Characterization and quantitative assessment of interspecific and intraspecific penetration of below-ground vegetation by cogongrass (Imperata cylindrica (L.) Beauv.) rhizomes     

D. CHRISTOPHER HOLLY  GARY N. ERVIN 《Weed Biology and Management》2006,6(2):120-123

Cogongrass ( Imperata cylindrica (L.) Beauv.), an invasive C4 perennial grass, negatively influences native plant communities by forming dense monotypic stands that alter ecosystem properties and lower local species diversity. A hypothesized mechanism by which cogongrass achieves competitive dominance is a novel use of below-ground vegetative disturbance of neighboring vegetation (i.e. puncturing). However, very little empirical evidence is found in the peer-reviewed literature to quantify this phenomenon, much less establish it as a true form of competitive interaction. The present field study was conducted to quantify the occurrence of rhizome-mediated, below-ground vegetative penetration, both interspecifically and intraspecifically, document how this phenomenon is influenced by spatial location relative to the cogongrass stand, and determine the role that above-ground and below-ground biomass might have in the process. Analyses of 100 sod samples indicated that rhizome-mediated, below-ground vegetative penetration is a much larger intraspecific phenomenon than an interspecific one. The data also strongly suggested spatial location as a significant factor, with most penetrations occurring in the interior of a cogongrass stand as opposed to the advancing border. Significant correlations between rhizome-mediated, below-ground vegetative penetration and above-ground cogongrass biomass were found in the overall plot analysis and most strongly in the advancing border of the cogongrass stands.  相似文献   

First report of the Q biotype ofBemisia tabaci in Japan by mitochondrial cytochrome oxidase I sequence analysis     

S. Ueda  J. K. Brown 《Phytoparasitica》2006,34(4):405-411

The recent upsurgence ofBemisia tabaci (Genn.) as an important insect pest and vector ofTomato yellow leaf curl virus (TYLCV) is directly linked to serious damage to tomato crops grown throughout Japan. The molecular genetic identification and phylogenetic relationships of 12B. tabaci populations collected from representative locations in Japan were determined based on the mitochondrial cytochrome oxidase I (mtCOI) sequence. Phylogenetic analysis of the whitefly mtCOI sequence indicated that both the invasive B and Q biotypes now occur in Japan. The Q biotype was found at four locations: Mihara in Hiroshima, Nishigoshi in Kumamoto, Miyanojo and Okuchi in Kagoshima prefectures; the remaining eight collections were identified as the B biotype. This is the first report of the introduction of Q biotype in Japan. http://www.phytoparasitica.org posting July 21, 2006.  相似文献   

Effects of previous leaf injuries to spring canola on western black flea beetle (Phyllotreta pusilla) feeding     

N. Demirel  W. Cranshaw 《Phytoparasitica》2006,34(1):87-91

Two trials were conducted in 2002 with 14-day-old spring canola (Brassica napus L.) seedlings to evaluate the effects of previous leaf injuries of different cultivars on subsequent injury by western black flea beetle (WBFB),Phyllotreta pusilla Horn (Coleoptera: Chrysomelidae), under greenhouse conditions in Colorado (USA). Previous leaf cutting was found to have only minor effects on subsequent infestation and injury by WBFB, and such effects may be cultivar-specific. Only IMC205 showed significant differences by more than one parameter during these studies; cultivars Excel and 46A65 showed no responses in injury or infestation between previously cut and uncut plants. http://www.phytoparasitica.org posting Nov. 14, 2005.  相似文献   

转基因植物对蜂类昆虫安全性     

田岩  ;张永军;赵奎军;吴孔明;彭于发;郭予元 《植物保护》2006,32(5):8-12

随着转基因植物的大规模商业化种植,其对蜂类等有益昆虫的影响成为研究转基因生物风险评估的主要内容。一方面蜜蜂等蜂类取食植物花粉,有可能直接接触到杀虫蛋白,产生毒性效应;另一方面转基因植物的性状、营养成分等可能发生变化,对蜜蜂的行为可能产生潜在影响。本文综述了目前转基因植物对蜂类昆虫安全性研究进展,并提出克服转基因植物对非靶标生物可能的负面效应的治理对策,以期对转基因植物生物安全性的研究提供科学依据。  相似文献   

我国园艺作物核心种质研究进展   总被引：1，自引：0，他引：1  

李保印  张启翔 《果树学报》2007,24(2):204-209

综述了我国园艺植物核心种质研究进展,针对目前园艺作物核心种质研究现状与问题,提出了今后园艺作物核心种质研究方向,即要加强对取样策略、分组原则等问题的研究,加速收集园艺作物种质资源的基础数据、特征数据、评价鉴定数据及分子检测数据,尽快建立一批我国原产的、重要的园艺作物的核心种质,以提高园艺作物种质资源利用效率,提升种质创新能力,从而推动我国园艺产业快速发展。  相似文献   

北方紫竹盆景制作技术     

罗镪 《北方园艺》2007,(8):175-176

综述了紫竹的地域分布、生态习性、现赏价值,重点从母竹的选择和挖掘方法、上盆技术、盆景的养护管理措施等3个方面研究总结了紫竹盆景制作的关键技术,比较分析了紫竹盆景最适宜的租摆场所和所表达的意境.  相似文献   

哀牢山壳斗科三种蜜源植物资源的初步研究     

张学文  李建军 《蜜蜂杂志》2007,27(10):8-9

壳斗科植物具有丰富花蜜和花粉.2007年4～7月,对云南哀牢山中山湿性常绿阔叶林壳斗科蜜源植物开发利用的潜力进行了初步研究.在该季节,中华蜜蜂可利用的壳斗科植物主要有木果石栎、景东石栎和腾冲栲.3种植物的花期均为50天左右.放置在原始森林林缘蜂群的取蜜量明显高于放置在原始森林内和附近次生林的蜂群.一群放置在林缘、群势为5标准框的中华蜜蜂蜂群,一个花期可以取蜂蜜约5 kg.  相似文献   

Analysis and modeling of gas exchange processes in Scaevola aemula     

Soo-Hyung Kim  Paul R. Fisher  J. Heinrich Lieth 《Scientia Horticulturae》2007

Scaevola aemula is a popular ornamental crop cultivated as a bedding plant or for hanging baskets. We characterized gas exchange properties of S. aemula ‘New Wonder’ in response to photosynthetically active radiation (PAR), carbon dioxide concentration, and leaf temperature. Net CO₂ assimilation rate (A) was responsive to CO₂, exhibiting a saturation when intercellular CO₂ concentration (C_i) was greater than 600 μmol mol⁻¹. Net CO₂ assimilation rate and dark respiration rate (R_d) were 23.1 and 2.3 μmol m⁻² s⁻¹, respectively, at 25 °C and PAR = 1500 μmol m⁻² s⁻¹. Net CO₂ assimilation rates were similar at leaf temperatures between 20 and 30 °C but significantly reduced at 15 °C. These gas exchange results were used to test the extendibility of a coupled gas exchange model previously developed for cut-roses. Utilizing the gas exchange data measured at 25 °C leaf temperature, several model parameters were independently determined for S. aemula. Model predictions were then compared with observations at different leaf temperatures. The model predicted the rates of net CO₂ assimilation and transpiration of S. aemula reasonably well. Without additional calibration, the model was capable of predicting the temperature dependence of net CO₂ assimilation and transpiration rates. Applying the model to predict the effects of supplemental lighting and CO₂ enrichment on canopy photosynthesis and transpiration rates, we show that this model could be a useful tool for examining environmental control options for S. aemula production in the greenhouse.  相似文献   

A method for mapping the distribution of willow at a catchment scale using bi-seasonal SPOT5 imagery   总被引：1，自引：0，他引：1  

M NOONAN  & C CHAFER 《Weed Research》2007,47(2):173-181

This study showed that seasonal imagery acquired at specific stages of phenology can be used to improve the mapping accuracy of invasive willow at a catchment scale. SPOT5 XI (10 m) satellite imagery was acquired for early autumn and winter to represent the phenological stages of leaf cover and leaf fall respectively. Four classification regimes were evaluated using single‐ and bi‐seasonal composite imagery to determine the most accurate method. Significant spectral noise was found in willow populations, especially in the winter image, due to the effects of undergrowth exposure, shadowing, topography and boundary‐mixed pixels. Two noise reduction techniques were applied to the bi‐seasonal composite image to improve the classification results. The noise‐reduced bi‐seasonal composite image was classified using the spectral angle mapper (SAM) algorithm before importation into a geographical information system. Aerial photography was used to reduce the errors of commission associated with misclassification of pastures. The class accuracy achieved for willow using the method described in this study was 77.5% (Kappa =0.87). The high cost of eradicating willow means that managers must establish priorities for control; this technique can provide a powerful tool for prioritizing control programmes and for monitoring results at a catchment scale.  相似文献   

浑善达克沙地药用种子植物区系分析     

王素巍  刘果厚 《干旱区资源与环境》2007,21(12):133-136

本文应用植物区系地理学的基本原理,对浑善达克沙地药用种子植物的科、属组成和属的地理成分进行了统计分析,结果表明:(1)本区有药用种子植物78科,270属,504种。(2)优势科现象明显;单种属、寡种属数量最多,属级水平的多样性丰富。(3)该区系包含14个分布区类型,温带性质的成分占绝对优势,热带性质的成分不多,特有程度低。(4)资源区域间分布差异大;有一定的古老成分。  相似文献