Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


The effect of glyphosate on immature internodal tissue of three sugarcane varieties was examined. Sucrose content (mg/g dry wt) increased after treatment application throughout the 7 week period of sampling in the experiment in all varieties examined. Increases in sucrose percent and commercially recoverable sugar per ton (CRS/T) determined by whole stalk analysis were observed in NCo 310 and CP 61-37 4 weeks after glyphosate application. A greater percent increase in sucrose content of immature internodal tissues over control than that observed by whole stalk analysis was noted at this time. The plant growth regulators glyphosine, ethephon, mefluidide and glyphosate applied to L 62-96 increased the sucrose content of immature internodal tissues examined. Glyphosate appeared to effect a larger increase in this response. The increase observed in sucrose content of these tissues was also observed in sucrose percent and CRS/T at 4 weeks after treatment application. The magnitude of the increase in sucrose content in immature internodal tissues was greater than that observed in whole stalk sugar analysis. The effect of glyposate on endogenous glucose and fructose levels in CP 65-357, CP 61-37 and NCo 310 was evaluated. These levels of glucose and fructose declined throughout the 7 weeks of the experiment. Reducing sugar levels declined more rapidly in glyphosate treated tissues when compared to controls. Sucrose uptake rates by slices of immature storage parenchyma tissue of sugarcane stalks were examined after glyphosate application. Increased sucrose uptake rates were observed in NCo 310 after glyphosate treatment. This response coincided with increased sucrose content of these same tissues in the experiment. Increases in the rate of sucrose uptake observed in tissue slices of CP 65-357 and CP 61-37 after glyphosate application were not statistically significant. Neither sucrose percent, average stalk weight nor CRS/T as determined by whole stalk analysis were correlated with seedling in vivo nitrate reductase (NR) activity in the 18 varieties examined. NR activity of greenhouse grown sugarcane seedlings was not indicative of those same seedlings grown in the field. No differences in NR activity were observed between glyphosate treated and untreated commercial varieties throughout the experiment.