西双版纳的王莲及过冬育苗技术

介绍西双版纳的王莲和过冬繁殖技术,解决在冬春低温的特殊年份王莲种植问题。     

Cascading effects of introduced Nile perch (Lates niloticus) on the foraging ecology of Nile tilapia (Oreochromis niloticus)

Abstract –  Nile tilapia ( Oreochromis niloticus L.) is the dominant of the introduced tilapiines in many East African lakes and has flourished in the presence of introduced Nile perch ( Lates niloticus L.). We explored the hypothesis that O. niloticus exhibits increased omnivory in response to a decline in abundance of haplochromine cichlids. First, we quantified variation in habitat use and diet of O. niloticus in Lake Nabugabo, Uganda. Second, we compared the diet of O. niloticus in lakes with (Nabugabo, Victoria) and without (Mburo, Wamala, Nyamusingiri, Kyasanduka) introduced Nile perch. In Lake Nabugabo, a higher level of phytoplanktivory was observed in small juveniles than in larger fish and in wetland ecotone areas where haplochromines were most abundant. An omnivorous diet dominated by detritus and invertebrates was recorded for O. niloticus in lakes Nabugabo and Victoria, while a predominantly herbivorous diet was characteristic of O. niloticus in lakes without Nile perch. Availability of a broad food base in lakes where inshore insectivores have been reduced may explain the increased omnivory recorded in lakes Nabugabo and Victoria.     

Victoria Blight,defense turned upside down

Genes that confer disease resistance to biotrophic pathogens typically encode nucleotide-binding, leucine-rich-repeat proteins (NB-LRRs). These proteins confer resistance by detecting the presence of virulence effectors secreted by biotrophic pathogens. Recognition triggers NB-LRR activation and subsequently, the defense response which often includes localized host cell death. The fungus, Cochliobolus victoriae, is a necrotrophic pathogen that causes a disease called Victoria Blight. Virulence of this fungus is dependent on its production of a peptide called “victorin” that has been traditionally described as a toxin. Only plants that respond to victorin are susceptible to Cochliobolus victoriae whereas those that do not are resistant to the fungus. Genetic and molecular analyses have revealed that victorin functions like a biotrophic effector recognized by a NB-LRR resistance protein in Arabidopsis. Further, numerous plant species express victorin sensitivity suggesting there are numerous NB-LRRs that recognize victorin. Thus, through expression of victorin, C. victoriae is able to exploit plant defense to cause disease and is capable of evoking this response in an array of different plants.     

Distribution of and reproductive isolation among color morphs of a rock-dwelling Lake Victoria cichlid (Haplochromis nyererei)

Geographical, macro- and microhabitat distribution of and mate recognition among color morphs of a complex of Lake Victoria cichlids was studied. The distribution of most morphs was mutually exclusive but two morphs overlapped extensively and differed only in microhabitat requirements. Coloration differences between them were inherited, and wild fishes were homozygous in this respect. Positive morph assortative female mate choice was demonstrated. Over the largest part of their common geographical range intermediate phenotypes are absent and the two morphs are to be considered two biological species. However, in populations at one end of the range intermediate phenotypes with continuously varying male coloration make up the majority of the individuals. It is suggested that the status of color morphs as phenotypes of one species or as separate biological species is a function of environmental conditions that vary considerably between the localities. The data support the hypothesis that polymorphisms can be a step preceding speciation in cichlid fish.     

Distribution of and reproductive isolation among color morphs of a rock-dwelling Lake Victoria cichlid (Haplochromis nyererei)

Abstract— The geographical and macro- and microhabitat distribution of and mate recognition among color morphs of a complex of Lake Victoria cichlids were studied. The distribution of most morphs was mutually exclusive, but two morphs overlapped extensively and differed only in microhabitat requirements. Coloration differences between them were inherited, and wild fishes were homozygous in this respect. Positive morph-assortative female mate choice was demonstrated. Over the largest part of their common geographical range, intermediate phenotypes are absent and the two morphs are to be considered two biological species. However, in populations at one end of the range, intermediate phenotypes with continuously varying male coloration make up the majority of the individuals. It is suggested that the status of color morphs as phenotypes of one species or as separate biological species is a function of environmental conditions that vary considerably between the localities. The data support the hypothesis that polymorphisms can be a step preceding speciation in cichlid fish.     

观音莲的组织培养

观音莲的顶芽或侧芽在MS+6-BA2.0 mg.L-1+TDZ0.03 mg.L-1培养基中,可诱导产生大量丛生泡叶状不定芽。以此作为增殖培养,每28 d增殖率达6.0以上。壮芽培养基宜用MS+6-BA0.3 mg.L-1+Y(多效唑)0.2 mg.L-1,周期30~35d,由此获得的合乎生根标准的不定芽比率约80%左右。切取3 cm以上具完全展开叶的芽在MS+6-BA0.3 mg.L-1+Y(多效唑)0.2 mg.L-1培养基中,根的诱导率(生根率)达100%。     

保定市维多利亚夏郡住区中央水景设计

从住区水景的基本要点、设计中易存在的问题入手,通过对维多利亚夏郡住区的中央水景进行设计,以期创造出更美好、更人性化的住区环境,为其他小区水景设计提供借鉴。     

The changing profile of water traders in the Goulburn-Murray Irrigation District, Australia

This paper examines the changing profile of water traders (both allocation and entitlement traders) in the Goulburn-Murray Irrigation District in Australia, and examines the efficiency of the water allocation and entitlement markets from 1998-99 to 2003-06. The results suggest that the profile of traders in the early and mature stages of the water allocation market differ greatly. In addition, the profile of allocation traders is significantly dissimilar from that of water entitlement traders at all stages of water market development. The decision to buy or sell water allocations was more likely to be associated with a farmer's socioeconomic characteristics and the type of farm, while the decision to buy or sell water entitlements was more likely to be associated with the extent of existing farm infrastructure and farm productivity. Finally, there was strong evidence to suggest that trading in the water allocation market has become more efficient over time, though there is no evidence to suggest the same for the water entitlement market.     

维多利亚紫花苜蓿在贵阳不同海拔地区的产量与营养成分含量研究

试验在贵阳市的4个不同海拔地区（950、1120、1210、1350m）设点,对维多利亚紫花苜蓿的生长、产量、营养成分进行了测定。结果表明：维多利亚紫花苜蓿秋季种植后141d可以第一次刈割,平均产量为1307．32kg。其生长速度与海拔高度呈负相关,海拔高度每升高100m,株高达到50cm的时间推迟5天,667m^2产量降低50kg。第一次刈割后66d株高达到50cm,平均产量为2304．5k。第二茬生长速度与海拔高度呈负相关,海拔高度每升高100m,株高达50cm的时间推迟4天,产量降低30kg左右。第三茬株高达到50cm的时间平均为74．5d,平均产量为2588．0kg,海拔高度每升高100m,植高达到50cm的时间推迟3天,产量变化不明显。在贵阳地区当年种植可以刈割3茬,利用时间282d,平均每茬产草量平均为2066．6kg／667m^2,年总产草量6199．8kg／667m^2;鲜草含水量平均为70．9％,干物质含量平均为29．1％,干物质中平均含CP26．3％、EE5．2％、CF25．9％、Ash9．6％、NFE33．0％、NDF36．1％、ADF32．6％、Ca1．7％、P0．8％、GE18．4MJ／k。     

Chlamydia psittaci: a suspected cause of reproductive loss in three Victorian horses

Chlamydia psittaci was detected by PCR in the lung and equine foetal membranes of two aborted equine foetuses and one weak foal from two different studs in Victoria, Australia. The abortions occurred in September 2019 in two mares sharing a paddock northeast of Melbourne. The weak foal was born in October 2019 in a similar geographical region and died soon after birth despite receiving veterinary care. The detection of C. psittaci DNA in the lung and equine foetal membranes of the aborted or weak foals and the absence of any other factors that are commonly associated with abortion or neonatal death suggest that this pathogen may be the cause of the reproductive loss. The detection of C. psittaci in these cases is consistent with the recent detection of C. psittaci in association with equine abortion in New South Wales. These cases in Victoria show that C. psittaci, and the zoonotic risk it poses, should be considered in association with equine reproductive loss in other areas of Australia.