管道3PE防腐涂层补口技术标准及规范对比分析

通过对比国内外热收缩带(套)补口技术规范及标准,分析了各项性能指标间的差异,包括材料性能指标、安装工艺及质量检验.指出管道表面处理及底漆涂装是影响热收缩带(套)安装系统性能的重要因素,提出了工程技术规范编制建议.     

TheEstimationofStemTaperCurvefromtheRadialInformationatThreeLocationsontheStem

该文探讨了不用编制削度表直接建立高精度立木干曲线的方法．当采用干曲线是３次多项式时，通常根据１０分法测定树干各部位直径，用最小二乘法求出该方程式的参数．从数学角度，只要知道树干任意３个部位的直径，就可以用最小二乘法或联立方程式求解干曲线参数．本文以樟子松为例，探讨用树干哪３个部位直径拟合的干曲线最接近实际干曲线，为建立立木干曲线提供有效方法．利用９个部位半径（方法Ⅰ）和利用其中３个部位半径（方法Ⅱ，２８种组合）分别拟合干曲线，结果表明方法Ⅱ的６种半径组合的精度良好，其中的３种组合，（ｒ１．３，ｒ０．３，ｒ０．７），（ｒ１．３，ｒ０．４，ｒ０．７）和（ｒ１．３，ｒ０．４，ｒ０．８）是拟合现实干曲线的有效方法．     

Simulating evolution of glyphosate resistance in Lolium rigidum II: past, present and future glyphosate use in Australian cropping

Glyphosate is a key component of weed control strategies in Australia and worldwide. Despite widespread and frequent use, evolved resistance to glyphosate is rare. A herbicide resistance model, parameterized for Lolium rigidum has been used to perform a number of simulations to compare predicted rates of evolution of glyphosate resistance under past, present and projected future use strategies. In a 30‐year wheat, lupin, wheat, oilseed rape crop rotation with minimum tillage (100% shallow depth soil disturbance at sowing) and annual use of glyphosate pre‐sowing, L. rigidum control was sustainable with no predicted glyphosate resistance. When the crop establishment system was changed to annual no‐tillage (15% soil disturbance at sowing), glyphosate resistance was predicted in 90% of populations, with resistance becoming apparent after between 10 and 18 years when sowing was delayed. Resistance was predicted in 20% of populations after 25–30 years with early sowing. Risks of glyphosate resistance could be reduced by rotating between no‐tillage and minimum‐tillage establishment systems, or by rotating between glyphosate and paraquat for pre‐sowing weed control. The double knockdown strategy (sequential full rate applications of glyphosate and paraquat) reduced risks of glyphosate and paraquat resistance to <2%. Introduction of glyphosate‐resistant oilseed rape significantly increased predicted risks of glyphosate resistance in no‐tillage systems even when the double knockdown was practised. These increased risks could be offset by high crop sowing rates and weed seed collection at harvest. When no selective herbicides were available in wheat crops, the introduction of glyphosate‐resistant oilseed rape necessitated a return to a minimum‐tillage crop establishment system.     

Functional analysis of the 3′ end of avrBs3/pthA genes from two Xanthomonas species

The phytopathogens Xanthomonas oryzae pathovar (pv.) oryzae and Xanthomonas axonopodis pv. citri each contain several avrBs3/pthA family genes. Structural features of these genes important for avirulence and/or virulence functions include a central region of multiple direct repeats and three nuclear localization signals (NLSs) and an acidic activation domain (AAD) at the 3′ end. To identify other regions critical to function in the 3′ ends of these genes, we constructed several chimeras using apl1 and apl2 from X. axonopodis pv. citri and avrXa10 and avrXa7 from X. oryzae pv. oryzae and evaluated their functions by inoculation to citrus and rice. The apl1 and avrXa7 genes are major virulence determinants in citrus and rice, respectively, while the contributions of apl2 and avrXa10 to virulence are negligible or not measurable. Constructs that contained a 417 bp HincII-SphI fragment from the 3′ end of apl1 in combination with the repeats from avrXa7, avrXa10, and apl1 caused a canker phenotype on citrus. Interchange of the HincII-SphI fragment between avrXa7 and avrXa10 abolishes avrXa7 avirulence function and reduces its virulence but it does not affect avrXa10 avirulence function in rice. avrXa7 caused a hypersensitive response (HR) in citrus and replacement of it's 3′ end with that of apl1 resulted in loss of canker and induction of HR. Thus, the HincII-SphI fragment of the avrBs3/pthA gene family is important for avirulence and virulence functions in two different plant species, Oryza sativa and Citrus natsudaidai HAYATA.     

旱地(土娄)土长期定位施肥土壤剖面硝态氮分布与累积研究

通过12a大田长期定位试验研究了在自然降水条件、冬小麦—大豆轮作(或休闲)种植制度下,0～400cm土娄土剖面硝态氮分布与积累的特点。结果表明,长期单施氮肥,氮的表观利用率特别低,仅0.51%,氮肥配施钾、磷肥,氮的表观利用率为25%～35%,氮磷钾平衡施肥及配施有机肥,氮的表观利用率达到50%;施N肥方式显著影响土壤硝态氮积累和淋移,旱地土娄土长期单施化学氮肥或氮钾、氮磷、氮磷钾肥使土壤NO-3-N大量积累和淋移;氮磷钾与有机肥的配合施用能有效地缓解土壤对硝态氮的积累,提高氮肥利用率。     

瓜类蔬菜光合特性研究进展

综述了瓜类蔬菜光合特性的研究进展，总结了光照、温度、CO2浓度、水分、矿质营养、叶龄、叶住及嫁接等因素对光合作用的影响，并提出了今后的研究方向。     

Comparison of an in vitro and a damping-off assay to test soils for suppressiveness to Pythium aphanidermatum

Testing of soil samples in greenhouse assays for suppressiveness to soilborne plant pathogens requires a considerable investment in time and effort as well as large numbers of soil samples. To make it possible to process large numbers of samples efficiently, we compared an in vitro growth assay with a damping-off assay using Pythium aphanidermatum as the test organism on tomato seedlings. The in vitro test compares the radial growth or relative growth of the fungus in soil to that in autoclaved soil and reflects suppressiveness of soils to the pathogen. We used soils from a field experiment that had been farmed either organically or conventionally and into which a cover crop (oats and vetch in mixture) had been incorporated 0, 10, 21, and 35 days previously. We obtained a significant, positive correlation between damping-off severities of tomato seedlings in damping-off assays and both relative and radial growth in vitro. In addition, radial and relative growth of P. aphanidermatum in the in vitro assay were positively correlated with several carbon and nitrogen variables measured for soil and incorporated debris. We did not find differences between the two farming systems for either growth measures of P. aphanidermatum or disease severities on tomato at different stages of cover crop decomposition. The in vitro assay shows potential for use with any fungus that exhibits rapid saprophytic growth, and is most suitable for routine application in suppressiveness testing.     

吡啶衍生物研究(IX):N-(1-甲氧羰基)乙基-N-[5-(2-氯吡啶-4-基)-1,3,4-噻二唑-2-基]酰胺的合成及除草活性

为了进一步研究前期发现的除草先导化合物2-仲丁氨基-5-(2-氯吡啶-4-基)-1，3，4-噻二唑(BCPT)的结构-活性关系并提高其除草活性，设计并合成了一系列N-(1-甲氧羰基)乙基-N-[5-(2-氯吡啶-4-基)-1，3，4-噻二唑-2-基]酰胺类化合物。其苗后除草活性测定结果表明，所有化合物的活性都远低于BCPT本身。说明BCPT可能具有与传统酰胺类除草剂不同的作用机制。     

玉米苗期耐碱性鉴定方法研究

在三叶一心期,用一定浓度梯度的Na2CO3溶液（5～25mmol&#183;L^-1）对玉米幼苗进行胁迫处理,观察其生长情况,7d后测定地上部分株高、鲜重、干重等生理指标。研究表明,各项生理指标均随Na2CO3溶液浓度的增加而降低,并在各碱浓度间、自交系间达极显著差异。综合苗情及各生理指标的变化,初步确定可以将25mmol&#183;L^-1 Na2CO3溶液作为玉米苗期耐碱性筛选的理想浓度,将该浓度下的苗情及株高、鲜重、干重及含水量变化率作为玉米苗期耐碱性筛选的鉴定指标。