The Extraction and Colorimetric Estimation of Indole-3-Acetic Acid and Its Esters in Developing Corn Kernels

Abstract

dye 2,3,5-triphenyltetrazolium chloride was only weakly reduced in the copper-deficient plants. Maxi To supplement biological methods of auxin assay, a colorimetric method was first described by Mitchell and Brunstetter (4). This procedure was later improved by Tang and Bonner (7), and by Gordon and Weber (2). Essentially, the method takes advantage of the red coloration formed through the mild oxidation of IAA. 4 This oxidation product will be described in another publication. stable colloidal suspensions. Since difficulties are encountered with extracts of plant materials, it seemed advisable to describe further refinements of the colorimetric methods developed in this laboratory and especially those procedures adapted for the quantitative determination of IAA and its esters in corn kernels during the various stages of development. EXPERIMENTAL COLORIMETRIC MEASUREMENTS:The procedure is modified from that of Gordon and Weber (2), in that 0.05 M ferric chloride in 10% (by volume) perchloric acid was used to develop the red oxidation product, maximum intensity of which was attained in 45 minutes when held at 30°C. The 10% perchloric acid was used in preference to 35% to facilitate extraction in the final separation. The red color was quantitatively extracted with isobutyl alcohol, and the isobutyl alcohol layer centrifuged to remove the suspended water droplets. Since the red color is unstable in this medium, the time after extraction to reading was standardized at five minutes; the absorbancy was determined at 530 m/i on a Beckman D.U. spectrophotometer. Under these conditions, Beer's law was obeyed over a concentration range of 0 to 0.8 mg/25 ml isobutyl alcohol and an absorbancy index of 2.7 ml (cm mg IAA)-l. APPLICATION OF THE METHOD TO PLANT MATERIAL:To ascertain the accuracy of the method, weighed amounts of IAA were added to 500 gm samples of immature corn kernels at the milk stage and macerated with ethyl acetate in a Waring blendor. The

A morphological and physiological investigation of the self-incompatibility of the Orlando tangelo /

“…There was a considerable increase in the concentration of promoter II in the twelfthand sixteenth-day samples of cross-pollinated ovar-es. This is evidence that the developing endosperm increased the level of promoter II, an assumption that is substantiated by reports of other workers (5,47,51,71,72,86,119,121).…”

Changes in growth‐substance contents during growth of wheat grains

“…The auxin content was much greater than that found in vegetative plant tissues. In winter rye most auxin was found in the grains 7 wk after anthesis when the grains were heaviest (Hatcher, 1945) and in maize most auxin was found in the intermediate milk stage (Hinsvark, Houff, Wittwer & Sell, 1954). The auxin rapidly disappeared as the wheat grains ripened, and none was found in ripe grains.…”

Comparative study between Salkowski reagent and chromatographic method for auxins quantification from bacterial production

“…The fact is that Salkowski reacts not only with auxin (i.e., IAA) but also with indole pyruvic acid (IPA), indole acetamide (IAM), and other indole analog compounds, as is presented in Figure 4. Salkowski's reaction is based on the reactivity of the nitrogen atom in the pyrrole ring, as was postulated by Hinsvark et al (1953). They demonstrated that the colored product was an oxidation of IAA in the presence of Fe II, forming the N-hydroxy-3-indole-acetic acid product, which could be formed from any other indole analog compound and yield other indole derivated.…”

“…The fact is that Salkowski reacts not only with auxin (i.e., IAA) but also with indole pyruvic acid (IPA), indole acetamide (IAM), and other indole analog compounds, as is presented in Figure 4 . Salkowski’s reaction is based on the reactivity of the nitrogen atom in the pyrrole ring, as was postulated by Hinsvark et al. (1953) .…”