美国红鱼继饥饿后的补偿生长及其机制

对两种不同规格 (8.2 5± 0 .5 0g ,4 0 .4 1± 2 .4 5g)的美国红鱼分别在 18～ 2 0℃和 2 0～ 2 4℃条件下进行了不同饥饿时间处理后再恢复投喂实验。在实验的 30d内 ,两次实验结果均表现为饥饿 5d组的美国红鱼生长略快于对照组 ,而饥饿 10d和 15d的鱼在相同的时间内 ,体重的增加量未能赶上对照组。各组间生长虽有差别 ,但都未达到显著水平。饥饿使鱼体水分、灰分含量增加 ,脂肪含量下降 ,蛋白质含量变化不大 ,但各成分从恢复投喂到实验结束时又恢复到对照组水平。各组间摄食量随饥饿时间延长而逐步下降 ,而饵料转换效率逐步上升。随着饥饿时间的延长 ,标准代谢率下降 ,而在恢复投喂之后又逐步回升至对照组水平。结果表明 ,美国红鱼的补偿生长效应主要是由降低标准代谢和提高食物转化率实现的     

‘国光’苹果及其红色芽变花青苷合成与相关酶活性的研究

 以‘国光’苹果及其红色芽变为试材, 测定了果实发育期间的花青苷含量及其相关酶活性,并研究了套袋对芽变花青苷合成的影响。结果显示: ①在果实发育期间, 芽变果皮的花青苷含量明显高于‘国光’, 尤其是成熟期芽变果皮花青苷含量为132170 U·g^-1FW, 而‘国光’仅为49140 U·g^-1FW; ②在果实发育期间, 两个品种间PAL 和UFGT的酶活性无明显差异, 但芽变的CHI和DFR酶活性明显高于‘国光’, 表明芽变花青苷合成能力的提高与CHI和DFR酶活性高有关; ③套袋抑制芽变果皮花青苷的合成, 但解袋后花青苷的含量极显著升高, 解袋后4种酶的变化趋势差异较大, CHI和UFGT活性均迅速升高, 明显高于对照, 这与解袋后花青苷迅速合成相吻合。综上结果, 芽变与原有品种在着色机理上的关键指标是果皮花青苷含量和CHI酶活性。     

Tomato yield, biomass accumulation, root distribution and irrigation water use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Florida is the largest producer of fresh-market tomatoes in the United States. Production areas are typically intensively managed with high inputs of fertilizer and irrigation. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on yield, irrigation water use efficiency (iWUE) and root distribution of tomato cultivated in a plastic mulched/drip irrigated production systems. Experimental treatments included three irrigation scheduling regimes and three N-rates (176, 220 and 230 kg ha⁻¹). Irrigation treatments included were: (1) SUR (surface drip irrigation) both irrigation and fertigation line placed right underneath the plastic mulch; (2) SDI (subsurface drip irrigation) where the irrigation line was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with irrigation and fertigation lines placed as in SUR and irrigation being applied once a day. Except for the “TIME” treatment all irrigation treatments were controlled by soil moisture sensor (SMS)-based irrigation set at 10% volumetric water content which was allotted five irrigation windows daily and bypassed events if the soil water content exceeded the established threshold. Average marketable fruit yields were 28, 56 and 79 Mg ha⁻¹ for years 1-3, respectively. The SUR treatment required 15-51% less irrigation water when compared to TIME treatments, while the reductions in irrigation water use for SDI were 7-29%. Tomato yield was 11-80% higher for the SUR and SDI treatments than TIME where as N-rate did not affect yield. Root concentration was greatest in the vicinity of the irrigation and fertigation drip lines for all irrigation treatments. At the beginning of reproductive phase about 70-75% of the total root length density (RLD) was concentrated in the 0-15 cm soil layer while 15-20% of the roots were found in the 15-30 cm layer. Corresponding RLD distribution values during the reproductive phase were 68% and 22%, respectively. Root distribution in the soil profile thus appears to be mainly driven by development stage, soil moisture and nutrient availability. It is concluded that use of SDI and SMS-based systems consistently increased tomato yields while greatly improving irrigation water use efficiency and thereby reduced both irrigation water use and potential N leaching.     

Integrated effect of transplanting date, cultivar and irrigation on yield, water saving and water productivity of rice (Oryza sativa L.) in Indian Punjab: Field and simulation study

Individual effect of different field scale management interventions for water saving in rice viz. changing date of transplanting, cultivar and irrigation schedule on yield, water saving and water productivity is well documented in the literature. However, little is known about their integrated effect. To study that, field experimentation and modeling approach was used. Field experiments were conducted for 2 years (2006 and 2007) at Punjab Agricultural University Farm, Ludhiana on a deep alluvial loamy sand Typic Ustipsamment soils developed under hyper-thermic regime. Treatments included three dates of transplanting (25 May, 10 June and 25 June), two cultivars (PR 118 inbred and RH 257 hybrid) and two irrigation schedules (2-days drainage period and at soil water suction of 16 kPa). The model used was CropSyst, which has already been calibrated for growth (periodic biomass and LAI) of rice and soil water content in two independent experiments. The main findings of the field and simulation studies conducted are compared to any individual, integrated management of transplanting date, cultivar and irrigation, sustained yield (6.3-7.5 t ha⁻¹) and saved substantial amount of water in rice. For example, with two management interventions, i.e. shifting of transplanting date to lower evaporative demand (from 5 May to 25 June) concomitant with growing of short duration hybrid variety (90 days from transplanting to harvest), the total real water saving (wet saving) through reduction in evapotranspiration (ET) was 140 mm, which was almost double than managing the single, i.e. 66 mm by shifting transplanting or 71 mm by growing short duration hybrid variety. Shifting the transplanting date saved water through reduction in soil water evaporation component while growing of short duration variety through reduction in both evaporation and transpiration components of water balance. Managing irrigation water schedule based on soil water suction of 16 kPa at 15-20 cm soil depth, compared to 2-day drainage, did not save water in real (wet saving), however, it resulted into apparent water saving (dry saving). The real crop water productivity (marketable yield/ET) was more by 17% in 25th June transplanted rice than 25th May, 23% in short duration variety than long and 2% in irrigation treatment of 16 kPa soil water suction than 2-days drainage. The corresponding values for the apparent crop water productivity (marketable yield/irrigation water applied) were 16, 20 and 50%, respectively. Pooled experimental data of 2 years showed that with managing irrigation scheduling based on soil water suction of 16 kPa at 15-20 cm soil depth, though 700 mm irrigation water was saved but the associated yield was reduced by 277 kg ha⁻¹.     

Simulation of transpiration, drainage, N uptake, nitrate leaching, and N uptake concentration in tomato grown in open substrate

Free-drainage or “open” substrate system used for vegetable production in greenhouses is associated with appreciable NO₃⁻ leaching losses and drainage volumes. Simulation models of crop N uptake, N leaching, water use and drainage of crops in these systems will be useful for crop and water resource management, and environmental assessment. This work (i) modified the TOMGRO model to simulate N uptake for tomato grown in greenhouses in SE Spain, (ii) modified the PrHo model to simulate transpiration of tomato grown in substrate and (iii) developed an aggregated model combining TOMGRO and PrHo to calculate N uptake concentrations and drainage NO₃⁻ concentration. The component models simulate NO₃⁻-N leached by subtracting simulated N uptake from measured applied N, and drainage by subtracting simulated transpiration from measured irrigation. Three tomato crops grown sequentially in free-draining rock wool in a plastic greenhouse were used for calibration and validation. Measured daily transpiration was determined by the water balance method from daily measurements of irrigation and drainage. Measured N uptake was determined by N balance, using data of volumes and of concentrations of NO₃⁻ and NH₄⁺ in applied nutrient solution and drainage. Accuracy of the two modified component models and aggregated model was assessed by comparing simulated to measured values using linear regression analysis, comparison of slope and intercept values of regression equations, and root mean squared error (RMSE) values. For the three crops, the modified TOMGRO provided accurate simulations of cumulative crop N uptake, (RMSE = 6.4, 1.9 and 2.6% of total N uptake) and NO₃⁻-N leached (RMSE = 11.0, 10.3, and 6.1% of total NO₃⁻-N leached). The modified PrHo provided accurate simulation of cumulative transpiration (RMSE = 4.3, 1.7 and 2.4% of total transpiration) and cumulative drainage (RMSE = 13.8, 6.9, 7.4% of total drainage). For the four cumulative parameters, slopes and intercepts of the linear regressions were mostly not statistically significant (P < 0.05) from one and zero, respectively, and coefficient of determination (r²) values were 0.96-0.98. Simulated values of total drainage volumes for the three crops were +21, +1 and −13% of measured total drainage volumes. The aggregated TOMGRO-PrHo model generally provided accurate simulation of crop N uptake concentration after 30-40 days of transplanting, with an average RMSE of approximately 2 mmol L⁻¹. Simulated values of average NO₃⁻ concentration in drainage, obtained with the aggregated model, were −7, +18 and +31% of measured values.     

基于MRFD的车载仪器并联减振半主动控制实验

采用3-PRRP~((4r))并联机构作为主体机构,在机构移动副处的主负荷方向上辅以磁流变阻尼器(MRFD),采用LQR最优控制算法对装置进行半主动控制,从而实现对车载仪器的多维减振.实验结果表明,该MRFD多维减振机构具有良好的多维减振效果.     

自走式棉秆联合收获机设计与试验

阐述了自走式棉秆联合收获机的基本结构及工作原理,对总体结构、底盘配置及喂入切碎机构进行了设计和参数计算,采用纵向对称配置、简化喂入机构、交错对称布置切碎滚筒动刀等方法,实现了棉秆收割、切碎、集箱、自卸的一体化.试验结果表明作业流程安排合理,适用性较好,是棉秆资源规模化工业利用的适用设备.     

基于粗糙集的属性约简算法在农业机械中的应用

传统的利用区分矩阵进行属性约简算法,其时间复杂度和空间复杂度很大.近年来提出了各种启发式算法,其时间复杂度由原来指数级递增降到了平方级递增,但此算法并不能保证找到最优解.为此,提出了属性约简的改进算法,其在时间复杂度和空间复杂度上都降低很多,易于求出最优解.把此算法用于对一款农业机械的评估判断和规则提取,用VC++和SQL Server 2000进行实现,并通过专家数据验证其正确性.     

水力机械空化空蚀问题的研究进展

从水力机械空化现象的产生机理出发,综述了国内外空化空蚀问题理论分析、数值模拟和试验研究的现状,简要叙述了各种研究方法的优点和特点.通过分析归纳理论分析、数值模拟和试验研究这三者之间的内在联系,指出空化模型理论和可视化空化试验是目前的研究重点.在对相关研究进行总结的基础上,阐述了水力机械空化空蚀研究的发展趋势为,数值模拟理论和技术的深入完善、可视化技术的广泛应用和空蚀在线监测系统的开发;而空化空蚀问题的确切机理将是未来研究工作的重点.     

西梅法兰西采前落果相关影响因子研究

【目的】筛选西梅品种法兰西采前落果的相关影响因子,为法兰西采前落果机理研究提供理论参考。【方法】以西梅优良品种法兰西为试验对象,以果实着色情况为依据,在50株试验树东、南、西、北方位的树冠内外和上中下层,分别摘取未着色正常果实(对照,CK)、30%着色果实(T1)、50%着色果实(T2)和80%着色果实(T3)各20个,并捡取掉落时间不到1 d的落果(100%着色,T4)100个,将每个同样着色程度重复的果实充分混匀后,从中随机选取30个果实测定单果鲜质量、果实纵横径、果形指数、果面色差值(L~*、a~*、b~*)等特征参数及果实养分含量等指标,分析法兰西采前果实着色程度与测定指标的相关性,筛选采前落果的主要影响因子。【结果】果面着色程度不同的法兰西单果鲜质量之间差异均不显著;果形指数随落果着色程度加深而呈逐渐增大趋势,其中CK与T4间差异达到显著水平;随法兰西落果着色程度加深,果面色差值L~*和b~*呈逐渐下降趋势,而a~*逐渐升高,果实颜色向黄、红色转变。法兰西采前落果中的全氮(N)、全磷(P)、锰(Mn)、铁(Fe)和硼(B)含量均随采前落果着色程度的加深呈下降趋势,而钾(K)、锌(Zn)、铜(Cu)和硒(Se)含量则随采前落果着色程度加深均呈上升趋势。相关性分析表明,果面色差值a~*与果形指数及果实K、Zn、Cu和Se含量间均存在极显著正相关关系,与色差值L~*、b~*及果实N、P、Mn、Fe和B含量间均存在极显著负相关关系,其中与L~*、b~*、N、Mn和Fe的相关系数均高于0.9。【结论】法兰西采前落果是果实营养不平衡导致的果实过早衰退而进入成熟期的表现。