Effects Of Combinations Of Para-Hydroxybenzoic Acid And Boron On Growth And Mineral Content Of Velvetleaf

Date of Graduation

Summer 2004


Master of Science in Plant Science (Biology)



Committee Chair

Frank Einhellig


Para-hydroxybenzoie acid (pHBA) is frequently implicated in plant to plant biochemical interactions (allelopathy), and it may inhibit growth by disturbing membrane functions. A primary focus of this study was to determine if levels of pHBA near the growth-inhibition threshold will alter mineral content of velvetleaf (Abutilon theophrasti Medic.) tissue. A second objective was to determine if the level of available boron (B) alters possible effects of pHBA on growth and nutrient accumulation in leaf tissue. Velvetleaf seedlings were grown in nutrient solution in a completely randomized factorial design under greenhouse conditions in three separate 3-4 week long trials. Trial 1 had crossed treatments of zero, 250, and 500 uM pHBA and 1, 10, and 50 uM B. Solutions were changed every 3 days. Later trials added 100 uM B treatments, and the growth media was aerated and adjusted to pH 5.5. Trial 1 showed significant main effects of B and pHBA on velvetleaf root, shoot, and leaf dry weights and leaf area with both 1 uM B and 500 uM pHBA suppressing growth. There was also a significant pHBA*B interaction on growth. Subsequent trials showed a significant main effect of B on growth with 1 uM B suppressing growth in pHBA-treated plants. Leaf tissue was analyzed for B, Fe, K, Mg, Mn, and P content using inductively coupled plasma-atomic emission spectrometry and Ca content using atomic absorption spectrophotometry. Compared to 10 uM B controls, leaf B concentrations decreased in 1 uM B tretments and increased in 100 uM B. In 500 uM pHBA, Trial 2 and 3 plants showed elevated levels of K, Mg, Mn and P leaf content. Environmental differences between trials appeared to affect the inhibition threshold of pHBA. This study rendered no conclusive evidence of B treatments altering allelopathic effects of pHBA.


allelopathy, boron, para-hydroxybenzoic acid, phenolic acid, velvetleaf

Subject Categories

Plant Sciences


© Melissa A. Remley