松嫩平原羊草草地水淹干扰恢复过程的群落动态

根据随机取样的测定数据，经过幂函数和多元回归分析及相关检验，揭示了草地水淹干扰对羊草 寸草苔、羊草 杂类草群范数量性状的变化规律。水淹干扰对草地植被的物种组成及其比例有明显的影响。水淹后基本恢复到正常草地的种类数量和生产量配置大约需要6—7年。随着生境水分减少和土壤变干，羊草种群的数量和生物量均以幂函数形式增加，而寸草苔和杂类草的数量和生物量则呈先增后降的变化过程。     

铅对草坪植物生物量与叶绿素水平的影响

通过盆载模拟试验研究了铅对植物生物量、叶片叶缘素含量变化的影响，以及植物中毒后的症状。结果表明，铅对植物根系生长发育影响极大，可使根冠细胞有丝分裂减少、根量减少。铅进入叶肉组织后导致叶片失绿，严重时使叶片枯黄死亡。试验早期植物中毒症状表现为根冠膨大变黑，严重时根系腐烂。当营养液中Pb浓度达5.0mol／m^3时，试验后期引起植物死亡且不易恢复。     

Differences in Wheat Cultivar Response to N Supply. I: Differences in Grain Yield Formation

Two-year field trials with winter wheat cultivars Batis and Toronto were conducted in Southern Bavaria, Germany, to investigate the possible causes of cultivar differences in response to N supply varying in total amount and time of application. Cultivar-related differences in grain yields were observed in treatments with low and medium N supply. High doses of N supply resulted in grain yield adjustment or grain yield advantage for cv. Toronto. The results of this study revealed a consistent, genotypic pattern in response to N fertilization in spite of strong seasonal effects. Systematic modifications in canopy growth rates in response to N supply were of particular relevance and a main factor for differences in tillering intensity resulting in modified stand densities. In the present study, cultivar differences in spike development and interactions with N supply related more to abortion than to initiation processes for number of spikelets and number of flowers per spikelet. High grain density (grains per m²) of cv. Toronto was evident during reproduction stages even under conditions of medium N supply. However, decreased growth rates during the later part of grain filling in combination with low 1000 grain weight, which was barely modified by N fertilization, allowed only partial utilization of this potential. It is assumed that sink limitations were of particular relevance for grain yield development in cv. Toronto, while cv. Batis combined a less intense response to N supply with more stability in the development of grain yield components.     

离子选择电极法测定NBPG与银、镉、汞的配合物组成和稳定常数

本文用离子选择电极法测定了N,N—二甲基膦酸基甘氨酸(NBPG)与银、镉、汞的配合物组成和稳定常数。结果表明,NBPG与Ag~ 、Cd~(2 )、Hg~(2 )均生成组成为1:1的多齿质子型配合物。其lgK_稳值分别为:AgL5.28、CdH_3L3.63、CdH_2L5.16、CdHL7.30、CdL11.56、HgH_3L6.06、HgH_2L7.55、HgHL8.24、HgL12.58。     

H7N2禽流感病毒分离株血凝素蛋白全基因的序列分析

为进一步分析H7N2禽流感病毒（AIV）分离株血凝素（HA）基因的特性,参照已发表序列设计了1对引物,采用RT-PCR获得了1条约1.7 kb的DNA片段,测序后进行了同源性比较、HA基因系统发育进化树分析和氨基酸编码分析.结果表明,所测的2个分离株的HA基因全长1 664 bp,编码除信号肽以外的HA蛋白的全部544个氨基酸,其中包括HA1的323个氨基酸,HA2的221个氨基酸.2个分离株HA基因核苷酸序列的同源性为99.4%;与GenBank中AIV标准株A/Afri.Star./Eng-Q/983/79（H7N1）的同源性最高,分别为99.4%和99.0%;与美国A/Chicken/NewYork/13142-5/94（H7N2）株同源性很低（仅65.0%）,而与以色列、意大利H7N2 AIV的同源性较高（为96%～97%）;2个分离株在HA基因进化树中均处于H7亚型AIV的欧亚群系分支内.推导氨基酸的序列分析表明,其HA蛋白裂解位点的氨基酸序列为-GR-GLF-,仅包含1个碱性氨基酸（R-）残基,符合低致病力AIV的基因特征.     

复合微生物肥料在无公害蔬菜栽培上的效应初报

施用复合微生物肥料使番茄产量提高 7.3 %～ 11.1% ,可溶性固形物含量提高 0 .9%～ 1.3 % ,硝酸盐含量降低 2 7.2 %～ 3 4 .8% ;苦瓜产量提高 10 .7%～ 16.1% ,硝酸盐含量降低 2 8.7%～ 3 6.1% ;菜薹产量提高 7.2 %～ 15.1% ,硝酸盐含量降低 55.6%～ 61.5%。各处理产品中的硝酸盐含量及有害元素的含量 ,均符合无公害蔬菜产品质量标准要求     

Variation of Parthenium hysterophorus in response to soil quality: implications for invasiveness

Summary The performance of Parthenium hysterophorus , native to the tropical Americas and invasive to several countries, was evaluated for response to soil quality. Phenological (six stages) and quantitative growth variables [relative growth rates in height (R_h) and diameter (R_d)] were measured every fortnight. Based on harvest data, the variables, root:shoot (R:S) ratio, specific leaf area (SLA), relative growth rate in biomass (R_w), net assimilation rate (NAR) and dry matter allocation to plant components, were determined. High clay content in soils prolonged the rosette stage, enhanced R_h and R_d and hampered root growth, but promoted biomass allocation to shoots. The extreme degree of plant mortality was observed, with only 33.3% individuals surviving to reproduce in the soils with highest clay contents. This appears to be one of the most important findings that certainly has a major bearing on the range of adaptation of the weed. Seed mass declined whereas seed production increased in relatively coarser soils with the exception of nearly pure sand. In soils rich in clay, plants produced a smaller number of larger seeds. These data suggest that variation in fundamental functional traits would enable P. hysterophorus to adjust to a variety of habitat conditions.     

Effect of take-all root infections on nitrate uptake in winter wheat

The effect of take-all root lesions on nitrate uptake of wheat was investigated in two experiments under controlled conditions. Plants were supplied with a nutrient solution labelled with ¹⁵N during stem elongation and flowering to assess the distribution of the isotopic tracer in the different plant organs, and particularly in root segments located on both sides of take-all lesions. The ¹⁵N atom percentage excess measured in root segments located below lesions longer than 1 cm was reduced on average by half compared with that in healthy roots and root segments above lesions, reflecting a reduction in nitrogen uptake by these root segments. This reduction probably resulted from the invasion and breakdown of phloem vessels by the fungus hyphae, interrupting energy supply and thus the uptake process. Severely infected plants showed an increase in the uptake rate per unit of efficient root, which appeared to be a compensatory response to reduction of efficient root biomass in order to satisfy shoot nitrogen demand. However, this compensatory response was insufficient to ensure nitrogen accumulation equivalent to that of healthy plants, as reductions in nitrogen accumulated in roots and aerial parts at flowering were up to 56 and 49%, respectively, for plants with more than 50% of the root system below lesions longer than 1 cm.     

施氮量对棉田主要害虫种群动态的影响

通过不同施氮肥量对棉田主要害虫种群动态影响的研究结果表明,在低、中、高3种施氮肥水平处理条件下,随着氮肥量的增加,棉田棉铃虫落卵量增加,棉苗蚜、棉叶螨种群数量减少,发生为害减轻,但棉伏蚜种群数量增加。中等施氮肥条件下,第二、三代棉铃虫幼虫数量高于低和高施氮肥处理,对棉铃虫幼虫的生长发育和存活较为有利。     

Weed:spring barley competition for applied nitrogen in pig slurry

Summary The experiments were carried out in the two spring barley fields of the organic six-course cattle:crop rotation at Foulumgaard, Denmark. The weed density was 300 and 1800 plants m⁻² respectively. Pig slurry was applied by hand in microplots by four methods: broadcasting followed by incorporation, or injected in bands to depths of 5, 10 or 15 cm. Spring barley and weeds were sampled separately six times during the tillering and elongation phase of the spring barley. The effect of application method on dry-matter (d.m.) production, nitrogen uptake and recovery of applied nitrogen in the spring barley and the weeds is reported. Slurry banding halved the weed d.m. and weed N uptake compared with broadcasting, irrespective of weed density. Weeds recovered up to 12% of the applied nitrogen, which made them a significant competitor when the slurry was broadcast and incorporated. Banding by direct injection reduced the slurry:soil contact and the weed:crop competition balance for applied nitrogen moved in favour of the crop. Thus, the crop recovery of applied nitrogen at the end of the sampling period was increased from approximately 45% for broadcast and incorporated to approximately 50% for injected slurry, and coincidental weed recovery was reduced to a maximum of 5%. As the nitrogen supply normally affects plant d.m. production, banding of slurry might well improve crop competitiveness and its tolerance to mechanical weed control.