Phytotoxicity of Euphorbia helioscopia L. on Triticum aestivum L. and Pisum sativum L.

Invasive field weeds, such as Euphorbia sp., represent main threat for crop productivity. The present work was conducted to evaluate the phytotoxicity of Euphorbia helioscopia on wheat (Triticum aestivum L.) and pea (Pisum sativum L.). The influence of aqueous extract from shoot of E. helioscopia, at different rates (1.0%, 2.5%, 5.0%, and 10.0%; w/v), on germination and early seedling growth of wheat and pea as well as some of the synchronized physiological aspects was investigated. E. helioscopia aqueous extract severely affected the germination in a concentration dependent manner. Plumule and radicle length, as well as their fresh and dry masses were markedly reduced. Moreover, amylase activity and total soluble sugars were significantly reduced in response to treatment with aqueous Euphorbia extract, in both test plants, whereas, proteolytic activity showed marked improvement. The linear regression analysis revealed the presence of positive linear correlation between germination rate and amylase activity. The stress markers such as proline, phenolics and flavonoids were markedly accumulated upon treatment with E. helioscopia extract. The increment in the level of total phenolics was concomitant with an improvement in phenylalanine ammonia lyase and peroxidase activities. High performance liquid chromatography analysis of E. helioscopia extract revealed the presence of two cinnamic acid derivatives (caffeic and p-coumaric acids), two benzoic acid derivatives (vanillic and syringic acids) and a flavanonol (Dihydroquercetin). To our knowledge, this is the first study to investigate the physiological implications underlying the phytotoxicity of E. helioscopia.