Characterization of the Amylolytic Activity of Araucana araucana (Mol.) Koch Germinating Seeds

Starch is the main reserve in Araucaria araucana (Mol.) Kochseeds. In an attempt to understand the regulation of starchmobilization during seed germination, amylase activity was characterizedand its levels were measured for the first 90 h after the startof seed imbibition. Amylase is present in both the embryo andmegagametophyte when seeds are quiescent. The enzyme activityof the embryo has two peaks during the 90 h, while amylase activityof the megagametophyte remains low and unchanged during thistime. Analysis of the products released by the enzyme and thermostabilityexperiments identify the amylase as a-amylase. Differentialcentrifugation of embryo homogenates under isoosmotic conditionsshows that the enzyme is soluble. Quantification of the endogenous gibberellins of the embryoshows a time correlation between the rise in amylase activityand the rise in specific gibberellin levels during the 40 hafter the start of imbibition. The growth retardant AMO-1618lowers enzyme activity to 37.3% of the control at this time.However, activity is almost completely restored when the gibberellinsfrom embryonic tissue are added in physiological doses to theimbibition medium containing AMO-1618. ³ Present address: Department of Biology, Washington University,St. Louis, Missouri, USA. (Received September 2, 1982; Accepted December 27, 1982)