| dc.description.abstract | Field experiments were conducted in 1993 and 1994 to examine the growth and development of six common cocklebur [Xanthium strumarium L.] selections collected from agricultural systems. A common garden grown under noncompetitive conditions was established with these selections: TX1 and TX2 from College station TX1 AR1 from Little Rock, AR1 AR2 from Mississippi County, AR1 KY from Lexington, KY1 and OK from Chickasha, OK. Plant height and width were measured and the nodes/main axis were counted weekly. Midseason and season-ending biomass harvests were performed, and date of floral initiation was noted. Root tip cells from each selection were examined to determine chromosome number. In both years, significant differences in growth and development of the common cocklebur selections were found. In the 1993 season, the TX1 and OK selections were typically the tallest, widest, and produced the most biomass. In the 1994 season, the OK selection was typically the tallest, widest, and produced the most biomass. In both years the TX2 and KY selections were the smallest in most measurements, and the two Arkansas selections were intermediate in most measurements both years. The OK and KY selections typically produced the most pistillate heads in both years, while the TX2 selection produced the fewest heads. In both years, the TX~ heads were among the largest, along with the OK selection in 1993, and the TX2 selection in 1994. The floral initiation corresponded to latitude of origin, with the most northern selection, KY initiating flowering the earliest, and the most southern selections, TX1 and TX2, initiating flowering the latest. No difference in chromosome number was found. Results indicate differences in many facets of growth and development of these common cocklebur selections when grown under Oklahoma conditions. These results indicate thatecotypes of common cocklebur are present. These ecotypic differences could have important implications for weed control, and soil seed bank dynamics could also be affected by the varied head production of the different selections. Nomenclature: Common cocklebur, Xanthium strumarium L. #1 XANST. | |
