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A pot experiment was carried out to study the effects of addition of leaf litter of Cinnamomum septentrionale on growth and resistance physiology of Brassica rapa during the decomposition process.Each pot contained 8 kg of soil mixed with 0,20,40,80 g leaf litter of C.septentrionale respectively.Seeds of B.rapa were sawed on 13th April,a week later after litter addition.Height,biomass,leaf area and several indexes of resistance physiology were determined at 30,40,50,60 and 70 d after sowing.Supplementary experiment was conducted as following: leaf litter of C.septentrionale after soaking in water for 48 h was steamed for 4 h,and the other methods were the same as above.The results were stated as following.(1) In formal experiment,height and biomass of B.rapa were inhibited significantly in 70 days.The activities of superoxide dismutase(SOD),peroxidase(POD) and catalase activity(CAT) in leaves of B.rapa increased on the condition of low litter content and short time of decomposition,but decreased on that of higher litter content and longer time of decomposition.The activities of CAT went up significantly in 70 d.The content of sugar and soluble protein in leaves of B.rapa increased in low litter content and short time of decomposition,whereas,decreased in that of higher litter content and longer time of decomposition.The affect intensity of leaf litter on B.rapa was from strong to weak in pace with prolonged decomposition time.The compound negative effect of 80 g treatment was the strongest,that of 40 g was weaker,and that of 20 g was the weakest.After 60 days,the discrepancy size of some indicators(e.g.biomass and SOD) of B.rapa among treatments had reduced.This implied that the effects were weakened.The reason might be that the allelochemicals in the litter of C.septentrionale had obviously reduced or almost no longer released.(2)In supplementary experiment,after sowing for 70 d,there was no obvious difference of morphological feature and no significant difference in biomass,height,leaf area between litter addition and control.It indicated that soil physical properties were not influenced obviously and the growth of B.rapa was not affected by addition of litter.On the whole,the leaf litter of C.septentrionale had a fierce allelopathic effect on B.rapa during its initial decomposition process in soil. |
