Effect of fulvic and humic acids on nitrificationpart ii: The nitrifying potential of cecil and davidson soils

Abstract

A disagreement exists in the literature regarding the effect of organic matter on nitrification. Therefore, this investigation was conducted to study the effect of fulvic (FA) and humic acids (HA) on nitrification by chemical means. In part I, results of an experiment showed a general trend for nitrite production to increase with increase application of FA and HA. On the other hand, nitrate production decreased in the presence of FA and HA. Since the previous experiment was conducted in vitro without soil, a second experiment was initiated as discussed below to include the use of a Cecil and Davidson soil. Soil samples mixed with 0 to 1000 mg HA/kg were incubated for 21 days according to the Schmidt and Belser's nitrifying potential procedure, and an alternate method. Ammonium sulfate was added as the N‐source. The soils were then extracted with 2M KC1 for analysis of initial and final nitrate concentrations with which the nitrifying potential was calculated. An additional experiment was included to study nitrification in the presence of plant growth. For this purpose corn plants were grown for 25 days in pots, receiving 0 to 1000 mg HA/kg, 100 mg (NH₄)₂SO₂/kg, and 1 ml of a mixed nitrifier extract. The soils were again extracted with 2M KCl for analysis of initial and final nitrate concentrations and the nitrifying potential. The Schmidt and Belser method yielded results indicating that the Cecil soil had a greater nitrifying potential than the Davidson soil. A tendency was noted in the Davidson soil for nitrification to decrease with added HA. The inhibitory effect of HA on nitrate production was clearly demonstrated by the alternate method, which yielded a linear decrease in nitrate concentrations with increased HA treatments. Plant growth, and humic acid treatments appeared to decrease the final nitrate concentrations in the third experiments. The effect was more pronounced in the Cecil than in the Davidson soil. The nitrifying potential of the Cecil soil under corn, ranging from 1.05 to 2.23 mg NO^‐ ₃‐N/kg, was three to eight times smaller than that detected in the experiments without plants. These observations are in support of results discussed in Part I.     

Na2CO3和NaCl处理对盐角草生长和抗氧化酶活性的影响

[目的]研究不同浓度Na2CO3和NaCl处理的盐生植物盐角草生长和抗氧化酶活性的变化,探究Na2CO3胁迫对盐生植物伤害的原因。[方法]以盐角草为实验材料,以相同Na+浓度的Na2CO3和NaCl处理盐角草,通过比较研究两种盐胁迫对盐角草生长和抗氧化酶系统的影响。[结果]NaCl处理显著促进盐角草生长和提高抗氧化酶系统中的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性,而相同Na+浓度的Na2CO3却明显抑制盐角草生长,SOD、POD和CAT的活性也受到抑制,超氧阴离子(O2.-)和丙二醛(MDA)含量的增加程度明显高于等渗的NaCl处理。[结论]Na2CO3处理下,盐角草抗氧化酶活性的显著下降明显不同于NaCl处理,这是导致Na2CO3处理下盐角草生长量降低的原因之一。     

陈齿爪鳃金龟对油橄榄挥发物的趋向反应

通过GC-MS分析,确定了油橄榄(Olea europaea)树叶挥发物的主要成分为:β-石竹烯(14.29%)、α-芹子烯(13.13%)、β-芹子烯(10.15%)、α-石竹烯(6.60%)、橙花叔醇(6.72%)、3-己烯-1-醇(5.03%)和苯乙醛(5.61%)等。利用"Y"型双向选择嗅觉仪进行的室内趋向反应试验发现,芳樟醇、β-石竹烯、α-石竹烯、α-芹子烯和β-芹子烯对陈齿爪鳃金龟(Holotrichia cheni)具有显著的引诱作用;3-己烯-1-醇和壬醛化合物对陈齿爪鳃金龟雌虫具有明显的驱避作用,苯乙醛具有明显的引诱活性;橙花叔醇对雌虫具有驱避作用,而对雄虫则表现引诱活性。     

云南主栽油橄榄品种果实品质综合评价

为了解云南主要栽培油橄榄品种果实的综合品质,测定9个油橄榄品种果实的经济性状指标,并对其进行主成分分析和综合评价。结果表明：各品种果实经济性状的变异程度明显不同,变异系数为2.99%~43.59%;主成分分析抽提出3个特征值大于1的主成分,累计贡献率为82.604%;综合评价得分高低顺序为科拉蒂>柯基>佛奥>豆果>莱星>皮瓜儿>鄂植8号>城固32号>软阿斯。     

两个油橄榄品种的开花特性及橄榄园花粉流时空变化分析

为了探明甘肃省武都区油橄榄坐果率低、产量低的原因,以当地主栽品种‘莱星’和‘鄂植8号’为试验材料,观察油橄榄花期物候、单花特征及开放进程,检测花粉/胚珠比、花粉活力与柱头可授性,并进行油橄榄园花粉散布时空变化规律及与气象因子关系的研究.结果表明:油橄榄园5月进入花期,花期持续约12d,散粉盛期约3d;油橄榄单花微小,花瓣4枚,雄蕊2枚,雌蕊1枚,单花开放约3d;油橄榄花粉流密度分布在水平方向无显著差异,垂直方向随高度增加显著减少.温度是影响油橄榄园花期的主要气象因子,与开花植株率呈极显著正相关(r=0.860**、r=0.827**);日照强度是影响油橄榄散粉的主要气象因子,与花粉流密度呈显著正相关(r=0.791*).油橄榄单花花粉量约90 000粒,胚珠4枚,P/O值约22 500;散粉初期‘莱星’和‘鄂植8号’花粉活力分别为(97.23±2.05)%和(95.21±1.05)%,散粉后24h下降至(60.41±1.54)%和(60.11±1.63)%;花后24h内,两品种柱头具有强可授性,花后约48h柱头可授性显著下降.甘肃省武都区油橄榄坐果率受花粉限制,不受传粉限制,花后24h内是最佳授粉期.     

大肠杆菌菌株ATCC 25922碱性磷酸酶的原核表达、纯化及其活性研究

使用常规PCR法以大肠杆菌菌株ATCC 25922基因组为模板,克隆到该菌株的碱性磷酸酶成熟肽基因,并将其构建到原核表达载体pET-30a(+)的Bam HⅠ、XhoⅠ之间,获得重组表达载体pET-30a-EAP。并且我们将pET-30a-EAP转化到大肠杆菌RosettaTM(DE3)pLysS中,经IPTG诱导表达后,获得大小为52ku的目的蛋白EAP。经试验证明该蛋白以可溶形式为主。进而,高效表达的重组碱性磷酸酶经亲和层析法纯化后被用于活性鉴定。pNPP的显色反应与去磷酸化试验证实来自ATCC 25922的重组碱性磷酸酶具有催化磷酸单酯水解活性,而且酶热稳定性高、有效工作温度范围大,与其他蛋白融合表达时仍保持酶活性。以上研究结果为大肠杆菌菌株ATCC 25922碱性磷酸酶的规模化生产及在免疫酶技术领域中的应用提供了重要的参考依据。     

盐环境下氮素对苗期盐角草氮同化关键酶活性的影响

【目的】 研究盐环境下施氮水平对盐角草幼苗对氮催化和同化的能力,了解盐角草对氮素吸收转化的机制。【方法】 采用盆栽试验方法,研究不同施氮水平对盐环境下生长的盐角草幼苗氮同化关键酶活性的影响。【结果】 与不施氮处理相比,在重度盐环境条件下,施氮可现在提高盐角草幼苗根、茎、同化枝NR、GS、GOGAT、GLDH的活性;施N(1.2 g/kg)时,盐角草幼苗根、茎、同化枝活体NR活性、茎活体GS、GOGAT活性达到最大值;施N(2.4 g/kg)时,盐角草幼苗根、同化枝活体GS、GOGAT活性及根、茎、同化枝活体GLDH活性达到最大值。【结论】 盐环境下施氮能够显著增强盐角草幼苗氮同化关键酶活性,提高了盐角草对氮素胁迫能力,增强其对高氮环境的适应性。     

Balanced fertilization improved soil ammonia-oxidizing bacterial community in latosolic red soil

Abstract

We investigated the impact of nitrogen (N), phosphorus (P), potassium (K) (NPK) and NPK plus glucose-balanced fertilization compared with N-only fertilization on the soil pH, NH₄ ⁺, NO₃ ^?, ammonia-oxidizing bacterial community, bacterial community and function during microcosm incubation. The NPK and NPK plus glucose treatments resulted in significantly reducing soil acidification and NO₃ ^? accumulation compared with the N-only fertilization. The terminal restriction fragment size measuring 283 (Nitrosospira) and 54 bp (unidentified) were predominant in the soil ammonia-oxidizing bacterial composition for all treatments. The N-only fertilization did not change the ammonia-oxidizing bacterial community, the bacterial community composition based on terminal restriction fragment length polymorphism analysis, and the bacterial functional diversity based on Biolog EcoPlate^TM incubation. The NPK and NPK plus glucose treatments resulted in a shift in the soil ammonia-oxidizing bacterial community and bacterial community composition, and significantly increased the bacterial functional diversity (average well colour development, Richness and Shannon index). Nitrosomonas species were detected in the soil upon NPK and NPK plus glucose treatment on incubation day 9 but not on days 1 and 31. The effect of NPK treatment on the bacterial community composition was transient; a new 116 bp fragment was present on incubation day 9, but the data returned to their original values by day 31. In contrast, treatment with NPK plus glucose resulted in the appearance of a new 116 bp fragment that remained until incubation day 31. These results demonstrated that the balanced fertilization of N, P, K and glucose, plays an important role in regulating ammonia-oxidizing bacterial community quickly, and promoting nitrification functions. The results also showed the importance of balanced fertilization in reducing acidification, improving bacterial community structure and function in latosolic red soil. Therefore, optimizing the ammonia oxidation process by balanced fertilization may be helpful to reduce the loss of soil nitrogen.     

Relationship of genetic structure of Pseudomonas savastanoi pv. savastanoi populations from Italian olive trees and patterns of host genetic diversity

A total of 360 Pseudomonas savastanoi pv. savastanoi isolates obtained from 11 Italian olive ( Olea europaea ) cultivars grown in different provinces were assessed with repetitive PCR using short interspersed elements of the bacterial genome as primers (ERIC, BOX and REP primer sets). The population structure of the isolates was determined by using three different hierarchical clustering algorithms: UPGMA, single-link and complete-link methods. REP primers were the most discriminatory. The various fingerprints obtained from the same cultivar and locality persisted over 2 years of knot sampling. Repetitive PCR and UPGMA analysis, using the three data sets combined, revealed 20 patterns with an overall similarity of 81%, with no grouping of the isolates. The resulting dendrogram shows a bush-like topology. Similar results were obtained with the other two clustering methods. In contrast, data obtained from the literature showed that the genetic structure of olive is characterized by bifurcated dendrograms and clear grouping of cultivars. Therefore it appears that the host plant and its pathogen did not cospeciate. The strict adaptation of the bacterium to olive would represent a case of association by colonization.     

Morphology,phylogeny and pathogenicity of Botryosphaeria and Neofusicoccum species associated with drupe rot of olives in southern Italy

Species of Botryosphaeria and Neofusicoccum are well known as pathogens of woody hosts. In this study the species that occur on rotting olive drupes in the main production areas of southern Italy were studied. Species were identified from the morphology of their conidial states in culture and from sequence data of the ITS rDNA operon and partial sequence of the translation elongation factor 1‐α gene. Botryosphaeria and Neofusicoccum species were isolated from more than 60% of the affected drupes, suggesting that they are the main contributors to this disease. The most common species was B. dothidea, which was isolated from 34% of the drupes. However, N. australe and N. vitifusiforme were also common and were isolated from 16 and 12%, respectively. Two other species (N. parvum and N. mediterraneum) were uncommon and occurred on less than 1% of the drupes. All five species were pathogenic on the two cultivars of olive tested. The most aggressive species was N. vitifusiforme, followed by N. australe and B. dothidea. The two olive cultivars differed in their susceptibility to the pathogens. The results show that B. dothidea, N. vitifusiforme and N. australe are important pathogens of olives.