Barley embryoless half seeds were incubated in medium containing 10μM GA. Time course activity changes of α-amylase were studied in extract and medium seperately by the addition of 0.1μM, 5μM and 10~M ABA in midcourse incubation of 10 hours after GA treatment. MAK profiles of nucleic acids in embryoless half seeds were compared either with 10μM GA treatment or concomitant treatment with 10μM GA and 10μM ABA after 10 hours incubation, Time course changes of weight increase, chlorophyll, protein and RNA consent in addition to RNase activity were studied in the presence of 10μM GA or 10μM ABA in barley coleoptile sections. After 20 hours incubation in the presence of plant hormones, MAK profiles of nucleic acids and reactive distribution of polysome and monosome were investigated. The above results were summarized as follows.
1) The production of α-amylase by treatment with GA alone increased at a linear rate in the incubation period and the active secretion of α-amylase began from 18 hours incubation in embryoless half seeds.
2) On the contrary to the partial inhibition by addition of 0.1 μM ABA, the production of α-amylase was completely inhibited by both 5μM and 10μM ABA within 4 hours. Regardless of concentration of GA, the addition of 5μM ABA in midcourse completely inhibited the production of α-amylase.
3) ABA treatment gave no effect on the secretion of α-amylase.
4) There were no differences in RNA fractions between GA treatment and concomitant treatment with GA and ABA in the barlye embryoless half seeds.
5) While GA treatment increased the r-RNA fraction, ABA treatment decreased it and increased the s-RNA fraction in the coleoptile sections.
6) GA treatment increased RNA-DNA fraction best ABA treatment decreased it in the coleoptile sections.
7) While GA treatment suppressed RNase activity, ABA treatment increased it in the coleoptile sections.
8) GA treatment gave no great effect on the total RNA but ABA treatment remarkably diminished it in the coleoptile sections.
9) While GA treatment increased the growth and chlorophyll content, ABA treatment decreased them in the coleoptile sections.
10) GA treatment increased the protein synthesis and polysome formation but ABA treatment decreased them in the coleoptile sections.
11) The inhibition effect of ABA on polysome formation seemed to be resulted from the inhibition of r-RNA synthesis by ABA.
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