Abstract
The State of Florida spends millions annually to control invasive exotic (non-native) plant species that have collectively disrupted thousands of acres of natural ecosystems throughout the state. Because some of the species that were introduced to the U.S. have become invasive, it would be useful to determine if practical methods can be developed to assess the potential invasiveness of non-native plant species prior to their introduction. The influence of light and temperature on germination was determined for Mexican petunia (Ruellia brittoniana Leonard ex Fernald;. Seeds were collected and germinated in incubators with light or darkness at 10,15, 24 or 33°C. In addition to incubator treatments, parallel greenhouse studies were conducted using 4-in pots filled with soil less mix. Seeds were placed on the soil surface or 1 cm below the soil surface. There was no significant interaction between light and temperature on seed germination. Germination occurred in all treatments, regardless of light, but highest germination occurred in the greenhouse (91-97%). Highest germination in the incubators occurred in those set at 15°C (62-74%). A separate experiment was conducted comparing nutrient uptake and photosynthesis of Ruellia grown in simulated wet (82-100% moisture) and dry (18-28% moisture) soil regimes. At 6 weeks, plants grown under wet conditions had greater shoot dry weight than plants grown under dry conditions, but photosynthetic rates were similar among treatments. Nitrogen content of root and shoot tissue was not affected by moisture treatments, but phosphorus content of shoots was higher when plants were grown in wet conditions.
