Abstract:

Exotic weeds have caused serious harm to crop production, orchards, lawns, natural environments and biodiversity in China. Studies on the physiological and ecological characteristics of newly introduced exotic weeds are of practical significance in the predication of their potential distribution areas and their habitats. Knowledge of the physiological response of exotic weeds in stressful environments is also useful in their integrative management. Solidago canadensis, a perennial plant originating from North America, was introduced into China as a horticultural plant in the 1970s. In east China, Solidago canadensis is mainly distributed in the areas along the Shanghai-Nanjing and Shanghai-Hangzhou railways. Solidago canadensis has caused damage to crops in dry fields, impeded the recovery of vegetation in abandoned fields, and was also recorded as one of the most common weeds in suburbs of Shanghai. Therefore, Solidago canadensis has become an invasive weed. In order to understand the adaptive characteristics of Solidago canadensis to invasive environments and predict its potential distributive regions, physiological traits, including the contents of free proline, MDA and soluble sugar, POD activity and POD isozymogram, under different stresses were determined. POD isozymes were examined by polyacrylamide gel electrophoresis, and their isozymograms were analyzed by using “Image Master to Lallab” software. The results show: 1) MDA content of Solidago canadensis treated with 0.00, 0.02 and 0.05 mol·L-1 NaCl solutions are 5.76, 7.29 and 8.06 μmol·g-1 FW respectively, increasing with the elevation of the concentration of NaCl in soil; 2) MDA content of the individuals planted in loamy soils, sandy soils and clay soils is 2.46, 3.25 and 3.96 μmol·g-1　FW respectively, and their POD activity is 4.12, 3.40 and 3.04 △OD min-1·g-1 FW respectively, that is to say, the individuals planted in loamy, sandy soils have lower concentrations of MDA and higher activity of POD than those in clay soil; 3) For the individuals planted under 5 ℃, 25 ℃ and 38 ℃, their soluble sugar content is 1.24%, 1.09% and 0.61% respectively, their free proline content is 53.80, 15.00 and 116.12 μg·g-1 FW, respectively, their POD activity is 2.80, 2.70 and 2.18 △OD min-1·g-1 FW respectively, and their MDA content is 7.35, 5.29 and 7.86 μmol·g-1 FW respectively. Individuals grown 38 ℃ had higher concentrations of MDA, free proline and soluble sugar, and lower POD activity; 4) Compared with plants grown at 25 ℃, the POD isozymogram of Solidago canadensis grown at 38 ℃ is obviously different, while the isozymogram from plants grown at 5 ℃ is similar, indicating that low temperature has little effect on Solidago canadensis. Based on the results above, the following conclusions could be drawn: 1) The well-aerated, slight acid soils with low NaCl concentration are suitable for the growth of Solidago canadensis; 2) higher temperatures are more harmful to Solidago canadensis than low temperatures. It is possible for Solidago canadensis to spread in subtropical and temperate areas in China. Additionally, Solidago canadensis can easy build its clones through its root system.