Search

Melon is an important horticultural crop worldwide.In recent years,melon cultivation has been significantly affected by increasingly serious continuous cropping problems.Allelopathy is an important factor in the continuous cropping problems of melon.Organic acids are allelochemicals that are commonly found in Cucurbitaceae crops.However,there have been no reports on the isolation and characterization of allelochemicals from melon.In this research,we analyzed the effects of seven organic acid allelochemicals on the melon germplasm 'New Silverlit'.We evaluated the allelopathic effects of malic acid,citric acid,hydroxybenzoic acid,cinnamic acid,ferulic acid,salicylic acid,and coumaric acid.Seeds and seedlings were treated with different concentrations of the seven organic acids and seed germination percentages,morphological indexes,and changes in protective enzyme systems of melon seedlings were determined.The results showed that the selected organic acids in the experiment affected seed germination and seedling growth to varying degrees.Different concentrations of the same organic acids had different effects.In general,lower concentrations of organic acids showed promoting effects,whereas higher concentrations inhibited seed germination and seedling growth.In some cases,the same concentration of different organic acids had different effects on the various germination and growth parameters.Malic acid and citric acid increased the seed germination percentage and germination index.Hydroxybenzoic acid resulted in decreased seed germination percentage and germination index,while ferulic acid and coumaric acid showed a promoting effect on these parameters at low concentrations and an inhibitory effect at high concentrations.Cinnamic acid inhibited seed germination.Salicylic acid promoted seed germination at low concentrations and inhibited it at high concentrations.Seedlings treated with malic acid,ferulic acid,salicylic acid,and coumaric acid showed significantly lower fresh weight compared with the control.Seedlings treated with low concentrations of citric acid,hydroxybenzoic acid,and cinnamic acid showed increased fresh weight compared with the control,but showed lower fresh weight than the control when treated with high concentrations of these organic acids.Malic acid promoted radicle growth but inhibited hypocotyl growth.Hydroxybenzoic acid,citric acid,cinnamic acid,and salicylic acid inhibited radicle growth at low concentrations and inhibited hypocotyl growth at high concentrations.Coumaric acid and ferulic acid inhibited radicle growth and hypocotyl growth.At high concentrations,cinnamic acid showed the strongest inhibitory effect on seed germination and hypocotyl growth among the tested organic acids,suggesting that it may be one of the main allelochemicals of melon.The changes in the protective enzyme system were relatively complex.The activity of superoxide dismutase(SOD) decreased with increasing concentrations of hydroxybenzoic acid and salicylic acid.SOD activity increased in response to low concentrations of citric acid,ferulic acid,and coumaric acid,but decreased in response to higher concentrations of these acids.Cinnamic acid and malic acid treatments tended to cause a decrease in SOD activity.All of the tested organic acids significantly enhanced catalase activity,but the trends in catalase activity differed among the various organic acids.Peroxidase activity did not show a particular trend in response to organic acids.The malondialdehyde contents in melon seedlings treated with the seven organic acids were lower than that in control seedlings.These experimental results partly reveal the allelopathic effect of seven organic acid allelochemicals on melon and the mechanisms involved in the response to these compounds.

Issues around the loss of diversity caused by fast-growing tree plantations such as Eucalyptus have aroused controversy for many years.It is generally believed that Eucaluptus plantations bring about a decrease of plant′s biodiversity by influencing resource competitions,allelopathy,or the level of soil fertility.Above and below-ground of forest ecosystems interact implicitly.Complex interactions between above-belowground biodiversity may provide important feedbacks regulating ecosystem.However,seldom information was available on the soil organism′s diversity in Eucalyptus plantations.Furthermore,most of the previous studies were being conducted in the short-term rotation Eucalyptus plantations with a certain plantation age,which might limit our understanding of the actual plantation ecosystem process.Therefore,the abundance and diversity of plants and soil biodiversity were simultaneously measured across a range of eucalypt plantation ages(1—10 years) in southwest China to determine how Eucalyptus grandis afforestation of agricultural lands affected the native biodiversity.The present results showed that afforestation of E.grandis caused changes in plant and soil biodiversity with soil depth and was dependent on the stand age.The species richness,abundance and the diversity of understory plants and soil organisms showed a parallel development during the process of the succession,viz.both of them increased significantly with time but with a 'dip' around 4 years old.CCA analysis showed that the plant′s life forms transited from liana,hemicryptophytes and therophytes into perennial herbaceous-phanerophytes and phanerophytes.Bacteria quantitatively dominated the soil microbe in E.grandis regardless of plantation age.The individual proportion of saprozoic group quantitatively dominated in the soils of the all the study sites,followed by omnivorous group.The proportion of saprozoic groups decreased in 1—7 year old stands and then increased significantly with time.The proportion of omnivorous group increased as S shape with the plantation age.The proportion of predators and phytophage groups decreased significantly with time.The individual percentage of nematode decreased with the plantation age,but that of acarina and the number ratio of the acarina and collembola present the S shape increasing trend over time.The multiple comparisons test showed that plant diversity of the understory vegetation in 1,2 and 4—7 years-old plantations were significantly lower than that in the control forests(Pinus massoniana).Plant diversity in 1—10 year-old E.grandis plantations were significantly higher than that of the control arable land.Soil biodiversity in the plantations before the rotation period has no significant differences compared with agricultural lands,but were significantly higher in the plantations on or after the rotation period than the crop land.There were significant correlations between the plant′ s and soil organism′s diversity index and the correlation coefficient decreased with soil depth.

Most methods for investigating bacterial diversity of soil microorganisms was lack of the ability to establish a causal relationship between function and community compositions.Recently,using stable isotopes to label phylogenetically informative biomolecules(phospholipid fatty acids,DNA,or RNA),has the advantage of providing more definitive evidence that a detected population is active in a specific process,if that process leads to assimilation of C or N into cellular constituents.In practice,Nucleic acid SIP is considerably more sensitive and more informative for taxonomic purposes,particularly among of those related organisms,and thus is more generally useful. Shawan cold spring provides a typical non-sulfide cold spring environment in the arid and semi-arid areas of Xinjiang.In the previous research,the first overview of microbial diversity in the Shawan cold spring had provided,and the results showed that bacterial communities in the Shawan cold spring were diverse which comprised of 11 phyla and maybe exist a diversity of functional groups.In this paper,we surveyed the carbon sources utilization functional bacteria and their diversity in the sediment of the cold spring by stable isotope probing(SIP) and 16S rDNA clone library.The functional bacteria were enriched using 13C-labeled glucose as substrate,and then 13C-labeled genomic DNA was separated directly from the sediment samples and then it used as template for the PCR amplification of bacterial 16S rRNA gene and construction of the gene clone library.Based on restriction fragment length polymorphism(RFLP),417 positive clones were picked up and grouped into 27 operational taxonomic units(OTUs) by Hae III digestion.Subsequently,unique clones were sequenced.The blast search in Genbank and phyogenetic sequence analysis showed that 27 OTUs were divided into 9 phyla of bacterial domain i.e.,Firmicutes,Chloroflexi,Nitrospirae,Actinobacteria,Proteobacteria,Bacteroidetes,Planctomycetes,Cyanobacteria and Acidobacteria.Of those,Firmicutes and Proteobacteria were the dominant groups,and accounted for 28.3% and 38.6% of the total clone library respectively. Compared with 86 OTUs in the previous publication,Gemmatimonadetes,Chlorobi and Verrucomicrobia were not captured in glucose-utilizing bacteria,and the number of OTUs in other phyla decreased evidently,especially in Acidobacteria,only 6.45% of OTUs was observed in this research(48% in the previous research).In sum,that only 31% OTUs utilized glucose as carbon source in the system,suggesting there maybe exist other carbon sources utilization bacteria in the environment.In addition,we found that the incubating time and substrate concentration are key factors for the detection of some species that in low lever in the environment.As the result of enriching in this paper,a lots of OTUs were detected for the first time,such as the phylum Chloroflexi and genus Desulfuromonas.Particularly,genus Desulfuromonas was an important supplement to previous research,because strains belonged to the genus could reduce the sulfur to H2S,and the reason why the genus exited in a non-sulfide cold spring need further study.Additionally,compared with previous research,we found that the proportion of OTUs in Firmicutes was increased obviously from 1 to 7,which were divided into order Clostridiales and order Lactobacillales,and replaced Acidobacteria as the second dominant groups.Hence,the results indicated that an appropriate and reasonable pre-culture could be a useful supplement to study microbial composition and diversity in environmental samples by using culture-independent methods.

The brown planthopper(Nilaparvata lugens(Stl)) and white-backed planthopper(Sogatella furcifera(Horvath)) represent two of the most important insect pests of rice in Asia,causing severe damage to rice production.Both belong to long-distance migratory insects but differ in the time when they reach maximum density during rice-growing season.S.furcifera generally reaches its peak of occurrence when rice is before the filling stage;while N.lugens reaches its peak at the rice filling stage.It is possible that the same rice stage might impact the two planthopper species differently,thus leading to such a seasonal difference in population growth.To test this,we inoculated newly-emerged adults onto rice plants at each of the three developmental stages,i.e.,early tillering stage(about 40-d old,with 2—3 tillers),jointing stage(about 60-d old,the longest internode 2 cm) and booting-to-heading stage(about 75-80-d old).The level of ovarian development and take-off rate were then measured daily from the 2nd to the 5th day and from the 1st to the 5th day after emergency,respectively.Ovarian development from 2nd to the 5th day was largely dominated by grade Ⅰ,Ⅱ,Ⅲ and Ⅳ,respectively,with three exceptions including the 4d-(dominated by grade Ⅱ) and 5d-old S.furcifera females(grade Ⅲ) at booting-to-heading stage plants,plus the 5d-old S.furcifera females(grade Ⅲ) at jointing stage plants.For ovarian development in N.lugens females,in vast majority of the cases the three rice stages showed comparable proportion of females at each of the detected ovarian development grades,we only observed significant difference between early tillering stage(73.2% of the females at grade Ⅳ) and booting-to-heading stage(89% at grade Ⅳ) on the 5th day.In contrast,the grade of ovarian development displayed much larger differences among the three rice stages for both 4d-and 5d-old S.furcifera females.In particular,over 86% of the females from rice early tillering stage developed into grade Ⅲ on the 4th day and into grade Ⅳ on the 5th day,versus less than one quarter of the females from the booting-to-heading stage.To a similar extent,the ratio of females at grade Ⅲ was 4.2:1 between jointing stage and booting-to-heading stage on the 4th day,along with a ratio of up to 6.8:1 between early tillering stage and jointing stage for the 5d-old females at grade Ⅳ.As for the take-off rate,while little variation was seen for N.lugens across the three rice stages,noticeable differences were revealed for 1d-,4d-and 5d-old S.furcifera adults,with early tillering stage being constantly associated with the lowest take-off rate and booting-to-heading stage with the highest take-off rate.Thus,our results demonstrated a profound effect on the development of S.furcifera by a change of rice stage,as compared to relatively limited effect on N.lugens development.Furthermore,among the three rice stages,early tillering stage is most favorable and booting-to-heading stage is least favorable for S.furcifera development,a trend appearing to be reversed in N.lugens.Taken together,our analysis offers a plausible explanation for why the peak of S.furcifera comes before that of N.lugens.

Grain-filling directly relates to the productivity and quality of rice,and the degree and rate of rice grain-filling differ considerably according to the position to the grain′s position on a panicle.In general,the earlier flowering and superior grains,which are located on the apical primary branches,are filled faster and formed larger and heavier grains,while the inferior grains are set on the proximal secondary branches with sterile or poor quality.To meet a high productivity requirement for the modern rice variety,the following issues have to be answered:(a) what is the molecular ecological process of grain-filling,(b) how can the grain-filling of inferior grains be enhanced,and(c) how can the yield of the large panicle rice,in particular,be increased.Previous studies have shown that nitrogen(N) fertilization has significantly positive effect on rice′s grain-filling.However,whether N fertilization in the post-growth stage of rice is appropriate largely depending on the dynamic transport of N in rice leaves,which plays an important role in the physiological activity and hence affects the grain-filling of rice.Furthermore,the underlying molecular ecological effect of N fertilization on the grain-filling is less investigated particularly in large-panicle rice in the field. The present study investigated the characteristics of protein expression and their response to different N fertilizations during the grain-filling stage of an indica large-panicle rice cultivar(Jinhui 809),by the 2D technique.The field experiments were carried out at the Experimentation Station of Fujian Agriculture and Forestry University,Fuzhou(119.280E,26.080 N),Fujian,China during the rice growing season(June-November) in 2006 and 2007.Field management was the same,except the N application ratios between the 2006 and 2007 experiments.In 2006,the 225 kg/hm2 N were applied with the regular fertilization.In 2007,the constant of the total N supply,but the N fertilizer was given in two early to late growth stage application ratios.i.e.,7∶3 and 6∶4,as the treatments.The grain samples were collected in 2006 and the superior and inferior grains samples under the different N application ratios were collected separately in 2007 were used for the protein extraction.Then,the extracted grain proteins were separated with the two-dimensional gel electrophoresis(2DE) with the Isoelectric focusing(IEF) tube gels for the first dimension,and sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) for the second dimension(2D) separation.A total of 32 differentially expressed proteins at different grain-filling phases were detected by the 2D maps of grain proteome.Among them,27 proteins were successfully identified by Mass Spectrometry(MS).And,these identified proteins in different grain-filling phases were grouped into five expression patterns according to their functions in starch synthesis,energy metabolism,signal transduction and gene expression,as well as their regulation in the defense response to stresses,etc..The differential expression patterns of proteins in superior and inferior grains at different phases responding to different N application ratios were then analyzed.The results showed that 22 out of 26 differentially expressed proteins were identified in inferior grains,while 7 out of 8 proteins with differential expressions were identified in superior grains.Our results indicated that the grain-filling of the superior grains,especially in the large-panicle rice,had a higher environmental stability,while the reverse was true in the case of inferior grains.The present study also showed that the increases in N supply at grain-filling phases of rice favored in the up-regulation of the genes involved in physiological activities of inferior grain filling,including the signals transduction,gene expression,energy accumulation for the material metabolism,and hormone production etc.in inferior grains of rice,in turn,leading to increased yield.This study adds new significant insights to our current understanding of the regulation of rice grain filling by N application.