Auxins Induce α-Amylase Activity in Pea Cotyledons

Abstract

The report documents how the development of a-amylase activity in detached cotyledons of Pisum sativum cv Alaska is accelerated 2-to 12-fold during incubation with 1 micromolar to 10 micromolar 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, or with 4-chloroindoleacetic acid, an endogenous auxin from Pisum sativum. It seems probable that auxin from the embryonic axis induces a-amylase in the attached cotyledons during germination.Mobilization of nutrients in barley, rice, and wheat does not occur in endosperms from which the embryo has been removed. A diffusible factor from the embryo promotes aamylase activity in the aleurone layer and has been identified as GA (10,14). It has also been shown that GA is involved in mobilization of nutrients in these cereals. The same simple method of analysis has been applied to other seeds, and in many cases removal of the embryo has been found to prevent or retard mobilization and to affect adversely the development of the monitored enzyme (2). Knowledge about mobilization of stored nutrients in seeds in which the cotyledons are the storage organs is limited. A number of researchers have used pea seeds for their experiments, but contradictory results have been reported, possibly because the experimental conditions were not standardized. In the case of a-amylase activity, the consequences of excision of cotyledons include inhibition (6, 13), promotion (15), and no appreciable effect (1). A reason for these contradictory results is reported. MATERIALS AND METHODS Plant MaterialPea seeds (Pisum sativum cv Alaska) were immersed in a 1% solution of sodium hypochlorite for 2 min and then rinsed with deionized water for 1 min. To maintain aerobic conditions and a steady supply of water to the cotyledons, the seeds were placed on filter paper that was supported by a small Petri dish in a large dish which contained deionized water or one ofthe test solutions. The seeds which were not submerged could take up water or the solution slowly through the filter paper. Incubations were conducted at 25°C under germ-free conditions in the dark. Preparation of EnzymeAfter incubation, each group of eight pairs of cotyledons was homogenized in a Waring Blendor with 5 volumes of 0.2 M Na-acetate buffer (pH 5.4) containing 3 mm CaC12. After the homogenate was passed through four layers ofcheesecloth, the filtrate was centrifuged at 25,000g for 15 min at 4°C and the supernatant was used for assay of a-amylase activity. The assay was carried out by a modification of procedures described by Rinderknecht et al. (11). With this assay, the determination of a-amylase in crude extracts is possible even in the presence of a-amylase which directly interferes with most assay methods (3). The reaction mixture consisted of 2 mL of 2% (w/v) starch azure (Sigma) which was heated slowly to boiling before the assay, 1 mL of 0.2 M Na-acetate (pH 5.4), 0.12 mL of 0.1 M CaC12, and 0.83 mL of deionized water. The reaction was started by the addition of 0.05 mL of supernatant. After incubation...

A comparative effect of IAA and 4-Cl-IAA on growth, nodulation and nitrogen fixation in Vigna radiata (L.) Wilczek

“…pea stem curvature growth, pea stem straight growth, oat and wheat coleoptile growth, mung bean hypocotyls growth and increased root initiation and ethylene evolution in leafy pea cutting) (Porter and Thimann 1965;Marumo et al 1974;Böttger et al 1978;Katekar and Geissler 1983;Ahmad et al 1987). This characteristic of 4-Cl-IAA is further expressed by the observed increase in the activity and/or inducibility of various enzymes (Hirasawa 1989;Ahmad and Hayat 1999;Ahmad et al 2001a) that speeded up the rate of photosynthesis and ultimately produced more seeds in Brassica juncea (Ahmad et al 2001b).…”

<italic>Arabidopsis</italic> inositol 1,3,4-trisphosphate 5/6 kinase 2 is required for seed coat development

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Two Apoplastic α-Amylases Are Induced in Tobacco by Virus Infection

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