cessation of growth ( Arteca, 1996 ). Johnson (1990) documented plant growth reduction on bahiagrass ( Paspalum notatum ) treated with the isopropylamine GP salt at 0.2 kg·ha −1 . EP and GA are classified as hormonal compounds because they are
Marco Volterrani, Nicola Grossi, Monica Gaetani, Lisa Caturegli, Aimila-Eleni Nikolopoulou, Filippo Lulli, and Simone Magni
Most of the studies on the effect of humic acids on micronutrient uptake by plants has been carried out in nutrient solutions. Commercial companies have tried, without adequate experimental support, to extend the conclusions of these studies to the production of vegetables in agricultural soils. The effect of humic acids on micronutrient uptake by plants has been attributed' to (a) the improved supply of micronutrients to the soil solution caused by a higher rate of release from soil minerals (probably via chelate formation by humic acids) and (b) the improved uptake of micronutrients as consequence of the larger root system promoted by hormonal compounds in the humic acids. In soils with limiting concentration of micronutrients (such as some calcareous soils) and low content of organic matter, chelation of micronutrients by added commercial humic acids might increase their availability to plants. However, in agricultural soils with and adequate content of organic matter, no significant effect of commercial humic acids on micronutrient uptake by plants can be detected.
’. Control of Bermudagrass Stolon Elongation Some hormonal compounds, herbicides, and fungicides have the potential to suppress vertical growth of turfgrass species, but little is known about their effect on horizontal stems and what application rate is
Marianne Andresen and Nina Cedergreen
and quality. Commercially registered growth regulators are all phytohormones and fall into the following categories: auxins, gibberellins, cytokinins, abscisic acid, and ethylene. Recently, however, several other hormonal compounds such as