两种吡虫啉种衣剂在棉花和土壤中的残留动态研究

采用田间试验方法，研究了两种吡虫啉种衣剂在棉花和土壤中的残留消解动态，并对其在棉花上使用的安全性作出了评价。结果表明，两种吡虫啉种衣剂无论在棉株中或土壤中消解动态没有显著差异，其消解速度相当缓慢，有较长的药效。试验还表明，无论是推荐药量还是加倍药量．在正常使用条件下，都不会造成棉子残毒污染和土壤的残留积累。     

基于改进生态足迹模型的西北地区生态可持续性评价

西北地区的生态可持续状况对于稳定生态环境,改善人地关系具有重要的现实意义。传统生态足迹模型(EFM)中存在诸多不足和缺陷,文中对原有模型进行了改进并对西北地区2012年生态可持续性进行了计算和评价。结果表明:1)西北地区人均生态足迹为2.90hm2/人,人均生态承载力为2.18hm2/人,人均生态赤字为0.72hm2/人,整体的生态结构不合理,处于不可持续状态;2)西北地区各省区的生态足迹差异明显,除青海和新疆为生态盈余外,其它省区均为生态赤字,其中陕西最大,甘肃最小;3)西北地区生态适度人口为0.74×108人,实际人口与生态适度人口的比例是1:0.75,人口数量整体处于超载状态;生态利用效率为0.65万元/hm2。改进生态足迹模型能够较好地评价生态可持续现状,研究方法和结果对于区域生态可持续发展研究具有一定的参考价值。     

Detection and quantification of Phytophthora species which are associated with root-rot diseases in European deciduous forests by species-specific polymerase chain reaction

Oligonucleotide primers were developed for the polymerase chain reaction (PCR)-based detection of selected Phytophthora species which are known to cause root-rot diseases in European forest trees. The primer pair CITR1/CITR2, complementing both internal transcribed spacer regions of the ribosomal RNA genes, gave a 711 bp amplicon with Phytophthora citricola. The Phytophthora cambivora specific primer pair CAMB3/CAMB4, producing a 1105bp amplicon, as well as the Phytophthora quercina specific primer pair QUERC1/QUERC2, producing a 842 bp amplicon, were derived from randomly amplified polymorphic DNA (RAPD)-fragments presented in this paper. All three primer pairs revealed no undesirable cross-reaction with a diverse test collection of isolates including other Phytophthora species, Pythium, Xerocomus, Hebeloma, Russula, and Armillaria. Under the PCR conditions described the detection of a well discernable amplicon was possible down to 100 pg (P. cambivora), 4pg (P. quercina), and 2pg (P. citricola) target DNA. This diagnostic PCR system was able to detect P. citricola, P. quercina, and P. cambivora in seedlings of pendunculate oak (Quercus robur) and European beech (Fagus sylvatica) which were artificially infected under controlled conditions.     

Reduced Sink Activity in Growing Shoot Tissues of Maize under Salt Stress of the First Phase may be Compensated by Increased PEP‐Carboxylase Activity

The effects of salt stress (100 mm NaCl for 6 days) on growing tissues (shoot apex, growing leaf segments, root tips) of young maize plants (Zea mays L. cv. Pioneer 3906) were investigated in comparison to an unsalinized control, focusing on assimilate supply from source leaves and the activity of sucrolytic enzymes in the sink tissues. The objectives were to test whether (i) phloem unloading in growing tissues is mainly symplastic, (ii) salinity reduces sink activity, determined either as sucrose synthase activity (indicator for the symplastic pathway) or as acid invertase activity (indicator for the apoplastic pathway), and (iii) PEP‐carboxylase activity is increased under salinity to compensate for reduced sink activity. For growing tissues of young maize shoots, it can be assumed that phloem transport of sucrose is mainly driven by symplastic unloading into the sink cells. In maize root tips, both, apoplastic and symplastic pathways, contributed to carbohydrate supply to the sink cells. The activity of acid invertase in growing shoot tissues was very low, and the alkaline invertase contributed less than 10 % to the cytoplasmic sucrolytic activity. Salt stress of the first phase (mainly osmotic stress) caused a significant inhibition of acid invertase activity in the growing leaf segments and in the root tips, which was also true for alkaline invertase activity in the root tips as well as for sucrose synthase activity in root tips and shoot apex. The decrease of sucrose synthase activity in shoot apex might be particularly detrimental for the plant growth, as this tissue with a high cell division rate relied entirely on cytoplasmic enzyme activities. Under salt stress, PEP carboxylase activity was significantly increased in growing leaves and the shoot apex of maize, whereas no significant effect was observed in the root apex. In conclusion, PEP carboxylase can have an anaplerotic function supporting the demand for metabolites in growing shoot tissues of young maize plants under salt stress. In root tips, an additional supply of organic acids to the tricarboxylic acid cycle is probably not needed, as sucrolytic sink activity, which was high even under saline conditions, can meet the demand of the sink cells.     

Leaf Cell‐Wall Components as Influenced in the First Phase of Salt Stress in Three Maize (Zea mays L.) Hybrids Differing in Salt Resistance

The leaf cell wall (CW) chemical composition of three maize (Zea mays L.) hybrids (salt‐resistant SR 03 and SR 12, salt‐sensitive Pioneer 3906) was investigated in the first phase of salt stress (100 mm NaCl) compared with the control (1 mm NaCl) treatment to investigate whether changes in CW composition were responsible for shoot growth reduction. Salt treatment caused a strong inhibition in shoot growth with a concomitant increase in the ratio between CW dry mass (DM) and shoot fresh mass (FM) and a decrease in CW cellulose concentrations in all hybrids. NaCl caused a large increase in the concentrations of total and non‐methylated uronic acid (UA) in salt‐sensitive Pioneer 3906 and salt‐resistant SR 12. The onset of the accumulation of non‐methylated UA was delayed in SR 12, which indicates that this may be one reason for the better growth performance of this hybrid under salt stress compared with Pioneer 3906. It is concluded that a low accumulation of non‐methylated UA in leaf CW may, among other mechanisms, contribute to salt resistance in the first phase of salt stress.     

基于质量分级的马铃薯贮藏温度特性的试验与研究

贮藏室内适宜的贮藏温度是进行科学贮藏和决定贮藏质量的重要条件.为研究相同贮藏条件下不同质量马铃薯堆内部温度的差异,以内蒙古半地下式马铃薯贮藏室为试验场地,将食用型"冀张226"马铃薯按单薯质量进行分级,以筐装方式进行堆码,同时用传感器采集贮藏过程中的温度数据,然后对数据进行分析、对比.结果表明:整个贮藏过程中,分级后的所有马铃薯堆的内部温度整体变化规律基本一致,均为先降低后升高,但单薯质量小的马铃薯堆内部温度的稳定性要优于单薯质量大的马铃薯堆.温度下降阶段,马铃薯堆的内部温度与马铃薯单薯质量大小呈负相关;温度上升阶段,马铃薯堆内部温度上升率与马铃薯单薯质量呈正相关;不同马铃薯堆在贮藏过程中的最低温度与马铃薯单薯质量呈负相关;分级后的马铃薯堆内部温度的稳定性要优于未分级的马铃薯堆.     

Banded surface flow maintained by convection in a model of the rapidly rotating giant planets

In three-dimensional numerical simulations of a rapidly rotating Boussinesq fluid shell, thermally driven convection in the form of columns parallel to the rotation axis generates an alternately directed mean zonal flow with a cylindrical structure. The mean structure at the outer spherical surface consists of a broad eastward flow at the equator and alternating bands of westward and eastward flows at higher latitudes in both hemispheres. The banded structure persists even though the underlying convective motions are time-dependent. These results, although still far from the actual motions seen on Jupiter and Saturn, provide support for theoretical suggestions that thermal convection can account for the remarkable banded flow structures on these planets.