Abstract
The allelopathic effect of Artemisia princeps L. and Launae sonchoids L. from Taif Governorate, Saudi Arabia was measured in terms of germination rate and radicle length of a bread wheat variety 'Ariana' (Triticum aestivum L.). Diluted extracts of shoot systems were applied to seeds of the test plant. The allelopathy of A. princeps and L. sonchoids varied with the concentration and type of species. The concentrated extracts (3.75 and 5% w/v.) were phytotoxic to germination of wheat. The reduction in the germination percentage reached 15 to 25% and 15 to 30% by treatment with A. princeps and L. sonchoids at concentration of 75 and 100% respectively after 8 days of treatment. The aqueous extract of Artemisia at 25% caused an increase in the root and shoot growth of the wheat seedlings in comparison with that of L. sonchoids and control. However, the growth of root and shoot gradually decreased with increasing extract concentration (50 to 100%). The biomass production parallel with that of root and shoot lengths were activated at low concentration and inhibited at high ones. The frequency and type of fungal species varies with different plants. The number of fungal population (CFU) on the rhizosphere of L. sonchoides was 562 colony/g, while it was 469 colony/g. in the rhizosphere of A. princeps. Ten different fungal genera were isolated from the rhizosphere of each of the two plants, the genus Aspergillus was the most frequent followed by Monilia, Rhizoctonia and Rhizopus.