Evaluation of Mediterranean-type vegetation for weedicide activity

Abstract

Important differences were found in the response of wheat and lettuce to the treatments, with wheat being generally unaffected. Conversely, a better agreement was found between the sensitivity of lettuce and P. minor. In three (C. villosa, C. ladanifer, and L. stoechas) out of the five donors bioassayed in both species, the same type of answer was found, with an amplification of the effect when P. minor was used. These results support the use of lettuce as a allelopathin indicator species, and suggest that the size of the seed may play a role in the sensitiveness of total germination of seeds to allelopathins. Only two out of the twenty donors investigated appear as promising weedicidal sources, with eight donors in wheat, (two in lettuce) unable to reduce or increase germination by more than 5%, or eleven in wheat and ten in lettuce if the higher concentration is not considered. However, this somehow low effectiveness of donors can be tentatively explained by the fact that only one recollection was made, in mid Winter, when according to previous studies with some of these species water soluble allelopathins are expected to be at low levels (21). Even so, two species, C. ladanifer and L. stoechas were able to reduce the total germination of P. minor by more than 90% without reducing the germination of wheat. Therefore these two species are worth of further studies. These studies should include the investigation of stability of results when soil is involved, which are under way, as well as the search for the compounds responsible for the observed effects.