Seed Germination and Seed Bank of Scutellaria Species

Florida skullcap, Scutellaria floridana Chapm. (Lamiaceae), is a federally threatened species found in the Florida Panhandle. Its habitat is a fire-prone, longleaf pine forest dominated by Aristida stricta Michx. var. beyrichiana (wiregrass). Other Scutellaria species used in the study are found in southeastern U.S., including two within the Florida Panhandle. The objective of this study was to compare several techniques to germinate seeds of Scutellaria incana, Scutellaria lateriflora, Scutellaria ovata ssp. ovata, and Scutellaria floridana, and to access the presence of a seed bank for S. floridana. For the germination study, Scutellaria lateriflora and S. ovata ssp. ovata were stratified for one and two months at 4oC, whereas S. floridana was stratified for 1.5 months. All four species were scarified with concentrated sulfuric acid for various times (15 to 60 minutes). Smoke treatments were: Wright’s® Natural Hickory Seasoning (1:100 to 1:1000) for all species, and also plant debris smoke (half and full strength) for S. floridana. Only S. floridana seeds were soaked in gibberellic acid (500 mg/L GA3) and tested for seed viability (40%). For each treatment, 3 replications of 10, 25 or 50 seeds per Petri dish with moistened filter paper were used depending on the species. After dusting with Thiram to prevent fungal contamination, dishes were placed in colorless tubs in a seed germination chamber with 16 hours light at 17 μmol·m-2·sec-1 and 25oC. Germinated seeds were counted for 30 days. Arcsine transformation of germination percentages were analyzed with a one-way analysis of variance at 5% level. The best treatment for all species, excluding S. floridana, was 15 minutes acid scarification for S. lateriflora with all other treatments yielding 13% germination or less for the 3 species. Control seeds of S. floridana germinated significantly higher than seeds with stratification, scarification, and plant debris smoke solutions, but were similar with Hickory Smoke Seasoning and GA3. For the control of S. floridana, 83% of viable seeds germinated. For the seed bank study, soil samples were collected in 2 years from 8 different sites with S. floridana in Florida by scraping the soil surface near plants to collect 600 mL per site. The first seed bank soils were collected in February 2012 and the second seed bank soils in December 2012 – January 2013. Soil texture particles varied from 0-100% sand, 0-88% silt, and 0-38% clay. Soil pH ranged from 4-5, and soil moisture was between 17-63%. Planting pots were filled with sterilized sand and a layer of soil on top, and placed in a growth chamber at 25oC with 16 hours light at 90 μmol/m2/sec for 64 days. Six replications per site were used. Emergence was recorded as either monocot or dicot seedlings. A total of 11 dicots and 7 monocots emerged from all three sites in the first study. For the second study, 73 monocots and 34 dicots emerged from the 7 sites. No seedlings of S. floridana emerged after 64 days. Overall, seeds of S. floridana responded differently than the other three Scutellaria species. Based on lack of dormancy, seeds of S. floridana are likely to germinate, but its seedlings were not observed in the seed bank, suggesting no seeds were present or seeds were not able to germinate and emerge in our conditions