Effect of ammonium sulfate on the phytotoxicity, foliar uptake, and translocation of imazamethabenz in wild oat
Experiments were conducted in greenhouse, growth chamber, and laboratory conditions to determine the effect of ammonium sulfate [(NH4)2SO4] on the phytotoxicity, foliar uptake, and translocation of imazamethabenz on wild oat. Rates of (NH4)2SO4 up to 5% (w/v) applied with a greenhouse sprayer did not affect the phytotoxicity of the herbicide when the mix was applied at the one- to two-leaf stage. However, inclusion of 1 and 2% (NH4)2SO4 increased the phytotoxicity of the herbicide when the mix was sprayed at the two- to three-leaf, or the three- to four-leaf stage. At 10%, (NH4)2SO4 decreased the phytotoxicity of the sublethal dosage of the herbicide. When the herbicide was applied as individual drops to the growth chamber-grown plants, inclusion of (NH4)2SO4 at 1% did not affect phytotoxicity as measured by shoot growth. The presence of (NH4)2SO4 did not affect the amount of imazamethabenz retained by wild oat foliage, but it decreased [14C]imazamethabenz absorption, slightly antagonized acropetal translocation, and increased the basipetal translocation of [14C]imazamethabenz. It was concluded that application methods greatly modify the effect of (NH4)2SO4 on imazamethabenz phytotoxicity. Herbicide absorption and translocation as determined by one method do not necessarily represent the absorption and translocation patterns when different application methods are used. Absorption and translocation were not the factors that were responsible for the observed effect of (NH4)2SO4 on the herbicide phytotoxicity.
Influence of Ammonium Sulfate, Imazapyr, Temperature, and Relative Humidity on the Absorption and Translocation of Imazethapyr
The effects of 1.24 kg ha−1 ammonium sulfate, 5 g ae ha−1 of the isopropylamine salt of imazapyr, and air temperatures of 18, 27, or 35 C at 40 or 100% relative humidity (RH) on the absorption and translocation of the ammonium salt of 14C-imazethapyr applied postemergence to pitted morningglory were evaluated. Absorption of 14C-imazethapyr was greater at 100 than at 40% RH (88 vs. 47%). At 40% RH, absorption was increased to 79% by the addition of ammonium sulfate. At 100% RH absorption was similar with all treatments. Translocation of 14C-imazethapyr applied alone was greater at 100 than at 40% RH (34 vs. 17%). Addition of ammonium sulfate increased translocation at 40% RH but not at 100%. Addition of imazapyr did not affect 14C translocation. Distribution of 14C throughout the plant was more acropetal than basipetal with the greatest distribution at 35 C.
STUDIES ON THE BIOLOGY OF WILD OATS. II. GROWTH.
Dry matter accumulation by wild oats (Avena fatua L.) in a growth cabinet, after an initial lag period, took place rapidly until 8 wk after emergence. Plant height and the number of leaves per plant increased at a nearly linear rate until 6 wk after emergence. Tillering occurred mainly during the period 2–4 wk after emergence. Low light intensity and short photoperiod severely restricted growth, and delayed heading and maturity. Plants grew best at day–night temperatures of 20–12 C, though initial growth was faster at higher temperature (28–20 C). In a black loam soil, plants responded to added nitrogen and phosphorus only under high light intensity. Both soil moisture and soil pH greatly influenced the growth of wild oats. Greatest dry matter accumulation was attained when soil pH was 7.5 or 8.5 and soil moisture was maintained above 75% field capacity. Hull color of the seed had no effect on the growth of wild oat plants. Plants produced from large seeds had higher dry weights than plants produced from ...