ORIGINAL PAPER Evaluation of in vitro shoots of Artemisia judaica for allelopathic potential H. Y. Zeng Æ A. R. Alan Æ P. K. Saxena Received: 22 August 2008 / Revised: 22 June 2009 / Accepted: 24 July 2009 / Published online: 23 August 2009 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2009 Abstract Allelopathic performance of in vitro fresh green shoot, green, and brown shoot extracts including dry shoot powders of Artemisia judaica was evaluated through bioassay-guided studies using lettuce under laboratory conditions. The dry powders caused strong germination and growth inhibition of the lettuce seed tested. The green and brown shoot crude extracts of A. judaica also produced a strong germination and growth inhibition. The magnitude of inhibition in experiments with the brown shoot extracts was higher than that with the green shoot extracts. The lettuce seed incubated together with the fresh green shoots showed that the growth of lettuce was stimulated, while the germination of seed was delayed. The results show that there are different allelochemicals present in the exudates and volatiles of A. judaica. The shoot extracts under assay conditions showed a dose-dependent free radical scaveng- ing effect of DPHH and a dose-dependent reduction of chlorophyll content from lettuce leaves. The antioxidant potential and total chlorophyll content of the lettuce leaf declined in all the shoot extract treatments. These results clearly indicate that the in vitro shoot of A. judaica con- tains some strong biologically active allelochemicals that are involved in plant growth regulation. Keywords Artemisia judaica  Allelopathy  Growth inhibition  Antioxidant activity  Lettuce Introduction Allelopathy is a phenomenon by which some plants release chemical compounds into the environment through root exudation, leaching by dew and rain, and volatilization or decaying plant tissues. Several classes of allelopathic substances, such as monoterpenes and phenols, are pro- duced naturally by most plant species. These compounds are usually synthesized in the leaves, which fall to the ground during periods of stress. The allelochemicals may affect the germinations and growth of other plants. Alle- lopathy plays an important role in agroecosystems leading to a wide range of influences and interactions in biotic communities. Such influences and interactions are mainly a result of the release of allelochemicals from donor plants that generally have harmful effects on the receiver plants but a selective benefit to the donor. The effects of alle- lopathy on the germination and growth of plants may occur through a variety of mechanisms including reduced mitotic activity in root and hypocotyl, suppressed hormone activ- ity, reduced rate of ion uptake, inhibited photosynthesis, respiration and protein formation, and decreased perme- ability of cell membranes and/or inhibition of enzyme action (Rice 1984). The allelochemicals are considered resources for developing herbicides, plant growth stimu- lators, and pharmaceuticals. The genus Artemisia is known to contain species with allelopathic tendencies, and several studies have reported allelopathic activity in the genus (Robertson 1947; Reid 1964; Friedman et al. 1977; Hoffman and Hazlett 1977; Escudero et al. 2000), identifying (possible) germination Communicated by B. Barna. H. Y. Zeng Institute of Biotechnology, University of Xiangtan, Xiangtan, Hunan 411105, China e-mail: hongyanzeng99@hotmail.com H. Y. Zeng  A. R. Alan  P. K. Saxena (&) Department of Plant Agriculture, University of Guelph, Guelph, ON N1G 2W1, Canada e-mail: psaxena@uoguelph.ca 123 Acta Physiol Plant (2009) 31:1237–1248 DOI 10.1007/s11738-009-0360-x