Study on environmental conditions of seed germination and seedling growth of invasive plant Amaranthus palmeri S. Watson.
To determine germination, seedling growth and vigor indices from the aspects of germination temperature, light, moisture, salt environment, and artificial aging, the germination test was performed on Amaranthus palmeri seeds under different environmental conditions. It was found that: i. Amaranthus palmeri seeds were capable of germinating at 15-40°C, and germination rate (GR) increased as temperature increased; ii. Seedling growth rate was highest at 25°C; iii. Light delayed seed germination and inhibited seedling growth; iv. Seed germination was inhibited when water potential was lower than -0.32 MPa, while a very low GR was detected when water potential was lower than -1.10 MPa; v. Seed GR was inhibited at 4 g/L salt levels, while seedling growth rates were strongly inhibited at 8 g/L salinity; vi. Seed vigor was inhibited after artificial aging for 6 days, and all growth indices were inhibited after artificial aging for 15 days, however, germinability was 69%. Amaranthus palmeri exhibited a higher risk of invasion in areas with hot and humid climates as well as with low degrees of soil salinization. Exposure of seeds to light can reduce the competitiveness of the Amaranthus palmeri population and seeds preserved in higher soil temperature can shorten their life.