Hydrogen peroxide as a systemic messenger in the photosynthetic induction of mulberry leaves

Mulberry(Morus alba L.)seedlings were used to test hydrogen peroxide(H_(2)O_(2))as a potential systemic messenger in photosynthetic induction.The upper leaf of mulberry was dark-adapted for 45 min and then illuminated with photosynthetically active radiation(PAR)of1000μmol m^(-2)s^(-1).Photosynthetic induction and H_(2)O_(2) content in the lower leaf was measured.The results show that pre-illumination of the upper leaf promoted photosynthetic induction and increased endogenous H_(2)O_(2) in the lower leaf.Without pre-illuminating upper leaf,exogenous H_(2)O_(2) treatment on the lower leaf promoted photosynthetic induction.The application of diphenyleneiodonium and trichloroacetic acid on petioles of the upper leaf inhibited H_(2)O_(2) increase in the lower leaf,indicating that H_(2)O_(2) transport was from upper leaves to lower leaves through the phloem.The results show that H_(2)O_(2) might serve as a signal messenger to promote rapid induction of photosynthesis of leaves in lower parts of the canopy and enable plants to use light energy more efficiently.

降雨年型变化及竞争对反枝苋和大豆生长的影响

为探索不同降雨年型及栽培方式下外来杂草与本地作物的竞争机制, 为未来全球变化背景下控制外来杂草提供理论依据, 本研究以广泛入侵东北农田生态系统的外来杂草反枝苋(Amaranthus retroflexus)和本地作物大豆(Glycine max)为研究对象, 在遮雨棚内人工模拟正常、欠缺、丰沛三种降雨年型, 采用盆栽实验的方法, 研究两种植物在单种和混种条件下的生长季节动态。结果表明, 降雨丰沛年两种植物的株高和总生物量均大于降雨正常年, 降雨欠缺年则均小于降雨正常年。生长季初期两种植物的根冠比均在降雨欠缺年最高, 说明两种植物均可通过增大根系的生物量分配, 减少地上生物量的分配来适应干旱环境。在三种降雨年型下, 混种时大豆的株高、相对生长速率及总生物量均显著小于单种大豆, 而反枝苋则相反, 尽管有时不显著, 说明种间竞争抑制大豆生长而促进反枝苋的生长, 两种植物之间的竞争是不对称竞争。总的来看, 降雨增加有利于提高大豆的竞争能力, 降雨减少有利于提高反枝苋的竞争能力, 随着生长发育的推移, 这种现象更明显。反枝苋可以在较广的降雨变化范围内保持较高的株高、相对生长速率及生物量, 这很可能是其成为全球范围成功入侵的外来杂草的重要原因之一; 干旱更有利于反枝苋入侵大豆田。