Absorption and Distribution of High Specific Radioactivity 2-¹⁴C-Abscisic Acid in Cotton Seedlings

Abstract

High specific radioactivity (26.3 mc/mmole) racemic 2-14C-abscisic acid was synthesized. An aliquot of abscisic acid, 1.2 X 10'-M in aqueous methanolic solution, was applied to the surface of either a cotyledon or the first true leaf of 8-to 32-dayold cotton seedlings (Gossypium hirsutum L.). After various intervals (6-192 hours), the seedlings were processed for autoradiography, counting, and identification of the radioactivity. After 6 hours, radioactivity was observed moving basipetally out of the treated leaf toward the roots. Four days later, radioactivity could be detected throughout the whole seedling. After 8 days, 10% of the recovered radioactivity was found in the roots, and 80% remained in the treated leaf blade. Neither leaf type nor age had any effect on the abscisic acid movement or pattern of distribution. Isolated radioactivity from the roots was identified as abscisic acid, based on comparison with an authentic standard by thin layer chromatography, gas-liquid chromatography, or gas-liquid chromatography-mass spectrometry.Abscisic acid has been isolated from cotton plants and identified (6, 24, 25). It has also been found in a large number of plant species (3, 11,18,22,23 MATERIALS AND METHODS Synthesis of High Specific Radioactivity 2-14C-Abscisic Acid. Although a synthesis of 1-"4C-methyl (triphenylphosphoranylidene) acetate has been published (5), the description given is incomplete, and the yield of the 1-4C-compound reported is lower than the yields in the macrosynthesis (17). A similar Wittig reagent was prepared with good yield as follows. Ethyl-2-"C-bromoacetate (21.0 mg) 28.7 mc/mmole, (ICN-Tracerlab) in 0.25 ml of benzene was transferred to a 15-ml graduated centrifuge tube, and the shipping vial was rinsed five times with 0.45 ml of benzene. Triphenylphosphine (132 mg, 0.503 mmole) was added, dissolved in the benzene, and the tube was covered with aluminum foil and allowed to stand at room temperature for 24 hr. The tube was then spun for 15 min at 3000 rpm, and the benzene was decanted. Fresh benzene (2.5 ml) was added, the tube was shaken and then centrifuged again for 15 min at 3000 rpm, and the benzene rinse was decanted. The tube was then dried 2 hr in a vacuum oven at about 250 mm Hg and 40 C to yield 50.22 mg of salt (93.0% of theory). Previous trial runs had given quantitative yields. The salt was dissolved in 2.5 ml of distilled water, and a drop each of 0.1% phenolphthalein alcohol solution and 1% Tween 20 solution was added followed by 4 drops of 10% KOH to a pink end point. The precipitated ethyl (triphenylphosphoranylidene)-2-'4C-acetate was spun down for 15 min at 3000 rpm, the supernatant was decanted, the precipitate was rinsed with 2.5 ml of water and recentrifuged, and the water was decanted. The product was then dried overnight at 250 mm Hg and 60 C to yield 35.67 mg, 87.5% of theory for this step and 81.4% over-all. Trial runs had given 84 + 2% of theory in this step.Next, 4-(2, 6, 6-trimethyl-1 -hydroxy-4-keto-2-cyclohexen-1-yl)-3-buten-2-one, 0.1024 mmole...

Effect of drought, on transport and metabolism of abscisic acid in aeroponically grown Helianthus annuus

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Transport and metabolism of labelled abscisic acid in broad‐bean plants (Vicia faba L.)

“…In intact plants, fast nnovements (> 20 cm h-' in Vicia faba) of radioactivity have been observed after application of labelled ABA to mature leaves (Shindy et al 1973, Goldbach and Goldbach 1977, Dewdney and McWha 1978 or to the roots (Hartung 1977). The mean speeds of transport measured with segments were substantially smaller: 20 to 35 mm h-* in petioles (Dorffling andBottger 1968, Davenport et al 1977) or young internodes (our data), and only 4 to 5 mm h"* in roots (Hartung and Behl 1974).…”

The r�le of abscisic acid in root growth and gravireaction: A critical review

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