Effects of Temperature on Seed Germination of Invasive Plant Rorippa amphbia (L.) Besser

Aims: Global warming and biological invasion are major environmental issues faced in the world. In the study, Rorippa amphibia, a perennial invasive clone plant in northern China, was used as a material to study the germination characteristics of the seeds at different temperatures.

Study Design: Germination test of R. amphibia seeds at different temperature was studied by means of laboratory culture. The germination percentage, germination index, germination potential, bud height and root length of the seeds were determined.

Place and Duration of Study: Samples were collected from the west side of the swimming pool of Shenyang Agricultural University of Liaoning Province in August 2017. Experiments were done in the College of Biological Science and Technology, between October 2017 and June 2018.

Methodology: The petri dish method was used in the experiment. Fifty seeds were randomly selected and soaked in distilled water for 12h. The seeds were placed in a petri dish covered with double filter paper, cultured at 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ and 40℃ in light incubators for 12h darkness and 12h light (4000lux), with 3 repeats per processing. Seed germination was based on embryo root breakthrough seed coat ≥ 1 mm. During the experiment, the numbers of seed germination were recorded every day, and the filter paper was kept moist until there was no new seed germination for 2 consecutive days, which was regarded as the end of germination. The numbers of seed germination should be counted regularly every day, and the beginning and duration of germination should be recorded. The germination rate, daily germination rate, germinating potential, germinating index and vigor index of R. amphibia seeds at different temperature were calculated by measuring bud height and radicle length on the 10th day after germination.

Results: The temperature range of seed germination of R. amphibia was wide, which could germinate at 15 - 40℃. Lower temperature delayed the peak period of seed germination at some extent and the germination rates of R. amphibia peak at 30 - 35℃, which were 44.67% and 50% respectively. At 35℃, germination potential and germination index were 25.33% and 29.46, reaching the maximum value.

Conclusion: The reason for the wide temperature range of seed germination and the low germination rate might be the candidate method for clonal plant population establishment in temperate zone. The higher germination rate of high temperature condition suggested that clone invasive plants in temperate regions were more invasive during global warming.