Effects of boron and para-hydroxybenzoic acid (pHBA) on velvetleaf.
The allelochemical pHBA potentially inhibits plant growth by
disturbing membrane functions. Greenhouse growth studies were conducted
to determine if pHBA levels near the growth-inhibition threshold altered
mineral content of velvetleaf (Abutilon theophrasti Medic.) tissue, and
if the level of available boron (B) modified pHBA effects. Seedlings
were grown 3-4 weeks in nutrient solution using a randomized factorial experimental design. Trial 1 had crossed treatments of zero, 250, and
500[micro]M pHBA and 1, 10, and 50[micro]M B. Trials 2 and 3 added
100[micro]M B treatments, and the growth media pH was adjusted to 5.5
and aerated. Trail 1 plants in 1[micro]M B and 500[micro]M pHBA had
reduced root, shoot, and leaf dry weights and leaf area. The pHBA*B
interaction was significant on growth. In subsequent trials, 1[micro]M B
levels reduced growth in pHBA-treated plants. Compared to 10[micro]M B
controls, leaf B content was significantly lower in plants grown in
1[micro]M B, and higher in the 100[micro]M B media. Plants grown with
500[micro]M pHBA had elevated K, Mg, Mn and P leaf content (ppm), but
there were no effects on Fe and Ca. Light and temperature growth
variations between trials affected the pHBA inhibition threshold. The
data was inconclusive regarding B augmentation overcoming allelopathic
effects of pHBA.
* Remley, M.A. and F.A. Einhellig. Departments of Agriculture and
Biology, Southwest Missouri State University.