松嫩平原苏打盐渍土钠吸附比的间接推算

土壤钠吸附比(SAR)的推算需要获得实测Na⁺浓度和推算Ca²⁺+Mg²⁺(二价阳离子)浓度,或者实测二价阳离子浓度和Na⁺浓度。本文应用两批土样数据,采用实测Na⁺浓度与电导率(EC)推导阳离子总浓度(TCC)计算二价阳离子浓度(方法一)、实测二价阳离子浓度与推算TCC计算Na⁺浓度(方法二)、实测Na⁺浓度与实测阴离子总浓度(TAC)推算二价阳离子浓度(方法三)、实测二价阳离子浓度与TAC计算Na⁺浓度(方法四)四种方法推算SAR。成对样本T检验结果表明,四种方法获得的SAR推算值与实测值间无显著性差异(Ｐ>0.05)。但是,第一和第三种方法推算SAR和实测值间回归方程斜率分别为0.66和0.79;而第二和第四种方法SAR推算和实测值回归方程斜率分别为0.96和1.10,非常接近1.0。这表明,实测Na⁺浓度和推算二价阳离子浓度方法推算的SAR准确性较差,采用实测二价阳离子和推算Na⁺浓度方法推算的SAR值准确性较高。因此,在实际工作中建议使用实测二价阳离子浓度的方法(方法二和方法四)推算SAR。     

鸭疫里默氏杆菌二价灭活疫苗株筛选及免疫原性研究

通过对山东省鸭疫里默氏杆菌病流行病学调查,发现山东省主要流行鸭疫里默氏杆菌的血清型为Ⅰ、Ⅱ型.将临床分离鉴定的两种血清型致病菌株进行毒力测定和抗原性分析,筛选出适合制成鸭疫里默氏杆茵二价灭活苗的种子菌株,并对其免疫原性进行了研究.     

广谱抗病基因chi和hrpZpsta双价表达载体的构建及其在大豆中的遗传转化

大豆的真菌性病害已经成为了限制大豆产量增长及品质提高的主要原因,利用基因工程技术培育出具有广谱性抗病能力的大豆新品种,已成为目前提高大豆抗性的有效途径之一。本研究构建了含2种广谱抗病基因chi和hrp Zpsta的双价植物表达载体,利用农杆菌介导技术导入大豆中,获得了能够在转录水平上表达2种外源抗病性基因的转基因大豆。对经抗性筛选得到的阳性苗及后代植株进行PCR检测、Southern杂交、荧光定量PCR检测,共得到T0代阳性植株7株,T1代阳性植株27株。转化植株的基因组在整合外源基因时出现不同情况,chi-hrp Zpsta双价载体分别以单价和双价两种形式随机整合到受体大豆基因组中并且能稳定遗传,同时在转录水平上亦有不同。     

表达鸡马立克氏病病毒gB基因的重组鸡痘病毒与火鸡疱疹病毒二价冻干疫苗的免疫效力

对高效表达鸡马立克氏病(MD)血清型疫苗毒株CVI998/Rispens gB基因的重组鸡痘病毒(rFPV-gB/R)和火鸡疱疹病毒(HVT)组成MD二价冻干疫苗时2种病毒的最适剂量配比进行了研究。试验表明,以对MD易感、MD和鸡痘病毒(FPV)抗体阴性SPF鸡为试验动物进行的试验中,不同免疫剂量的rFPV-gB/R(1×106、1×105、1×104PFU)同HVT组成的二价苗产生的免疫效力相当;以对MD易感、MD和FPV抗体阳性的狼山鸡进行的试验中,不同免疫剂量的rFPV-gB/R同HVT组成的二价苗产生的免疫力随rFPV-gB/R免疫剂量的降低而降低;所有的rFPV-gB/R+HVT的二价苗组均有一定的免疫保护作用。     

Considerations on cross‐linking by bivalent cations in soil organic matter with low exchange capacity

A soil's cation exchange capacity (CEC) is expected to be relatively inert against changes in cation loading. In this study, we treated a soil sample originating from the organic layer of a forest soil with various bivalent cations after removing the native cations. Sorption isotherms and cation exchange capacity were determined, the latter using the BaCl₂ method. Sorption showed Langmuir characteristics, with the maximum coverage (Q_max) increasing in the order Ba²⁺ < Ca²⁺ < Mg²⁺, but being clearly smaller than the initial load of native exchangeable cations. The Langmuir coefficient, k_Me, depended oppositely to the order obtained for Q_max. CEC increased upon cation treatment and it varied by a factor of almost two. The unexpected variation of CEC was explained by the low cation exchange capacity of the organic matter such that not all functional groups are close enough to be bridged and the second charge of a bivalent cation is not neutralized by the organic functional group. The Langmuir sorption type, and Q_max being smaller than the content of sorption sites and being largest for Mg, suggested that only a part of the sites can be cross‐linked and at least part of the cross‐links are formed by hydrated cations. Thermodynamic considerations allowed reconstruction of two contrasting processes during CEC determination by Ba²⁺: Case A: the disruption of cross‐links, which increases with the cationic strength and the cation load before CEC determination, but does not require structural re‐orientation in the SOM matrix, and Case B: the formation of new cross‐links during CEC determination, depending only on the content of unoccupied sites before CEC determination and requiring structural re‐organization of the matrix and thus a minimum matrix flexibility. The use of bivalent cations for CEC determination may thus result in an overestimation of CEC for organic matter with low CEC. This has, however, promising potential when comparing CEC determined with monovalent cations and bivalent cations. Using a set of bivalent cations, may allow probing distribution of distances between functional groups in the organic matter and even characterize the matrix rigidity of the cation‐cross‐linked network.