Abstract: Iva xanthiifolia is an alien invasive plant species, with serious threat to biodiversity in Northeast China. In this study, we measured the 1000grain weight, water content, germination indices and endogenous gibberellin levels of seeds collected in different years. To elucidate the germination characteristics of Iva xanthiifolia seeds and their roles in invasion, we explored the effects of photoperiod, cold stratification time, and freezing stress on seed germination and seedling growth with seeds collected in 2019. Results showed that the 1000-grain weight of seeds collected in different years was 1.172-1.311 g, water content was 0.93%-1.26%, and germination rate and endogenous gibberellin content were decreased significantly with the increasing storage time. Iva xanthiifolia seeds required light for germination. The germination rate tended to increase significantly with the duration of light exposure. However, light treatment significantly inhibited seedling hypocotyl elongation. With the time extension of cold stratification at 4 ℃, there was an initial increase and then a decreasing trend for seed germination characteristics. The highest germination rate of 68.3% was obtained after 15 d of treatment. Germination rate, endogenous gibberellin content of seeds, fresh weight of seedlings were significantly reduced by freezing treatment at -20 ℃ and -40 ℃, but the hypocotyl length of seedlings was not significantly affected. Our results showed that deep ploughing before sowing would be an effective measure for field control of Iva xanthiifolia.

Key words: Iva xanthiifolia, seed germination, low temperature, gibberellin.