非充分灌溉条件下水稻生长发育及生理机制研究

本文以水稻非充分灌溉试验的大量实测资料为基础，分析了水分胁迫对水稻主要形态指标、生理机制及产量的影响，对非充分灌溉条件下水稻所持有的生理机制进行了较细致的研究。研究结果对于指导有效、省水的稻田灌溉具有重要意义。     

用水户协会管理模式比较与改进对策

发展农民用水户协会,激励农民参与灌溉管理,明确小型水利产权和管护主体。以奥斯特洛姆的多中心治理理论为基础,分析用水户协会管理模式与多中心治理理论原则的耦合性,从自主治理的视角对典型用水户协会管理模式进行比较,分析各种管理模式存在的问题,从多中心治理角度提出完善用水协会多元决策机制和多中心治理结构等改进对策。     

水分胁迫对紫花苜蓿根系吸水与光合特性的影响

变水条件下(利用PEG-6000模拟水分胁迫48 h,ψs=0.2MPa,之后复水48 h),测定紫花苜蓿(Medicago sattva L,品种阿尔冈金和陇东苜蓿)幼苗根系水力学导度与光合参数变化规律,旨在研究变水条件下紫花苜蓿光合作用的响应机制、植株水分吸收能力的变化规律及地上与地下部可能的相关关系.结果表明:干旱胁迫使得紫花苜蓿根系水力学导度(Lpr)受到显著影响.随着水分胁迫时间的延长,根系吸水能力呈现快速--缓慢下降趋势,即根系水力学导度逐渐下降,气孔导度(Gs)、蒸腾速率(Tr)、净光合速率(Pn)和叶片水势亦随之而显著降低,胞间二氧化碳浓度(Ci)先随之降低但最终上升而累积.复水后,根系水导呈现缓慢--慢速的恢复趋势,Pn、Gs、Tr、叶片水势随着根系水导速率的增加而逐渐恢复;Ci则随复水时间的延长而逐渐下降.但各参数除Ci外,均没有恢复到胁迫前水平.紫花苜蓿根系水导与光合参数在复水后的恢复程度说明,紫花苜蓿对干旱逆境的抵御与适应能力相对较弱,但陇东苜蓿对水分胁迫的忍耐能力强于阿尔冈金.     

水分胁迫和复水对紫花苜蓿幼苗叶绿素荧光特性的影响

利用PEG-6000模拟水分胁迫(ψs=-0.2MPa,胁迫时间:48 h,复水48 h),研究了紫花苜蓿(Medicago sativa L)品种陇东苜蓿和阿尔冈金叶片叶绿素荧光特性和光合色素含量的变化,旨在探讨紫花苜蓿水分胁迫条件下的光合反应机制.结果表明:光化学淬灭系数(qP)和PSII线性电子传递的有效量子产额(YIELD)以及非光化学淬灭系数(qN)和表观光合电子传递效率(ETR)在胁迫前后随光合有效辐射(PAR)的变化规律分别可用公式:Y=aLn(X) b(Y:qP或YIELD,X:PAR,X≠0)和Y=aX2 bX c(Y:qN或ETR,X:PAR)来表示;在受到干旱胁迫后,PSII最大光能转化效率(Fv/Fm)、PSII潜在活性(Fv/Fo)和光合色素含量均明显低于对照,在任意光强下的qP、YIELD和ETR值也极显著低于对照的相应值,qN值则极显著高于对照的相应值;同时,和对照相比,qN和ETR光响应曲线顶点所对应的光强值在受到胁迫后亦明显下降,表明光抑制初始点的降低和最大光保护能力的减弱,甚至光抑制的提前到来.干旱胁迫使得PSⅡ反应中心结构和功能遭到破坏而部分关闭,光合电子传递受阻,光能利用与光化学转化与能力下降,吸收的光能更多的以热能形式耗散.复水后,虽然有光保护机制的存在,但除陇东苜蓿光合色素含量及阿尔冈金类胡萝卜素外,各参数均未能恢复到对照水平,因此旱后复水不能完全解除干旱对PSII反应中心所带来的伤害.紫花苜蓿幼苗对干旱胁迫较为敏感.供试品种相比,陇东苜蓿耐旱性优于阿尔冈金.     

Urinary catecholamine and metanephrine to creatinine ratios in healthy dogs at home and in a hospital environment and in 2 dogs with pheochromocytoma

BACKGROUND: Measurement of high concentrations of urine catecholamines and metanephrines is useful in diagnosing pheochromocytoma in humans. Stress increases catecholamine excretion in urine. HYPOTHESIS: Stress of a hospital visit increases urinary catecholamine and metanephrine excretion in dogs. ANIMALS: Fourteen clinically normal dogs, 2 dogs with pheochromocytoma. METHODS: Voided urine samples were collected by the owners 7 days before (t-7), during the hospital visit immediately after diagnostic procedures (t0), as well as 1 (t1) and 7 days (t7) after the hospital visit. Urine catecholamine and metanephrine concentrations were measured using high-pressure liquid chromatography and expressed as ratios to urine creatinine concentration. RESULTS: In client-owned dogs epinephrine and norepinephrine ratios at t0 were significantly higher compared with ratios at t7. Metanephrine and normetanephrine ratios at t-7, t0, and t1 did not differ significantly from each other; however, at t7 they were significantly lower compared to values at t-7. In staff-owned dogs no significant differences were detected among the different collecting time points for any variable. Metanephrine and normetanephrine ratios were significantly higher in client-owned dogs compared to staff-owned dogs at t-7, t0, and t1 but not at t7. CONCLUSIONS AND CLINICAL IMPORTANCE: Stress associated with a hospital visit and with the sampling procedure causes increases in urine catecholamine and metanephrine excretion. Urine collection for the diagnosis of pheochromocytoma probably should take place at home after adaptation to the sampling procedure.     

Quantification of stress sensitive markers in single fecal samples do not accurately predict excretion of these in the pig

All feces produced during 24 h were collected from five pigs and cortisol and immunoreactive cortisol metabolites (CICM), and IgA were quantified. Within pigs, the concentrations of CICM and IgA varied extensively between random samples obtained from a single fecal dropping, and deviated in most cases significantly from the true concentration measured in total fecal output (CV 6.7-130%). The CICM and IgA contents varied considerably (CV 8.1-114%) within and between individual fecal droppings from the same pig compared to the total fecal excretion. In conclusion, single random samples could not be used to reliably quantify the total fecal concentration or excretion of CICM or IgA in pigs. Analyses of all feces collected during shorter periods than 24 h did not provide an accurate estimate of the daily excretion of CICM. Thus, the concentration of stress sensitive molecules in random single fecal samples as an indicator of animal welfare should be interpreted with prudence.     

测定应力集中系数的灰色建模方法

通过对带轴肩的扭转圆轴、带双凹槽的拉伸板条、带偏心孔的纯弯曲梁等几种典型构件在应力集中处进行应变电测，利用灰色系统理论对测试数据进行累加生成处理、模型识别，建立了应变分布的灰色模型，用该模型求出了应力集中处的应力集中系数。结果表明：与目前常用的数据处理方法比较，灰色建模方法具有所需测试数据少、预测精度高等优点，非常适用于构件应力集中系数的实时测定。     

地表多水门管道畦灌试验研究

多水门管道灌溉是采用多水口管道替代水沟的一种地表灌溉方式。１９９３至１９９５年试验结果表明，多水门管道灌溉和传统水沟灌溉相比，具有节水、节能、改善灌水分布均匀度，提高灌溉质量，缩短灌溉时间和扩大作物种植面积等优点     

宁南旱区苜蓿草地土壤水分消耗规律及粮草轮作土壤水分恢复效应研究

对宁南旱区不同生长年限紫花苜蓿草地土壤水分消耗及粮草轮作水分恢复效应进行了研究。结果表明:(1)随着苜蓿生长年限延长,在1￣6年内苜蓿草地土壤湿度下降迅速,产草量逐年上升,7年后土壤湿度下降趋于平缓,但苜蓿产草量下降迅速,表明苜蓿生长强烈耗水引起深层土壤干燥化,导致苜蓿生长逐渐衰败,苜蓿平均降水生产效率逐年下降;(2)苜蓿草地土壤垂直剖面可分为降水入渗恢复层(0￣200cm)、根系发达枯竭层(200￣500cm)和根系衰老缓耗层(500cm以下)三个层次。随苜蓿生长年限延长,苜蓿剖面的主要土壤干层逐渐上移,并且干层厚度呈现减小趋势;(3)耕翻的苜蓿茬后轮作粮食作物的年份越长,土壤水分恢复越好,实行草粮轮作的苜蓿最迟不超过生长的第10年。     

湿地松优良半同胞家系蛋白质及糖类对水分胁迫的生理响应

为研究湿地松优良半同胞家系蛋白质及糖类对水分逆境的生理响应，采用盆栽试验和吸光度测定结合的方法，以湿地松普通种子为对照（CK），测定了七个湿地松半同胞家系在正常水分状态（土壤相对含水量为70%）、弱度水分胁迫（土壤相对含水量为55%~60%）、中度水分胁迫（土壤相对含水量为35%~40%）和强度水分胁迫（土壤相对含水量为20%~25%）条件下的可溶性蛋白质、还原性糖、可溶性糖的含量，研究结果表明：无论是不同水分梯度还是不同家系水平，蛋白质、还原性糖、可溶性糖含量的差异均达极显著性水平。随着水分胁迫程度的加剧，各家系蛋白质含量呈先升后降的趋势，在水分胁迫初期，各家系蛋白质含量增加，水分胁迫中、后期各家系蛋白含量呈直线下降；随着水分胁迫的加剧，各家系还原性糖、可溶性糖含量呈直线上升。家系1027、101、464在水分胁迫条件下具有较高的可溶性糖含量，其抗旱性较其它家系要强，是这三个家系速生、高产的生理原因之一。