Influence of 2,4-Dichlorophenoxyacetic Acid on Pathways of Glucose Utilization in Bean Stem Tissues

Abstract

is essentially the same as described in a previous paper (2). The air flow rate through each train can be checked and adjusted independently by means of a bypass manifold attached to a flowmeter. Respiratory CO2 from each flask was continuously swept out by a stream of CO.,-free air and absorbed in individual CO, traps. Flasks were shaken continuously in the light for six hours at 260 C. The respiratory CO., samples obtained during an experiment were precipitated as BaCO1 and the radioactivity determined with a thin mica window GAI counter (1.8 mg per cm2). At the end of a 6 hour incubation period, sections were removed from the me(lium, rinsed with water, and homogenized with 25 ml ethyl alcohol. The radioactivity of the medium, alcohol extract of the tissues, and the alcohol insoluble residue were also determined by the conventional method in order to get necessary information on total C14 recovery. Total glucose uptake by stem tissues was calculated from the summation of radioactivity found in respiratory C0, alcohol insoluble residue and alcohol extract. In general, eight separate flasks (two stem samples from untreated plants ancl two stem samples each from plants treated with various amounts of 2,4-D) were carrie(d out simultaneously in a single run. The weight of tissue used in each flask was adjusted to within 20 mlg between samples in the first three experiments and to within 5 mg in the later runs. Unless otherwise indicated, the fresh weight of stem tissues used in each flask was between 1.7 and 1.8 gm.Radiochemicals were purchased fromi Volk Radiochemical Co. and Nuclear Chicago Corp. All labele(d substrates were adjusted to either 1 Ac or 2 uc per mg of glucose prior to administration. RESULTS AND DISCuSSIONUsing C14 labeled glucose, the effect of 2.4-D on glucose utilization of bean steml tissues has been measured directly. It is assunmed that the oxidation of radioactive carbon atoms from the absorbed glucose which subsequently was recovered in respiratorv C1409 was used to furnish the energy, while the radioactivity found in 80 % ethanol insoluble residue was presumably used in the syntlhesis of cell wall nmaterials.As shown in table I, the percent of absorbed glucose-U-C14 recovered as C1402 had an average value of 5.0 (± 0.4) from six individual runs in control stem tissues. In all cases, the radiochemical yields of respiratory C140.2 hadl greatly increased in 2,4-D treated 405www.plantphysiol.org on May 11, 2018 -Published by Downloaded from

Organ-specific effects of the auxin herbicide 2,4-D on the oxidative stress and senescence-related parameters of the stems of pea plants

“…Thus, the acetyl-CoA produced by the stimulation of the fatty acids beta oxidation might have entered the Krebs cycle instead of the glyoxylate cycle in the pea stems. Previous studies showed that 2,4-D increased the respiration rate in the stems of susceptible plants (Fang et al 1960(Fang et al , 1961Key et al 1960). Other studies also showed that the stems of 2,4-D-treated plants, in which an abnormal overgrowth took place, contained more proteins and nucleic acids, and less nuclease activity, than the stems of untreated plants (Key and Hanson 1961;Chrispeels and Hanson 1962;Shannon et al 1964;Cárdenas et al 1968).…”

Effect of 2,4-dichlorophenoxyacetic acid on utilization of labeled acetate by bean leaf & stem tissues

“…Whlen bean stem tissue was usedl in a ra(lio-respirometric experiment, 2,4-D causedl a dlecrease in the anmounlt of glucose catabolized via the pentose phosphate pathway (1). Since acetate occupies a key positioln in the metabolic patbiways of amino acids, carbohydlrates, and fatty acids, the effect of In the experiments with steml tissue, the total amount of 2,4-D was applied to each plant along the midrib of one primary leaf, wNhile in the experinments with leaf tissue, the aimiount of 2,4-D was equally divide(l and applied to both primary leaves.…”

Influence of Hormones on Respiratory Metabolism of Healthy & Rust-Affected Tissues

“…Altlhough the basic mechanism of action of plant hormones is not known, there is some evidence that indole-acetic acid (IAA) exerts an effect on pathways as well as rates of respiratory metabolism (7,9,10,15). The influence of plant hormones on metabolism may be critically important to understanding obligate parasitism.…”