study of allelopatic mechanism of ferula flabelliloba aquatic extract in germinating alyssum szivitsianum seeds

some reports indicated that terpenoides allochemicals material induced oxidative stresses during seed germination phase. α-pinnen, as one of important allechemical monoterpenoids, reported from species of several plant family and especially ferula flabelliloba from apiaceae. in order to investigate the allelopatic effect of f. flabelliloba and the time of sampling on physiological and biochemical processes during seed germination of a. szivitsianum a factorial experiment was conducted in a completely randomized design with four replication. the first factor was allelopatic materials in three levels including 10% leaf aquatic extract of f. flabelliloba (gathered in vegetative period), 5 mg l-1 α-pinnen and control and the second factor was time of sampling in 5 levels including sampling in 24,48,72,96 and 120 hour after imbibitions. results showed that, both leaf aquatic extract of f. flabelliloba and α-pinnen solution decreased a. szivitsianum seed germination and viability. the velocity of seed losses viability was faster in the seeds exposed in plant extract. the amount of solute leakage, hydrogen peroxide and malondialdehyde increased in seeds treated with allelochemical materials. in addition, the activities of the antioxidative enzymes of superoxide dismutase (sod), catalase (cat), ascorbare peroxidase (apx) and glutathione reductase affected by allelochemicals and time of sampling. the highest activities of antioxidative enzymes and h2o2 concentration were measured in seeds that germinated under plant water extract and sampled after 120 hours. my results demonstrated that despite the activation of antioxidant system by f. flabelliloba phytotoxin and α-pinnen, reactive oxygen species accumulation caused cellular damage, which resulted in the decrease of seed viability. it seems that the increased level of scavenging enzymes indicated their induction as a defence mechanism in response to allelochemicals.