Qualitative and quantitative changes in mRNA of castor beans during the initial stages of germination

The increase in extractable RNA during the initial germination stages of castor bean was measured, for both the embryonic axis and the storage endsperm. The extractable rRNA increased between 24 and 72 h after initial imbibition in the embryo and 48-72 h in the endosperm. The mRNA species present over the first 6 days of germination were identified by the products from in vitro translation. The mRNA from dry seeds gave predominantly low molecular weight polypeptide products. Between 0.5 and 1 h of initial imbibition new mRNA species were detectable and the qualitative changes were largely complete by 8 h, some 16 h-40 h before the detectable quantitative changes. Despite the large variations in enzyme activity occurring 48 h-192 h after imbibition, the mRNA species qualitatively varied very little, after this initial change, up to 144 h after imbibition. In the light of this large, early, qualitative change in mRNA, the possible importance of long-lived mRNA in seed germination is discussed.