Allelopathy effects of aqueous rinses of Dittrichia viscosa (L.) on the photosynthesis and cell proliferation of N2-fixing soil cyanobacteriaK Stamatakis1, M Konstantopoulou1Institute of Biology, NCSR Demokritos, Aghia Paraskevi, 15310, Athens,

Abstract

Dittrichia viscosa (L.) W. Greuter (syn. Inula viscosa (L.) Aiton) (Asteraceae) is an evergreen shrub, widespread in the Mediterranean region. Leaf surface of D. viscosa is covered with an epicuticular material that contains numerous terpenoids and phenolic compounds. Aqueous rinses of leaves of D. viscosa showed strong allelopathic effects against a spectrum of different organisms, including plants and pathogens. Rain rinses of D. viscosa end up in the soil. In the present study we investigated the allelopathy effects of the epicuticular rinses from D. viscosa on growth, photosynthetic activity, respiration and heterosyst formation of the N2-fixing soil cyanobacteria Nostoc sp. PCC 7413 and Anabaena sp. PCC 6309. Epicuticular substances from leaves of D. viscosa inhibited cell proliferation of these cyanobacteria in a dose-related manner. These substanses, however, exerted no effect on light-induced photosynthetic electron transport (from water to ferredoxin). This indicates inhibitory action on dark metabolic processes, such as CO2 fixation and respiration. We observed also increased heterocyst formation in the presence of the epicuticular material. This work was supported by a grant (99ED 121) from the Greek Ministry of Industry, Energy and Technology and the European Social Fund.