Seed germination and seedling emergence of Iberian starthistle (Centaurea iberica)

Centaurea iberica has become a problematic weed in some regions of western Iran. Little published data are available in the literature regarding its seed germination and seedling emergence. Therefore, this study was conducted in order to evaluate the effects of different factors on C. iberica seed germination. The highest level of germination of C. iberica was achieved at fluctuating temperatures of 15/25°C (night/day). The seed germination of C. iberica was stimulated by light and little germination occurred under continuous darkness. The pH solution did not have any effect on its seed germination. Centaurea iberica was tolerant to both salt and water stress. The level of seedling emergence was greatest for the seeds that were located on the soil surface, declining with depth, and no seedling emerged from a soil depth of 4 cm. These results indicated that C. iberica has the potential to infest more fields in the western parts of Iran, particularly rainfed areas. Based on the results of this study, crops with a dense canopy and/or planted in narrow‐row intervals could be used to diminish the seed germination of C iberica. In addition, the adoption of tillage systems that bury the seeds of C. iberica under the 4 cm depth would effective in its management.     

变温对烟蚜茧蜂低温贮藏存活特性的影响

 【目的】明确变温对烟蚜茧蜂低温存活的影响,以及不同寄主僵蚜经低温贮藏后羽化率的差异,寻找烟蚜茧蜂在低温贮藏过程中的最适条件及寄主。【方法】以烟蚜和麦二叉蚜僵蚜为试验材料,经不同变温（4℃ 22 h/20℃ 2 h,4℃ 46 h/20℃ 2 h,4℃ 70 h/20℃ 2 h）处理后,比较烟蚜茧蜂羽化率、雄虫比和后足胫节长度的变化。【结果】经不同变温处理的僵蚜与恒定低温（4℃）处理相比,烟蚜茧蜂的羽化率有所提高,寄主为烟蚜的僵蚜羽化率经过4℃ 22 h/20℃ 2 h（T1）处理2周后最高,为78.33%;寄主为麦二叉蚜的僵蚜羽化率经过4℃ 46 h/20℃ 2 h（T2）处理1周后最高,为68.33%。雄虫比变化不显著,均在0.3—0.5。低温贮藏后,寄主为烟蚜的僵蚜羽化率略高于麦二叉蚜,且雄虫比和后代蜂雌雄蜂后足胫节长度差异不显著。【结论】变温处理后的烟蚜茧蜂羽化率高于恒定低温,且变温与恒低温贮藏后雄虫比例均比雌虫比例低。变温贮藏技术更适于烟蚜茧蜂的繁殖与释放。