Ribosomes can be released from highly purified preparations of the cell walls of barley shoots by passing the suspension of cell walls through a French press. The sedimentation coefficients and base composition of the cell-wall ribosomes are identical with those of cytoplasmic ribosomes. It is suggested that the ribosomes isolated from the walls were originally incorporated into the wall structure during formation of the primary wall.
A method for isolating extensively purified cell walls from higher plants is described; the preparations contain no detectable chloroplast or nuclear material and the protein content (2–5% of the dry wt. of walls) indicates that there is little contamination with cytoplasm. Incubation of purified cell walls with 0·3 n -potassium hydroxide for 17hr. at 37° liberates ribonucleotides, which can be purified by adsorption on charcoal and by ion-exchange chromatography. Ribonucleotides are also liberated by incubating the walls with ribonuclease, but not with deoxyribonuclease. The RNA content varies from 0·5 to 6mg./g. dry wt. of walls, depending on the nature and age of the tissue, and at 3mg./g. dry wt. of walls accounts for about 7% of the total RNA of the tissue. Less than 0·2% of the RNA of the walls is due to the presence of bacteria in the preparation. The base composition of the cell-wall RNA is identical with that of ribosomal RNA.