The role of zeatin and gibberellic acid in breaking of the abscisic acid-induced dormancy in Triticale caryopses

Abstract

The investigations were conducted on the germinating embryos and the whole caryopses of <em>Triticale</em>. During preimbibition and 24 hours germination caryopses were treated with abscisic acid (ABA), which produced 63% inhibition of embryo growth. Gibberellin-A<sub>3</sub> (GA<sub>3</sub>) reversed the ABA effect in 18%, while zeatin in 22%. The clear synergic reaction was observed (36%) when both stimulators acted together. There was no significant effect of ABA, ABA and GA<sub>3</sub>, as well as ABA and zeatin on the synthesis of polyribosomal RNA in the initial period of germination of excised embryos. However, during 24 hours germination of whole caryopses ABA caused a twofold decrease in <sup>3</sup>H-uridine incorporation into the total fraction of embryonic ribosomes. While the incorporation of <sup>14</sup>C-aminoacid mixture into ribosomal proteins was even three-fold lower. Effect of GA<sub>3</sub> and zeatin on breaking of the ABA-induced "dormancy" was studied. It was confirmed that the higher polyribosome contribution to the sum total of ribosomes the more intensive synthesis of ribosomal proteins. No higher <sup>3</sup>H-uridine incorporation into polyribosomal fraction was observed. From the results it may be inferred that in the initial period of germination of <em>Triticale</em> caryopses regulation of protein biosynthesis occurs rather at the translation than transcription level.