicted cell densities were substantially correspondent to experimental data. Under various N:P ratios and D values, characteristics of domination for each species were predicted, indicating that Cyclotella sp. tended to be dominant under high P concentrations (P ≥ 0.36 mg-P L^?1) when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1). It was also suggested that the dilution rate leading to the Cyclotella sp. domination required 0.20 day^?1 or higher regardless of the N:P ratios.

Open image in new window

Graphical Abstract ? M. aeruginosa and Cyclotella sp. could be a superior competitor in nutrient-limited and nutrient-rich conditions, respectively. ? The simulation model in this study indicated that the predicted cell density and nutrient concentration were substantially correspondent to experimental data. ? The model predicted that Cyclotella sp. tended to be dominant at the P ≥ 0.36 mg-P L^?1 when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1).

     

C-banded karyotype of <Emphasis Type="Italic">Thinopyrum bessarabicum</Emphasis> and identification of its chromosomes in wheat background

C-banded pattern in two accessions of Thinopyrum bessarabicum (Save ex Rayss) A. Löve (2n = 2x = 14, E^bE^b) and their idiogram was established. C-banding analysis was further used to identify the chromosomes of Tritipyrum amphiploid (2n = 6x = 42, AABBE^bE^b) and a BC₁F₂ genotype from wheat and Tritipyrum. Two 18S-26S rDNA loci were detected on Th. bessarabicum chromosomes by in situ hybridization using an 18S-26S rDNA probe. E^b chromosomes in Tritipyrum generally were identified by their distinctive C-banding patterns which reflected heterochromatin regions. C-banding procedure resulted in sharp and distinct bands in one or both ends of E^b chromosomes without interval bands. Observed C-bands in E^b genome mainly reflected the telomeric and subtelomeric sequences which also showed more strong signals in genomic in situ hybridization. Results showed the importance of the C-banding technique as a screening tool in identification of addition and substitution lines in the progenies of wheat and Tritipyrum crosses during segregating generations.     

Effects of cover crop in an apple orchard on microbial community composition,networks, and potential genes involved with degradation of crop residues in soil

Changes in the soil microbial communities and networks were monitored after planting the cover crop for 9 years. The field experiment included plots with a cover crop and without a cover crop but with weed control, and two subplots with or without chemical fertilizer (192 kg N ha^?1, 108 kg P₂O₅ ha^?1, and 168 kg K₂O ha^?1 each year). After applying the cover crop and chemical fertilizer for 9 years, the composition and activity of bacterial and fungal communities changed significantly (p?<?0.05), with the cover crop had greater effects than the chemical fertilizer on the composition of the soil microbial community. The relative abundances of 22 selected genera (in Firmicutes and Bacteroidetes) and two selected classes (Ascomycota) related to cover crop residue degradation increased significantly in the presence of the cover crop (p?<?0.05). Network analysis showed that the cover crop decreased the number of positive links between bacterial and fungal taxa by 25.33%, and increased the negative links by 22.89%. The positive links among bacterial taxa increased by 16.63% with the cover crop, mainly among Proteobacteria (increase of 39), Firmicutes (16), Actinobacteria (five), and Bacteroidetes (10). The links among fungal taxa were less than among bacterial taxa and were not significantly affected by cover crop. Taxa such as Thaumarchaeota, unidentified_Nitrospiraceae, unidentified_Nitrosomonadaceae, Faecalibacterium, Coprococcus_3, and Ruminococcaceae_NK4A214_group dominated the network without the cover crop but they were not dominant with the cover crop. The relative abundances of potential genes involved with the degradation of cellulose, hemicellulose, and cello-oligosaccharides increased significantly with the cover crop. Therefore, the SOC and TN contents were enhanced by the cover crop with the increase of the soil enzyme activities. Thus, the apple yield was improved by the cover crop.     

Estimation of natural outcrossing rate and genetic diversity in Lima bean (<Emphasis Type="Italic">Phaseolus lunatus</Emphasis> L. var. <Emphasis Type="Italic">lunatus</Emphasis>) from Brazil using SSR markers: implications for conservation and breeding

Lima bean (Phaseolus lunatus L.) is an important food source in Brazil, especially in the northeast region, where its production and consumption are high. The goals of the present study were to estimate natural outcrossing rates and genetic diversity levels of Lima bean from Brazil, using ten microsatellite loci to obtain information for their conservation and breeding. Fourteen accessions were selected from an experiment in field with open-pollinated and with the presence of pollinating insects. Twelve seeds of each of the 14 selected accessions were grown in screenhouse for tissue harvest and DNA extraction. The multilocus model was used to determine the reproductive system. The outcrossing rate was 38.1 % (t_m = 0.381; t_s = 0.078), and the results indicated a mixed mating system with a predominance of selfing (1 ? t_m = 61.9 %). The biparental inbreeding rate was high (t _m  ? t _s  = 0.303) and the multilocus correlated paternity was quite high (r _p(m) = 0.889), indicating that the progeny was mostly composed of full sibs. The average effective number of pollen donors per maternal plant (N _ep ) was low (1.12), and the fixation index for maternal genotypes (F _m ) was 0.945, indicating that most genitors resulted from inbreeding. The studied families presented considerable genetic variability: A = 6.10;  %P = 30; H _e  = 0.60 and H _o  = 0.077. Total diversity was high (H _T = 0.596), and a portion was distributed within families (H _S = 0.058). In addition, diversity was higher between families (D _ST = 0.538), and genetic differentiation was high (G _ST = 0.902). The results presented here can be used in the implementation of Lima bean conservation and breeding programs in Brazil.     

Growth and nitrogen uptake of jack pine seedlings in response to exponential fertilization and weed control in reclaimed soil

We evaluated the impact of exponential fertilization in nursery and weed removal in the field on growth and nitrogen (N) retranslocation and uptake from the soil of jack pine (Pinus banksiana Lamb.) seedlings planted on an oil sands reclaimed soil. Exponential fertilization is a method of supplying nutrients at an exponential rate to achieve constant internal nutrient concentrations in seedlings without changing their size during their growth in the nursery. The N retranslocation in seedlings was traced using ¹⁵N isotope labeling. Exponential fertilization increased nutrient reserve in the seedling in nursery production, and increased height (P = 0.003), root collar diameter (P < 0.001), total biomass (P < 0.001), and N content (P < 0.001) of seedlings at the end of first growing season in the field growth. Conventionally fertilized seedlings allocated a greater percent of biomass to roots than to current-year needles. The ¹⁵N isotope analysis showed that 59 to 82% of total N demand of new growth was met by retranslocation from old tissues. Exponential fertilization increased N retranslocation by 147% (P < 0.001) and N uptake from the soil by 175% (P = 0.012). Weed removal marginally increased (P = 0.077) N uptake from the soil but decreased (P = 0.046) N retranslocation with no net effect on total N content in new tissues. We conclude that exponential fertilization improves the early growth of jack pine and can help improve revegetation in reclaiming disturbed oil sands sites.     

Testing the influence of sediment granulometry on heterotrophic respiration with a new laboratory flow-through system

Purpose

Increased sedimentation due to land use intensification is increasingly affecting carbon processing in streams and rivers around the globe. This study describes the design of a laboratory-scale flow-through incubation system as a tool for the rapid estimation of sediment respiration. The measurements were compared with those obtained using an in situ closed chamber respiration method. The influence of sediment size on respiration rates was also investigated.

Materials and methods

Measurements were conducted on a pre-alpine gravel-bed river sediment separated into the following grain size fractions: > 60 mm (14.3%), 60–5 mm (60.2%), 5–2 mm (13.7%), 2–0.063 mm (11.1%) and <0.063 mm (0.6%). Concurrently, in situ and laboratory measurements were carried out on a naturally heterogeneous sediment. In situ respiration was determined in closed chambers as O₂ consumption over time, while in the laboratory, respiration was determined using flow-through respiration chambers. Oxygen concentrations were measured using a fibre-optic oxygen meter positioned at the inflow and outflow from the chamber.

Results and discussion

The mean respiration rates within naturally mixed riverbed sediments were 1.27 ± 0.3 mg O₂ dm^?3 h^?1 (n = 4) and 0.77 ± 0.1 mg O₂ dm^?3 h^?1 (n = 3) for the flow-through chamber system and closed chamber system, respectively. Respiration rates were statistically significantly higher in the flow-through chamber system (t test, p < 0.05), indicating that closed chamber measurements underestimated the oxygen consumption within riverbed sediments. Sediment grain size was found to significantly affect respiration rates in both systems (ANOVA, p < 0.001) with the fine sediment fraction (particle size <0.063 mm) having the highest respiration rate (r_flow-through = 51 ± 23 mg O₂ dm^?3 h^?1). The smallest fractions (2–0.063 and <0.063 mm), which represent approximately 12% of total sediment volume, contributed 60% of total respiration.

Conclusions

The study demonstrated that flow-through respiration chambers more accurately estimate the respiration rate within riverbed sediments than in situ closed chambers, since the former experiment imitates the natural conditions where continuous interstitial flow occurs in the sediments. We also demonstrated that fine sediments (<5 mm) substantially contribute to heterotrophic respiration in the studied gravel-bed river.

     

Optimization of <Emphasis Type="Italic">o</Emphasis>-Chlorophenol Biodegradation by Combined Mycelial Pellets Using Response Surface Methodology

In the present study, the immobilizing fermentation characteristics and o-chlorophenol biodegradation of Rhodopseudomonas palustris using mycelial pellets as a biomass carrier were investigated. To improve the o-chlorophenol degradation efficiency of the combined mycelial pellets, eight cultivation variables including glucose concentration, yeast extract concentration, spore inoculum size, pH, and agitation speed were optimized with an integrated strategy involving a combination of statistical designs. First, Plackett-Burman experiments identified glucose, yeast extract, and spore inoculum size as three statistically significant factors important for o-chlorophenol removal. Then, the steepest ascent method was used to access the optimal region of these significant factors. Finally, response surface methodology by Box-Behnken optimization was used to examine the mutual interactions among these three variables to determine their optimal levels. The ideal culture conditions for maximum o-chlorophenol removal according to a second-order polynomial model were as follows: 15.60 g/L glucose, 3.09 g/L yeast extract, and 9% (v/v) spore inoculum size, resulting in an expected o-chlorophenol removal rate of 92.60% with an o-chlorophenol initial concentration of 50 mg/L and 96-h culture time. The correlation coefficient (R ² = 0.9933) indicated excellent agreement between the experimental and predicted values, whereas a fair association was observed between the predicted model values and those obtained from subsequent experimentation at the optimized conditions.     

Taxon-specific responses of soil microbial communities to different soil priming effects induced by addition of plant residues and their biochars

Purpose

This work investigated changes in priming effects and the taxonomy of soil microbial communities after being amended with plant feedstock and its corresponding biochar.

Materials and methods

A soil incubation was conducted for 180 days to monitor the mineralization and evolution of soil-primed C after addition of maize and its biochar pyrolysed at 450 °C. Responses of individual microbial taxa were identified and compared using the next-generation sequencing method.

Results and discussion

Cumulative CO₂ showed similar trends but different magnitudes in soil supplied with feedstock and its biochar. Feedstock addition resulted in a positive priming effect of 1999 mg C kg^?1 soil (+253.7 %) while biochar gave negative primed C of ?872.1 mg C kg^?1 soil (?254.3 %). Linear relationships between mineralized material and mineralized soil C were detected. Most priming occurred in the first 15 days, indicating co-metabolism. Differences in priming may be explained by differences in properties of plant material, especially the water-extractable organic C. Predominant phyla were affiliated to Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Firmicutes, Planctomycetes, Proteobacteria, Verrucomicrobia, Ascomycota, Basidiomycota, Blastocladiomycota, Chytridiomycota, Zygomycota, Euryarchaeota, and Thaumarchaeota during decomposition. Cluster analysis resulted in separate phylogenetic grouping of feedstock and biochar. Bacteria (Acidobacteria, Firmicutes, Gemmatimonadetes, Planctomycetes), fungi (Ascomycota), and archaea (Euryarchaeota) were closely correlated to primed soil C (R ²?=??0.98, ?0.99, 0.84, 0.81, 0.91, and 0.91, respectively).

Conclusions

Quality of plant materials (especially labile C) shifted microbial community (specific microbial taxa) responses, resulting in a distinctive priming intensity, giving a better understanding of the functional role of soil microbial community as an important driver of priming effect.

     

Genetic diversity and relationships of wild and cultivated <Emphasis Type="Italic">Zanthoxylum</Emphasis> germplasms based on sequence-related amplified polymorphism (SRAP) markers

The genus Zanthoxylum, belonging to Rutaceae, has a long history of cultivation both for economic and chemical values in China. To effectively conserve and sustainably utilize this genus resource, a study on genetic diversity and relationships of Zanthoxylum germplasms was carried out by employing SRAP markers. We used 16 primer combinations to assess genetic variations and relationships among 175 accessions from eight cultivated provenances, including Shandong, Henan, Shanxi, Shaanxi, Gansu, Sichuan, Guizhou and Yunnan. A total of 145 clear repetitive and intense bands were yielded, and the percentage of polymorphic bands was 100 % for per primer combination, indicating a relatively high diversity among Zanthoxylum germplasms. From a geographic perspective, the highest genetic diversity level was observed within Guizhou provenance (N _a  = 1.97, Ne = 1.52, H = 0.31, I = 0.46) while Henan provenance had the lowest genetic diversity (N _a  = 1.68, Ne = 1.45, H = 0.25, I = 0.37). Based on AMOVA results, the abundant genetic variation was mainly caused by variation of intra-provenances (84.96 %), rather than among provenances (15.038 %). The results indicated low genetic differentiation (G _st  = 0.133) and high gene flow (N _m  = 3.2605) among provenances. The neighbor-joining tree revealed that the 175 accessions could be divided into four groups, and groupings indicated a divergence between the cultivated accessions of Zanthoxylum bungeanum Maxim. and Z. armatum DC. Moreover, three accessions of Z. piperitum DC. var. inerme without prickles introduced from Japan gathered one cluster. Cluster IV is composed of accessions of different geographical origin, including 11 wild species and 10 cultivated accessions of Z. bungeanum. The cluster analysis also reflected a relatively close relationship between the geographical origins and the classification of accessions in cluster I. Structure analysis indicated that collected Zanthoxylum accessions could be divided into two major groups. The information obtained from our research would benefit to make use of Zanthoxylum germplasms and assist the management of a Zanthoxylum germplasms collection.     

Changes in methane emission and methanogenic and methanotrophic communities in restored wetland with introduction of <Emphasis Type="Italic">Alnus trabeculosa</Emphasis>

Purpose

The dynamics and uncertainties in wetland methane budgets affected by the introduction of Alnus trabeculosa H. necessitate research on production of methane by methanogenic archaea and consumption by methane-oxidizing microorganisms simultaneously.

Materials and methods

This study investigated methane emission in situ by the closed chamber method, and methanogenic and methanotrophic communities using denatured gradient gel electrophoresis (DGGE) and quantitative PCR based on mcrA (methyl coenzyme M reductase), pmoA (particulate methane monooxygenase) genes in the rhizosphere and non-rhizosphere soils in the indigenous pure Phragmites australis T., and A. trabeculosa–P. australis mixed communities in Chongxi wetland.

Results and discussion

Methane flux rate from the pure P. australis community was 2.4 times larger than that of A. trabeculosa–P. australis mixed community in the rhizosphere and 1.7 times larger in the non-rhizosphere, respectively. The abundance of methanogens was lower in the mixed community soils (3.56?×?10³–6.90?×?10³ copies g^?1 dry soil) compared with the P. australis community (1.47?×?10⁴–1.89?×?10⁴ copies g^?1 dry soil), whereas the methanotrophs showed an opposite trend (2.08?×?10⁶–1.39?×?10⁶ copies g^?1 dry soil for P. australis and 6.20?×?10⁶–1.99?×?10⁶ copies g^?1 dry soil for mixed community soil). A liner relationship between methane emission rates against pmoA/mcrA ratios (R ²?=?0.5818, p?<?0.05, n?=?15) was observed. The community structures of the methane-cycling microorganism based on mcrA and pmoA suggested that acetoclastic methanogens belonging to Methanosarcinaceae and a particular type II methanotroph, Methylocystis, were dominant in these two plant communities.

Conclusions

The introduction of A. trabeculosa would promote the proliferation of methanotrophs, especially the dominant Methylocystis, but not methanogens, ultimately diminishing methane emission in the wetland.

     

The Magnetic Susceptibility and Iron Oxides of Aquic Soils in Southern Iran

An investigation of the effect of aquic conditions on Fe-oxides distribution and magnetic susceptibility (χ_lf) was conducted on selected soils from Southern Iran. Seven pairs of adjacent soil pedons with different soil moisture regimes (aquic and non-aquic), were selected. The average concentrations of poorly crystalline Fe (Fe_o) and total free Fe (Fe_d) in aquic soils were 0.2 and 0.07% respectively, and 0.45 and 0.9% in non-aquic soils, respectively. The ratio of Fe_o/Fe_d varied from 0.03 to 0.64. χ_lf ranged from 1.8 to 113 × 10^?8 m³ kg^?1 in the soil studied. The variation of χ_fd ranged from 0.0 to 9.65%. The χ_fd values observed in non-aquic soils were larger than in aquic soils (4.00% vs. 1.37%). Positive correlations were observed between χ and clay contents in both aquic and non-aquic soils; however, non-aquic soil samples showed a larger coefficient of determination. A positive correlation existed between χ_fd and χ in aquic and non-aquic soils. Higher values of χ_fd were observed at the soil surface of non-aquic soil samples than at deeper levels, suggesting a greater proportion of ultrafine grains. Of the soil properties that were assessed, clay, cation exchangeable capacity (CEC), Fe_d, Fe_o/Fe_d ratio, χ_lf and χ_fd contents, changed significantly in response to the aquic condition.     

Phenetic and genetic diversity in Indian <Emphasis Type="Italic">Luffa</Emphasis> (Cucurbitaceae) inferred from morphometric,ISSR and DAMD markers

Genetic variations and relationships among cultivated and wild genotypes of five taxa of Indian Luffa were examined using inter simple sequence repeats (ISSR), directed amplification of minisatellite DNA (DAMD) markers and morphological characterization. Morphometric evaluation of 21 discrete characters in 51 representative accessions segregated the five taxa of Luffa in three main clusters: the two wild species (L. echinata, L. graveolens) in the first, and the cultivated L. aegyptiaca (smooth gourd) and L. acutangula (ridged gourd)/L. hermaphrodita (Hermaphrodite luffa) in the second and third clusters, respectively. Cumulative data analysis of 15 ISSR and seven DAMD markers revealed high percentage polymorphism (97.67 %), moderate genetic distance (0.06–0.72, avg. 0.51), and low heterozygosity and Shannon index values (H = 0.15; I = 0.22) across all the 76 genotypes assayed. A UPGMA dendrogram, based on the combined marker data, resolved the five taxa in two main clusters with high bootstrap support. The morphological and molecular trees showed incongruence in the number of main clusters resolved and in the disposition of the wild and cultivated taxa in different sub-clusters. The cluster analyses and PCoA plots revealed a nested grouping of the hermaphrodite luffa within the ridge gourd group. The Bayesian STRUCTURE analysis identified three genetic clusters for the five assumed taxa. Outcrossing test revealed a mixed mating system in Indian Luffa. This is the first ever report on the mating system in Luffa using molecular markers. The study also demonstrates the utility of using more than one DNA marker in the assessment of molecular diversity in a widely cultivated crop genus like Luffa with a narrow genetic base.     

Effect of Cadmium Stress on Growth and Electrical Impedance Spectroscopy Parameters of <Emphasis Type="Italic">Cotinus coggygria</Emphasis> Roots

The use of plants for ecological remediation is an important method of controlling heavy metals in polluted land. Cotinus coggygria is a landscape plant that is used extensively in landscaping and afforestation. In this study, the cadmium tolerance level of C. coggygria was evaluated using electrical impedance spectroscopy (EIS) to lay a theoretical foundation for broad applications of this species in Cd-polluted areas and provide theoretical support to broaden the application range of the EIS technique. Two-year-old potted seedlings of C. coggygria were placed in a greenhouse to analyse the changes in the growth, water content and EIS parameters of the roots following treatment with different Cd concentrations (50, 100, 200, 500, 1000 and 1500 mg kg^?1), and soil without added Cd was used as the control. The roots grew well following Cd treatments of 50 and 100 mg kg^?1. The Cd contents increased with the increase in Cd concentration in the soil. However, the lowest root Cd content was found at 4 months of treatment. The extracellular resistance r_e and the intracellular resistance r_i increased first overall and then decreased with the increasing Cd concentration, and both parameters increased with a longer treatment duration. The water content had a significant negative correlation with the Cd content (P?<?0.01) and the r_e (P?<?0.05). C. coggygria could tolerate a soil Cd concentration of 100 mg kg^?1. There was a turning point in the growth, water content and EIS parameters of the C. coggygria roots when the soil Cd concentration reached 200 mg kg^?1. The root water content and r_e could reflect the level of Cd tolerance in C. coggygria.     

An overlooked nitrogen loss linked to anaerobic ammonium oxidation in estuarine sediments in China

Purpose

Despite its importance, anammox (anaerobic ammonium oxidation) in estuarine sediment systems remains poorly understood, particularly at the continental scale. This study aimed to understand the abundance, diversity, and activity of anammox bacteria and to determine the main factors influencing the anammox process in estuarine sediments in China.

Materials and methods

Estuarine sediments were collected from 18 estuaries spanning over 4000 km. Experiments using an ¹⁵ N–tracer, quantitative PCR, and clone library construction were used to determine the activity, abundance, and diversity of anammox bacteria. The impact of environmental factors on anammox processes was also determined.

Results and discussion

The abundance of the anammox-specific hydrazine synthase (hzsB) gene ranged from 1.8 × 10⁵ ± 3.4 × 10⁴ to 3.6 × 10⁸ ± 7.5 × 10⁷ copies g^?1 dw. Candidatus Scalindua, Brocadia, Kuenenia, Jettenia, and two novel unidentified clusters were detected, with Scalindua dominating the anammox population. Additionally, the abundances of Scalindua, Kuenenia, and Brocadia were found to be significantly correlated with latitude. The anammox rates ranged from 0.29 ± 0.15 to 13.68 ± 3.98 nmol N g^?1 dw h^?1 and contributed to 2.39–82.61% of total N₂ production. Pearson correlation analysis revealed that the anammox rate was positively correlated with total nitrogen, total carbon, and temperature, and was negatively correlated with dissolved oxygen (DO). The key factors influencing the hzsB gene abundance were ammonium concentration, salinity, and DO. Ammonium concentration, pH, temperature, and latitude were main variables shaping the anammox-associated bacterial community.

Conclusions

Our results suggested that anammox bacteria are ubiquitous in coastal estuaries in China and underline the importance of anammox resulting in N loss at a continental scale.

     

Nuclear and cytoplasmic contributions from <Emphasis Type="Italic">Erianthus arundinaceus</Emphasis> (Retz.) Jeswiet in a sugarcane hybrid clone confirmed through genomic in situ hybridization and cytoplasmic DNA polymorphism

A hybrid between Erianthus arundinaceus (Retz.) Jeswiet and Saccharum spontaneum L. which are wild related species of sugarcane (Saccharum L., Family Poaceae), was repeatedly crossed as female parent with sugarcane commercial varieties to develop near commercial sugarcane clones. The cytoplasm type of the hybrid derivatives were confirmed to be of E. arundinaceus through the mitochondrial and chloroplast DNA polymorphism of nad 4/3-4 intron segment and psbC–trnS segment, respectively. The E. arundinaceus × S. spontaneum hybrid with somatic chromosome number 2n = 62 was confirmed to have 30 chromosomes from E. arundinaceus through genomic in situ hybridization (GISH). The (E. arundinaceus × S. spontaneum) × sugarcane hybrid (2n = 118) had 24 chromosomes from E. arundinaceus whereas its next generation hybrid with sugarcane (2n = 108) had only 12 Erianthus chromosomes. The commercial sugarcane hybrid Co 15015, which is the third generation hybrid with 2n = 106 was confirmed to have two E. arundinaceus chromosomes through GISH. It is the first report of sugarcane with both alien cytoplasm and chromosome contributions from E. arundinaceus.     

Effect of biochar amendment on water infiltration in a coastal saline soil

Purpose

Increasing data have shown that biochar amendment can improve soil fertility and crop production, but there is little knowledge about whether biochar amendment can improve water infiltration in saline soils. We hypothesized that biochar amendment could promote water infiltration in saline soil. The aims of this study were to evaluate the effects of biochar amendment on water infiltration and find the suitable amendment rate and particle size of biochar as a saline soil conditioner.

Materials and methods

We measured water infiltration parameters in a coastal saline soil (silty loam) amended with non-sieved biochar at different rates (0.5, 1, 2, 5, and 10%, w/w) or sieved biochar of different particle sizes (≤?0.25 mm, 0.25–1 mm, and 1–2 mm) at 1 and 10% (w/w).

Results and discussion

Compared with the control, amending non-sieved biochar at 10% significantly decreased water infiltration into the saline soil (P?<?0.05). In contrast, sieved biochar of ≤?0.25 mm significantly improved water infiltration capacity, irrespective of the amendment rate. Sieved biochar of 1–2 mm was less effective to improve soil porosity and when amended at 10%, it even reduced the water infiltration capacity. The Philip model (R²?=?0.983–0.999) had a better goodness-of-fit than the Green-Ampt model (R²?=?0.506–0.923) for simulation of cumulative infiltration.

Conclusions

Amending biochar sieved to a small particle size improved water infiltration capacity of the coastal saline soil compared with non-sieved biochar irrespective of the amendment rate. This study contributes toward improving the hydrological property of coastal saline soil and rationally applying biochar in the field.