Molecular integrity of plant ribosomal ribonucleic Acid

Thermal denaturation of plant ribosomal RNA followed by gel fractionation shows that although a large percentage of molecules contain breaks in the polynucleotide chain, 25S and 18S RNAs do exist as unique molecular species. Values for the rate constant of hydrolysis under routine denaturing conditions are of the order of 10⁻⁷ to 10⁻⁸ sec^{− 1} and these are shown not to be a result of ribonuclease activity. This high rate of hydrolysis and the use of insensitive fractionation procedures may account for the reported absence of a 25S rRNA molecule and its apparent conversion to a molecule similar in size to 18S RNA.