Ribonucleic acids and ribosomal proteins synthesis during germination of unripe and aged wheat caryopses

Abstract

Caryopses collected at milk, wax and full ripeness as well as aged ones stored at air humidity of 30, 60 and 80 per cent were subjected to germination. The more unripe were the caryopses the lower was their germination capacity and dry mass increment of the sprouts, the same was true for fully ripe but aged caryopses. After 48 h of germination in the presence of radioactive precursors the embryos were removed from the caryopses and used for isolation of the total ribosomal fraction and RNA. Distinct synthesis of three basic total RNA fractions and of the polyribosomal fraction was observed in all samples and in embryos from grain which had completely lost its germination capacity. High radioactivity was recorded in preparations of total RNA and polyribosomal ones from 48-h sprouts growing from caryopses collected at milk ripeness and in those of aged caryopses stored under air humidity of 30 and 60 per cent. According to the authors, the depressed amount of latent forms of RNA (preformed mRNA, tRNA and ribosomes) is the cause of intensive ³H-uridine incorporation into RNA in embryos from unripe and aged caryopses. For germination of grains with a reduced amount of latent forms the biosynthesis mechanisms must be based to a much higher extent on newly synthesised molecules of ribonucleic acids.