0971-4693/94 US $ 5.00 Allelopathy Journal 14(1): 59-64 (2004) ©International Allelopathy Foundation 2004 Table: 1, Fig : -
SHORT COMMUNICATION
Activity of water extracts of Cistus ladanifer and Lavandula stoechas in soil on germination and early growth of wheat
and Phalaris minor
ALEXANDRA S. DIAS, L. S. DIAS* and ISABEL P. PEREIRA1
Chemical Ecology Unit, Centre of Ecology and Environment, Universidade de Évora, Ap. 94, 7002-554 Évora, Portugal.
E-Mail: lsdias@uevora.pt
(Received in revised form : September 28, 2004)
Keywords: Allelopathy, Cistus ladanifer, early growth, germination, Lavandula stoechas,Phalaris minor, soil, weed control, wheat.
INTRODUCTION
Phalaris minor Retz. (lesser canary-grass) is an important weed in the Iberian Peninsula (23) and in wheat (Triticum aestivumL.) crop in several countries (18). In 1991, resistance to isoproturon was found in P. minor in wheat crop and since then to other herbicides (9), strengthening the appeal to use naturally occurring chemicals with herbicide activity as an alternative toP. minor control in wheat crops (15).
Two main strategies for discovery of natural products with herbicide activity can be followed. (A). screening of species, cultivars or accessions to select promising sources of phytotoxic products (6,7,14,16), followed by bioassay-directed isolation and identification of active compounds. (B). Fractionation-driven strategy coupling separation and spectroscopic methods and involving the structure elucidation, followed by bioassays of new compounds (4,5).
Regardless of the strategy, to be acceptable as specific herbicides, natural products should inhibit weeds without inhibiting crops. Following the first strategy, we found in a previous screening of 19 shrubs and trees using Petri dish bioassays that only water extracts of Cistus ladanifer L. and Lavandula stoechas L. inhibited the germination of P. minor without affecting wheat (3). However, because of decreased bioavailability of allelopathins in soil, phytotoxicity levels found there are frequently less than those found in laboratory bioassays (17).
Therefore, water extracts of shoot tops of C. ladanifer and L. stoechas were investigated, primarily to find if the inhibition of germination found in laboratory bioassays is changed in soil and, additionally, to evaluate the effects of secondary metabolites ofC. ladanifer andL. stoechas on early growth of the crop and the weed, to decide on the worthiness ofC. ladanifer and L. stoechas as sources of specific herbicides.
Correspondence author,
1Instituto de Ciências Agrárias Mediterrânicas, Universidade de Évora, 7002-554 Évora, Portugal.
