Potential Allelopathic Interference of <i>Abutilon theophrasti</i> Medik. Powder/Extract on Seed Germination, Seedling Growth and Root System Activity of Maize, Wheat and Soybean

The velvetleaf (Abutilon theophrasti Medik.) is a strong and competitive weed in fields that inhibits the growth of crops. Reports have suggested that allelopathy is one of the reasons for this inhibition; however, the mechanism of this allelopathy remains unclear. In this study, velvetleaf powder/extracts were shown to inhibit seed germination, growth and yield in maize, wheat and soybean through petri dish, pot and field control experiments. We observed a concentration-dependent inhibition of the seed germination rate for all three crops. The root tip structure changed significantly and the embryo even died when irrigated with a high concentration of the extract (10 mg·mL−1). After adding velvetleaf powder, the malondialdehyde (MDA) content in crop seedlings was dose-dependent, and the superoxide dismutase (SOD) activity of maize, wheat and soybean showed the maximum values under treatment with 1.25, 5 and 5 mg·cm−3, respectively. The activity of peroxidase (POD) showed the highest value under the 5 mg·cm−3 treatment in maize and wheat seedlings and under 10 mg·cm−3 treatment in soybean seedlings. However, sugar, protein content and root activity in all three crops was the lowest under the 10 mg·cm−3 treatment. Therefore, velvetleaf may decrease the productivity of three crops by changing the antioxidant enzyme activities, root system activities and root tip structures