The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi...The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi-arid region of North America, the species of European annual grass Bromus tectorum L. is an outstanding example of these problems, which not only increase the fire density and change the fire regime, but replace native communities. Therefore, there are amount of researches on B. tectorum, including resource acquisition, water use efficiency and growth. Whereas the relevant research on the morphology of diaspore is scare. Diaspores have a fundamental role in seed germination and seedling establishment. Besides, as an important link between different generations, diaspores have a vital significance on individual reproduction and population extension. Hence, dias- pores under selection for studying have an important implication. This study compares differences in seed mor- phology for Bromus tectorum collected from the United States, Kazakhstan, and Xinjiang of China. The following indices of B. tectorum diaspores were analyzed： size, thickness of covering layers, and micromorphological char- acteristics of the base, middle and transition area of diaspores as well as of the awn. Micromorphology of the lemma and the cross-section of the diaspore were observed by scanning electron microscopy. Results showed that thick- ness of the lemma and the palea of diaspores from B. tectorum-infested grasslands in the United States were re- duced （P〈0.05）, likely because of environmental influences. This reduction facilitated the germination of diaspores and lowered the resistance of B. tectorum to adverse environmental conditions. The length of the awn also in- creased significantly （P〈0.05）, which helped in dispersal and anchoring of diaspores. Therefore, B. tectorum adapted ecologically to its new environment in the United States by strengthening its establishment ability. However, the defense capability of B. tectorum decreased. These results fit the evolution of increased competitive ability hy- pothesis （EICA） of invasive species. Analysis of various cells on the lemma revealed that prickle densities and col- lapsed, long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation. However, the form and the position of silica cells, which were not greatly influenced by environmental factors, might be genetically controlled. Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment. This study has a reference value for future studies on B. tectorum.展开更多
The aim of the present study was to investigate the potential allelopathic effects of different concentrations of Zygophyllum album （donor species） aqueous extract （2.5, 5, 7.5 and 10%） on germination percentage, ...The aim of the present study was to investigate the potential allelopathic effects of different concentrations of Zygophyllum album （donor species） aqueous extract （2.5, 5, 7.5 and 10%） on germination percentage, plumule and radicle length ofBromus tectorum （weed） and Triticum aestivum （crop species） under laboratory conditions to have the greatest inhibitory allelopathic effect on the recipient species in mixed culture compared to that pure culture. The germination percentage, plumule and radicle length ofB. tectorum in mixed culture was completely inhibited at the highest concentration of aqueous extracts of the donor species level the exerted weak measures as affected by the highest concentration level of donor in pure culture. This inhibition was markedly in obvious B. tectorum that is more sensitive to tested donor. The domineering effect of aqueous extract of the donor was more prominent on weeds than crop species. The variant response to the allelopathic substance could be related to the species specific growth regulatory effect of allelochemicals and concentration dependent. There is possibility of using these allelochemicals directly or as structural leads for the discovery and development of environment friendly herbicides to control weeds.展开更多
AIM:To investigate the effects of tectorigenin on human hepatocellular carcinoma(HCC)HepG2 cells.METHODS:Tectorigenin,one of the main components of rhizome of Iris tectorum,was prepared by simple methods,such as extra...AIM:To investigate the effects of tectorigenin on human hepatocellular carcinoma(HCC)HepG2 cells.METHODS:Tectorigenin,one of the main components of rhizome of Iris tectorum,was prepared by simple methods,such as extraction,filtration,concentration,precipitation and recrystallization.HepG2 cells were incubated with tectorigenin at different concentrations,and their viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Apoptosis was detected by morphological observation of nuclear change,agarose gel electrophoresis of DNA ladder,and flow cytometry with Hoechst 33342,Annexin V-EGFP and propidium iodide staining.Generation of reactive oxygen species was quantified using DCFH-DA.Intracellular Ca2+was monitored by Fura 2-AM.Mitochondrial membrane potential was monitored using Rhodamine 123.Release of cytochrome c from mitochondria to cytosol was detected by Western blotting.Activities of caspase-3,-8 and-9 were investigated by Caspase Activity Assay Kit.RESULTS:The viability of HepG2 cells treated by tectorigenin decreased in a concentration-and timedependent manner.The concentration that reduced the number of viable HepG2 cells by 50%(IC50)after 12,24 and 48 h of incubation was 35.72 mg/L,21.19 mg/L and 11.06 mg/L,respectively.However,treatment with tectorigenin at 20 mg/L resulted in a very slight cytotoxicity to L02 cells after incubation for 12,24 or 48 h.Tectorigenin at a concentration of 20 mg/L greatly inhibited the viability of HepG2 cells and induced the condensation of chromatin and fragmentation of nuclei.Tectorigenin induced apoptosis of HepG2 cells in a time-and dose-dependent manner.Compared with the viability rate,induction of apoptosis was the main mechanism of the anti-proliferation effect of tectorigenin in HepG2 cells.Furthermore,tectorigenininduced apoptosis of HepG2 cells was associated with the generation of reactive oxygen species,increased intracellular[Ca2+]i,loss of mitochondrial membrane potential,translocation of cytochrome c,and activation of caspase-9 and-3.CONCLUSION:Tectorigenin induces apoptosis of HepG2 cells mainly via mitochondrial-mediated pathway,and produces a slight cytotoxicity to L02 cells.展开更多
Natural scientists have long recognized that regions with similar climate tend to have similar vegetation.Preliminary observations suggest that shrub steppe communities of the western US and western China may be two s...Natural scientists have long recognized that regions with similar climate tend to have similar vegetation.Preliminary observations suggest that shrub steppe communities of the western US and western China may be two such regions with similar annual precipitation,temperature,land use,and vegetation.These cold dry shrub steppes have traditionally been grazed.Despite these similarities,patterns of species dominance are different.Annual species that are rare in China become dominant when introduced to the United States.The objective of this study was to investigate how climate,land use and community structure may explain these patterns of species dominance.Community structure and grazing intensity were measured at 5 sites in each region.This information was combined with a broader review of the literature describing the history of grazing in both basins.Climate was analyzed based on a spatially-gridded,interpolated weather time series （monthly records） and climatological summary （1961-1990 mean conditions） data set from the Climate Research Unit.We found that differences in summer precipitation and winter minimum temperature,land use intensity,and shrub size may all contribute to the dominance of annual species in the Great Basin,particularly Bromus tectorum.In particular,previous work indicates that summer precipitation and winter temperature drive the distribution of Bromus tectorum in the Great Basin.As a result,sites with wet summers and cold springs,similar to the Chinese sites,would not be expected to be dominated by Bromus tectorum.A history of more intense grazing of the Chinese sites,as described in the literature,also is likely to decrease fire frequency,and decreases litter and shrub dominance,all of which have been demonstrated to be important in Bromus tectorum establishment and ultimate dominance.Further research is necessary to determine if other annuals that follow the same pattern of scarcity in the Junggar Basin and dominance in the Great Basin are responding to the same influences.展开更多
Squirreltail (Elymus elymoides [Raf] Swezey) can grow in cheatgrass (Bromus tectorum L.) stands, and has reduced the biomass production of cheatgrass in its immediate vicinity. A field experiment was conducted to dete...Squirreltail (Elymus elymoides [Raf] Swezey) can grow in cheatgrass (Bromus tectorum L.) stands, and has reduced the biomass production of cheatgrass in its immediate vicinity. A field experiment was conducted to determine: 1) if competition for nitrogen resources occurs between seedlings of squirreltail and seedlings of cheatgrass, under low, medium, and high nitrogen levels, and;2) if competition for nitrogen resources in the seedling stage is a mechanism that allows squirreltail to establish in cheatgrass stands. Five accessions of squirreltail were each seeded with a single accession of cheatgrass in a cultivated field near Ephraim, Utah in the fall of 1995 and again in 1996. A completely randomized strip-plot design with 3 replications was used including the 5 joint seedings as well as pure seedings of each accession of both species. Three nitrogen levels representing high, medium (control), and low were applied. The study was replicated over 2 years in different areas of the same field. Harvests of above-ground biomass of squirreltail and cheatgrass within each treatment were conducted in July of 1996 and 1997. Using biomass production as a measure of efficient nitrogen use, cheatgrass competed for and used nitrogen resources more efficiently than squirreltail when nitrogen was not limiting. All squirreltail accessions were able to compete for and use nitrogen more efficiently than cheatgrass when there was low availability of nitrogen. Some accessions of squirreltail competed for nitrogen resources more efficiently than others both in the control and at the reduced nitrogen level. White Rocks and Sublette squirreltail accessions were the best competitors with cheatgrass at the low nitrogen level reducing the cheatgrasss biomass by as much as 75% and 67% respectively. An intermediate competitor with cheatgrass was the Gunnison accession. The Washakie and Pueblo accessions were poor competitors with cheatgrass at low nitrogen levels.展开更多
AIM: To investigate the chemical constituents of Iris tectorum Maxim. METHOD: The chemical constituents were isolated and purified by solvent extraction together with various chromatographic techniques. The structures...AIM: To investigate the chemical constituents of Iris tectorum Maxim. METHOD: The chemical constituents were isolated and purified by solvent extraction together with various chromatographic techniques. The structures were elucidated on the basis of chemical evidence and spectral data. RESULTS: Seven compounds were isolated from the EtOAc extracts of the rhizome of Iris tectorum Maxim.,which were apocynin (Ⅰ),rhamnocitrin (Ⅱ),tectorigenin (Ⅲ),iristectorigenin A (Ⅳ),β-sitosterol(Ⅴ),dihydrokaempferide (Ⅵ) ,irigenin(Ⅶ);seven compounds were isolated from the n-BuOH extracts,which were tectoridin (Ⅷ),androsin (Ⅸ),n-Butyl-β-D-fructopyranoside (Ⅹ),iristectorin B (Ⅺ),iridin (Ⅻ),tectorigenin-7-O-β-glucosyl-4′-O-β-glucoside (),daucosterol (■). CONCLUSION: Compound Ⅱ,Ⅵ,Ⅹ were isolated from Iris for the first time.展开更多
基金supported by the International Science and Technology Cooperation Program of China (2010DFA92720-06)with partial support to RSN from the US National Science Foundation (1047575) and the Nevada Agricultural Experiment Station
文摘The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi-arid region of North America, the species of European annual grass Bromus tectorum L. is an outstanding example of these problems, which not only increase the fire density and change the fire regime, but replace native communities. Therefore, there are amount of researches on B. tectorum, including resource acquisition, water use efficiency and growth. Whereas the relevant research on the morphology of diaspore is scare. Diaspores have a fundamental role in seed germination and seedling establishment. Besides, as an important link between different generations, diaspores have a vital significance on individual reproduction and population extension. Hence, dias- pores under selection for studying have an important implication. This study compares differences in seed mor- phology for Bromus tectorum collected from the United States, Kazakhstan, and Xinjiang of China. The following indices of B. tectorum diaspores were analyzed： size, thickness of covering layers, and micromorphological char- acteristics of the base, middle and transition area of diaspores as well as of the awn. Micromorphology of the lemma and the cross-section of the diaspore were observed by scanning electron microscopy. Results showed that thick- ness of the lemma and the palea of diaspores from B. tectorum-infested grasslands in the United States were re- duced （P〈0.05）, likely because of environmental influences. This reduction facilitated the germination of diaspores and lowered the resistance of B. tectorum to adverse environmental conditions. The length of the awn also in- creased significantly （P〈0.05）, which helped in dispersal and anchoring of diaspores. Therefore, B. tectorum adapted ecologically to its new environment in the United States by strengthening its establishment ability. However, the defense capability of B. tectorum decreased. These results fit the evolution of increased competitive ability hy- pothesis （EICA） of invasive species. Analysis of various cells on the lemma revealed that prickle densities and col- lapsed, long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation. However, the form and the position of silica cells, which were not greatly influenced by environmental factors, might be genetically controlled. Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment. This study has a reference value for future studies on B. tectorum.
文摘The aim of the present study was to investigate the potential allelopathic effects of different concentrations of Zygophyllum album （donor species） aqueous extract （2.5, 5, 7.5 and 10%） on germination percentage, plumule and radicle length ofBromus tectorum （weed） and Triticum aestivum （crop species） under laboratory conditions to have the greatest inhibitory allelopathic effect on the recipient species in mixed culture compared to that pure culture. The germination percentage, plumule and radicle length ofB. tectorum in mixed culture was completely inhibited at the highest concentration of aqueous extracts of the donor species level the exerted weak measures as affected by the highest concentration level of donor in pure culture. This inhibition was markedly in obvious B. tectorum that is more sensitive to tested donor. The domineering effect of aqueous extract of the donor was more prominent on weeds than crop species. The variant response to the allelopathic substance could be related to the species specific growth regulatory effect of allelochemicals and concentration dependent. There is possibility of using these allelochemicals directly or as structural leads for the discovery and development of environment friendly herbicides to control weeds.
基金Supported by The National Natural Science Foundation of China,No.NSFC30801417Natural Science Foundation of Jiangsu Province,No.BK2009010 and BK2008267+1 种基金Doctoral Fund of Ministry of Education of China,No.RFDP200802841004Science Fund of Ministry of Health of China,No.LW201008
文摘AIM:To investigate the effects of tectorigenin on human hepatocellular carcinoma(HCC)HepG2 cells.METHODS:Tectorigenin,one of the main components of rhizome of Iris tectorum,was prepared by simple methods,such as extraction,filtration,concentration,precipitation and recrystallization.HepG2 cells were incubated with tectorigenin at different concentrations,and their viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Apoptosis was detected by morphological observation of nuclear change,agarose gel electrophoresis of DNA ladder,and flow cytometry with Hoechst 33342,Annexin V-EGFP and propidium iodide staining.Generation of reactive oxygen species was quantified using DCFH-DA.Intracellular Ca2+was monitored by Fura 2-AM.Mitochondrial membrane potential was monitored using Rhodamine 123.Release of cytochrome c from mitochondria to cytosol was detected by Western blotting.Activities of caspase-3,-8 and-9 were investigated by Caspase Activity Assay Kit.RESULTS:The viability of HepG2 cells treated by tectorigenin decreased in a concentration-and timedependent manner.The concentration that reduced the number of viable HepG2 cells by 50%(IC50)after 12,24 and 48 h of incubation was 35.72 mg/L,21.19 mg/L and 11.06 mg/L,respectively.However,treatment with tectorigenin at 20 mg/L resulted in a very slight cytotoxicity to L02 cells after incubation for 12,24 or 48 h.Tectorigenin at a concentration of 20 mg/L greatly inhibited the viability of HepG2 cells and induced the condensation of chromatin and fragmentation of nuclei.Tectorigenin induced apoptosis of HepG2 cells in a time-and dose-dependent manner.Compared with the viability rate,induction of apoptosis was the main mechanism of the anti-proliferation effect of tectorigenin in HepG2 cells.Furthermore,tectorigenininduced apoptosis of HepG2 cells was associated with the generation of reactive oxygen species,increased intracellular[Ca2+]i,loss of mitochondrial membrane potential,translocation of cytochrome c,and activation of caspase-9 and-3.CONCLUSION:Tectorigenin induces apoptosis of HepG2 cells mainly via mitochondrial-mediated pathway,and produces a slight cytotoxicity to L02 cells.
基金funded by the US National Science Foundation(1047575)with additional support from the Nevada Agricultural Experiment Station and National Science Foundation Cooperative Agreement(EPS-0814372)
文摘Natural scientists have long recognized that regions with similar climate tend to have similar vegetation.Preliminary observations suggest that shrub steppe communities of the western US and western China may be two such regions with similar annual precipitation,temperature,land use,and vegetation.These cold dry shrub steppes have traditionally been grazed.Despite these similarities,patterns of species dominance are different.Annual species that are rare in China become dominant when introduced to the United States.The objective of this study was to investigate how climate,land use and community structure may explain these patterns of species dominance.Community structure and grazing intensity were measured at 5 sites in each region.This information was combined with a broader review of the literature describing the history of grazing in both basins.Climate was analyzed based on a spatially-gridded,interpolated weather time series （monthly records） and climatological summary （1961-1990 mean conditions） data set from the Climate Research Unit.We found that differences in summer precipitation and winter minimum temperature,land use intensity,and shrub size may all contribute to the dominance of annual species in the Great Basin,particularly Bromus tectorum.In particular,previous work indicates that summer precipitation and winter temperature drive the distribution of Bromus tectorum in the Great Basin.As a result,sites with wet summers and cold springs,similar to the Chinese sites,would not be expected to be dominated by Bromus tectorum.A history of more intense grazing of the Chinese sites,as described in the literature,also is likely to decrease fire frequency,and decreases litter and shrub dominance,all of which have been demonstrated to be important in Bromus tectorum establishment and ultimate dominance.Further research is necessary to determine if other annuals that follow the same pattern of scarcity in the Junggar Basin and dominance in the Great Basin are responding to the same influences.
文摘Squirreltail (Elymus elymoides [Raf] Swezey) can grow in cheatgrass (Bromus tectorum L.) stands, and has reduced the biomass production of cheatgrass in its immediate vicinity. A field experiment was conducted to determine: 1) if competition for nitrogen resources occurs between seedlings of squirreltail and seedlings of cheatgrass, under low, medium, and high nitrogen levels, and;2) if competition for nitrogen resources in the seedling stage is a mechanism that allows squirreltail to establish in cheatgrass stands. Five accessions of squirreltail were each seeded with a single accession of cheatgrass in a cultivated field near Ephraim, Utah in the fall of 1995 and again in 1996. A completely randomized strip-plot design with 3 replications was used including the 5 joint seedings as well as pure seedings of each accession of both species. Three nitrogen levels representing high, medium (control), and low were applied. The study was replicated over 2 years in different areas of the same field. Harvests of above-ground biomass of squirreltail and cheatgrass within each treatment were conducted in July of 1996 and 1997. Using biomass production as a measure of efficient nitrogen use, cheatgrass competed for and used nitrogen resources more efficiently than squirreltail when nitrogen was not limiting. All squirreltail accessions were able to compete for and use nitrogen more efficiently than cheatgrass when there was low availability of nitrogen. Some accessions of squirreltail competed for nitrogen resources more efficiently than others both in the control and at the reduced nitrogen level. White Rocks and Sublette squirreltail accessions were the best competitors with cheatgrass at the low nitrogen level reducing the cheatgrasss biomass by as much as 75% and 67% respectively. An intermediate competitor with cheatgrass was the Gunnison accession. The Washakie and Pueblo accessions were poor competitors with cheatgrass at low nitrogen levels.
文摘AIM: To investigate the chemical constituents of Iris tectorum Maxim. METHOD: The chemical constituents were isolated and purified by solvent extraction together with various chromatographic techniques. The structures were elucidated on the basis of chemical evidence and spectral data. RESULTS: Seven compounds were isolated from the EtOAc extracts of the rhizome of Iris tectorum Maxim.,which were apocynin (Ⅰ),rhamnocitrin (Ⅱ),tectorigenin (Ⅲ),iristectorigenin A (Ⅳ),β-sitosterol(Ⅴ),dihydrokaempferide (Ⅵ) ,irigenin(Ⅶ);seven compounds were isolated from the n-BuOH extracts,which were tectoridin (Ⅷ),androsin (Ⅸ),n-Butyl-β-D-fructopyranoside (Ⅹ),iristectorin B (Ⅺ),iridin (Ⅻ),tectorigenin-7-O-β-glucosyl-4′-O-β-glucoside (),daucosterol (■). CONCLUSION: Compound Ⅱ,Ⅵ,Ⅹ were isolated from Iris for the first time.
