Seed ecology of Illinois bundleflower (Desmanthus illinoensis).

Abstract

Seed ecology of Illinois bundleflower (Desmanthus illinoensis) was studied by looking at several aspects of ecology. Germination at varying temperatures with six different scarifying techniques was assessed. Scarification, which included mechanical and chemical, was observed at 10C, 13C, 17C, and 24C. Germination rates varied from 2% to 99%, depending on treatment. Germination increased with all scarification treatments and suggests that germination is inhibited by an extremely hard seed coat. Heat treatments simulating fire were applied for eight seconds and thirty seconds at temperatures ranging from 100C to 500C at 50C intervals. Germination percentage of all heat-treated seeds was greater than the control. This indicates that Illinois bundleflower could be considered a fire species. The effect of moisture stress on Illinois bundleflower seed germination was determined using mannitol as the osmoticum. Mannitol solutions varying from -0.033 MPa to -2.5 MPa were used to germinate Illinois bundleflower seeds after a 10 minute scarification in concentrated sulfuric acid. Illinois bundleflower seeds germinated at water potentials as low as -1.0 MPa. This suggests that Illinois bundleflower seeds can germinate at relatively low soil water potentials. Xylem pressure potentials of Illinois bundleflower seedlings were measured to determine lethal water potentials reached before death. Scarified seeds (10 minutes in concentrated sulfuric acid) were germinated, then planted 50 to a pot and placed in the greenhouse. Plants were watered every other day until they were 6" high. Two pots were kept as watered controls and water was withheld from all other plants. Xylem pressure potentials of the plants were checked with a pressure chamber. After obtaining xylem pressure potentials, the plants were watered and observed to see if plants recovered or died. Illinois bundleflower seedlings withstood 15 days of drought conditions and a xylem pressure potential of -3.5 MPa. Any xylem pressure potential below -3.5 MPa resulted in death for the seedlings. The possibility for ley farming techniques was applied using Illinois bundleflower in an established wheat field. Plots were established and seeded at a rate of 10 lbs/a, or 171 seeds in a 9 ft2 plot. Seeds were scarified in concentrated sulfuric acid for 10 minutes before planting. Rows of Illinois bundleflower were planted between wheat rows and the plots were checked periodically for establishment. Plants were counted by row and plot. Biomass will be checked after this year's wheat harvest (i.e. year 2).