Do cover crops change the lability of phosphorus in a clayey subtropical soil under different phosphate fertilizers?

Plants have developed different mechanisms to absorb and solubilize phosphorus (P) in the soil, especially in environments with low P availability. This study evaluated the effects of different winter cover crops on soil P availability in a clayey subtropical (Hapludox) soil receiving soluble P fertilizer and a rock phosphate applied to the summer crop, under no‐tillage. The experiment was carried out over 3 yrs (2009–2011) with five different cover crop species: common vetch, fodder radish, ryegrass, black oat, white clover and fallow as control. The soil was sampled after the third year of cover crop cultivation and analysed for inorganic and organic P forms according to the well‐established Hedley fractionation procedure. Phosphate fertilizers promoted accumulation of both labile and nonlabile P pools in soil in the near surface layer, especially under rock phosphate. Fertilizer applications were not able to change P fractions in deeper layers, emphasizing that the Brazilian clayey soils are a sink of P from fertilizer and its mobility is almost nil. Although the cover crops recycled a great amount of P in tissue, in a short‐term evaluation (3 yrs) they only changed the content of moderately labile P in soil, indicating that long‐term studies are needed for more conclusive results.     

便携式XRF仪现场快速测定土壤中Pb的可行性研究

便携式XRF分析仪具有轻便、快速和可测对象较多与测量元素较广等特点而广泛应用于矿石、土壤等方面快速检测,但土壤的现场快速测定结果的准确性有待进一步研究与探讨。以安宁河谷平原土壤中Pb为研究对象,通过对便携式XRF仪现场快速检测结果与实验室分析结果的对比和影响因素的分析,建立基于安宁河谷平原表层土壤快速测定结果的线性函数为y=1.170 9x-17.326 0(R~2=0.992 9,x为现场检测结果),探讨其影响因素,为该区域表层土壤中Pb快速检测结果提供依据。     

饲料异亮氨酸水平对卵形鲳鲹消化酶活性和免疫指标的影响

实验旨在研究饲料异亮氨酸(Ile)水平对卵形鲳鲹(Trachinotus ovatus)消化酶活性和免疫指标的影响。以鱼粉、豆粕、花生粕和L-晶体氨基酸为蛋白源,配制含粗蛋白430 g·kg~(-1)的6种等氮饲料,各组分别含有13.2 g·kg~(-1)、15.7 g·kg~(-1)、18.2 g·kg~(-1)、20.7 g·kg~(-1)、23.2 g·kg~(-1)和25.7g·kg~(-1)(以干物质计)异亮氨酸。每组3个重复,每个重复随机放置20尾鱼[初始体质量(6.36±0.03)g],实验时长8周。结果显示,各实验组的肠淀粉酶和胃蛋白酶活性、血清总抗氧化能力(T-AOC)、溶菌酶(LZM)活性、免疫球蛋白M和补体(C3和C4)浓度均随着饲料Ile水平的升高而先上升后下降,这5个指标的较高值出现在18.2 g·kg~(-1)和20.7 g·kg~(-1)组,而较低值则出现在13.2 g·kg~(-1)和25.7 g·kg~(-1)组,上述4组与其他2组差异显著。血清尿素氮和丙二醛(MDA)浓度的变化趋势则与上述7个指标相反,较低值出现在18.2 g·kg~(-1)和20.7 g·kg~(-1)组,且显著低于其他4组。血清超氧化物歧化酶(SOD)活性则随着饲料Ile水平的增加而显著升高,18.2~25.7 g·kg~(-1)这4组SOD活性没有显著性差异。综上所述,饲料Ile水平为18.2~20.7 g·kg~(-1)时,卵形鲳鲹具有较好的消化性能和免疫机能。     

气象因子对寒地水稻鞘腐病发生的影响

为明确主要气象因子对黑龙江省水稻主产区水稻鞘腐病发生的影响,从2007年开始连续10年进行定点调查,收集水稻鞘腐病发生时期的气象因子及病情指数,采用通径分析及逐步回归的方法,对影响水稻鞘腐病病情指数的气象因子进行了研究。结果表明,8月份的平均温度是对水稻鞘腐病影响最大的气象因子,其次为8月份的平均降雨量和9月份的平均日照时数。试验结果为适期施药防治水稻鞘腐病奠定了基础。     

火龙果茎多糖的超高压提取及抗氧化活性研究

为研究火龙果茎多糖的超高压提取工艺及抗氧化活性。在单因素试验基础上,采用Box-Behnken设计和响应面分析方法,确定超高压提取的最优工艺,并从清除ABTS自由基和DPPH自由基能力方面来评价火龙果茎多糖的体外抗氧化能力。结果表明,火龙果茎多糖的超高压提取的最佳工艺条件为:液固比10∶1(m L∶g)、超高压压力300 MPa、超高压时间4 min。在此工艺条件下多糖得率为(2.83±0.02)%。火龙果茎对ABTS自由基和DPPH自由基具有清除作用,对ABTS自由基和DPPH自由基的清除率IC_(50)分别为浓度为4.3 mg/m L和5.5 mg/m L时。     

Seasonal variations of immune parameters in the coelomic fluid of sea cucumber Apostichopus japonicus cultured in pond

In order to understand the effects of seasonal change on the immunity of sea cucumber Apostichopus japonicus cultured in pond, A. japonicus with body weight of 12.2 ± 4.5 g (sample A) and 32.6 ± 7.1 g (sample B), respectively, were collected monthly and randomly from a typical pond during a year cycle and employed for the evaluation of immunocompetence. Simultaneously, the environmental factors in the pond including water temperature, pH, salinity and dissolved oxygen (DO) were measured using a handheld multiparameter meter. The activities of acid phosphatase (ACP), alkaline phosphatase (ALP), lysozyme (LYZ), phenoloxidase (PO), superoxide dismutase (SOD), catalase (CAT) and myeloperoxidase (MPO) in the coelomic fluid were selected for the evaluation of A. japonicus immunocompetence and determined using biochemical methods. The results showed that in both samples, the activities of all determined enzymes had small values in winter and early spring, and LYZ, CAT and MPO activities also presented small values in summer, suggesting that pond‐cultured A. japonicus underwent immunosuppression twice during a year cycle, and the immunosuppression occurred in winter and early spring was more severe than that occurred in summer. In addition, most of the determined enzymes showed different variations between the two samples, and had significantly negative correlation with protein concentration, which was significantly and negatively correlated with water temperature, revealing that body weight and water temperature might have crucial effects on the immunity of A. japonicus cultured in pond.     

The influence of dietary fatty acid and fasting on the hepatic lipid metabolism of barramundi (Lates calcarifer)

For many fish species, dietary fish oil (FO) has been substituted with other oils such as poultry oil (PO) without affecting growth performance. However, in barramundi, the mechanisms by which fatty acid metabolism is regulated are poorly understood, and the effects of FO substitution are unknown. This study defined changes in the expression of genes controlling the metabolism of fatty acids in barramundi over a 24‐h time period after a single meal. From one to 12 h after a single feeding event, the expression of fatty acid synthesis genes in the liver was upregulated, while genes involved in the β‐oxidation showed minimal alteration. However, the expression of β‐oxidation genes was significantly correlated with the expression of genes regulating fatty acid synthesis. In a second experiment, the changes in liver fatty acid composition and gene expression were defined after FO was substituted with PO. Liver fatty acid profile reflected the diet composition, with some subtle exceptions supporting the enrichment of certain long‐chain polyunsaturated fatty acids in the liver. The fish from all experimental groups preferentially retained more docosahexaenoic acid than eicosapentaenoic acid in the liver, suggesting a bioconversion of this fatty acid to intermediate fatty acids. Replacement of FO with PO significantly regulated genes controlling both fatty acid synthesis and catabolism pathways, potentially related to a higher percentage of monounsaturated fatty acids, in the livers of fish fed these diets. The results demonstrated that diet composition significantly altered the lipid metabolism in barramundi and that there was a balance between direct dietary effects and endogenous synthetic capacity.     

急性操作胁迫对四指马鲅幼鱼肝脏组织结构和氧化应激的影响

为探究急性操作胁迫对四指马鲅(Eleutheronema tetradactylum)幼鱼肝脏组织结构以及氧化应激的影响,该研究在离水操作胁迫后不同时间取样,观察肝脏显微结构的变化,并检测相关抗氧化酶活性。结果显示,随着离水胁迫时间的延长,肝脏组织损伤程度呈现先上升后下降的趋势,胁迫第24小时肝脏基本结构与对照组相似。超氧化物歧化酶(SOD)和过氧化氢酶(CAT)有相同的变化趋势,胁迫后第2小时显著增加(P0.05)并达到最高值,然后开始下降,最后其值显著低于对照组(P0.05);丙二醛(MDA)含量在胁迫第2~第12小时呈现先升高后下降的变化趋势,第12小时后又有所上升;还原型谷胱甘肽(GSH)含量胁迫2 h没有显著变化(P0.05),之后呈先下降后上升的趋势,但其含量仍显著低于对照组(P0.05);总抗氧化能力(T-AOC)胁迫第2小时显著上升(P0.05),之后下降,实验结束时显著低于对照组(P0.05)。结果表明离水操作胁迫对四指马鲅幼鱼肝脏组织结构以及抗氧化酶产生一定的影响,但随着胁迫时间的延长,其组织结构以及抗氧化能力都有一定的恢复趋势。     

电子束辐照不同虫态玉米象保护酶系活力变化研究

研究了玉米象Sitophilus zeamais(Motschulsky)不同虫态(2~3龄幼虫、1~2龄蛹和羽化1天成虫)体内三种保护酶过氧化氢酶(CAT)、过氧化物酶(POD)和超氧歧化酶(SOD)活力在电子束5个辐照剂量下酶活性的变化。试验结果表明,不同虫态玉米象CAT活力为:羽化1d成虫1~2龄蛹2~3龄幼虫;POD活力为:1~2龄蛹羽化1d成虫2~3龄幼虫;SOD活力为:1~2龄蛹2~3龄幼虫羽化1d成虫。辐照处理后,保护酶活力随辐照剂量的增加呈现先上升后下降的趋势,本实验结果有助于阐明电子束辐照加强对储粮害虫生理生化效应研究。