Allelopathy Effects Of Two Tree Species Of Agroforestry System

Agroforestry ecosystem is an economical, efficient and sustainable land use pattern, which has important economical, social and ecological benefits. In this study, biological testing method was adopted to measure allelopathy effects of aqueous extracts of Eucommia ulmoides and Acer truncatum leaves on seed germination and seedling growth of different crops. Moreover, activities of protective enzyme(SOD, POD, CAT), soluble protein content and membrane lipid peroxidation product MDA of leaves taken from crops watering by different concentrations of aqueous extracts of the two kinds leaves during the same growth period, were determined to probe into the best model of agroforestry. The conclusions are as follows:Aqueous extract of E. ulmoides inhibited seed germination and seedling growth of the three crops. Different concentrations of the aqueous extracts had various effects. The allelopathy showed dual effects on soybean germination and root growth, but not significant. As the aqueous extracts concentration increased, the inhibition effects enhanced, especially on mung bean seedlings growth as well as pepper seed germination and seedling growth. Furthermore, it had different effects on different organs of plant, and the plant height was more easily affected compared to the root length.Aqueous extracts of A. truncatum promoted the seed germination and seedling growth of soybean and mung bean. The inhibition rate were depended on the concentration of the extracts and increased significantly with the concentration of the extracts on seed germination and seedling growth of hot pepper. But whether a lower concentration of the extracts(less than 0.05g/ml) showed inhibiting effects or not needed a further research. Sensitivity of different organs to the allelopathy of A. truncatum was different, and the plant height was more easily affected compared to the root length.Physiological indicators of the three crops were significantly different under different concentrations of water extracts of E. ulmoides leaves. SOD activity of three kinds of receptors was higher than that of control; except pepper, low-concentration of aqueous extracts increased the POD activity of other two crops; high concentration (0.1 g / ml) of water extracts reduced the POD activity of pepper but showed dual effects on the CAT activity of pepper; the MDA content of soybean and pepper was significantly increased compared to the control, indicating the injury to the membrane system was great; it promoted soluble protein content in seedling growth of soybean and mung bean but the high concentration of extracts could reduced soluble protein content of pepper. Aqueous extracts of A. truncatum could make SOD, POD activity of soybeans and POD activity of mung bean increased compared with the control; it promoted the CAT activity of pepper but showed dual effects on that of mung bean; the MDA content of three kinds of receptors was almost the same as that of control, that means aqueous extracts of A. truncatum didn't do damage to the membrane system; it made soluble protein content of the three kinds of receptors increased in fruit period.Considering the facts above, it is suggested that intercropping models of E. ulmoides-mung bean, A. truncatum -soybean, and A. truncatum- mung bean were better.