青麻epsps基因在酵母中表达

将青麻epsps基因构建到酵母胞内表达载体pPIC3.5K中,利用电转化法将构建好的表达载体转入巴斯德毕赤酵母中,PCR技术筛选出阳性转化子,证明外源epsps基因已经整合到巴斯德毕赤酵母的基因组上,经诱导表达后SDS-PAGE分析获知外源基因在酵母中获得了表达。并且通过草甘膦压力筛选出耐性较好的重组酵母菌株,证明所获得的epsps基因具有生物学功能。     

磨盘草不同营养器官中总黄酮和总酚含量测定

分别以芦丁和没食子酸为对照品，测定了磨盘草不同营养器官（根、茎、叶）中总黄酮和总酚的含量。结果表明，磨盘草叶、茎、根中总黄酮含量分别为1．96％、1．20％、o．78％，总酚含量分别为8．61％、6．03％、4．31％。     

苘麻/聚乙烯复合材料性能的研究

我国的麻类资源非常丰富,将麻纤维用于复合材料的制备能扩大麻纤维的应用范围,有效提高麻纤维的使用价值.将苘麻纤维（AF）作为增强材料,通过热压工艺制备了苘麻/聚乙烯（PE）复合材,并探讨了该复合材的各项性能.通过热重分析确定了苘麻纤维的加工温度为180℃,对比分析AF/PE复合材的力学性能,确定制备复合材时AF含量控制在60％范围内能得到性能优异的复合材,AF与PE的最佳质量比为55∶45.苘麻纤维经硅烷偶联剂处理后,AF/PE复合材的弯曲性能和拉伸性能都有明显提高,吸水厚度膨胀率明显降低.由红外光谱分析发现,硅烷偶联剂与苘麻纤维表面的羟基发生化学反应生成了硅-氧-碳共价键,硅烷偶联剂使麻纤维表层与PE基质层之间产生分子结合,因此提高了PE基质与苘麻纤维的结合强度.     

Increased herbicidal activity of triazine herbicides by piperonyl butoxide

Piperonyl butoxide (PB) is a known Synergist which enhances the activity of insecticides by inhibiting their biotransformation to less active products. We have evaluated the possible use of PB as a herbicide synergist using triazine herbicides in sensitive, tolerant, and resistant plants. The effects of PB, triazine herbicides, and their combinations were examined in whole plants as well as in chloroplasts isolated from triazine-sensitive (S) and -resistant (R) weed biotypes. PB itself, applied postemergence (0.1–0.5%, v/v), was slightly toxic to the plants tested. However, foliar application of PB combined with atrazine, terbutryn or prometryn to maize seedlings significantly increased the phytotoxicity of the herbicides. Low rates of atrazine, prometryn, and terbutryn in a tank-mixture with PB, effectively controlled Solatium nigrum L. and Abutilon theophrasli Medik. PB enhanced atrazine efficacy in both S and R biotypes of Lolium rigidum Gaud. The synergistic effect of PB was evident also in vitro when atrazine and methabenzthiazuron were used to inhibit photosystem II electron transport in chloroplasts isolated from resistant weeds. These data demonstrate the potential of PB as a herbicide synergist and its possible utilization as an aid for improving the activity of triazine herbicides in sensitive, tolerant and resistant plants.     

Glyphosate efficacy is contributed by its tissue concentration and sensitivity in velvetleaf (Abutilon theophrasti)

Glyphosate efficacy was examined in young velvetleaf plants from the standpoint of its tissue distribution and sensitivity. In whole plant assays, manual application of a sub-lethal dose to the first leaf resulted only in meristem injury while other tissues remained visually healthy. Our studies showed that this differential tissue response was caused by a combination of differential distribution as well as sensitivity to glyphosate. Using [¹⁴C]glyphosate, we measured tissue injury and glyphosate residue, and calculated tissue threshold for 50% growth inhibition. Our studies showed that roots and meristem have high glyphosate distribution (45 and 34% of translocated, respectively) and low inhibition thresholds (0.23 and 0.21 ppm, respectively) resulting in tissues that were easily killed by glyphosate. In contrast, the base stem contained a much higher inhibition threshold (8.4 ppm) with only intermediate distribution (10%) resulting in a tissue that was most difficult to kill. We observed a linear relationship between glyphosate dose and tissue concentration; furthermore, tissue distribution pattern was independent of dose or surfactants class. At a sub-lethal dose, sensitive tissues that received a large distribution of glyphosate were preferentially killed. As the dose was increased, more glyphosate was available for distribution, and all tissues received a proportionately greater amount of glyphosate. Plant death occurred when the applied dose was sufficient to attain the lethal threshold in all tissues.     

Comparative ecophysiology of grain sorghum and Abutilon theophrasti in monoculture and in mixture

Selection of crop genotypes that are more competitive with weeds for light interception may improve crop yield stability in the presence of weeds. The effects of interference on ecophysiological characteristics of Abutilon theophrasti Medic. and three morphologically diverse grain sorghum hybrids was evaluated to determine the relative tolerance and suppressive ability of the three hybrids and specific traits that may contribute to those differences. A tall hybrid was more tolerant to A. theophrasti interference than two medium stature hybrids. Early leaf area growth of two medium-stature sorghum hybrids was reduced by A. theophrasti interference, whereas early growth of a tall hybrid was unaffected. The height of A. theophrasti was greater than two moderate-stature hybrids but lower than the tall hybrid. Greatest leaf area density (L_D) of the tall sorghum hybrid was above that of A. theophrasti , whereas greatest L_D of medium-stature hybrids was below that of the weed. In monoculture, the partitioning of new biomass to various plant organs was similar among sorghum hybrids, whereas the tall sorghum hybrid partitioned less biomass to leaves and more to stems than medium hybrids in mixture. The results indicate that the three hybrids differ in their susceptibility to A. theophrasti competition. Crop traits that may contribute to greater crop competitiveness include greater maximum height and its growth rate and greater height of maximum leaf area distribution.     

Model of crop:weed competition applied to maize:Abutilon theophrasti interactions. I. Model description and evaluation

A complex set of interactions among crops, weeds and their environment determines the impact of weed interference on crop productivity. These interactions can be simulated with dynamic crop:weed competition models, such as ALMANAC. In this study, ALMANAC was modified to simulate maize: Abutilon theophrasti competition. In the modified ALMANAC model, daily increases in leaf area index (LAI), height and rooting depth are attenuated on the basis of accumulated above-ground biomass and by environmental stress. Also, a simple, flexible method is adopted to partition radiation in a mixed canopy. A maize: A. theophrasti competition study conducted near Aurora, NY, in which a range of weed densities (0–16 plants m⁻²) were established in a maize crop, was used to evaluate the model. The modified ALMANAC proved to be a useful tool for segregating the maize response to competition in 1991 (simulated loss of 35% at the highest weed density) from those in 1992–94 (simulated losses not greater than 16%). Based on these findings, the modified ALMANAC model is judged to be capable of distinguishing between environmental conditions that facilitate large yield losses and those that allow maize to outcompete A. theophrasti .     

An unusual isolate of turnip mosaic potyvirus fromAbutilon theophrasti in Piedmont, Italy

An isolate of the poty virus turnip mosaic virus (TuMV-Ab) showing severe mosaic symptoms inAbutilon theophrasti from Piedmont (northwestern Italy) in 1993, has been found to be of an unusual pathotype and serotype. The isolate was easily transmitted byAphyis gossiypii and Myzus persicae and was not seed-transmitted inA. Theophrasti. The host range of TuMV-Ab was different from that of another Piedmont isolate of TuMV fromAlliaria officinalis and from a TuMV isolate fromBrassica napus. TuMV-Ab was characterized using the reactions on the fourB. Napus lines S4, R4, 165 and S1 as the rare pathotype 7, found only once previously in Europe. Tests with polyclonal antisera indicated that TuMV-Ab was only distantly related to the two other TuMV isolates. Serological characterization with a panel of 30 monoclonal antibodies showed that TuMV-Ab belonged to one of the less common serotypes (JPN).