Competitive and allelopathic interference between soybean crop and annual wormwood (Artemisia annua L.) under field conditions     

C.M. Morvillo  E.B. de la Fuente  A. Gil  M.A. Martínez-Ghersa  J.L. González-Andújar 《European Journal of Agronomy》2011,34(4):211-221

Annual wormwood interference on soybean crop growth and yield may result from competition and allelopathy, which are modulated by crop management. Allelochemicals released by annual wormwood (e.g. artemisinin) may affect the crop directly or indirectly through the effect on the nitrogen fixing symbiont, Bradyrhizobium japonicum. The objectives were (i) to quantify the crop response (i.e. biomass production, nodulation and yield) to weed interference and (ii) to determinate the relative change of competition and allelopathy interferences, when a sublethal dose of herbicide is applied. Two split plot field experiments with three replications were used. The experiment involved a factorial combination of five weed–crop density (soybean/annual wormwood, plants m^?2) levels: D1, pure soybean, 40/0 plants m^?2; D2, 40/2 plants m^?2; D3, 40/4 plants m^?2 and D4, 40/8 plants m^?2, and D5, pure annual wormwood, 0/8 plants m^?2, two activated carbon (allelopathy) levels: C?, with activated carbon (reduced allelopathy) and C+, non activated carbon applied (with allelopathy) and two herbicide levels: H?, untreated and H+, treated with a sub-lethal dose of glyphosate. Activated carbon to adsorb allelochemicals (with and without activated carbon) and glyphosate application (with and no herbicide) were assigned to sub-plots. Increasing weed density did not affect crop biomass at flowering, but changed nodule number and soybean yield with a different pattern depending on carbon and herbicide treatment. Relative crop yield decreased with increasing relative weed biomass. This decrease was particularly drastic when allelopathy was reduced by activated carbon and without herbicide application. The maximum yield losses of 33% in 2006 and 17% in 2007 were observed with the highest weed density (8 plants m^?2). In contrast, without carbon (high allelopathy level), soybean yield remained stable within the explored range of annual wormwood biomass, despite the fact that weed biomass at high densities (D4) was high enough to generate competition. The lack of response to increasing weed density could be related to the indirect effect of allelochemicals interacting with soil microorganisms (i.e. B. japonicum) that positively affected the nodulation (e.g. larger nodules in 2006 and increased nodules biomass due to higher number of roots in 2007 at high densities). With herbicide application, soybean yield of both carbon treatments remained stable when biomass of annual wormwood increased. This research provided strong evidence in support of the existence of positive effect of allelopathic and competitive interactions between annual wormwood and soybean crop under field conditions that may be overridden under herbicide application.  相似文献   

Water allocation and management in an emerging spate irrigation system in Makanya catchment, Tanzania     

Hans Charles Komakech  Marloes L. MulPieter van der Zaag  Filbert B.R. Rwehumbiza 《Agricultural Water Management》2011,98(11):1719-1726

Although spate irrigation systems are risk-prone, they can be an important component for livelihood security in semi-arid areas. Spate uses water (flood water), which upstream users often do not require, as rainfall during these periods is more than sufficient. The use of this flood water for spate irrigation is therefore a good opportunity to convert water with a low opportunity cost to high value water. As more rivers are closing, due to socio-economic and climate changes, spate irrigation may become increasingly relevant in semi-arid areas. Spate irrigation systems pose institutional and technical challenges: collective action is challenged by complex upstream-downstream interactions between users within the system, and the high labour demands for regular reconstruction of temporary diversion weirs and intake structures. This paper describes a spate irrigation system in Makanya village, Tanzania that emerged in response to increased upstream water use. We use three of the four dimensions (hydrological, hydraulic and sociological) of spate irrigation proposed by Van Steenbergen (1997) to assess the Makanya spate irrigation system. The Makanya spate irrigation system has an organisational structure that is similar to the canal irrigation (furrow) committees located upstream, and effectively deals with the institutional demands of managing water in spate irrigation systems. Water allocation is reminiscent to the water sharing arrangements existing in the full irrigation system, which previously was in place at the site and in the high- and midlands of the Makanya catchment and therefore set this system apart from the traditional spate irrigation practice elsewhere. Technically, a major challenge is the reconstruction of the head works after each flood. Another aspect is the changes in the river bed. Flash floods carry sediments that deposit on the fields, raising the elevation of the irrigated land every year and making it increasingly difficult for the river water to enter the plots. Improving system efficiency through modernisation of the diversion and distribution structures in this case is not feasible due to the huge amounts of sediments delivered to the system each year. Instead investments in conjunctive use of groundwater could be the solution because it involves a relatively small intervention, minimises the physical disturbance of the system, and therefore is likely to respect the existing locally developed water management arrangements.  相似文献   

提高小麦产量潜力性状论述   总被引：1，自引：0，他引：1  

M.P.Reynolds  M. van Ginkel  B. Skovmand  杨春玲  韩勇  李晓亮  贾秀勇 《安徽农业科学》2008,36(24)

该文对小麦产量形成的库、源、流限制与促进进行了研究。在研究库的过程中,得出了小麦抗叶锈病基因Lr19对产量、物质分配、产量构成因素、生育期、开花习性和生理生化等方面的主要影响,并指出了增加产量潜力的几个途径和维持库、源平衡对产量潜力充分发挥所起的作用。  相似文献   

Germline allele-specific expression of TGFBR1 confers an increased risk of colorectal cancer     

Valle L  Serena-Acedo T  Liyanarachchi S  Hampel H  Comeras I  Li Z  Zeng Q  Zhang HT  Pennison MJ  Sadim M  Pasche B  Tanner SM  de la Chapelle A 《Science (New York, N.Y.)》2008,321(5894):1361-1365

Much of the genetic predisposition to colorectal cancer (CRC) in humans is unexplained. Studying a Caucasian-dominated population in the United States, we showed that germline allele-specific expression (ASE) of the gene encoding transforming growth factor-beta (TGF-beta) type I receptor, TGFBR1, is a quantitative trait that occurs in 10 to 20% of CRC patients and 1 to 3% of controls. ASE results in reduced expression of the gene, is dominantly inherited, segregates in families, and occurs in sporadic CRC cases. Although subtle, the reduction in constitutive TGFBR1 expression alters SMAD-mediated TGF-beta signaling. Two major TGFBR1 haplotypes are predominant among ASE cases, which suggests ancestral mutations, but causative germline changes have not been identified. Conservative estimates suggest that ASE confers a substantially increased risk of CRC (odds ratio, 8.7; 95% confidence interval, 2.6 to 29.1), but these estimates require confirmation and will probably show ethnic differences.  相似文献   

Uroporphyrinogen decarboxylase structural mutant (Gly281----Glu) in a case of porphyria   总被引：10，自引：0，他引：10  

H de Verneuil  B Grandchamp  C Beaumont  C Picat  Y Nordmann 《Science (New York, N.Y.)》1986,234(4777):732-734

Uroporphyrinogen decarboxylase deficiency in man is responsible for familial porphyria cutanea tarda and hepatoerythropoietic porphyria. A recent study of a family with hepatoerythropoietic porphyria showed that the enzyme defect resulted from rapid degradation of the protein in vivo. Cloning and sequencing of a complementary DNA for the mutated gene revealed that the mutation was due to the replacement of a glycine residue by a glutamic acid residue at position 281. This base change leads to a protein that is very rapidly degraded in the presence of cell lysate. Characterization of the mutation will allow comparison of this defect in a homozygous patient with defects in other patients with familial porphyria cutanea tarda.  相似文献   

Samuel Alfred Mitchell,Solar and Stellar Astronomer     

van de Kamp P 《Science (New York, N.Y.)》1960,132(3422):281-282

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Groningen Radiocarbon Dates III     

de Vries H  Waterbolk HT 《Science (New York, N.Y.)》1958,128(3338):1550-1556

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Primates--a natural heritage of conflict resolution     

de Waal FB 《Science (New York, N.Y.)》2000,289(5479):586-590

The traditional notion of aggression as an antisocial instinct is being replaced by a framework that considers it a tool of competition and negotiation. When survival depends on mutual assistance, the expression of aggression is constrained by the need to maintain beneficial relationships. Moreover, evolution has produced ways of countering its disruptive consequences. For example, chimpanzees kiss and embrace after fights, and other nonhuman primates engage in similar "reconciliations." Theoretical developments in this field carry implications for human aggression research. From families to high schools, aggressive conflict is subject to the same constraints known of cooperative animal societies. It is only when social relationships are valued that one can expect the full complement of natural checks and balances.  相似文献   

Nuclear waste disposal: can the geologist guarantee isolation?     

de Marsily G  Ledoux E  Barbreau A  Margat J 《Science (New York, N.Y.)》1977,197(4303):519-527

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褐飞虱Nilaparvata lugens(S"非汉字符号"l)肌动蛋白基因3′-RACE及基因表达的RT-PCR检测     

刘美德  洪晓月  杜建光  程遐年 《南京农业大学学报》2003,(3)

通过锚定的 3′ RACE筛选实验 ,确定锚定效率最好的下游引物 ,用于褐飞虱各发育期肌动蛋白基因表达的RT PCR检测。结果表明 :3个锚定引物中 ,0 4 2 2 7( 5′ >TCACACAGGAAACAGCTATGACTTTTTTTTTTTTTTA <3′)的锚定效率最好 ,可以扩增出 5条褐飞虱的肌动蛋白基因 3′末端片段 ,依其大小命名为BPH A、BPH B、BPH C、BPH D、BPH E。RT PCR检测表明 :BPH A从 3龄开始到成虫期都有常量表达 ;BPH B、BPH C、BPH E从 2龄开始到成虫期都有表达 ;BPH D在整个幼虫期都有表达 ,而在成虫期则检测不到  相似文献