Allelopathic Effects of Conyza canadensis Water Extract on Seed Germination and Seedling Growth

In order to investigate the effects of allelo-pathic substances of Conyza canadensis on seed germination and seedlings, this study was designed to explore the allelopathic effects of Conyza canadensis water extract (CCE) on pakchoi, spinach and lettuce. Germination rates of three crops (pakcholi, spinach, and lettuce) during the seed germination, root length, seedling height, and fresh weight of two crops (pakcholi and lettuce) during the seedling were measured under different concentrations of CCE treatment (20, 40, 60, 80, 100 g/L). The allelopathic effect index was also calculated. The results showed that CCE had a varying degree of inhibitory effect on the germination rate of the seeds of the three crops. Spinach and lettuce have significant allelopathic effects from C. canadensis. At higher concentration of CCE, the germination rate of spinach and lettuce significantly decreased (P<0.01). After germination, the root length, seedling height, and fresh weight of the crop were measured, and the allelopathic effects were also calculated. It was found that the CCE had a significant inhibitory effect on root length, but it showed a promoting effect on seedling height and fresh weight of pakchoi, and CCE had a "low promotion-high inhibition" effect on seedling height and fresh weight of lettuce.