动物饲料国际贸易、养殖密度与环境氮磷平衡的关系

粮食和饲料的国际贸易促进了许多国家农业生产系统的专业化和集约化。专业化动物养殖越来越多地依赖进口大豆和玉米,虽然提高了动物生产力,但也促使作物和动物生产系统在空间上的分离。本文综述了几十年来全球范围内大豆和玉米的贸易变化,并将其与养殖密度和整个食品系统中营养平衡的变化联系起来。这一变化与不同的营养管理条例的差异和动物饲养密度的空间变化有关。深入解析这些变化有助于理解动物饲料国际贸易、养殖密度与氮磷平衡之间的复杂关系。     

水分胁迫对荔枝幼树根系与梢生长的影响

以盆栽沙培1年生荔枝空中压条苗为试材,研究了水分胁迫对荔枝幼树根系和梢生长的影响以及二者的相互关系。3个处理为:沙体积含水量为7.5%(严重缺水),15.0%(一般缺水),22.5%(充分供水)。结果表明:水分胁迫严重抑制荔枝幼树地上部分和各级侧根的生长,使地上部枝梢生长严重受阻,叶片数量、平均叶面积、叶片厚度均显著变小;根总干重、侧根长度、根表面积显著减少。水分胁迫下促进须根的生长,须根的长度、根表面积比水分充足时显著增加。水分胁迫时叶片淀粉含量下降,而根系积累更多的淀粉。比较不同处理的根梢比发现,干旱对根系生长的抑制作用比枝梢更显著。     

青海湟水流域水资源及水环境

目前，湟水流域水量不足，水质污染，已成为该流域经济发展的制约因素。为此，防治湟水流域水污染，保护水资源，改善水环境，维护流域生态平衡，是我省经济和社会发展中的一项刻不容缓的紧迫任务。     

果树水分胁迫研究进展

从水分胁迫对果树叶、根的形态指标及显微结构 ,叶片气孔行为、光合作用、光抑制、活性氧代谢、脂氧合酶代谢、多胺代谢、脯氨酸、核酸代谢、内源激素变化等生理生化方面综述了近十几年来的研究成果 ,为全面研究果树抗旱机理及进一步制定抗旱措施奠定理论基础     

祁连山水源涵养林综合效能的计量研究

以马克思级差地租理论,建立了祁连山水源涵养林综合效能的评价模型:E=E_d+E_e+E_s;以E与生产投资I的比值为计量水源林的效能指数T,T=E/I。并以祁连山寺大隆森林生态定位研究站实测资料和社会调查数据为计量评价参数,确定其经济评价指标体系和计量系统。结果表明:祁连山水源涵养林综合效能指标为11.93;其中生态效能和社会效能分别是直接经济效能的4.51倍和6.05倍。说明祁连山水源涵养林现行的保护、发展和综合利用的经营方针是正确的。建议河西各受益部门应按水资源效能总收入的0.5％缴作水源林再生产费,以确保国民经济建设的长远发展。     

直列4缸内燃机双轴平衡系统设计

直列4缸平面布置曲轴内燃机存在不平衡的二阶往复惯性力,采用兰氏双轴平衡系统,可以平衡二阶往复惯性力,使内燃机的噪声和振动明显下降。     

Physiological Indices and Selection of Methods on Rapid Identification for Sweet Potato Drought Resistance

The relationships between the changes of relative water content （RWC）, malondialdehyde （MDA） contents, superoxide dismutase （SOD） activity and free proline contents in sweet potato leaves, and drought resistant ability under different concentration of polyethylene glycol （PEG） treatment applied at rhizosphere of sweet potato seedlings were studied. A highly positive correlation between RWC and drought resistance （r =0.783, P〈0.01）, a highly negative correlation between MDA contents and drought resistance （r = -0.848, P〈0.01）, a highly positive correlation between SOD activity and drought resistance （r = 0.777, P〈0.01） was observed. Free proline contents in leaves was not related obviously to the sweet potato drought resistance under 25% PEG treatment. The stronger the drought resistance of variety, the less decrease of RWC and increase of MDA contents, the more increase of SOD activity. By determining these physiological indices in sweet potato leaves under 25% PEG treatment, rapid identification of drought resistant ability of different varieties can be obtained in the lab.     

37 ℃持续热应激肉鸡血气改变的动态分析

80只25日龄雄性AA肉鸡,随机分为对照组(21～24 ℃,相对湿度50%±5%)和试验组(37 ℃±0.5 ℃,相对湿度70%±5%),自由采食和饮水.在12 d的试验期间,动态检测血气指标、呼吸频率、直肠温度和生产性能的变化.结果显示热暴露初期呈现代偿性呼吸性碱中毒,其特点为动脉血二氧化碳分压(3.82±0.36)降低,pH(7.48±0.04)升高;中期呈现失代偿性代谢性酸中毒,其特点为血浆HCO-3浓度(19.00±2.55)降低,pH(7.37±0.06)显著下降(P＜0.05);后期酸碱平衡趋于正常.热应激后,肉鸡日增重和日采食量极显著下降(P＜0.01)、料肉比极显著升高(P＜0.01);呼吸频率极显著升高(P＜0.01);热暴露第1、5、7、9和12天体温极显著升高(P＜0.01).动脉血氧分压与呼吸频率呈极显著负相关(P＜0.01),与体温呈显著负相关(P＜0.05);血氧饱和度与体温极显著负相关(P＜0.01).表明37 ℃持续热应激的肉鸡呈现由代偿性呼吸性碱中毒转变为失代偿性代谢性酸中毒,最后趋于正常的动态变化过程.     

PEG诱导水分胁迫对柑桔幼苗细胞质膜透性及脯氨酸含量的影响

柑桔叶片相对含水量(RWC)随聚乙二醇(PEG)处理渗透势的降低而依次降低;叶片细胞质膜透性随PEG处理浓度的增加而依次增大;幼苗叶片累积脯氨酸的数量随水分胁迫时间和强度递增。     

Physiological Basis of Irrigation Scheduling for Seed Production in Egyptian Clover Syn. Berseem (Trifolium alexandrinum L.) Crop

A field experiment was conducted to find out the critical physiological stages of irrigation schedules inducing better growth, physiological efficiency and seed yield potential of berseem ( Trifolium alexandrinum L., Var. S-99-1). For this purpose eight irrigation treatments were made comprised of four treatments of three irrigation (W₁, W₂, W₃ and W₄), three treatments of four irrigation (W₅, W₇ and W₈) and one treatment of five irrigation (W₆) at various physiological stages i. e. regeneration, flower initiation, full bloom, seed initiation and advance seed development stage.
Thus based on the experimental results the physiological role of watering in berseem seed production could be discussed as:
With-holding of irrigation either at regeneration or at full bloom stage developed potential water stress in plants as indicated by high proline content of irrigation treatments — W₄, W₁ and W₇; and further brought out disturbance on the formation of carotene, synthesis of water soluble sugar and translocation of sugar towards reproductive organs during grain development stage. These stresses adversely affected the plant growth and flowering behaviour. The irrigation at seed initiation stage increased the seed yield. Continuous irrigation did not appear to be useful. Thus it can be concluded that irrigation at three critical physiological stages i. e. regeneration, full bloom and seed initiation was found to be essential for obtaining potential seed yield of berseem.