Lesions in the ribosomes of non-viable pea (Pisum arvense) embryonic axis tissue.

Ribosomes isolated from either dry viable or non-viable pea embryonic axis tissue were equally effective in the support of polyphenylalanine synthesis in a poly(U)-directed cell-free protein-synthesising system. Ribosomes isolated from imbibed non-viable axis tissue were impaired in their ability to support polyphenylalanine synthesis in the cell-free system. RNA isolated from ribosomes and 40-S ribosomal subunits of dry or imbibed viable axis tissue was found not to be degraded, whereas the equivalent RNA species isolated from non-viable axis tissue showed an increased degree of breakdown as imbibition proceeded. Even though rRNA of imbibed non-viable axis tissue was degraded, the ribosomes and ribosomal subunits of these embryos appeared intact. In viable embryonic axis tissue the percentage of ribosomes present in the cell in the form of polysomes increased during imbibition whereas no polysomes could be detected in ribosomal preparations from dry or imbibed non-viable axis tissue. The breakdown of rRNA in ribosomal particles from non-viable axis tissue may be a contributory factor to senescence and loss of viability in Pisum arvense.