STUDIES ON THE CHANGES IN THE MAJOR NUCLEIC-ACID COMPONENTS OF TOMATO SEEDS (LYCOPERSICON-ESCULENTUM MILL) RESULTING FROM OSMOTIC PRESOWING TREATMENT

Extensive accumulation of nucleic acid may be 1 factor involved in the acceleration of tomato seed germination by osmotic presowing treatment. The experiments reported here were designed to characterize the changes in the major nucleic acids during osmotic pretreatment and subsequent germination. Polyacrylamide gel electrophoresis showed that ribosomal [r] RNA comprised the major part of this net synthesis, but it was more difficult to ascertain whether or not there was a proportional increase in s(soluble)RNA, as part of the latter peak may comprise comigrating fragments of degraded rRNA. The mass ratio of 25S:18S rRNA extracted from dry seeds was near unity; during normal germination and during pretreatment this ratio increased to about 1:9:I, close to the theoretical ratio assuming 25S and 18S rRNA occur in equimolar proportions. Replacement of old ribosomes may occur during early germination and pretreatment, although this would not account for all the synthetic activity observed during the latter process. Use of the diphenylamine color reaction showed that no increase in DNA results from pretreatment and that the onset of the first S-phase during subsequent germination of pretreated seeds was commensurate with the advancement of the time of 50% germination.