This study was conducted to assess the effects of 2,4-epibrassionolide (EBR) on mold decay caused by Rhizopus stolonifer and its capability to activate biochemical defense reactions in postharvest peaches. The treatment of EBR at 5 μM possessed the optimum effectiveness on inhibiting the Rhizopus rot in peach fruit among all treatments. The EBR treatment significantly up-regulated the expression levels of a set of defense-related enzymes and PR genes that included PpCHI, PpGns1, PpPAL, PpNPR1, PpPR1 and PpPR4 as well as led to an enhancement for biosynthesis of phenolics and lignins in peaches during the incubation at 20 °C. Interestingly, the EBR-treated peaches exhibited more striking expressions of PR genes and accumulation of antifungal compounds upon inoculation with the pathogen, indicating a priming defense could be activated by EBR. On the other hand, 5 μM EBR exhibited direct toxicity on fungal proliferation of R. stolonifer in vitro. Thus, we concluded that 5 μM EBR inhibited the Rhizopus rot in peach fruit probably by a direct inhibitory effect on pathogen growth and an indirect induction of a priming resistance. These findings provided a potential alternative for control of fungal infection in peaches during the postharvest storage.
Authors:H. Bu, X. Chen, Y. Wang, X. Xu, K. Liu, and G. Du
In this paper, 633 species (involving 10 classes, 48 families, 205 genera) collected from the alpine meadow on the eastern Qinghai-Tibet plateau were studied. We tested potential factors affecting variation in mean germination time (MGT), i.e., plant traits (adult longevity, dispersal mode and seed size) or phylogeny, to evaluate if these factors were independent or they had interaction. Nested ANOVA showed that taxonomic membership accounted for the majority of MGT variation (70%), and in the generalized linear model, family membership could explain independently the largest proportion of MGT variation (29%). The strong taxonomic effect suggests that MGT variation within taxonomic membership is constrained. The other plant traits could also explain MGT variation independently (1% by adult longevity and dispersal mode, respectively, and 2% by seed size). Thus, the phylogeny was an important constraint to maintain the stability of species, and we could simplify the question if we regarded the phylogeny as an individual factor, but we could not negate the adaptive significance of the relationship between other plant traits and seed MGT. In addition, a large percentage of the variance remained unexplained by our model, thus important selective factors or parameters may have been left out of this analysis. We suggest that other possible correlates may exist between seed germination time and additional ecological factors (for example, altitude, habitat and post-dispersal predation) or phylogenetic related morphological and physiological seed attributes (e.g., endosperm mass) that were not evaluated in this study.
Authors:M. Li, Z. Du, H. Pan, C. Yan, W. Xiao, and J. Lei
Plant-plant interaction plays a key role in regulating the composition and structure of communities and ecosystems. Studies of plant-plant interactions in forest ecosystems have mainly concentrated on growth effects of neighboring plants on target trees. Physiological effects of neighboring plants on target trees, in particular understorey effects on physiology of overstorey trees, have received less attention. It is still unclear what is the physiological mechanisms underlying positive growth effects of understorey removal, although understorey removal has been applied to improve the wood production for hundreds of years worldwide. Only 17.5% of published works dealt with understorey-overstorey interactions and only a few of those researched the understorey effects on the physiology of overstorey trees. Case studies indicated that overstorey Abies faxoniana trees grown with different understorey shrubs showed significantly different levels of tissue nitrogen and mobile carbohydrates. Removal experiment showed that nitrogen and mobile carbohydrates concentrations in Cunninghamia lanceolata trees grown in the absence of understorey shrubs differed significantly (pure stand > mixture) with those in trees grown in the presence of understorey shrubs, in particular during the dry season. This review highlighted that the neighboring woody plants affect Cand N-physiology in overstorey trees. These effects may be mainly resulted from underground competition for soil water rather than for other resources as the effects were more pronounced during the dry season. The present review suggests that positive effects of neighboring removal (e.g., understorey removal, thinning) on overstorey trees can be expected more rapidly and strongly in stressful area (e.g., low rainfall, nutrient-poor site) than in areas with optimal growth conditions. Hence, ecophysiology-based management strategies for dealing with neighboring plants in forest ecosystems should take into account: 1) site conditions, 2) timing, duration and frequency of management practices, and 3) species-specific properties and other aspects such as biodiversity conservation and soil erosion.
Authors:Y. Jing, Y. Hao, H. Qu, Y. Shan, D. Li, and R. Du
Chitosan was obtained from cuticles of the housefly
larvae. Antibacterial activities of different Mw chitosans were examined against six bacteria. Antibacterial mechanisms of chitosan were investigated by measuring permeability of bacterial cell membranes and observing integrity of bacterial cells. Results show that the antibacterial activity of chitosan decreased with increase in Mw. Chitosan showed higher antibacterial activity at low pH. Ca
could markedly reduce the antibacterial activity of chitosan. The minimum inhibitory concentrations of chitosans ranged from 0.03% ∼ 0.25% and varied with the type of bacteria and Mw of chitosan. Chitosan could cause leakage of cell contents of the bacteria and disrupt the cell wall.
Authors:W. Qi, X. Zhou, M. Ma, J. M. H. Knops, W. Li, and G. Du
Despite a long history of alpine meadows studies, uncertainty remains about the importance of environmental factors in structuring their assembly. We examined the functional and phylogenetic structure of 170 alpine Tibetan meadow communities in relation to elevation, soil moisture and shade. Functional community structure was estimated with both communityweighted mean (CWM) trait values for specific leaf area (SLA), plant height and seed mass and functional diversity (Rao’s quadratic index) for their traits individually and in combination (multivariate functional diversity). We found that shade induced by woody plants significantly increased the phylogenetic diversity and functional diversity of SLA of co-occurring species, suggesting that woody plants behave as “ecosystem engineers” creating a different environment that allows the existence of shade tolerant species and thereby facilitates the coexistence of plant species with different light resource acquisition strategies. We also found evidence for a clear decrease in phylogenetic diversity, CWM and functional diversity related to plant height in the two extreme, both the dry and wet, soil moisture conditions. This indicates that both drought and excess moisture may act as environmental filters selecting species with close phylogenetic relationships and similar height. Moreover, we detected significant decreases in both CWM and functional diversity for seed mass along elevational gradients, suggesting that low net primary productivity (NPP) limits seed size. Finally, because of different individual trait responses to environmental factors, the multivariate functional diversity did not change across environmental gradients. This lack of multivariate response supports the hypothesis that multiple processes, such as environmental filtering, competition and facilitation, may operate simultaneously and exert opposing effects on community assembly along different niche (e.g., water use, light acquisition) axes, resulting in no overall functional community structure change. This contrast between individual and multivariate trait patterns highlights the importance of examining individual traits linked with different ecological processes to better understand the mechanisms of community assembly.
Authors:D. H. Mu, J. Z. Du, D. J. Li, H. Q. Song, S. P. Yan, and Y. J. Gu
The comprehension of the behavior of radioactive nuclides in aquifer requires the study of the sorption processes of nuclides
in various geochemical conditions. The sorption/desorption of 65Zn(II) on surface sediments (0-2 cm) was investigated by batch method in sea water (pH 8.20, 35‰ salinity, filtered by 0.45mm)
at ambient temperature. The surface sediments were obtained from four stations around the Daya Bay of Guangdong Province (China),
where the first nuclear power station of China has been running from 1994. The sorption process is fast initially and around
39% average of sorption percentage (SP%) can be quickly obtained in 15 minutes for all the surface sediments. Then, the sorption
percentage becomes constant. In 30 days of contact time 79.6% sorption percentage and Kd=3.9. 103ml/g distribution coefficient was obtained. The value of Kdbecame constant, 4.0. 103ml/g, in contact time more than 120 hours. The distribution coefficient Kddecreases with increasing sediment concentration from 4.0 to 250 mg/l from 1.31. 104to 1.68. 103ml/g, respectively. Then the value of Kdgoes up to 5.38. 103ml/g with sediment concentration of 3000 mg/l. The desorption experiments suggest that the sorption of Zn(II) is irreversible
with a hyteresis coefficient of 66%.
Authors:W.M. Du, F.H. Wang, H.Y. Zhang, B.Z. Jiang, X.Y. Chen, W. Zhang, Y. Xie, and Z.T. Sheng
Present research on prebiotics focuses on either polysaccharides or polyphenols. This study compared the individual and combined impact of polysaccharide, quercetin, and gallic acid (GA) treatment on three human faecal strains. In vitro pure culturing and correlation analysis confirmed that the growth of both beneficial microbe B. longum subsp. longum (0.695, 0.205: R2, slope, respectively) and pathogenic C. perfringens (0.712, 0.085: R2, slope, respectively) increased due to polysaccharide treatment, and only GA treatment would inhibit C. perfringens (0.789, –0.165: R2, slope, respectively) growth. In vivo studies also revealed that genome copies of Bifidobacterium increased and C. perfringens decreased in the faeces, when a blend of the three nutrients rather than single polysaccharide or polyphenols were fed to rats. These data suggested that combined prebiotic treatment improved human faecal strain composition better than single treatment.
Authors:Y.-F. Yang, X.-Y. Lai, G.-L. Huang, Y.-H. Chen, X.-P. Du, Z.-D. Jiang, F. Chen, and H. Ni
Bee pollen is a health food with a wide range of nutritional and therapeutic properties. However, the bioactive compounds of bee pollen have not been extensively revealed due to low efficacy in separation. High-speed counter-current chromatography (HSCCC) and solvent extraction were applied to separate tyrosinase inhibitors from camellia pollen in this study. The camellia pollen extracts prepared with petroleum ether, ethyl acetate, and n-BuOH have tyrosinase inhibitory activity. Acidic hydrolysis could promote the tyrosinase inhibitory activity of crude sample. Three fractions with tyrosinase inhibitory activity were separated from the hydrolysate by a one-step HSCCC procedure. Among the fractions, two chemicals were sufficiently purified and identified to be levulinic acid (LA) and 5-hydroxymethylfurfural (5-HMF). The recovery was 0.80 g kg−1 pollen for LA and 1.75 g kg−1 pollen for 5-HMF; and their purity was all over 98%. The study demonstrates that HSCCC method is powerful for preparative separation of tyrosinase inhibitors from camellia pollen.
Authors:Y.H. Xu, T. Li, W.L. Yang, M.Y. Sun, R.Z. An, and W.M. Du
There have been contradicting observations regarding the prebiotic efficacy of feruloylated oligosaccharides (FOs) extracted from different varieties of cereals with varying oligosaccharides and ferulic acid (FA) levels. The present study was performed to determine whether the mass ratio of xylooligosaccharide (XOS) to FA influences their combined effects on faecal FA content, short chain fatty acid (SCFA) output, and gut stress of d-galactose-treated aging rats. The results show that there was no significant difference in the faecal FA levels of rats fed with 5:1 and 10:1 XOS:FA diet, although the FA level in the 5:1-supplemented diet was twice as much as in the 10:1 diet. More utilisation of FA decreased butyric acid and SCFA output in the faeces for diet 5:1 compared with diets 10:1 XOS:FA or XOS alone. Furthermore, compared with 10:1 XOS:FA or XOS alone treatments, the 5:1 XOS:FA diet resulted in increased 1-diphenyl-2-picrylhydrazyl activity and higher ratios of Bifidobacterium or Lactobacillus to Escherichia coli (P < 0.05), while not increasing the number of probiotic Bifidobacterium and Lactobacillus. These findings suggest that under the specific stress level set for this study, the sufficient amount of FA added to XOS (5:1) can stimulate FA utilisation to modify gut redox balance, while reducing faecal SCFA output.