The effect of the plant growth retardants AMO-1618 and CCC on the synthesis of ribonucleic acids and proteins in triticale embryos during the initial phase of germination

Abstract

Triticale var. Grado caryopses were subjected to imbibition and germination in the presence of the growth retardants, AMO-1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride) and CCC (2-chloroethyl)-trimethylammonium chloride) at the following concentrations, 3 x 10^-4 M and 10^-3 M. These compounds exerted a very strong inhibitory effect on the initiation of germination processes, growth of embryos and the germination capacity of the caryopses. At the concentration of 10^-3 M, AMO-1618 showed an especially strong effect, lowering the germination capacity of the caryopses to about 50%. It was also shown that both retardants are decidedly more effective on the germination of whole, intact caryopses than on that of isolated embryos. During the very earliest hours of germination, these retardants already inhibited RNA synthesis. The participation of the polyribosome fraction in the total ribosome fraction of embryos in the control sample after 24 hrs of germination of caryopses equalled about 70%, while in the samples treated with CCC (10^-3 M)- about 57%, in the samples treated with AMO-1618 (10^-3 M) about 35%,. The inhibition of incorporation of ¹⁴C-amino acids into ribosomal proteins in the polyribosome fraction was in the case of CCC about 13%, while in the samples treated with AMO-1618, about 55%. In the monosome fraction (80S), the inhibition by CCC was about 23%, whereas in the samples treated with AMO-1618 it reached around 73%. From this data it is evident that the studied retardants have a significant influence on the synthesis of ribonucleic acids as well as on ribosome proteins. These results also suggest the existance of another mechanism, aside from that of inhibition of gibberellin biosynthesis, inhibiting the growth and development of cells. The high percentage of ribosome subunits in the samples treated with CCC, in comparison with controls and samples treated with AMO-1618, points to different mechanisms by which these two compounds affect protein biosynthesis.