[Allelopathy of rape on seed germination and seedling growth of three crops]

Rape is an important green manure crop in China. It could increase soil fertility, but might have allelopathic effect on subsequent crops. We examined the effects of rape water-extract (at 0.025, 0.05 and 0.1 g·mL^-1 concentrations) on seed germination, seedling growth, physiology and biochemistry of three crops including oat (Avena sativa), corn (Zea mays), and sunflower (Helianthus annuus). The results showed that water extract of rape did not affect seed germination rate of three crops. Oat had a trend of "low promotion and high inhibition", while sunflower had a trend of inhibition. High concentration of rape water extract inhibited root and stem length of oat seedling, corn seedling stem length and sunflower seedling root length, while low concentration treatment promoted root and stem length of corn seedling. The highest protein contents in oats and sunflower presented at the treatment of 0.05 g·mL^-1, and that of corn at the treatment of 0.025 g·mL^-1, which were significantly higher than that of control. The proline contents in sunflower decreased significantly in different treatments, while the proline content of corn was significantly higher than that of control at 0.05 g·mL^-1. POD activity of corn was at a maximum at 0.05 g·mL^-1, and that of sunflower was at 0.025 g·mL^-1, which were significantly higher than control. There was no significant difference between control and other concentration treatments. The SOD activity of oat was significantly decreased at 0.025 g·mL^-1. There was no significant difference in CAT activity between the three crops and the control. The MDA content in sunflower seedlings increased significantly at 0.1 g·mL^-1, while that in corn seedlings was significantly lower than control. Our results indicated that the allelopathic inhibitory effect of rape water extract was the strongest on sunflower, followed by corn and oat.