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 Triticale. During preimbibition and 24 hours germination caryopses were treated with abscisic acid (ABA), which produced 63% inhibition of embryo growth. Gibberellin-A₃ (GA₃) 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 GA₃, 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 ³H-uridine incorporation into the total fraction of embryonic ribosomes. While the incorporation of ¹⁴C-aminoacid mixture into ribosomal proteins was even three-fold lower. Effect of GA₃ 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 ³H-uridine incorporation into polyribosomal fraction was observed. From the results it may be inferred that in the initial period of germination of Triticale caryopses regulation of protein biosynthesis occurs rather at the translation than transcription level.