池塘生态系基质C/N比对游离细菌群落生长和有机N矿化作用的影响

本文研究了向高产鱼池中人工添加有机C（葡萄糖）和有机N（甘氨酸）对水中游离细菌生长及其分解矿化有机N的影响。研究结果表明，向池塘水中添加有机C促进了细菌生长和细菌对N素的吸收；而添加有机N对细菌生长的影响不明显，但增强了有机N的矿化作用。在池塘水营养条件下，溶解有机C限制了细菌的生长，细菌在鱼池生态系统N循环中起着有机N分解者的作用。     

赤霉素对黄瓜幼苗在根区亚低温下生长与氮积累的影响

为了探讨赤霉素(GA)对黄瓜在根区亚低温下氮(N)吸收和代谢的影响机理,以营养液栽培的‘中农26’黄瓜为试材,研究了外源GA对黄瓜在根区亚低温下叶片叶绿素荧光参数、光合参数和碳(C)、氮代谢平衡调节酶活性的影响。结果表明:与根区适温处理相比,根区亚低温使黄瓜幼苗生长受抑,叶片光系统Ⅱ(PSⅡ)的光化学活性、光合放氧速率、净光合速率(Pn)、磷酸烯醇式丙酮酸羧化酶(PEPCase)和蔗糖磷酸合成酶(SPS)活性等降低,单株C与N积累量的比值(C/N)升高,N代谢消耗的能量减少。外源GA处理缓解了根区亚低温对黄瓜生长的抑制,使PSⅡ光化学活性、光合放氧速率、Pn、PEPCase和SPS活性都有不同程度的提高,C/N值和N代谢消耗的能量恢复至与根区适温处理相当的水平。表明,外源GA可以通过增强光能捕获和CO_2同化能力,调节N、C代谢平衡,促进根区亚低温下黄瓜对N的吸收与代谢。     

青海湖环湖区表土有机碳氮储量估算

分析了沿青海湖湖岸采集的81个表土样品的总有机碳和氮含量得出：环湖区表土有机碳储量为27.81×10^6t,总氮储量为30.24×10^5t。占研究区面积最大的栗钙土,其表层土壤有机碳密度（8.19kg/m^2）显著高于同类研究,氮含量（3.63mg/g）亦高于青海省同类土壤的平均值,说明环湖区表土碳氮储量都是相当大的...     

Effects of partial replacement of nitrate with different nitrogen forms on the yield,quality and nitrate content of Chinese kale

In this study, the yields, nutritional qualities and nitrate (NO₃) content of Chinese kale were studied with two cultivars, following partial replacement of nitrate (20%) with ammonium (NH₄), urea and glycine in hydroponics. The results showed that, compared with the full nitrate treatment, ammonium replacement increased the fresh weight by 18.1% and 8.0% of ‘Zaobao’ and ‘Lvbao’ cultivars respectively, whereas urea and glycine replacements decreased the biomass significantly. Adding different nitrogen (N) forms significantly improved the contents of vitamin C, soluble sugar, free amino acid, protein, soluble phenol and flavonoids in Chinese kale. Adding the three alternative N forms also reduced nitrate content significantly, in which glycine replacement was the lowest. According to the results obtained, different forms of N replacement could be used for different purposes. Glycine replacement could be the best alternative only to improve qualities, while ammonium replacement could be the best alternative to improve both the yield and qualities.     

人造林窗对粗枝云杉人工林土壤微生物量的影响

通过对川西亚高山云杉低效林不同大小林窗(面积50 m2、100 m2、150 m2)改造,以未处理作为对照,采用氯仿熏蒸浸提法研究了林窗改造对土壤微生物生物量碳、氮含量及其垂直分布特征的影响。结果表明:通过林窗改造,林下土壤微生物量碳、氮具有显著提升,其中,林窗面积越大,提升效果越显著。各土层土壤微生物量碳、氮含量均表现为:150 m2(L3)100 m2(L2)50 m2(L1)对照(CK);3种大小面积林窗和对照土壤微生物量碳、氮含量随着土层深度的增加而降低,均表现为上层(0~5 cm)中层(5 cm~10 cm)下层(10 cm~15 cm);且林窗改造降低了土壤微生物量碳、氮的表层富集特性,林窗面积越大,上层土壤微生物量碳、氮所占比例越低。     

日粮维生素D和钙水平对冬毛期水貂生长性能、营养物质消化率及氮、钙、磷代谢的影响

本试验旨在研究当日粮钙磷比一定时,维生素D和钙水平对冬毛期水貂生长性能、营养物质消化率及氮、钙、磷代谢的影响。随机选取（135±5）日龄、健康雄性水貂117只,分成9组,每组13个重复,每个重复1只。采用3×3双因素随机试验设计,设3个维生素D水平,分别为2 300、4 300、6 300 IU/kg;设3个钙水平,分别为2.0%、2.4%、2.8%,钙磷比固定为1.7∶1,配制9组试验日粮,分别为：Ⅰ组（2 300 IU/kg维生素D＋2.0%钙）、Ⅱ组（4 300 IU/kg维生素D＋2.0%钙）、Ⅲ组（6 300 IU/kg维生素D＋2.0%钙）、Ⅳ组（2 300 IU/kg维生素D＋2.4%钙）、Ⅴ组（4 300 IU/kg维生素D＋2.4%钙）、Ⅵ组（6 300 IU/kg维生素D＋2.4%钙）、Ⅶ组（2 300 IU/kg维生素D＋2.8%钙）、Ⅷ组（4 300 IU/kg维生素D＋2.8%钙）、Ⅸ组（6 300 IU/kg维生素D＋2.8%钙）。预试期13 d,正试期60 d。结果表明：①各组水貂料重比差异极显著（P<0.01）,Ⅱ组最低。钙水平对料重比有显著影响（P<0.05）,维生素D水平对料重比有极显著影响（P<0.01）。②钙水平可极显著影响粗脂肪消化率（P<0.01）,其中2.8%水平极显著低于2.0%和2.4%水平（P<0.01）。③日粮维生素D和钙水平对水貂氮代谢指标均无显著影响（P>0.05）。④各组水貂粪钙、粪磷、钙消化率、磷消化率均差异极显著（P<0.01）,其中Ⅱ组钙消化率、磷消化率最高,Ⅲ组次之。钙水平可极显著影响粪钙、粪磷、钙消化率、磷消化率（P<0.01）,2.0%水平可极显著降低粪钙、粪磷含量（P<0.01）,极显著提高钙消化率及磷消化率（P<0.01）。维生素D水平对钙消化率影响显著（P<0.05）,对粪磷、磷消化率影响极显著（P<0.01）,2 300~4 300 IU/kg维生素D水平有利于提高钙消化率、磷消化率,降低粪磷含量。综合考虑各项指标,在本试验条件下,日粮中钙磷比为1.7∶1,维生素D水平为2 300~4 300 IU/kg、钙水平为2.0%时,冬毛期水貂料重比及钙、磷排放量较低,而粗脂肪、钙、磷消化率较高。     

Quantifying the nitrogen retention capacity of natural wetlands in the large-scale drainage basin of the Baltic Sea

We estimate the nitrogen retention capacity of natural wetlands in the 1.7 million km² Baltic Sea drainage basin, using a wetland GIS data base. There are approximately 138,000 km² of wetlands (bogs and fens) in the Baltic Sea drainage basin, corresponding to 8% of the area. The input of nitrogen to natural wetlands from atmospheric deposition was estimated to 55,000–161,000 ton y¹. A map of the deposition of both wet and dry nitrogen is presented. The input from the human population was estimated to 255,000 ton y¹ in terms of excretory release in processed sewage water. There may also be leakage from forests and agricultural land into the wetlands. Due to lack of data on hydrology and topography, such potential nitrogen sources are not accounted for here. The capacity of the wetlands to retain the atmospheric deposition of nitrogen was estimated to 34,000–99,000 ton y¹. The potential retention by wetlands was estimated to 57,000–145,000 ton y¹ when the nitrogen input from the human population was added. If drained wetlands were to be restored and their area added to the present wetland area, the nitrogen retention capacity was estimated to increase to 196,000–261,000 ton y¹. Our results indicate that existing natural wetlands in the Baltic Sea drainage basin annually can retain an amount of nitrogen which corresponds to about 5–13% of annual total (natural and anthropogenic) nitrogen emissions entering the Baltic Sea. The ecosystem retention service performed by wetlands accounts for a substantial nitrogen removal, thereby reducing the eutrophication of the Baltic Sea.     

OPG/RANKL/RANK系统的生理功能

 骨是一个代谢活跃的器官,在整个生命周期中都在进行不断的更新与重建。在骨形态发生和重建的过程中主要受到细胞因子和激素的调节,同时骨代谢也受到OPG/RANKL/RANK系统的调控。论文主要对骨骼生理结构与骨组织细胞之间的关系,骨代谢和骨的形成过程,OPG/RANKL/RANK系统的生理功能,OPG/RANKL/RANK系统的影响因子以及骨代谢紊乱所引起的疾病几个方面作一综述。     

氮肥对水稻叶冠层捕食性天敌种群及其自然控制能力的影响

为了公正地评价氮肥对整个稻田生态系统的影响，在国际水稻研究所试验场分别设立0、100和200kg／hm^2三个氮肥水平，测定了水稻主要特性参数和叶冠层捕食性天敌的种群动态，同时以果蝇蛹作为替代猎物的方法在田间模拟评价了叶冠层捕食性天敌对害虫的自然控制能力。结果表明，虽然施用200kg／hm^2氮肥稻田的稻株高度、叶面积和稻草干重显著比施用100kg／hm^2氮肥稻田的高，但每丛分蘖数和稻谷产量则没有明显差异。在水稻叶冠层中，肖蛸、圆蛛、黑肩绿盲蝽、稻红瓢虫和捕食性螅等为稻飞虱主要捕食性天敌。肖蛸在水稻孕穗期的数量最高，圆蛛的种群随水稻的生长而下降，但黑肩绿盲蝽、稻红瓢虫和捕食性螅的数量却均随水稻的生长而增加。施用氮肥后稻田中肖蛸和稻红瓢虫的种群数量显著减少。在水稻孕穗期，叶冠层上蜘蛛网的数量和蜘蛛网总面积均随氮肥施用量的提高而显著减少。在水稻孕穗期和乳熟期，不施用氮肥稻田中的捕食性天敌对替代猎物果蝇蛹的捕食能力显著高于其它两个施用氮肥的稻田中的捕食能力。而在乳熟期施用100kg／hm^2氮肥稻田的捕食能力又显著比施用200kg／hm^2氮肥稻田的高。结果说明过量施用氮肥可削弱天敌对害虫的自然控制作用。     

Relation between milk urea content and nitrogen excretion from lactating cows

Abstract

Thirty-two Chinese Holstein lactating cows were used to investigate the relationship of milk urea nitrogen (MUN) and nitrogen excretion loading to the environment. Cows were fed a similar amount of forage, and concentrates according to milk production. Total collection of urine and faeces were conducted continuously for three days. The milk urea nitrogen was significantly correlated to total nitrogen excretion (R ²=0.70), urinary nitrogen excretion (R ²=0.85), and nitrogen excretion from faeces (R ²=0.22). The following equation was proposed to predict total nitrogen excretion (TNE) (g/d) based on milk urea nitrogen (MUN) (mg/dl): TNE?=?15.46(±1.83)×MUN?+?193.40(±28.79). The results obtained in this study suggested that MUN might be used to predict TNE from lactating cows.