5种沉水植物无性繁殖和定居能力的比较研究

 竹叶眼子菜(Potamogeton malaianus)、微齿眼子菜(Potamogeton maackianus)、苦草(Vallisneria spiralis)、穗花狐尾藻(Myriophyllum spicatum)、黑藻(Hydrilla verticillata)是长江中下游湖泊主要的沉水植物。在栽培条件下,它们的无性繁殖速率(单位时间内新增个体数)大小顺序为黑藻>微齿眼子菜>竹叶眼子菜>苦草>穗花狐尾藻。同时采用抛掷实验的方法观察研究了这5种沉水植物及其无性繁殖体的存活和生根情况;完整植株存活率为黑藻>穗花狐尾藻>微齿眼子菜>竹叶眼子菜>苦草,无性繁殖体部分存活率为黑藻>苦草>穗花狐尾藻>微齿眼子菜>竹叶眼子菜。生根能力和其存活时间长短相关,而且生根能力与存活率大小基本一致。在实验中,只有穗花狐尾藻的断枝存活率和生根能力存在差异,故无性繁殖体生根能力为黑藻>苦草>微齿眼子菜>竹叶眼子菜>穗花狐尾藻。     

Effect of Carbohydrate Demand on the Remobilization of Starch in Stolons and Roots of White Clover (Trifolium repens L.) after Defoliation

White clover plants were grown from stolon tips in growth cabinetsand then defoliated. Thereafter, changes in the contents ofnon-structural carbohydrates such as starch, sucrose, glucose,fructose, maltose, and pinitol in stolons and roots were monitored.Initial contents of carbohydrate reserves, photosynthetic supplyof new carbohydrates and carbohydrate demand after defoliationwere varied by growing the plants at various CO₂ partial pressures,by varying the extent of defoliation and by removing eitherroots or stolon tips at the time of defoliation. Remobilization of carbohydrate reserves in stolons increasedproportionally to their initial contents and was greater whenplants had been severely defoliated, suggesting that carbohydrateswere remobilized according to availability and demand. Starchwas the predominant reserve carbohydrate. Starch degradationwas associated with decreased contents of sucrose, glucose andfructose in young stolon parts and roots but not in old stolonparts suggesting that starch degradation was not strictly controlledby the contents of these sugars. A decrease in the demand forcarbohydrates by removal of roots did not decrease starch degradationbut increased the contents of sucrose, glucose, and fructose.Removal of stolon tips decreased starch degradation and contentsof sucrose, glucose, and fructose. The results suggest thatstarch degradation was controlled by a factor other than sucrose,glucose, and fructose which was exported from stolon tips, e.g.gibberellin. Key words: White clover, storage carbohydrates, remobilization, regrowth     

The Function of Urease in Citrullus Seeds

Urease is present in considerable quantity in the cotyledonsof Citrullus, though elsewhere in the plant it is present onlyin traces or is absent; urease activity in the cotyledons changesduring growth, showing an initial rise followed by an abruptdrop almost to zero. These changes, under a wide variety ofconditions, are not correlated with those in the major nitrogenfractions; they are, however, closely correlated with cell extensionand the associated changes in water content and respiration.A connexion with chlorophyll formation is possible but unlikely.It is suggested that the changes in cotyledonary urease constitutemerely one aspect of the ‘protoplasmic differentiation’that takes place as a cell matures.     

Characterization of new microsatellite loci from Vitis vinifera and their conservation in some Vitis species and hybrids

We present here characterization data for seven new microsatellite markers designed from new microsatellite loci isolated from a microsatellite‐enriched DNA library from Vitis vinifera. The observed heterozygosity varied from 0.73 up to 0.93 and the number of alleles per locus ranged from 12 to 26. This high polymorphism makes these new markers interesting for use in genotyping studies and completing the set of microsatellite markers already available for V. vinifera. Additionally these seven new markers appear to be conserved in four other Vitis species and 15 Vitis hybrids used as rootstocks for V. vinifera cultivation.     

Understanding chromatin and chromosomes: from static views to dynamic thinking

The 106th Boehringer Ingelheim Fonds International Titisee Conference, ‘Reconstituting Chromatin: From Self‐assembly to Self‐organization’, took place in October 2012. The organizers, Andrea Musacchio and Tom Muir, brought together biologists, chemists and physicists to discuss the principles of chromosome assembly and organization. Topics of discussion ranged from new insights gained from the static views provided by crystal structures to analyses of chromatin dynamics inside living cells.     

Cohesin in determining chromosome architecture

Cells use ring-like structured protein complexes for various tasks in DNA dynamics. The tripartite cohesin ring is particularly suited to determine chromosome architecture, for it is large and dynamic, may acquire different forms, and is involved in several distinct nuclear processes. This review focuses on cohesin's role in structuring chromosomes during mitotic and meiotic cell divisions and during interphase.