| A pot experiment was conducted to study the effects of decomposing leaf litter of Cinnamomum camphor a on growth oflmpatiens balsamina. (receptor). Each pot contained 8 kg soil mixed with different amount of leaf litter (0 g-pot-1, CK; 20 g-pot-1, Ti; 40 g-pot-1, T2; and 80 g-pot-1, T3) respectivly, and morphological feature, resistance physiology and photosynthetic characteristics of Impatiens balsamina were determined on 60 d,80 d and 100 d respectively. Supplementary experiment was carried out to test if there was inhibitory effects of the leaf litter on receptor caused by the chage of physical properties of soil which might disturbed by addition of leaf litter. Leaf litter were steaming for 2 d, to eliminate most of the secondary metabolites of leaf litter, the other methods for experiment were the same as above, the growth indicators were determined on 60 d; Leaf litter and steamed leaf litter were detected by GC-MS respectively to investigate the secondary metabolites, and to make clear that wheather the metabolites in leaf litter were eliminated by steaming, and whether the eliminated conpounds were major allelochemicals or not. The results are as follows:1. The ground diameter and plant height of I, balsamina were inhibited significantly by leaf litter of C. camphora, and the inhibition effect was getting stronger with the increasing amount of the leaf litter addition; On 80 d, the inhibition effect decreased, but the difference were significant as well (P<0.05).2. Photosynthetic pigments and gas exchange parameters of I. balsamina were inhibited significantly on the early decomposition of leaf litter of C. camphora, and the inhibition effect was getting stronger with the increasing amount of the leaf litter addition; On 60d, the Pn, WUE and Ls decreased significantly with the increasing amount of leaf litter (P<0.05), but the difference between all treatments were not significant on 80 d and 100 d (P>0.05); AQY, RY, Lcp, Pnmax and the range of available light intensity decreased with the increasing amount of leaf litter; The chlorophyll fluorescence kinetics parameters of I. balsamina decreased with the increasing amount of leaf litter as well. The results showed that the allelochemicals released by decomposing leaf litter of C. camphora inhibited the photosynthetic characteristics by their inhibitory effects on photosynthetic activity of mesophyll cells, then the growth of I. batsamina were inhibited.3. After 60 d, the activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) increased significantly with the increasing amount of leaf litter (P< 0.05). Malondialdehyde (MDA) content increased significantly with the increasing amount of leaf litter (P<0.05), it indicated that the I. balsamina could not stand the allelochemicals released by decomposing leaf litter of C. camphora, the cell membrane were damaged; The osmotic regulation substances were significantly influenced as well, the free proline content and soluble sugar contents were significantly lower than that in CK, and the protein contents showed a upward trend, it indicated that the substance metabolism of I. balsamina changed considerably by the leaf litter of C. camphora, this may came from the effects on development process of I. balsamina.4. The flowering times of I. balsamina occurs from July to mid-August, and last 6～ 30 d for individual plant. Flowering progress is a unimodal curve with progressive line, which belongs to the pattern of concentrated flowering. The amplitude of flowing decreased significantly under leaf litter treatments; The first bud day, first flower day and full-bloom stage delayed with the increasing amount of leaf litter. The flower quantity decreased with the increasing amount of leaf litter as well, and to a large extent this reduced the ornamental of I. balsamina.5. GC-MS analysis revealed that, the leaf litter contained 57 compounds, and the relative amount of camphor (15.57%) and linalool (14.18%) were highest. Most terpenoids of leaf litter were eliminated after steaming, and there were 15 compounds. The terpenoids such as camphor, linalool and eucalyptol may be major allelochemicals of leaf litter of C. camphora.6. There was no obvious difference of morphological feature and no significant difference in growth indicators between steamed leaf litter treatments and CK. The differences of ground diameter, plant height, Pn, antioxidant protective enzyme and the osmotic regulation substances of steamed leaf litter treatments were not significant compared with CK (P>0.05), and there was no obvious difference in florescence and flower yield between all treatments, this indicated that leaf litter may not significantly inhibit the wheat through its effects on soil physical properties and physical barrier of root growth, and the allelochemicals released by leaf litter of C. camphora may be the main reason of the inhibitory effects on the growth of I. balsamina.Taking into account of various parameters, leaf litter of C. camphora contained allelochemicals such as camphor, linalool and eucalyptol, they may be released into soil on the decomposition process, and then exert significant effects on morphological feature, resistance physiology, photosynthetic characteristics and phenology of I. balsamina. This indicated that leaf litter of C. camphora may show strong allelopathic potential on the decomposition process, therefore, the application of C. camphora should be reasonable in the placement of garden plants and afforestation works, and we should select ornamental plants with strong endurance to allelopathy as possible, to match with C. camphora scientificly and reasonably, so as to maximize ornamental values; In addition, we need to select crops (such as vegetables) with strong endurance to allelopathy, to match with C. camphora, so as to effectively develop ecological and economic benefits of undergrowth crops. |
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