排序方式： 共有3条查询结果，搜索用时 0 毫秒
1
1.
In recent years flaxleaf fleabane has become a widespread and difficult-to-control weed in no-tilled fallowed fields, where weeds are controlled by applications of glyphosate, in annual cropping systems of north-east Australia. Fifty-two populations, collected in a national survey from agricultural and non-agricultural areas, were tested in two glyphosate dose-response pot experiments. In two subsequent pot experiments, a sub-set of these populations was tested with a field rate of glyphosate when weeds of two ages were grown at different soil moistures. In the first and second experiments, most populations collected from chemical fallowed or cropped fields in north-east Australia had GR50 (estimated dose for 50% biomass reduction) values three to six times greater than the susceptible populations, indicating low levels of glyphosate resistance. Several populations from roadsides adjacent to chemical fallowed or cropped fields also had higher GR50 values, indicating movement of seeds from resistant plants. In the third experiment, weed biomass of all populations from chemical fallowed or cropped fields was 70-98% of unsprayed compared to 2-3% for the susceptible populations, irrespective of weed age or soil moisture. In the fourth experiment which treated older weeds, the response of several resistant populations to glyphosate was unaffected by differences in weed age and soil moisture, whereas the biomass of the other resistant populations was greater following spraying of older and/or moisture stressed plants compared with smaller non-stressed plants. Thus, exclusive reliance on glyphosate for fallow weed control in this region has resulted in the evolution of resistance in flaxleaf fleabane populations in a cropping system with annual non-transgenic crops. Prolific production of windborne seeds, combined with poor control associated with spraying large moisture-stressed weeds, is likely to have contributed also to flaxleaf fleabane becoming such a problem weed. 相似文献
2.
小飞蓬(Conyza canadensis(L.)Cronquist)是我国分布最广的入侵植物之一。根据文献搜集和生物信息数据库,获得有效数据共325个,结合ArcGIS与SPSS相关性分析筛选获得8个气象因子,基于最大熵模型(MaxEnt)预测了小飞蓬的潜在适生区。结果表明:基于MaxEnt模型预测小飞蓬在中国的潜在适生区ROC曲线,AUC平均值为0.971,预测结果极好;通过刀切法(jackknife method)分析表明,最热季度的降水量(BIO_18)、温度季节性变化标准差(BIO_4)、年平均气温(BIO_1)、最冷季度的降水量(BIO_19)4个气象因子对小飞蓬的分布影响最大;小飞蓬在中国的潜在适生区分布广泛,秦岭淮河以南的各个省份以及秦岭淮河以北至辽宁省南部均为小飞蓬高适生区范围。随着气候变化,2050年小飞蓬潜在适生区面积与当前相比增加了559 016.09km2,2070年小飞蓬潜在适生区面积与当前相比增加了68 423.65km2。本研究结果实现对小飞蓬入侵动态预警,为进一步防范工作提供了一定的理论基础。 相似文献
3.
为了科学地掌握克朗奎斯特被子植物分类系统，按不同的分类等级对我国常见果树进行电脑分级管理，制成课件形式，其中被子植物部分按现今较流行的克朗奎斯特分类系统。首先对各亚纲、目及科进行了一个总的叙述，针对所选取的常见的科、属、种，列举了各种果树的简要文字说明和图片，使其图文并茂，构成一个可视化平台。在该平台中不仅可以浏览网页，还也可以查询某种果树。在论文的电子版制作中，基于B／S系统，主要采用Microsoft Frontpage、Dremweaver ，还结合 Ultraedit手写源代码制作网页，采用 Microsoft Access数据库与ASP（Active Server Pages）制作查询系统。其中用到Photoshop等图像处理软件对网页进行美化处理，易于掌握，可一定程度上满足园艺专业的老师和学生对果树知识教与学的要求。 相似文献
1