STUDYING THE ALLELOPATHIC EFFECTS OF SHOOT AND ROOT WATER EXTRACTS OF HOARY CRESS (Cardaria draba L.) ON GERMINATION AND SEEDLING GROWTH OF WHEAT

In order to evaluate the effect of water extracts of above-ground, below-ground and a mixture of above-ground and below-ground organs of hoary cress on germination and seedling growth of wheat, a factorial experiment based on completely randomized design with four replications was conducted at faculty of agriculture, islamic azad university, birjand branch, iran in 2008. treatments included water extracts of different organs of hoary cress (above-ground, below-ground and an equal mixture of above-ground and below-ground) and five levels of water extract concentration including 5, 10, 20, 40 and 80% (v/v) plus a control (distilled water). results showed that different organs of hoary cress and concentration of water extracts had a significant effect on germination and seedling growth wheat compared with control. increasing concentration of water extract of different organs of hoary cress significantly decreased germination percentage, germination rate and also length and weight of radical and coleoptile of wheat. estimation of three-parameter logistic model showed that concentration required for 50% reduction of maximum germination was 18.72, 43.36 and 37.02% for aboveground, belowground and mixture of organs, respectively, suggesting a stronger allelopathic impact of aboveground organs of hoary cress compared with belowground organs.