Seasonal variations in UV-B absorbing capacity and allelopathic potential of Dittrichia viscosa leaf rinsates

Abstract

The seasonal variations in the amount and the allelopathic potential of the water-soluble, leaf epicuticular exudates in the Mediterranean ruderal Dittrichia viscosa were investigated. Both parameters peaked during the dry, hot, and sunny summer, confirming the prediction that the seasonal fluctuations should be commensurate with the ascribed antitranspirant and phytotoxic functions. In particular, the drainage of the material to the soil with the heavy autumn rains provides excellent timing for exerting its strong allelopathic interference on seed germination, affording D. viscosa a considerable competitive advantage. Key words: allelopathy, Dittrichia viscosa, leaf rinsates, seasonal variations.