See more from this Session: Graduate Student Oral Competition: Weed and Insect Management; Pesticide Fate
Separate experiments were conducted on mature ‘Riviera’ common bermudagrass (Cynodon dactylon (L.) Pers.) and ‘Tifway’ hybrid bermudagrass (Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy.) maintained at a 2 cm in a glasshouse. Each study was arranged as a 3 x 3 factorial randomized complete block design with three replications. Plants were treated with three rates of mesotrione (0.28, 0.35, and 0.42 kg ha-1), topramezone (0.018, 0.025, and 0.038 kg ha-1), and tembotrione (0.092, 0.184, and 0.276 kg ha-1). Percent visual bleaching and chlorophyll fluorescence data were collected 3, 7, 14, 21, 28, and 35 days after application. Immediately following data collection, leaf material above 2 cm was harvested from individual plants and frozen at -80°C. Chlorophyll and carotenoid pigments were extracted from leaf tissue and quantified via high-performance liquid chromatography.
Chlorophyll, lutein and xanthophyll cycle pigment concentrations were regressed over visual bleaching and chlorophyll fluorescence data. Comparisons of R-squared values indicated no distinct advantage to using chlorophyll fluorescence in place of visual ratings as a means of evaluating HPPD inhibiting herbicide activity. While several significant linear relationships were detected, R-squared values never exceeded 0.65, suggesting neither evaluation method can accurately quantify physiological changes in carotenoid and chlorophyll pigment concentrations following HPPD inhibiting herbicide treatment.