Ecological consequences of variation in standard metabolism and dominance among salmon parr

Abstract – Standard metabolic rate (SMR, closely related to basal and resting metabolism) varies by up to threefold among juvenile Atlantic salmon, Salmo salar L., of similar size at common temperature. Here, consequences of this variation are predicted by combining empirically derived relationships between SMR, specific dynamic action, energy budgets, water velocity, food level in the environment and food availability to fish. The range of velocities across which growth is predicted to occur is inversely related to a fish’s SMR. Growth is positively related to SMR at high but negatively related to it at low‐food levels. The relationship between food level and the range of velocities over which lower SMR fish can grow but higher SMR fish cannot is asymmetrically bi‐phasic and peaked. It is predicted that maternal manipulation of offspring SMR would generate fitness benefits through bet‐hedging against unpredictability in food level and increases in the overall range of velocities that the family of offspring can occupy and thrive in.     

浅谈给水排水工程节能节水措施

作者针对给排水系统工程特点并依据多年设计实践,总结了几点节能节水措施;阐明了通过减少不必要的浪费,可以达到节约水资源、节约能源的目的。     

农业重量物装卸机械应用现状及发展趋势

分析了目前国内外普遍采用的重量物装卸机械的应用及研究现状,介绍了它们各自的特点,并指出存在的问题,展望了未来农业重量物装卸机械的发展趋势。     

Response of confection sunflower (Helianthus annuus L.) grown in a semi‐arid environment to planting date and early termination of irrigation

Adjustments on planting date and on the time to terminate irrigation may reduce agricultural water use. However, such management practices in regions with extreme weather conditions have the potential to negatively affect yield. A 3‐year (2012–2014) study was conducted on a clay‐loam soil in a cool, semi‐arid environment to (i) determine the response of confection sunflower to planting date and irrigation termination timing and (ii) identify the relative importance of yield components in irrigated confection sunflower across planting dates. Early May planting had considerable negative effects on all studied variables, except on the percentage of large seeds. The highest yield of total and large seeds was obtained from the late May plantings, averaging 3,777 and 3,379 kg/ha, respectively. None of the irrigation strategies affected the measured variables. However, the interaction between planting date and termination of irrigation significantly affected the 1,000‐seed weight. Our study revealed the last week of May as suitable planting period for confection sunflower in the semi‐arid north‐western region of Wyoming, USA, and that irrigation on heavy soils may be terminated as early as at R5.5 stage without a significant yield reduction. The path‐coefficient analysis indicated head diameter and the number of seeds per head as important traits that significantly influence the yield of confection sunflower across planting dates.     

水利建设可持续发展刍议

首先分析了水利建设与可持续发展的关系,即可持续发展对水利建设提出了新要求、丰富了新思路,水利建设实践推动了水利可持续发展研究,并基于此提出水利建设可持续发展思路,即树立可持续发展意识,推进水利建设制度创新;人水协调,加强水利现代化建设.     

农业科研单位年鉴编纂工作的思考

结合河北省农林科学院年鉴编纂工作的实际情况,针对存在的部分问题,提出健全编辑队伍、加强业务培训、完善激励机制、重视编校质量、创新编纂工作的建议。     

水利施工的大体积混凝土抗裂技术

混凝土是水利施工中的主要的应用材料之一，为了保证水利施工中的安全与质量，必须保证混凝土的质量。文章全面分析了大体积混凝土产生裂缝的原因，并给出了相应的控制方法。     

5‐Aminolevulinic Acid Activates Antioxidative Defence System and Seedling Growth in Brassica napus L. under Water‐Deficit Stress

The present study assesses the effects of 5‐aminolevulinic acid (ALA, 0, 0.1, 1 and 10 mg l^?1) on the growth of oilseed rape (Brassica napus L. cv. ZS758) seedlings under water‐deficit stress induced by polyethylene glycol (PEG 6000, 0 and ?0.3 MPa). Water‐deficit stress imposed negative effects on seedling growth by reducing shoot biomass, cotyledon water potential, chlorophyll content and non‐enzymatic antioxidants (glutathione and ascorbic acid) levels. On the other hand, water‐deficit stress enhanced the malondialdehyde (MDA) content, reactive oxygen species (ROS) production, enzymatic antioxidants activities, reduced/oxidized glutathione ratio (GSH/GSSG) and reduced/oxidized ascorbic acid (ASA/DHA) ratio in seedlings. Application of ALA at lower dosages (0.1 and 1 mg l^?1) improved shoot weight and chlorophyll contents, and decreased MDA in rape seedlings, whereas moderately higher dosage of ALA (10 mg l^?1) hampered the growth. The study also indicated that 1 mg l^?1 ALA improved chlorophyll content, but reduced MDA content and ROS production significantly under water‐deficit stress. Lower dosages of ALA (0.1 and 1 mg l^?1) also enhanced GSH/GSSG and ASA/DHA as compared to the seedlings under water‐deficit stress. The antioxidant enzymes (ascorbate peroxidase, peroxidase, catalase, glutathione reductase and superoxide dismutase) enhanced their activities remarkably with 1 mg l^?1 ALA treatment under water‐deficit stress. It was also revealed that 1 mg l^?1 ALA treatment alone induced the expression of APX, CAT and GR substantially and under water‐deficit stress conditions ALA treatment could induce the expression of POD, CAT and GR to a certain degree. These results indicated that 0.1–1 mg l^?1 ALA could enhance the water‐deficit stress tolerance of oilseed seedlings through improving the biomass accumulation, maintaining a relative high ratio of GSH/GSSG and ASA/DHA, enhancing the activities of the specific antioxidant enzymes and inducing the expression of the specific antioxidant enzyme genes.     

种植密度对滴灌马铃薯生长、产量的影响

为了了解耕培土滴灌条件下种植密度对马铃薯生长、产量以及水分利用效率的影响.试验共设密度分别为7.28×10⁴ 株/hm²(RS25),6.67×10⁴ 株/hm²(RS35),5.55×10⁴ 株/hm²(CK)3个处理.结果表明:随着种植密度的增加,株高、茎粗、干物质积累量以及商品薯率均有降低的趋势;产量、水分利用效率随种植密度的增加表现出先增大后减少,其中RS35处理产量和水分利用效率均表现最高,分别达到47 325 kg/hm²和12.05 kg/m³;在马铃薯品质方面,种植密度对马铃薯粗蛋白含量的影响不具有统计学意义;淀粉和维生素C随着密度的大幅增加而降低,其中RS25处理的淀粉较CK降低了5.57%,RS25处理的维生素C较CK降低了7.96%,同时RS35与CK处理不具有统计学意义.综上所述,种植密度为6.67×10⁴ 株/hm²的RS35处理马铃薯高产优质,且水分利用效率最高,为黑龙江地区滴灌马铃薯较为适宜的种植密度.     

北京水系中腐霉和疫腐霉种类调查

为研究北京地区水系中腐霉和疫腐霉种类分布,采用叶饵法从北京水系中诱集菌株,共分离到腐霉、疫腐霉182株,利用Single-strand conformation polymorphism (SSCP)进行分析,筛选出不同基因型的代表菌株,并依据形态学特征及ITS序列对这些菌株进行种类鉴定。结果共发现6个已知种和3个可能的新种,其中:湖滨疫腐霉Phytopythium litorale和果胶裂解腐霉Pythium pectinolyticum为国内新记录种;旋柄疫腐霉Pp.helicoides、异丝腐霉P.diclinum、簇囊腐霉P.torulosum和袋囊腐霉P.marsipium为北京地区新记录种。研究结果可为未来监测北京地区水系中病原菌的分布情况提供基础数据。