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Xanthomonas campestris pv. vitians , the causal agent of bacterial leaf spot of lettuce (BLS), can be seedborne, but the mechanism by which the bacteria contaminates and/or infects lettuce seed is not known. In this study, the capacity of X. campestris pv. vitians to enter and translocate within the vascular system of lettuce plants was examined. The stems of 8- to 11-week-old lettuce plants were stab-inoculated, and movement of X. campestris pv. vitians was monitored at various intervals. At 4, 8, 12 and 16 h post-inoculation (hpi), X. campestris pv. vitians was recovered from 2 to 10 cm above (depending on stem length) and 2 cm below the inoculation site. Xanthomonas campestris pv. vitians was also recovered from surface-disinfested stem sections of spray-inoculated plants. Together, these results are consistent with X. campestris pv. vitians invading and moving systemically within the vascular system of lettuce plants. To investigate the mechanism of seed contamination, lettuce plants at the vegetative stage of growth were spray-inoculated with X. campestris pv. vitians and allowed to develop BLS. Seed collected from these plants had a 2% incidence of X. campestris pv. vitians external colonization, but no bacteria were recovered from within the seed. 相似文献
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Yoram Barak Eddie Cytryn Iliya Gelfand Michael Krom Jaap van Rijn 《Aquaculture (Amsterdam, Netherlands)》2003,220(1-4):313-326
Phosphorus dynamics were examined in a prototype, zero-discharge, marine-recirculating system. Operation of the system without discharge of water and sludge was enabled by recirculation of effluent water through two separate treatment loops. Surface water from the fish basin was pumped over a trickling filter in one loop, while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other treatment loop. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor were the main biological features of this treatment system. Orthophosphate concentrations did not exceed 15 mg PO4–P/l in the culture water during more than 1 year of system operation. Much of the phosphorus was retained within the sedimentation basin and fluidized bed reactor. In these treatment stages, the phosphorus content of organic matter was as high as 17.5% and 19%, respectively. High concentrations of total phosphorus and low concentrations of soluble orthophosphate were measured in the initial stages of sedimentation under oxic and anoxic conditions, suggesting that most of the phosphorus was associated with organic matter. Depletion of oxygen and nitrate in the sludge layers of the sedimentation basin coincided with sulfate reduction to sulfide and a release of soluble orthophosphate. The observed phosphorus dynamics in this marine system supported findings from previous studies in which it was demonstrated that denitrifiers underlie phosphorus immobilization under these conditions. 相似文献
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Lignin, an important component of plant tissues, adsorbed five systemic fungicides and one herbicide (carbendazim, triadimefon, nuarimol, triarimol, fenarimol and fluometuron) more strongly than bovine serum albumin, cellulose, ethylcellulose or sodium polygalacturonate. Significant correlations were found between the extent of the adsorption of the pesticides on the lignins extracted from three different plant species, and the log Poet (Poet is the octan-1-ol/water partition coefficient) of the compounds. The more lipophilic fungicides triarimol and fenarimol (log Poet about 2.6) were adsorbed to the greatest extent. Fluometuron, triadimefon and nuarimol (log Poet about 2.0) were moderately adsorbed, whereas carbendazim with the lowest log Poet (1.34 at pH 5.0), was adsorbed more than expected from its Poet value. The anomaly of carbendazim is discussed; it is ascribed to it's partial protonation at pH 5.0, whereas the other pesticides were non-ionised. 相似文献
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Introduction of the clonedErwinia chrysanthemi pelB orpelE genes intoEscherichia coli enabled the latter to cause blackleg disease symptoms in potato similar to those observed with the pathogenErwinia carotovora. TheE. coli cells multiplied in the roots and moved systemically in the potato stems, concomitant with the appearance of disease symptoms.E. coli cells expressing the clonedpel genes also interacted with the fungal pathogen,Verticillium dahliae, as observed previously withErwinia spp. The results indicate that either of two clonedpel genes permitsE. coli to cause relatively sophisticated diseases in potato plantlets. 相似文献
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黄斑星天牛硫酰氟检疫熏蒸技术研究 总被引：3，自引：1，他引：3
黄斑星天牛 (Anoplophoranobilis)硫酰氟熏蒸的毒力试验结果说明 ,当熏蒸时间为2 4h ,4.4℃、1 0 .0℃、1 5.5℃和 2 1 .1℃条件下推算出死亡机率值 9要求的CT值分别为70 0 4.2 0、3 2 96.97、974.63和 52 7.0 4g .h/m3;当熏蒸时间为 48h ,4.4℃和 2 1 .1℃分别为 2 82 8.2 2和 50 5.45g .h/m3。室内验证试验中 ,1 5.5℃和 2 1 .1℃投药剂量为 1 0 4g/m3,能够全部杀灭杨树携带的黄斑星天牛幼虫、蛹 ,以及芳香木蠹蛾东方亚种 (Cossuscossusorientalis)和杨干透翅蛾 (Spheciasiningensis)幼虫 ;而在 1 0℃以下 ,黄斑星天牛或芳香木蠹蛾东方亚种和杨干透翅蛾幼虫没有完全死亡。 相似文献
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木质包装集装箱溴甲烷检疫熏蒸技术研究 总被引：5，自引：1，他引：5
对集装箱装运的出口货物木质包装进行了溴甲烷熏蒸试验 ,结果说明 ,当环境温度为 2～ 1 6℃时 ,采用溴甲烷投药剂量 80 g/m3 ,熏蒸 2 4h能够全部杀死黄斑星天牛幼虫 ,其CT值为 1 1 2 5 8～ 3345 3g h/m3 ;环境温度为 5～ 2 0℃时 ,采用 6 4g/m3 投药剂量 ,同样熏蒸 2 4h ,CT值为 1 2 1 0 8～ 1 51 0 8g h/m3 ,黄斑星天牛幼虫同样全部死亡。溴甲烷汽化后直接从集装箱门上部投药能够使药剂分布均匀。熏蒸结束后通风散气 2 4h ,集装箱到达美国后其内部溴甲烷残留气体浓度低于 5× 1 0 -6。 相似文献
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It is usually assumed that enhanced spiking activity in the form of persistent reverberation for several seconds is the neural correlate of working memory. Here, we propose that working memory is sustained by calcium-mediated synaptic facilitation in the recurrent connections of neocortical networks. In this account, the presynaptic residual calcium is used as a buffer that is loaded, refreshed, and read out by spiking activity. Because of the long time constants of calcium kinetics, the refresh rate can be low, resulting in a mechanism that is metabolically efficient and robust. The duration and stability of working memory can be regulated by modulating the spontaneous activity in the network. 相似文献
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Aharoni Ran Klymiuk Valentyna Sarusi Benny Young Sierra Fahima Tzion Fishbain Barak Kendler Shai 《Precision Agriculture》2021,22(1):267-286
Precision Agriculture - Yellow rust (YR) wheat disease is one of the major threats to worldwide wheat production, and it often spreads rapidly to new and unexpected geographic locations. To cope... 相似文献
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