Regulation of C/N Interaction in Model Plant Species

Summary

Carbon (C) and nitrogen (N) metabolisms are two major metabolic pathways which have been intensively studied in plants. Both N and C metabolisms are tightly linked in numerous plant biochemical pathways. Therefore the C to N ratio has to be carefully regulated to ensure proper functioning of the huge metabolic network. In order to maintain a viable C/N status under a large range of growth conditions plants have evolved complex mechanisms to regulate the delicate network of these two major assimilatory pathways. C and N metabolisms are both highly regulated. We will present the current knowledge on the regulation of N and C metabolisms by sugars and N metabolites. Players involved in these regulatory processes are just starting to be uncovered and possible signaling molecules involved in these regulations as well as known or potential candidate regulatory genes willbe discussed.     

Impact of excreted nitrogen by grazing cattle on nitrate leaching

Abstract. At De Marke experimental farm, data on water and nitrogen flows in the unsaturated zone were gathered on two grazed pastures on sandy soils during the years 1991 to 1994. These provided a basis for calibration and validation of simulation models. The different levels of nitrate-N concentrations of the two plots could largely be explained by differences in crop uptake and simulated denitrification as influenced by different groundwater levels. The irregular distribution of excreta was taken into account by a simulation study quantifying the variability of nitrate-N concentrations under a grazed field. The resulting distribution of simulated nitrate-N concentrations explained the average and peak values of the measured concentrations. Temporal variability of weather was used to assess the nitrate leaching risk under urine patches deposited in either July or September. At site A the probability of exceeding the EC-directive by drinking water (11.3 mg/1 nitrate-N) under a urination deposited in either July or September was respectively 10 and 25%. The average field concentration at this site will hardly ever be a high risk for the environment under the current farm management. At site B the EC-directive will be exceeded under any urine patch in almost 100% of the years, affecting the field average concentration. In field B careful grazing management would result in less nitrate leaching, but the environmental goals would not be reached.     

Parameterization of the MACRO model to represent leaching of colloidally attached inorganic phosphorus following slurry spreading

Abstract. The dual porosity soil water and contaminant transport model MACRO was tested for its suitability to represent water flows and leaching of phosphorus (P) through field drains following spreading of slurry. These flows are characterized by very high loadings of P, including a high proportion in colloidally attached form, for about one week following winter spreading of slurry, followed by quite a rapid decline to the low background level. Use was made of the option in MACRO for representing colloid facilitated contaminant transport. The model simulates transport through macropores and soil matrix pores (micropores) of contaminant carrying colloids, as well as trapping of colloids by straining and filtration using an adaptation of standard filtration equations. Calibration involved selecting soil hydraulic parameters, colloid filtration coefficients and P sorption characteristics for two soils from measured and literature values. Both P in solution and P attached to colloids were represented in simulated outputs. Reasonable agreement was found between simulated and measured water and leached P flows. Work with the model suggests that macropore flow through the soil to field drains of colloidally transported P is an important component of water pollution associated with slurry spreading     

Numbers of nitrate-reducing bacteria in the rumen as estimated by competitive polymerase chain reaction

Cell numbers of known species of nitrate- and nitrite-reducing bacteria, Selenomonas ruminantium, Veillonella parvula and Wollinella succinogenes , in the rumen of goats (25–30 kg) were estimated by competitive polymerase chain reaction (PCR). The number of S. ruminantium was the largest of the three species examined, and tended to be greater in goats fed a high-concentrate diet (5.6 × 10⁷ cells/mL rumen fluid) than in goats fed a high-roughage diet (1.3 × 10⁷ cells/mL). The number of V. parvula tended to be greater when goats were fed a high-roughage diet (6.7 × 10³/mL) than when fed a high-concentrate diet (3.2 × 10³/mL). The number of W. succinogenes was below the detectable level (< 1.0 × 10²/mL) when a high-concentrate diet was fed, but was significantly increased by feeding a high-roughage diet (1.6 × 10³/mL). Addition of potassium nitrate (6 g/day) to the high-concentrate diet tended to increase V. parvula , and significantly increased W. succinogenes , indicating that these two bacteria can be increased by feeding a diet containing nitrate.     

复合阻燃剂对思茅松胶合板性能的影响

选用5种磷-氮-硼复合体系阻燃剂对思茅松单板进行真空加压处理,用于制备阻燃胶合板,测试思茅松阻燃胶合板的胶合强度、燃烧性能、吸湿性和抗流失性.结果表明:当阻燃剂载药率为10%时,阻燃胶合板的胶合强度均≥1.15 MPa,超过Ⅱ类胶合板标准0.8 MPa;极限氧指数值均>38%,达到日本JIS难燃一级指标要求.当载药率为15%时,FR-a,FR-b和FR-c 3种阻燃剂处理的阻燃胶合板的极限氧指数值为53%~59%.5种阻燃剂中,FR-a会显著增加木材的吸湿性,其他阻燃剂对吸湿性影响不大.与阻燃剂的水溶性相对应,FR-a和FR-b抗流失性较差,FR-d和FR-e具有优良的抗流失性,FR-c则有一定的抗流失性.5种阻燃剂相比较,FR-c的综合性能最优.     

柳枝浸提液对小麦籽粒发芽的抑制作用研究

研究了柳树枝叶浸提液对小麦籽粒发芽的抑制效应，结果表明：抑制作用的大小随浸提时间和浸提液浓度的不同而异，煎煮时间对小麦种子发芽抑制强度依次为4h〉3h〉2h〉0．5h，浸提液不同浓度的抑制效果为280g／L〉200g／L〉120g／L〉40g／L。     

Genetics of nitrate content of lettuce, 1: Analysis of generation means

Summary The genetics of nitrate content in butterhead lettuce (Lactuca sativa L.) was studied using the mean values of five parental genotypes and several generations obtained from crosses between them. One high nitrate parental genotype was chosen and four low nitrate ones. A diallel analysis showed additive genetic effects to be the major source of variation in generation means. Estimates of additive genetic effects differed significantly between experiments, indicating genotype x experiment interactions. Effects of dominance were relatively small. The size and direction of dominance varied between experiments. Reciprocal differences were of very limited size and also varied between experiments. The inheritance of nitrate content in lettuce fitted the additive-dominance genetic model.     

潮州产13种野菜中硝酸盐和亚硝酸盐的含量

根据潮州产13种野菜中硝酸盐和亚硝酸盐含量的测定结果,参考蔬菜中硝酸盐含量分级评价标准和我国的无公害蔬菜亚硝酸盐含量限量标准(≤4.0mgkg),对13种野菜的品质进行了评价。结果显示,菜、酢浆草、野茼蒿、黄鹌菜和腋花蓼硝酸盐含量低于轻度污染水平,亚硝酸盐含量低于我国制定的无公害蔬菜亚硝酸盐含量的限量标准(≤4.0mgkg),属于一级无公害野菜,可以安全食用;少花龙葵、马齿苋、鳢肠、叶下珠、铁苋菜、小藜和牛繁缕的硝酸盐含量高于432mgkg,而低于785mgkg,亚硝酸盐含量低于限量标准(≤4.0mgkg),属于二级野菜,不宜生食,煮熟和盐渍可安全食用;鼠曲草的硝酸盐含量高于785mgkg,低于1440mgkg,属于三级野菜,不可生食和盐渍,可熟食。     

4种荚蒾属植物种子内源抑制物存在特征初探

通过荚蒾种子浸提液对小白菜种子萌发的抑制作用,分析探讨荚蒾种子内源抑制物主要存在部位及其可溶性化学特征,为荚蒾属植物种子破除休眠提供科学依据。实验结果表明:4种荚蒾种子水和甲醇浸提液对小白菜种子萌发和胚根生长都有抑制作用,种皮水溶性抑制物活性:蒙古荚蒾朝鲜荚蒾暖木条荚蒾鸡树条荚蒾,胚乳水溶性抑制物活性:蒙古荚蒾鸡树条荚蒾暖木条荚蒾朝鲜荚蒾;种皮脂溶性抑制物活性:暖木条荚蒾蒙古荚蒾朝鲜荚蒾鸡树条荚蒾,胚乳脂溶性抑制物活性:鸡树条荚蒾朝鲜荚蒾蒙古荚蒾暖木条荚蒾。鸡树条荚蒾、朝鲜荚蒾、暖木条荚蒾内源抑制物主要是脂溶性物质,前两者较集中分布于胚乳,后者多存在于种皮;蒙古荚蒾以胚乳中水溶性抑制物为主。