Thesis Title

Interactive Effects of Ferulic Acid and Irradiance on Plant Growth and Photosynthetic Rate

Date of Graduation

Fall 2002


Master of Science in Plant Science (Biology)



Committee Chair

Frank Einhellig

Subject Categories

Plant Sciences


The focus of this research was to determine how levels of irradiance modify plant response to a known allelochemical stress. Using a split plot design, the effects of irradiance and ferulic acid (FA) on growth, biomass allocation and plant photosynthetic capacity were monitored in summer greenhouse experiments. The experimental design consisted of two levels of irradiance (ambient sun conditions and ~60% reduction by one layer of shade cloth) defining the main plot and three concentrations of FA (500, 250, and 0 uM) defining the subplot factors. The bioassay plants were soybean and velvetleaf seedlings grown in nutrient culture with treatments beginning 10 days after germination. Plants were harvested for dry weights and leaf area 28 to 30 days later. For soybean, both FA and irradiance had a significant effect on mean final dry weight and they interacted. These effects were seen in root, shoot, and leaf components. The combination of shade detriment of FA was less in shade than in the sun. Photosynthetic light response curves recorded for shade-grown soybean at all FA levels indicated lower light compensation points, light saturation estimates, and maximum net photosynthetic rates than counterparts in the sun. In contrast to soybean, irradiance did not have a significant effect on mean velvetleaf total plant weight. Shade-grown velvetleaf showed an overall trend toward greater mean leaf area than sun plants at all FA concentrations. While FA effects are modified by irradiance conditions, it appears that alterations in photosynthesis are only part of the explanation for soybean plant growth reductions in these experiments.


© Will McClain II


Open Access