Studies in Plant Metabolism. VI. Effect of 2,4-D on the Metabolism of Aspartic Acid and Glutamic Acid in the Bean Plant.

Abstract

In studying the effect of 2,4-D treatment on the chemical composition of bean plants, Sell et al (7) reported that the stem of 2,4-D treated plants contained almost twice as much crude protein as do stems of control plants. Later, Weller et al (9) found that 2,4-D treatment caused a slight decrease in crude leaf protein while the crude root protein remained approximately the same. The amino acid composition in the crude protein from 2,4-D treated stems were different from those of the control plants. A small difference was noted in the leaf and root proteins. These data suggested to the authors that a change had occurred in the character of the protein. Using potato tubers, Payne et al (5) found that 2,4-D caused an increase in free glutamic acid and a decrease in eleven amino acids including aspartic acid. The decrease was explained as an increased catabolism of the free amino acids. In a preliminary investigation on the effects of 2,4-D 2,4,5-T and indoleacetic acid treatment, we have found that the amounts of total aspartic and glutamic acids decreased in both the stems and roots of 2,4-D and 2,4,5-T treated plants, with the greatest change occurring in the stems. Two possible explanations may be given: 1) the 2,4-D treatment might inhibit the synthesis of these amino acids or 2) this treatment nmight increase the rate of oxidation of the amino acids.In order to clarify this point, the present investigation, using carbon 14 as a tracer to study the rates of synthesis of both glutamic acid and aspartic acid in 2,4-D treated and control plants was figure 1. This system consisted of a bell jar large enough to contain one set of four plants, a column of calcium chloride to absorb the excess moisture, a generator to produce radioactive CO2 from BaC1403 after the system was sealed, a Geiger-Muller tube to detect the radioactivity, and a pump to circulate the atmosphere.One day after treatment, the first set of bean plants was placed in the closed system and exposed to an atmosphere containing C1402 for a period of 12 hours in light and 12 hours in darkness. Two 40-watt fluorescent lamps which have a light intensity of 200 fc were set 6 inches from the bell jar on opposite sides. The radioactivity readings of the atmosphere were taken periodically in order to check the amount of radioactivity absorbed by the plants.The second and third sets of bean plants were exposed to C1402 in a similar manner, three days and seven days, respectively, after the treatment with 2,4-D. The amounts of BaC1403 used for these three experiments were 4.3 mg, 6.3 mg, and 5.1 mg respectively (20.6 pxc/mg).After exposure to radioactive C02, the entire plants were harvested and dried overnight at 550 C in a vacuum oven. The samples were then weighed, ground and stored in an evacuated desiccator.RADIOACTIVITY M1EASUREMENTS: Weiglhed aliquots of each sample were oxidized by dry combustion (2). The carbon dioxide was quantitatively absorbed in carbonate-free sodium hydroxide solution and precipitated as barium carbonate. The radioactivit...

Some effects of 2,4-dichlorophenoxyacetic acid on the carbohydrate methobolism of etiolated corn seedlings / by Clanton Candler Black.

“…0.2 ml of 3-PGA (0.375 A); 1.5 ml of Tris buffer (pH 7.4, 0.1 .4); 0.2 ml of MgCl^(O.l -l) ; 0.2 ml of ADP (0.1 .1); 0.1 ml of 2,3-diphosphoglycerate (2, (30 mg/5 ml); 0.1 ml of KCl (0.5 .4); 0.2 ml of extract;…”

“…The triose phosphate hydrazones formed were treated with alkali, and tlie color produced by the addition of 2,4-dinitrophenylhydrazine (2, and NaCSi P ho?pho qlyceric kins^s^. The activity of phosphoglyceric kinase was determined by the procedure of Axelrod and Banduski (7) in which the 1,3-diphosphoglycerate (1,3-DPGA) formed from 3-phosphoglyceric acid in the reaction below, was trapped by hydroxylamine, forming hydroxamic acid:…”

Plant responses to sublethal concentrations of 2,4-D

“…Plants treated with 2,4-D tend to show a rapid depletion of sugars and starch in a wide variety of plants (2,19,38,46,52,57,75,86) . Klingman and Ahlgren (46) propose that r~serve carbohydrates are rapidly hydrolyzed to reducing sugars which are in turn oxidized through an active catabolic system, resulting in a total loss of dry weight .…”