Puig Carolina G, Reigosa Manuel J, Valentão Patrícia, Andrade Paula B, Pedrol Nuria
Department of Plant Biology and Soil Science, University of Vigo, Vigo, Spain.
REQUIMTE/LAQV, Laboratory of Pharmacognosy, Department of Chemistry, University of Porto, Porto, Portugal.
PLoS One. 2018 Feb 13;13(2):e0192872. doi: 10.1371/journal.pone.0192872. eCollection 2018.
In the worldwide search for new strategies in sustainable weed management, the use of plant species able to produce and release phytotoxic compounds into the environment could be an effective alternative to synthetic herbicides. Eucalyptus globulus Labill. is known to be a source of biologically active compounds responsible for its phytotoxic and allelopathic properties. Our previous results demonstrated the bioherbicide potential of eucalyptus leaves incorporated into the soil as a green manure, probably through the release of phytotoxins into the soil solution. Thus, the aims of this study were to understand the phytotoxicity of the eucalyptus leaves aqueous extract applied in pre- and post-emergence, and to identify and quantify its potentially phytotoxic water-soluble compounds. The effects were tested on the germination and early growth of the model target species Lactuca sativa and Agrostis stolonifera, and on physiological parameters of L. sativa adult plants after watering or spraying application. Dose-response curves and ED50 and ED80 values for eucalyptus aqueous extracts revealed pre-emergence inhibitory effects on both target species, effects being comparable to the herbicide metolachlor. While spraying treatment reduced the aerial and root biomass and increased the dry weight/fresh weight ratio of lettuce adult plants, watering application reduced protein contents and chlorophyll concentrations with respect to control, reflecting different modes of action depending on the site of phytotoxin entry. Via HPLC analyses, a total of 8 phenolic compounds (chlorogenic, two ρ-coumaric derivatives, ellagic, hyperoside, rutin, quercitrin, and kaempferol 3-O-glucoside) and other 5 low weight organic acids (citric, malic, shikimic, succinic and fumaric acids) were obtained from aqueous extract, the latter being identified for the first time in E. globulus. Despite some phytotoxic effects were found on lettuce adult plants, the use of eucalyptus aqueous extract would be discarded in post-emergence, whereas it was promising as a pre-emergence bioherbicide.
在全球范围内寻找可持续杂草管理新策略的过程中，利用能够产生并向环境中释放植物毒性化合物的植物物种，可能是替代合成除草剂的一种有效方法。蓝桉（Eucalyptus globulus Labill.）是已知的具有生物活性化合物的来源，这些化合物赋予了它植物毒性和化感作用特性。我们之前的研究结果表明，作为绿肥掺入土壤中的桉树叶具有生物除草剂潜力，这可能是通过向土壤溶液中释放植物毒素实现的。因此，本研究的目的是了解桉树叶水提取物在芽前和芽后施用时的植物毒性，并鉴定和定量其潜在的植物毒性水溶性化合物。对模式目标物种莴苣（Lactuca sativa）和匍匐翦股颖（Agrostis stolonifera）的发芽和早期生长，以及莴苣成年植株在浇水或喷雾施用后的生理参数进行了测试。桉树叶水提取物的剂量-反应曲线以及ED50和ED80值显示，对两种目标物种均有芽前抑制作用，其效果与除草剂异丙甲草胺相当。喷雾处理降低了莴苣成年植株的地上部和根部生物量，并增加了其干重/鲜重比，而浇水处理相对于对照降低了蛋白质含量和叶绿素浓度，这反映了取决于植物毒素进入部位的不同作用方式。通过高效液相色谱分析，从水提取物中总共获得了8种酚类化合物（绿原酸、两种对香豆酸衍生物、鞣花酸、金丝桃苷、芦丁、槲皮苷和山奈酚3-O-葡萄糖苷）和其他5种低分子量有机酸（柠檬酸、苹果酸、莽草酸、琥珀酸和富马酸），其中后5种有机酸是首次在蓝桉中鉴定出来的。尽管在莴苣成年植株上发现了一些植物毒性作用，但桉树叶水提取物在芽后施用时不适用，而作为芽前生物除草剂则具有前景。
