Allelopathy Effect Of Decomposing Leaf Litter Of Cinnamomum Camphora On Pharbitis Nil

In plant configuration of landscaping, the herbaceous plant is often inter planted with ornamental tree species. But unreasonable plants collocation will reduce the effectiveness of afforestation due to the inhabitation effect of tree on the growth of understory, and further more affect the greening effect. Cinnamomum camphora is widely planted in landscaping accompanying with the herbaceous plant just as Pharbitis nil. But it was reported that camphor has allelopathic effect on its adjacent plant, therefore the correct selection and collocation of plants have important significance to obtain on good greening effect. A pot experiment, was conducted to study the effects of decomposing leaf litter of Cinnamomum camphora on growth, phenological traits of Pharbitis nil, as well as modification of these effects by nitrogen application.Three application rates of C camphora leaf litter including 25,50 and 100 g/pot ?denoted by L25, L50 and L100. respectively? and a control ?CK? were implemented. Nitrogen application began on the 35th d of decomposition ?0.39 g urea was divided into three equal portions and added to each pot continuously?. The results were as follows:?1? At early period?after sowing 35 days?, adding leaf litter of Cinnamomum camphora made the content of Nitrate N. decreased significantly and made the content of Microbial Biomass N and Microbial Biomass C increased significantly. With the leaf litter of Cinnamomum camphora decomposition aging increase it released the large amounts of nutrients, which lack of Nitrate N. in soil would be replenished and the content of soil Nitrate N. increased significantly. But changes of nitrogen competition caused by high C/N ratio in the leaf litter could not explain this phenomenon completely. It confirmed that allelochemical released from leaf litter of Cinnamomum camphora and the shortage of nitrogen may inhibite growth of Pharbitis nils together.?2? Fierce suppressive effects of decomposing camphor tree leaf litter were observed on leaf expansion, height, basal diameter and biomass accumulation of morning glory, despite that the leaf litter application rate ranged from 25 to 100 g per 10 kg soil, and the inhibition effect increased with the increasing leaf litter in both the intensity and stability.?3? After adding leaf litter of Cinnamomum camphora, high dose ?L100? treatment of POD activity only decreased significantly at 60 days of seedling growth, and increased significantly at 90 days. By this time, high dose?L100? treatment of SOD activity compared with CK increased significantly, it showed that antioxidant cnzyme had certain scavenging capacity to remove leaf litter of Cinnamomum camphora which released allelochemical, but the content of H₂O₂ and MDA were not change, which could prove that Pharbitis nil had not been hurt of membrane peroxidation.?4? After adding leaf litter of Cinnamomum camphora, except high dose treatment of soluble protein ?SP? decreased significantly at 45 days of seedling growth, others were not changing obviously, but the content of soluble protein?SP? increased significantly from 75 to 90 days of seedling growth and the content of soluble sugar ?SS? was contrary.?5? After adding leaf litter of Cinnamomum camphora, the content of chlorophyll and carotenoid of Pharbitis nil were increased significantly. At the same time, the ratio of chlorophyll a and chlorophyll b were increased, but the gas exchange characteristic were not affected significantly.?6? The flowering dynamics of Pharbitis nil was impacted greatly by the leaf litter with the flower initiation later and the flowering duration longer compared to the control. Although the leaf litter-treated plants exhibited more flowers than the control, their quality was decreased, and hundred-grain weight of the seed was decreased with the increasing leaf litter.?7? Nitrogen ?Urea? application was able to alleviate the allelopathic effect of decomposing leaf litter on growth of Pharbitis nils.The foregoing analysis showed that leaf litter of Cinnamomum camphora in the soil released allelochemicals and it would make available nitrogen lack in the soil of plants. The photosynthetic system and the membrane system of Pharbitis nils could not be damaged, but it would inhibit significantly the leaf area increased, result the diameter and the biomass accumulation reduced. The leaf litter of Cinnamomum camphora which had allelochemicals inhibited the vegetative growth stage in the early days, which postponed the early blooming and the Full-bloom stage in reproductive growth stage and made the total amount and the quality of flowering decline. At last, the ornamental value of Pharbitis nil would be declined. Nitrogen application could be added into the soil which lack of nitrogen and it would ease the inhibitory effect on growth and reproduction of Pharbitis nil.