The effect of gibberellic and salicylic acid on germination characteristics and antioxidant enzymes of anise seed under allelopathic effect of four weed species

In order to study the effect of gibberellic and salicylic acid on germination characteristics and growth of anise under the influence of aqueous extracts of the four weed species: Whitetop (Cardaria draba), Corn Buttercup (Ranunculus arvensis), Wild lettuce (Lactuca virosa) and Cleaver (Galium aparine), with a concentration of 25 gr/l, an experiment was conducted as factorial arranged base on completely randomized design with four replications at the seed science laboratory of Agricultural faculty, Yasouj University in 2015. In this experiment, priming with gibberellic acid was used at two levels of 200 and 400 mg/l for 15 hours at 15°C and salicylic acid in two levels 0.3 and 0.6 mM for 48 hours at 25°C. The results showed that priming with 0.3 and 0.6 mM salicylic acid and control, compared to 200 and 400 ppm gibberellic acid, decreased some characteristics such as rate and percentage of germination, root and shoot length and seedling vigor index anise under allelopathic effect of aqueous extract of Whitetop, Wild lettuce and Cleaver, and non allelopathic condition while gibberellic acid did not have any significantly different with control. The aqueous extract of Corn Buttercup priming prevents germination. Also, among of the antioxidant enzymes, catalase showed the most important role in counteracting the effects of oxidative stress caused by allelopathic effect of aqueous extract of Whitetop, Wild lettuce and Cleaver on anise seed rather than peroxidase and polyphenol oxidase.