Effects of Stimulatory and Inhibitory Levels of 2,4‐D, Iron, and Chelate Supplements on Juvenile Growth of Field Beans¹

Abstract

S OME growth regulators stimulate plant growth at low concentrations but inhibit growth at high concentrations. Most reports on the effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on plants deal with inhibitory aspects of herbicidal concentrations (8). Juvenile beans have been used extensively in studies of the herbicidal effects of 2,4-D (1, 3, 4), but few studies deal with stimulatory concentrations on young bean plants. Taylor (5, 6) was among the first to report an increase in soybean plant dry weight from low rates of 2,4-D in nutrient solutions. Weaver (7) applied 2,4-D aqueous solution to the leaves of young red kidney beans and soybeans at rates of 0.001, 0.01, and 0.1 grams actual chemical per square yard. All treatments, measured 31 days after application, reduced plant weight and delayed pod appearance. Swanson (4) reported significant increase in cambial activity in young red kidney beans with the lethal rate of 0.1% aqueous foliar-applied 2,4-D sprays. Leonard (3) reported that aqueous solutions of the triethylamine salt of 2,4-D (150 ppm) slightly increased fresh weight of bean plants 14 days after application to seedling plants. Wort (9, 10) reported that foliar-applied composite dusts or sprays containing a high concentration of 2,4-D and micronutrients increased the early growth and ultimate yield of several crop plants, including beans. The herbicidal and injurious effects of 2,4-D sprays and dusts were decreased or completely eliminated by previous, simultaneous, or subsequent foliar application of salts of iron or copper. This study was designed to extend available data on 2,4-D by determining stimulatory levels as well as herbicidal concentrations. It was of additional interest to determine the effects of foliar-applied iron, chelate iron, and a

Effects of 2,4‐D‐Nutrient Dusts on the Growth and Yield of Beans and Sugar Beets

“…The inclusion of compounds of the microelements Cu, Zn, Fe, Mn, and B augmented the stimulatory action of the hormone and widened the range of concentrations that could be safely used to increase growth. A similar effect of 2,4-D applied in water solution to Sutter Pink field beans (Phaseolus vulgaris) has been reported ( 4,5). In these instances, however, only iron as the sulfate or chelate, was added to the solution of 2,4-D.…”

“…Miller et a!. ( 4,5) have reported that a spray containing 100 ppm 2,4-D and iron sulfate or chelate had a stimulatory effect on the growth and yield of field beans. Yield responses that varied from negative, through increases that lacked significance, to statistically significant increases when 2,4-D-nutrient dusts were applied to the foliage of field grown cereals in Western Canada were described by Ripley ( 6) and Sexsmith ( 7).…”

Statistical Tests for Hormesis and Effective Dosages in Herbicide Dose Response

“…Several authors have noted that, for low dosages of herbicide, a hormetic effect can occur that raises the average response for low dosages above the control value (Miller et al, 1962; Freney, 1965; Wiedman and Appleby, 1972). Allender (1997) and Allender et al (1997) suggested that influx of Ca 2+ may be involved in the growth stimulation associated with hormesis.…”

Influence of Sublethal, Foliar Applications of 2,4‐D on Burley Tobacco Yield and Composition1

“…including 2,4-dichlorophenoxyacetic acid (2,4-D), has been reported. Huffaker et al (7) obtained yield increases when barley, wheat and beans were sprayed with small amounts of 2,4-D and Miller et al (8) showed that foliar applications of 2,4-D at very low levels increased the growth of young bean plants. At the cellular level, low dosages of 2,4-D are sometimes used to enhance growth of tobacco (Nicotiana tabacum L.) callus tissue in vitro (11).…”