共查询到20条相似文献，搜索用时 46 毫秒
1.
风沙区参考作物需水量计算模式的研究 总被引：9，自引：0，他引：9
根据包头气象站30a逐旬气象资料和2001年作物生长期逐日资料,用Penman-Monteith公式、Blaney-Criddle公式、Hargreaves公式、Priestley-Taylor公式、Markkink公式估算逐旬和逐日的参考作物需水量(ET0),以Penman-Monteith方法计算结果作为标准来评价其它4种计算方法。经比较分析,用其它4种方法和Penman-Monteith方法计算出的逐旬ET0值均具有较好的相关性,其中以Blaney-Criddle法估算结果最好。4种方法估算的逐日ET0误差较大,相比而言,Markkink法优于其它3种方法。同时,分析了ET0与气温的关系,并建立了适合该地区ET0计算的经验公式,用经验公式估算ET0方法简单,且具有较高的精度。 相似文献
2.
岷江上游干旱河谷山杏幼林地绿肥种植研究 总被引：4，自引：0，他引：4
在岷江上游干旱河谷山杏幼林地连续4 a利用雨季种植绿肥压青,增加土壤肥力,提高水分利用率,促进幼树生长研究,结果表明:(1)种植红豆草的土壤0-40 cm含水量旱季增加0.39 g·kg-1,0-20 cm土壤容重降低0.01 g·cm-3;种植草木樨土壤0-40 cm含水量旱季增加0.55 g·kg-1,0-20 cm土壤容重降低0.04 g·cm-3;种植沙打旺土壤0-40cm含水量增加0.30 g·kg-1,0-20 cm土壤容重降低0.03 g·cm-3;(2)种植绿肥压青,土壤有机质增加0.10-0.46 g·kg-1,土壤CaCO3含量下降0.93-1.04 g·kg-1,有效氮增加5.9-19.3 mg·kg-1,有效磷含量增加1.26-2.46 mg·kg-1,CEC比对照增加0.68-1.00 mg·100 g-1;(3)种植红豆草、草木樨、沙打旺绿肥压青对山杏树高、径生长有显著作用,尤其种植红豆草的山杏幼树生长最好,高、径生长为对照的2.1和2.2倍。 相似文献
3.
本文通过分析塔克拉玛干沙漠腹地能见度仪、自动气象站观测沙尘暴的资料,得到:(1)在沙尘暴过程中,器测能见度越小,持续时间越短,随着器测能见度增大,持续时间呈波动增长,持续时间最长的等级是800m,时间为419min。(2)在沙尘暴过程中,器测能见度200m,500m是两个明显的分界点,在分界线左右的能见度持续时间变化较大,最大相差20倍,在<200m,200-500m,500-1000m三段范围内器测能见度持续时间变化不大,最大相差0.8倍,(3)沙尘暴过程中,平均风速的变化趋势是随着器测能见度增大而减小,平均风速最大值出现在能见度400m处,最小值出现在能见度接近1000m处,平均风速11.9m/s,最大风速21.1m/s。器测能见度从400m变化到500m风速有较大减小。气压和相对湿度以器测能见度500m为界,能见度<500m,数值较大,能见度>500m数值较小。(4)根据器测各能见度持续时间、气象要素变化和统计检验,沙尘暴中,在器测能见度500m处各气象要素变化很大,这对沙尘暴分级有积极意义。(5)器测能见度与人工观测值有较大差距,但它们之间有较好相关性,其相关系数是R=0.7993,通过了t检验(α=0.01)。它们之间拟合方程是y=5.746X0.8523。 相似文献
4.
Ching M. Wang Toshio Narahashi Jun-ichi Fukami 《Pesticide biochemistry and physiology》1975,5(2):119-125
The mechanism of action of chlordimeform on the frog sciatic nerve-sartorius muscle preparation has been studied by means of microelectrodes. Chlordimeform (0.1 mM) suppresses the amplitude of spontaneous miniature end-plate potentials without much changing their frequency. At 1 mM, it completely blocks the miniature end-plate potentials. The resting membrane potential is not affected. The end-plate potential evoked by nerve stimulation is also suppressed, while the action potential from the nerve terminal is not impaired. The sensitivity of the end-plate membrane to the transmitter substance as examined by iontophoretic applications of acetylcholine is effectively decreased by chlordimeform. The quantal content of transmitter release is not affected. It is concluded that the block of neuromuscular transmission by chlordimeform is due primarily to a depression of the end-plate sensitivity to the transmitter. 相似文献
5.
研究结果表明:储水滴灌为干旱山地果树生长提供了一个比较稳定而持久的水分供应系统。土壤含水量比对照平均提高13%,主要分布在21-80cm土层;同时改善了土壤物理性状和提高了养分含量,土壤比重随土层深度逐渐增加,土壤空隙度发育表层为54.35%,其余各层变动在48-51%之间;土壤容重较对照区降低了0.19g/cm3、空隙度增加了10.6%、碱解氮提高了5.7 mg.kg-1、速效磷提高2.8 mg.kg-1、速效钾提高8.4 mg.kg-1。改变了苹果新梢生长节律,促进春梢生长,抑制秋梢生长;百叶重提高了13.3%,座果率提高了76.8%,平均单果重提高了40.3%,产量提高了156.6%,优果率达到了90.5%。 相似文献
6.
Abstract An outstanding property of the bipyridylium herbicides is the rapidity with which they are inactivated in contact with soils. The initial inactivation is attributable to strong adsorption on soil colloids and, as may be expected, is governed by the nature of the soil. Subsequent degradation may be induced by ultraviolet radiation or, below the soil surface, by the activity of the microflora. The agronomic significance of these mechanisms is described by reference to recent work on paraquat. 相似文献
7.
Abdul Latif Mian 《国际虫害防治杂志》2013,59(4):482-490
Abstract Red rot is a very serious disease of sugarcane. It was first described by Went in 1893 (56). Since then it has been found to cause epiphytotics in different countries. The surest symptom of the disease is the reddening of the internal internodal tissues with crossbars of white patches in the reddened area. This red colour is caused by a dye which is secreted by the host and is antagonistic to the red rot fungus. Infection takes place through mother setts, holes in the nodal regions, the cut ends of the seed canes and other injuries. The disease causes damage to the sugarcane drop mainly by reducing the crop stands and by reducing the sucrose content of the cane juice. Methods of chemical control are mentioned, although the importance of good husbandry is stressed. Use of resistant varieties of sugarcane is recommended. 相似文献
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10.
J. M. Osgerby 《Pest management science》1973,4(2):247-258
The main processes which affect herbicide action in soil are considered to be the extent to which the herbicide is adsorbed by soil particles, the rate of absorption of the herbicide solution by plant roots and the rate at which the herbicide is lost from the soil by decomposition, evaporation or leaching. An attempt is made to show how these factors are interrelated and the possible use of mathematical models to optimise the performance of herbicides is briefly discussed. 相似文献
11.
Atrazine 10?4M rapidly inhibits sulfate uptake by excised barley roots. When humic substances are present in the uptake solution the inhibition is reduced. This effect is enhanced by 10 to 16 hr incubation of the roots in the presence of humus. Humus action is accompanied by the stimulation of leucine incorporation into protein, which, on the contrary, is unaffected by atrazine. The same experiments carried out with barley seedlings, in nutrient solution containing either atrazine or humus, or both, confirm the inhibitory action of atrazine on SO42? absorption by the whole plant and the inhibition reduction by humic substances. 相似文献
12.
中亚天仙子生物碱成分的研究 总被引：1，自引：0，他引：1
中亚天仙子在我国仅产于新疆，属于莨菪烷类生物碱资源植物，采用比色法或电位滴定法测定了植株内总碱含量为０．１１％，种子中的总碱含量为０．３０％，又使用薄层层析法测定植株内莨菪碱含量为０．０４５％，东莨菪碱含量为０．０１６％。 相似文献
13.
植被作用下的土壤干化及其发生机制探讨 总被引：8，自引：0，他引：8
通过分析黄土高原不同类型植被下的土壤水分状况,探讨了植被作用下土壤干化的特征和机制,以正确认识其实质,并提供可调控的依据。结果表明,植被作用下的土壤干化具有相对稳定性,其数量指标可采用田间稳定湿度值衡量。在黄土高原气候及地质条件下,土壤干化是植被作用下易于发生的现象,但它并不是植被建造的必然结果。人为营造大片耗水性强的植被类型,高密度以及追求高生产量,是其发生的关键因素。通过了解人工林草物种特点的二重性、合理配置群落结构的必要性以及人工与天然起源的植被在植物竞争效应方面的差异,可对其实施有效管理。植被下土壤干化的普遍发生,不应当妨碍黄土高原进一步开展林草植被建设。 相似文献
14.
Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV) are two criniviruses that are emerging worldwide, and induce similar yellowing diseases in tomato crops. While TICV is transmitted only by Trialeurodes vaporariorum , ToCV is transmitted by three whitefly species in two genera Trialeurodes vaporariorum , T. abutilonea and Bemisia tabaci . The efficiency of transmission by T. vaporariorum from plants infected by one virus or by both was compared, and the probability of virus transmission by a single whitefly was derived from group testing experiments. The estimated transmission probabilities ranged from 0·01 to 0·13, and were not significantly different between ToCV and TICV, or between single and mixed infections. Experiments using B. tabaci as a vector and source plants infected by TICV and ToCV did not reveal any functional trans-complementation for transmission of TICV by ToCV, suggesting that if this phenomenon occurs in nature, it is at a very low frequency. Possible reasons why TICV did not establish in southern France while ToCV is now endemic are discussed. 相似文献
15.
陇东地表湿润指数的年际变化特征 总被引：5，自引：0，他引：5
利用能够代表陇东气候类型的三个代表站1971~2005年月平均气温和降水资料,分析该地地表湿润指数的时空变化特征。结果表明:地表湿润指数变化多年平均,东南部的正宁最大,中部的西峰次之,北部的环县最小,呈现由东南向中部和北部逐渐干旱的空间变化特征;东南部的正宁和中部的西峰地表湿润指数以0.0028/a和0.0034/a的速率减小,地表趋于干旱化,北部的环县以0.005/a的速率增加,地表湿润程度有所增加;地表湿润指数的季节分布以春季最小,秋季次之,夏季最大,且春季和秋季有逐年减小的趋势,干旱化程度逐年加重,夏季呈增加趋势,地表湿润状况有所改善;地表湿润指数变化主要依靠降水的影响,但同时也受温度变化的影响,温度高,地表水分蒸发蒸散量大,地表易于变干,温度低,水分蒸发蒸散量小,地表不易变干。 相似文献
16.
Prophenol oxidase (PPO) (EC 1.14.18.1) is isolated from pupae of blowfly (Sarcophaga bullata) and purified by employing ammonium sulfate fractionation, ion-exchange chromatography on DEAE-cellulose, and gel filtration through Sephadex G-100 column chromatography. The enzyme exists in a latent or inactive state. Cetylpyridinium chloride (CPC), a cationic detergent, is found to activate the PPO activity. The activation of the enzyme by CPC has first been studied by using the kinetic method of the substrate reaction described by Tsou. The results show that the enzyme is activated by a complexing scheme that has not been previously identified. The enzyme first reversibly and quickly binds CPC and then undergoes a slow reversible active course. The activation reaction is a single molecule reaction and the apparent activation rate constant is dependent on the CPC concentration with the function relationship fit with a hyperbola. The micro rate constants of activation and the association constant are determined from the measurements. Substrate binding does not affect the micro rate constants of activation by CPC. 相似文献
17.
半抗原的间隔臂长度对免疫识别的影响 总被引：5，自引：0，他引：5
分别以2甲4氯和二氯喹啉酸的3种不同间隔臂长度(0、4、6个碳)的包被抗原及相应的3种抗体为研究对象,通过抗体效价的测定及包被抗原与抗体的亲和性正交试验,讨论了半抗原的间隔臂长度对免疫识别的影响。结果表明,两种化合物均以接有4个碳链长度间隔臂的半抗原诱导产生的抗体效价最高;同一抗体更易识别间隔臂较长(6个碳)的抗原;对于同一包被抗原,抗2甲4氯抗体中均以不接臂的半抗原诱导产生的抗体的识别能力最强,而抗二氯喹啉酸中则以接有4个碳长间隔臂的半抗原诱导产生的抗体的识别能力最强,表明抗体的识别能力可能与IgG蛋白的空间构型有关。 相似文献
18.
Alfred J. Keys 《Pest management science》1983,14(3):313-316
Photorespiration in plants is defined and discussed. The possibility of increasing crop yields by controlling photorespiration, particularly by inhibiting the initial reaction, is considered. 相似文献
19.
北疆春小麦蒸散规律及蒸散量估算研究 总被引：4，自引：1，他引：4
通过对2002～2003年北疆春小麦田试验数据的分析结果表明,北疆春小麦全生育期蒸散量在410～430mm左右,蒸散强度为4.11～4.14mm,蒸散量和蒸散强度均在抽穗～乳熟期达到最大,平均棵间蒸发占总蒸散量的比例为38.3%～42.0%。叶面积指数与蒸散强度关系极为密切,可用复合曲线方程来描述二者的关系。通过采用Penman-Montieth模式配合单值平均作物系数和水分胁迫系数估算农田蒸散量的方法,对当地春小麦田的日蒸散量进行估算,精确度检验结果表明该方法是切实可行的。 相似文献
20.
转录相关因子与特异DNA位点结合受染色质空间构象变化的调节,通过染色质重塑机制可以解除染色质高度紧密的折叠状态,改变组蛋白与DNA链间的作用力,控制基因的表达与沉默。ATP依赖的染色质重塑复合物、组蛋白的乙酰化/去乙酰化和甲基化/去甲基化共价修饰等是染色质修饰的主要类型,植物能通过染色质重塑复合物和组蛋白修饰酶复合物直接或间接介导的染色质重塑作用调控防御基因的转录,控制植物对病原体侵染的防御应答。本文结合近年来的研究进展,对植物染色质重塑如何调控防御相关基因的表达及病原体蛋白T3SEs、6b和VirE等如何利用染色质重塑干预植物防御系统的分子机制进行了论述。 相似文献