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61.
《Scandinavian Journal of Forest Research》2012,27(3):208-217
The purpose of this study was to determine the influence of temperature applied during short day-induced budset on induction of dormancy in six ecotypes of Betula pubescens Ehrh. and two ecotypes of Betula pendula Roth. Seedlings were grown in a phytotron at constant temperatures of 9–21°C under a 12 h photoperiod (SD) during dormancy induction. Induction of dormancy was monitored by following bud flushing and shoot growth after transfer to long photoperiod conditions (24 h) at 18°C. Chilling requirement was studied in seedlings exposed to 10 weeks of SD. In both species induction of bud dormancy developed most rapidly at 15–18°C, and both 9–12°C and 21°C delayed the induction of dormancy. Raising the temperature (from 9 to 21°C) applied during induction of dormancy significantly increased the chilling requirement. These responses were noted for all ecotypes tested, but in general the northern ecotypes entered dormancy more quickly than the southern ones. No such trend was recorded for chilling requirement, although a B. pubescens ecotype from Iceland and another from the coast of northern Norway appeared to require a longer chilling treatment than the other ecotypes. In conclusion, induction and depth of bud dormancy in birch are significantly affected by temperature conditions and these effects may explain some of the annual variation in dormancy and chilling requirement observed in nature. 相似文献
62.
《Communications in Soil Science and Plant Analysis》2012,43(6):453-461
Abstract The uptake and distribution of 32P from labelled monocalcium phosphate by white radish (Raphanus Sativus) roots at five phosphorus fertilization rates were studied. After on initial period of degradation (approximately 6 weeks), there is a sharp decline of phosphorus uptake. Graphical representation in Tables and Figures of the phosphorus distribution is presented. 相似文献
63.
E. Donahaye 《Phytoparasitica》1990,18(3):189-202
Adult populations of the red flour beetle,Tribolium castaneum (Herbst), were exposed for 40 generations to an atmosphere containing 99.5% N2 and 0.5% O2 at 95% RH, in order to select a strain resistant to the low oxygen concentration (LOC) atmosphere. Selection pressure was
maintained at between 50% and 70% mortality. At the 40th generation comparison of sensitivity between the selected strain
and the original non-selected strain indicated a resistance factor at the 50% mortality level (LT50) of x 5.2. However, throughout
the selections, log-time against probit-mortality curves remained roughly parallel from generation to generation and the slope
remained low. These findings indicate a multiplicity of genetic factors that at a high level of selection contribute together
towards an adaptation of the insects to survival in the LOC atmosphere. Removal of selection pressure from a sub-population
of the selected strain from the 13th to 21st generation revealed that resistance was partially retained with a decrease in
resistance factor of 23%. Although the study revealed that the insects were able to develop a strain resistant to hypoxia,
exposures were at 95% RH to minimize the desiccation effect. This does not reflect field situations, where ambient relative
humidities are generally below 70%. 相似文献
64.
65.
Organoclays were assayed as matrices in which to associate herbicides, with the aim of decreasing product losses that could give rise to water contamination from agricultural activities. Fenuron was selected as model of a very mobile and highly water-soluble herbicide. Two different organoclays of high (A-HDT) and low (H-C18) reversible fenuron sorption were selected. Herbicide-organoclay complexes were prepared from the two organoclays and with two different fenuron contents (20 and 40 g AI kg-1) and two different mixing times, so as to form a series of weak and strong complexes. The release of fenuron from those complexes into water and water/soil suspensions gave values of T50 (time to release 50% of the fenuron content) ranging from 0.3 min to 2400 h. The total fenuron released in these closed systems ranged from 48 to 80% of the fenuron in the complex. The organoclay type (high or low sorptivity) had the greatest influence on fenuron release, followed by the strong or weak complex, suggesting that herbicide-organoclay interactions are the main factors controlling release. Soil column leaching experiments showed fenuron-organoclay complexes to be effective in reducing the peak herbicide concentration in the leachate to a half (6 microns) or a quarter (3 microns) of that obtained from the free technical compound (12 microns). Herbicide lost through leaching was reduced from 78% for the free technical fenuron to 50-30%, depending on the organoclay used as carrier and the strength of the complex. Bioassay with ryegrass showed that the weak fenuron/H-C18 complex (40 g AI kg-1) gave the same herbicidal activity as technical fenuron. The potential suitability of low-sorptive organoclays for conferring slow-release properties on the fenuron complex has been demonstrated. 相似文献
66.
67.
简要介绍了兽药缓控速释剂型的产生、发展、动力学过程及其分类,并着重阐述了兽药缓控速释药的应用现状、发展动力、研究热点与趋势,分析了兽药缓控速释剂型研究中存在的问题,旨在为广大兽医药工作者研制兽药新剂型提供参考。 相似文献
68.
鄂尔多斯高原外流区地下水开发利用方式研究 总被引:1,自引:1,他引:1
王玮 《干旱区资源与环境》2006,20(3):64-69
针对鄂尔多斯高原外流区地下水资源可持续开发利用问题,建立了理想数值模型.采用控制性数值试验方法以及定性与定量分析相结合的方法,通过典型稳定流分析、无第四系稳定流分析、参数灵敏度分析,对在鄂尔多斯沙漠高原外流区开采地下水资源中的井位、过滤器顶部埋深、过滤器合理长度、开采目的层等关键技术问题进行了分析研究,研究结果表明,在鄂尔多斯沙漠高原外流区宜采用中段悬挂式非完整井远离河流单一开采白垩系含水层地下水,同时指出控制性数值试验方法以及定量分析定性分析相结合的方法,在地下水资源可持续开发利用乃至地下水科学领域,是值得重视和进一步发展的研究方法. 相似文献
69.
双重排水条件下控制措施对银南灌区水稻田水盐关系的影响分析 总被引:4,自引:0,他引:4
针对宁夏银南灌区目前存在的排水过量问题,研究者提出了利用控制排水措施,在适当时段减少排水量的建议。然而,灌区在农沟以及更深层的支、干沟及黄河(低地)的影响下,受着深层排水和浅层排水的双重作用。其中深层排水一般不会受到田间措施的影响,它的存在“淡化或中和”了由于浅层排水的减少引起的田间含盐量的增加。本文在对双重排水情况下的水盐运动进行概化的基础上,建立了基于特定地区排水特性的“浅层排水与深层排水比-浅层排水控制率-排水含盐量增加率”的关系。最后结合根据地下水洗淋的临界情况,确定了达到这一目标控制指标以及浅层地下水控制率。结果显示,对于研究的典型情况,当地下水的盐分含量达到临界的1.62 g/l时,可以将1m深的农沟控制至30cm深;这时的浅层地下水仅为现状的14%,即从731mm减少到了102mm。 相似文献
70.
The effects of field aging (0–28 days) and pheromone loading rate on the longevity of red rubber septa loaded with the sex
pheromone blend of the oriental fruit mothGrapholita molesta (Busck), were evaluated in North Carolina apple orchards in 2002. Separate field tests examined the influence of trap height
and pheromone loading rate of rubber septa on trap catches of adultG. molesta males in an abandoned orchard. The loss of the major pheromone component, (Z)-8-dodecenyl acetate (Z8–12:OAc), from red rubber
septa over a 4-week period exhibited a relatively constant release rate with 30, 100 and 300 μg pheromone. Trap catch was
significantly higher in pheromone traps placed in the upper canopy than in those in the lower canopy. Pheromone traps baited
with 100μg lures caught more moths compared with those loaded with 300 μg. There was no apparent relationship between pheromone
trap catch and septa age, with trap catch appearing to be primarily a function ofG. molesta population density.
http://www.phytoparasitica.org posting May 14, 2006. 相似文献