Effects of Temperature and Humidity on Foliar Absorption and Translocation of 2,4-Dichlorophenoxyacetic Acid and Benzoic Acid

Abstract

Little is known concerning the effect of humidity on the absorption of foliarly applied materials or their subsequent translocation. It is generally believed that the higher the humidity at any one temperature, the larger the amount of a foliarly applied material that penetrates the leaf per unit time. Most of the evidence for such an effect has been obtained indirectly. Koontz and Biddulph (16) found that the amount of phosphorus translocated from a given compound seemed to be related to the drying time of the solution on the leaf. By adding glycerine to the treatment solution, the translocation of P32 from an application of KH,PO4 solution was increased. Other workers have reported increased penetration of foliarly applied materials by additives which increase moisture retention. The recent review by Currier and Dybing (7) covers this work. It has been suggested that thin aqueous films on the leaf surface are important in promoting the absorption of nutrient sprays, the existence of the film depends upon the vapor pressure gradient at the leaf surface (4).In general, increasing temperature, within physiological limits, has been found to result in increased penetration. Rice (19) using red kidney bean plants studied the absorption of the ammonium salt of 2,4-D. He found that the amount absorbed was positively correlated with temperature over a three-level range of 46 to 580 F, 79 to 820 F and 86 to 920 F. Other workers using soybeans as the test plant found that with increasing temperature, there was an increase in the absorption of the sodium salt of 2,4-D (5,10). Barrier and Loomis (2) reported a temperature effect on the absorption of 2,4-D by soybean seedlings, but no effect upon the absorption of P32. Increased rates of absorption with increasing temperature have been reported for Co60 (9) temperature or humidity gave an increase in absorption of the maleic hydrazide. The preponderance of evidence to date indicates a maximum in translocation over the range of 20 to 300 C. At temperatures below and above this range translocation is reduced (2, 12, 22). MATERIALS AND METHODSSelected seed of Phlaseolus vulgaris L. var. Red Kidney was used. Seeds were germinated at 250 C in Vermiculite saturated with distilled water. All temperatures reported are accurate within ± 10 C and relative humidities are accurate to + 3 % as measured by a hair hygrometer calibrated periodically with a hand phychrometer. Forty to 42 hours after sowing, 90 germinated seeds with radicles between 1.5 cm and 1 cm long were selected and planted in 4 inch pots containing Yolo clay loam soil fertilized with 16 ppm N and 6 ppm P on an oven dry weight basis. After subirrigation the pots were transferred to a growth chamber where they remained at 250 C until the 5th day after sowing, when the lights were turned on at 5:30 A.M. At this time the beans were in the crook stage. Subsequent growth conditions were: 1 5Y2 hours light, temperature 250 C, relative humidity 60 to 76 % and 8/2 hours dark, temperature 15°C, relative humidity 85 to 95 %. Lig...

2,4-D Past, Present, and Future: A Review

“…Uptake doubled under highhumidity conditions in poplar, and when spray droplets were rewetted after drying under lowhumidity conditions, 2,4-D uptake increased (Sharma and Vandenborn 1970). Uptake was greater at humidity levels ranging from 70 to 74% compared with 34 to 48% and a difference was not measured between the drying times of herbicide spray droplets under the two humidity levels (Pallas 1960). Uptake of 2,4-D was greater when the humidity level was 100% as compared with 40%, and the rate of translocation to the meristematic region and rhizomes was much faster at 100% relative humidity in wolftail (Carex cherokeensis Schwein) (Burns et al 1969).…”

Effects of High Humidity on Translocation of Foliar-Applied Labeled Compounds in Plants Part: I

“…Went and Carter (14) found that uptake of sucrose by tomato leaves was indepen-lent of humidity levels. Other workers reported that high humidity increased the absorption of foliarapplied urea, 2,4-D, and maleic hydrazide (Volk & McAuliff, 13; Zukel et al, 16;Pallas,10). It has been reported also that plants might absorb water fronm humid air through the leaves by a reversal of the normal transpiration stream, a process termed "negative transpiration" (Stone et al,12; Breazeale et al, 2,3).…”

Resistance Mechanisms of Oxalis Pes-Oaprae (Soursob) to 2,4-Dichlorophenoxyacetic Acid

“…Other work (Butts and Fang 1956;Weintraub, Reinhart, and Scherff 1956;Ashton 1962;Morgan and Hall 1962;Slife et al 1962) has shown that differential absorption is not always correlated" with resistance or susceptibility. That the degree of absorption from the leaf surface cannot be taken as a basis for interpreting inherent resistance or susceptibility is strengthened by the evidence that absorption is influenced by external conditions like temperature and humidity (Barrier and Loomis 1957;Pallas 1960) and the pH of the solution (Crafts 1956), and that widely variable absorptions can be obtained for a given species under identical conditions (Holley, Boyle, and Hand 1950). Nevertheless, the amount taken up reflects at least part of the fate of the applied substance.…”