ABSTRACrPolyamine metabolism and its relation to the induction of a-amylase formation in the aleurone layers of barley seeds (Hordeum vulgare cv Himalaya) in response to gibberellic acid (GA3) has been investipted. A high-performance liquid chromatographic system has been employed for qualitative and quantitative analyses of putrescine (Put), cadaverine (Cad), spermidine (Spd), spermine (Spm), and agmatine (Agm).Active polyamine metabolism occurs in the aleurone cells of deembryonate barley half seeds during imbibition. The aleurone layers isolated from fully imbibed half seeds contain about 880 nanomoles of Put, 920 nanomoles of Spd, and 610 nanomoles of Spm as free form per gram tissue dry weight while the levels of Cad and Agm are relatively low. The polyamine levels do not change significantly in the aleurone layers in response to added GA3 (1.5 micromolar) during the 8-hour lag period of the growth substance-induced formation of a-amylase. Also, the polyamine levels are not altered by the presence of abscisic acid (3 micromolar) which inhibits the enzyme induction by GA3. Kinetic studies show that both applied IU-"Cqornithine and lU-'4Carginine are primarily incorporated into Put during 2 hours of incubation, but the incorporation is not significantly affected by added GA3. Additionally, added GA3 does not affect the uptake and turnover of 11, nor research (18,37,38). Experiments with the aleurone layers of barley seeds have shown a number of biochemical events related to the synthesis of a-amylase in response to added GA3. The mass synthesis of a-amylase begins 8 to 10 h after exposure of the tissue to the growth substance (9). Syntheses and accumulation of a-amylase mRNA (17) and ER (38) start as early as 2 to 4 h after treatment of the growth substance. For efficient expression of a-amylase gene(s), it has recently been suggested that a newly synthesized protein is required (26). If GA3 has effects on translation, the synthesis ofthe unidentified protein factor could occur shortly after addition of the growth substance. Thus, it would be interesting to investigate possible biochemical changes within 2 h after exposure of the aleurone layers to GA3, and to determine whether any changes are related to the effects of the growth substance on the transcriptional and/or translational events described.The diamine Put2 and polyamines Spd and Spm are ubiquitous in biological materials (1, 33,35 (1,12,32,36). Several lines of evidence indicate that polyamines may be involved in regulation of structure, function, and/or biosynthesis ofmacromolecules (10,16,24,28). In higher plants, polyamine metabolism has been related to the action of plant growth substances on regulation of plant growth and development (7, 8, 13, 22). In the internodes of light-grown dwarf peas the contents of Put and Spd per internode have been shown to increase during the elongation induced by exogenously applied GA3 (13). Also, it has been reported that the addition of GA3 results in 4-fold increase in the activity ofornithine decarboxyla...