Detachment of the cotyledons from the lentil (Lenis culinaris Med.) embryonic axis causes in the latter an increase in total peroxidase activity which is shown to be due to enhancement of specific cathodic isoperoxidases. The level or the balance of growth-promoting hormones and natural growth inhibitors seems to control many plant growth processes (1,8,13, 15). Cytokinins have been shown to oppose the actions of abscisic acid (2, 3, 6, 7, 13-15, 23 '4. 27, 28, 30 culinaris Med. (Vicia lens) were soaked for 5 min in 1 % sodium hypochlorite solution, washed, and then stirred for 2 hr in distilled water. Embryos were obtained by gently squeezing them out of the seedcoats. Thirty embryos or axes (obtained by detaching the two cotyledons) per series were grown on 50 ml of 0.75% bacto-agar in a Petri dish (13 cm diameter, dark, 26 C) containing one or two of the following substances: 6-furfurylaminopurine (kinetin from Fluka) or ABA (HoffmanLa Roche), or IAA (Sigma).Peroxidase Activity. Crude enzymic extracts were prepared by grinding 20 embryonic axes or the same weight of axes with 1 ml of 0.2 M phosphate buffer, pH 7.8, at 2 C. After 30 min the breis were centrifuged (25,000g; 10 min), and the supernatant was used as the enzyme. Guaiacol-peroxidase activity (incubation mixtures: 8 ml of phosphate buffer, pH 6.1, + 1 ml of H202, 0.2 volume, + 1 ml of 1 % guaiacol + 0.1 ml of enzyme) was determined spectrophotometrically by measuring the increase of absorbancy at 420 nm (11). Protein was assayed by the method of Lowry et al. (21). Starch gel electrophoresis was adapted from Scopes (25) and described in detail elsewhere (4). Electrophoretic runs were made for 3 to 4 hr at 300 v at 0 C. The gels were stained for isoperoxidases using o-dianisidine (sometimes guaiacol) as a substrate (4). The curves are composed of average data from at least three concordant assays.
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