Factors Affecting Seed Germination of the Invasive Species Symphyotrichum lanceolatum and Their Implication for Invasion Success

Invasive species Symphyotrichum lanceolatum (Willd.) G. L. Nesom is spreading uncontrollably along wet habitats as well as in disturbed ecosystems. All those habitats function as corridors that facilitate seed dispersal. One way to prevent the spread of invasive species is to know their reproductive ecology. The present study evaluates the potential for generative reproduction of S. lanceolatum and determines how different temperatures, amounts of nutrients, and light regimes, affect seed germination. Seeds collected from 13 natural populations were germinated at four fluctuating temperature regimes (15/6, 20/10, 30/15, and 35/20 °C). To test the influence of nitrate on seed germination, two KNO(3) concentrations were used (5 mM and 50 mM solution). For each treatment, three replicates of 30 seeds were placed in complete darkness or a 14 h photoperiod. The results showed that the germination increased with increasing temperature. The optimal temperature regimes were 30/15 °C and 35/20 °C with approximately 88% germination. The overall effect of KNO(3) on germination was positive. The concentration of 50 mM KNO(3) had a less stimulating effect compared to 5 mM KNO(3). Seeds showed sensitivity to lack of light during germination but were able to germinate in a significant percentage in such conditions. Considering that S. lanceolatum often occurs in disturbed sites, these results suggest that seed reaction to alternating temperature, nutrients concentration, and light can be determining factors that affect seed germination of this species and, thus, its spread.