| In order to ascertain the allelopathic potential and mechanisms of different varieties of Trifolium repens under different growth stages,and the seed germination,seedling growth andthe indexes of physiologicalresistance of Echinochloa crus gall i and Echinochloa caudatatreated by aqueous extracts of four different varieties(Persistent.Haifa,Huia,Koala)of Trifolium repens at different concentrations(0.10,0.15,0.20,0.25g·m-1)weredetermined by the indoorbioassaymethod during the seedling,branching and flowering stages.The results are as follows:1.The aqueous extracts of four varieties of white clover on seedling stage significantly inhibited the seed germination and seedling growth of barmyardgrass and long-awn barnyardgrass.The germination potential,germination rate,seedling height,root length,seedling dry weight and root dry weight per plant showed downtrend with increasing concentration of the extracts.Haifa significantly inhibited germination rate of barmyardgrass and long-awn bamyardgrass at 0.25g·mL-1 concentration(P<0.05).The allelopathic effects of donor plants on seedling growth and dry matter accumulation of-receiver materials had significant varietal differences,and had a correlation with the concentration of aqueous extracts.On the whole,the allelopathy of koala on the seedling stagewas moresignificant,and showed inhibition on seed germination and seedling growth of two kinds of receptors,andfrom the combined effect of allelopathic index,we could see that the suppressed effect of koala on bamyardgrass was much stronger thanlong-awn barnyardgrass.In addition,from the enzyme activityand cell membrane permeability of receptors,theaqueous extracts of Persistent and Huia increasedSOD activity of barnyardgrass under 0.10g·mL-1,0.15g·mL-1,0.20g·mL-1 and 0.25g·mL-1 concentrations(P<0.05);Persistent significant increased CAT activity of long-awn barnyardgrass at 0.15g·mL-1 concentration(P<0.05);Huia reduced POD activity of bamyardgrass at 0.10g·mL-1,0.15g·mL-1,0.20g·mL-1 and 0.25g·mL-1 concentrations(P<0.05),butPOD activity of long-awn bamyardgrass showed increasing trend undertreatment of 0.25 g·mL-1;Huia significantly increased MDAcontent of barnyardgrass at 0.20g·mL-1 and 0.25g·mL-1 concentrations(P<0.05),while MDA content of long-awn bamyardgrass had an increasing trend under treatment of four varieties at 0.10g·mL-1,0.15g·mL-1,0.20mL-1 and 0.25g·mL-1 concentrations.2.The aqueous extracts of different varieties of white clover on branching stage had different inhibition on seed germination and seedling growth of two receiver materials.Huia and Haifa inhibited the seed germination of barnyardgrass and long-awn bamyardgrass,respectively;the aqueous extracts of four varieties inhibited seedling height of barnyardgrass and long-awn bamyardgrass,the aqueous extracts of Huia promoted root length and seedling dry weight per plant of barnyardgrass at low concentration,and inhibited them at high concentration.Koala inhibited root lengthof barnyardgrass and long-awn barnyardgrass at high concentrations(P<0.05);The four varieties significantly inhibited seedling dry weight per plant of long-awn bamyardgrass at 0.25g·mL-1 concentrations(P<0.05),but allelopathic effect on its root dry weight per plant was not sigrifieant.Taken together,Huia on branching stage showed a stronger inhibitory effect on seed germination and seedling growth of two receptors.In addition,SOD activityof barnyardgrass decreased under the treatment of Persistent and Haifa,Huia and koala increased the SOD activity of barnyardgrass and long-awn bamyardgrass,respectively;koala significantly increasedPOD activity of barnyardgrass under0.10g·mL-1 eoneentration(P<0.05),but POD activity of long-awn bamyardgrass was significantly decreased at 0.25g·mL-1 concentration(P<0.05),the changes of CAT activity of two receptors were significantly different,and CAT activity of bamyardgrass first increased and then decreased under treatment of Persistent and Haifa and koala,while CAT activity of long-awn bamyardgrassfirst increased and then decreased under treatment of Haifa.MDA content of bamyardgrass had an increasing trend under treatment of four varieties,while MDA content of long-awn bamyardgrassincreased significantly under treatment of Haifa at 0.25g·mL-1 concentration(P<0.05).3.The aqueous extracts of different varieties of white clover on flowering stage had different impact on seed germination and seedling growth of receiver materials,and had a concentration effect.Overall,the inhibition effect of Huia on seed germination of two kinds of receptors were significantly stronger than the other three varieties.The inhibition effect of Persistent on seedling height of barnyardgrass and long-awn barnyardgrass was strongest.In addition,Huia had strongest inhibition on root length of barnyardgrass and long-awn bamyardgrass;Persistent had strongest inhibition on seedling and root dry weight per plant of barnyardgrass.Persistent,Haifa and Huia significantly inhibited seedling dry weight per plant of long-awn bamyardgrass at 0.25g·mL-1 concentrations(P<0.05).Haifa and Huia had stronger inhibitory effect on root dry weight per plant of long-awn bamyardgrass.In addition,aqueousextractsof four varieties had no significant effect on SOD activity of bamyardgrass and long-awn barnyardgrass(P>0.05);Persistent significantly increased CAT activity of barnyardgrassat 0.15g·mL-1 concentration(P<0.05),but significantly reduced CAT activity of long-awn barnyardgrass at 0.10g·mL-1,0.15g·mL-1,0.20g·mL-1 and 0.259·mL-1 concentrations(p<0.05);Huia significantly increasedPOD activity of two receptorsat 0.10g·mL-1 concentration(P<0.05),and Huia significantly increased MDA content of bamyardgrass at 0.15g·mL-1 eoncentration(P<0.05),but four varieties had no significant effect on MDA content of long-awn bamyardgrass(P>0.05). |
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