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41.
应用传统统计学和地统计学方法,分析了2005年4~11月期间烟台农科院苹果园土壤电导率的空间变异性,并进行了Moran’s I系数分析和Kriging估值。结果表明:土壤电导率具有明显的空间变异性,半方差函数和Moran’s I系数分析说明了4月30日、6月29日和11月16日的空间自相关范围较大,相关性较强;4月20日、7月14日和8月16日的变程偏小,空间相关性较弱。土壤电导率的均值和变异系数随时间变化总体上近似呈现出先增加后减小的趋势,在空间分布上不同时期果园表层土壤电导率分布格局差异较大,土壤电导率的破碎化比较严重。 相似文献
42.
Lourdes Fernández-Calvino Dionisio López-Abella Juan José López-Moya Alberto Fereres 《Phytoparasitica》2006,34(3):315-324
Two different aphid species,Myzus persicae (Sulzer) andHyalopterus pruni (Geoffroy) (Homoptera: Aphididae), were used to analyze their ability to transmit two different potyviruses,Potato virus Y (PVY) andPlum pox virus (PPV), to pepper (Capsicum annuum) andNicotiana benthamiana plants, respectively. In parallel experiments,M. persicae consistently transmitted both viruses with high efficiency, whereasH. pruni always failed to transmit either virus. This is in contrast to previous reports describingH. pruni as a vector of these potyviruses. Different aphid probing behavior among individual aphids of each species was obtained in
electrical penetration graph (EPG) experiments performed on pepper plants. This suggested thatH. pruni did not transmit these potyviruses due to behavioral differences during probing that impeded virus acquisition and/or inoculation.
It was found thatM. persicae usually makes its first probe within the first 2 min, whereasH. pruni individuals remained for more than 10 min on the plant before starting to probe. Furthermore,M. persicae individuals displayed their first intracellular puncture during the first minute of probing whereasH. pruni needed ∼ 15 min to penetrate the cell plasmalemma with their stylets. In addition, intracellular stylet punctures occurred
very frequently forM. persicae but was a rare event, never exceeding a single one, forH. pruni. The relevance of these findings for the epidemiological spread of potyviruses by different aphid species is discussed.
http://www.phytoparasitica.org posting May 14, 2006. 相似文献
43.
微孔草叶细胞冻害研究 总被引:5,自引:0,他引:5
针对微孔草常因低温环境而受到冻害,造成产量下降的问题,用电导法测其渗出液的电导率,计算渗出电解质百分率即细胞伤害率并配以Logistic方程求其拐点温度及半致死温度的定量范围,以确定其抗寒能力。结果表明,微孔草叶组织在0.5h低温处理的半致死温度是-10.79℃,1.0h处理是-7.01℃,1.5h处理是-1.68℃,由此认为,微孔草是中等抗寒植物,测量渗出液的电导率是一种定量估计冻害的好方法。 相似文献
44.
Simulation of transpiration, drainage, N uptake, nitrate leaching, and N uptake concentration in tomato grown in open substrate 总被引:3,自引:0,他引:3
M. Gallardo J.S. Rodríguez M.D. Fernández J.J. Magán 《Agricultural Water Management》2009,96(12):1773-1784
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. 相似文献
45.
M. Carof S. De Tourdonnet Y. Coquet V. Hallaire & J. Roger-Estrade 《Soil Use and Management》2007,23(3):230-237
We studied soil hydraulic conductivity (K) and porosity in five combinations of soil tillage and cover crop management systems. Treatments were winter wheat (Triticum aestivum L.) grown on a conventionally tilled soil (CT), on a no‐till soil (NT), and on an NT with three different cover crops: red fescue (Festuca rubra L.; Fr), bird's‐foot‐trefoil (Lotus corniculatus L.; Lc) and alfalfa (Medicago sativa L.; Ms). Measurements were made on a loamy soil in Grignon, France, in November 2004, May 2005 and October 2005. K and mean size of hydraulically active pores were measured in situ at three water potentials (?0.6, ?0.2 and ?0.05 kPa) at the soil surface and at 10 cm depth. In November 2004 and May 2005, pore space was described using 2D image analysis of pores on undisturbed soil samples in the 0–10 cm layer and in the 10–20 cm layer. The major differences were caused by soil tillage that created two heterogeneous soil layers and increased K in the 0–10 cm layer relative to NT. The effects of cover crop on K and porosity were not affected by the root type: there were no major differences between the grass cover crop (fibrous‐root type) and the leguminous ones (tap‐root type). However, we recorded larger functional pores and more tubules in the no‐till treatments with a cover crop, compared with the no‐till treatment without cover crop; this was probably the result of root activity. Although these changes generally did not result in larger values of K, they participated in the maintenance of soil structure and K over time. 相似文献
46.
47.
《Communications in Soil Science and Plant Analysis》2012,43(15-16):2562-2578
The purpose of this investigation was to evaluate the effects of clear‐cutting and skidding impacts on surface soils in an alder coppice and aboveground herbaceous biomass. For this purpose, experimental sites used in the study were a randomized complete block with four replications. Some soil properties were measured at 60 pits at 0 to 5 cm and 5 to 10 cm deep in control, normal harvest, and main skid trail sites. In the main skid trail site, as compared to the control and normal harvest site, the bulk density increased from 0.90 to 1.52g cm?3, the soil organic‐matter content decreased from 4.77% to 1.65%, and saturated hydraulic conductivity decreased from 86.34 to 9.6 cm h?1 at 0 to 5 cm deep. Optimization of harvesting time and rehabilitation of skid roads needed to be done to prevent and minimize negative impacts of the skid roads on soils. 相似文献
48.
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50.
为比较杭白菊主栽品种早、晚小洋菊对菊小长管蚜Macrosiphoniella sanborni、棉蚜Aphis gossypii、桃蚜Myzus persicae的抗性,通过刺吸电位技术(electrical penetration graph,EPG)研究菊蚜在菊顶叶上刺吸行为,并检测了菊顶叶主要化合物。结果表明:在晚小洋菊上,菊小长管蚜的E1、E2波平均持续时间4.31、3.47 min,分别短于在早小洋菊上的4.63、3.75 min;棉蚜、桃蚜的E1、E2波平均持续时间分别为4.32、4.72 min和4.92、4.64 min;3种蚜虫的平均刺探次数均大于在早小洋菊上的平均刺探次数。聚类分析结果显示,2个主栽品种之间抗性存在差异。早小洋菊顶叶平均可溶性糖和可溶性蛋白含量分别为2.71 mg/g和25.36 mg/g,均高于晚小洋菊;早小洋菊顶叶总酚含量为0.24 mg/g,显著低于晚小洋菊;早、晚小洋菊总黄酮含量分别为3.46 mg/g和3.37 mg/g。早小洋菊顶叶可溶性糖、可溶性蛋白含量基本上与每种菊蚜的E1、E2波持续时间显著正相关,总酚含量、总黄酮含量与每种菊蚜的E1或E2波持续时间显著负相关。推测早小洋菊对于菊长管蚜的抗性稍弱于晚小洋菊,2种杭白菊对棉蚜或桃蚜的抗性相当,且菊叶中的这4种物质含量与抗蚜性相关。 相似文献