Soil microorganisms alleviate the allelopathic effect of Eucalyptus grandis × E. urophylla leachates on Brassica chinensis

Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis x E. urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden (soil A) or a Eucalyptus plantation (soil B) and half of each soil was sterilized to remove microbes. These soils were then treated with E. grandis x E. urophylla leachates for 0-72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachate-treated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils. Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.

广林九号桉叶精油的抑菌活性研究

研究了广林九号桉[Eucalyptus urophylla×Eucalyptus grandis(Guanglin 9)]叶精油的抑菌活性。利用气相色谱-质谱联用技术分析桉叶精油的化学成分,采用滤纸片法评价其抑菌活性,以平板稀释法测定了精油的最小抑菌浓度。广林九号桉叶精油的主要成分有:1,8-桉叶油素(40.844%)、α-蒎烯(24.221%)、α-松油醇(4.661%)、反式-松香芹醇(3.735%)、龙脑(2.762%)、乙酸α-松油脂(3.592%)和松香芹酮(1.978%)。广林九号桉叶精油对测试的菌种均有良好的抑菌活性,但对细菌和霉菌的抑菌效果有所差异。对金黄色葡萄球菌(Staphylococus aureus)、枯草芽孢杆菌(Bacillus subtilis)、大肠杆菌(Escherichia coli),黄曲霉(Aspergillus flavus)、黑曲霉(Aspergillus niger)和橘青霉(Penicillum citrinum)的最小抑菌浓度分别为10、20、20、10、10、5 mL/L。