EFFECT OF PROTEIN-SYNTHESIS INHIBITORS ON TOBACCO SEED-GERMINATION AND SEEDLING EMERGENCE

This study is based on two earlier reports, one demonstrating that dark preincubation improves tobacco (Nicotiana tabacum L.) seed germination rate and the other demonstrating genetic variability in tobacco seed response to germination temperature. Each of these situations involves special classes of proteins: the phytochrome molecule and heat shock proteins, respectively. A better understanding of either process at the molecular level would involve investigations on the regulatory role of the protein synthesis mechanism. This study was undertaken to characterize the temporal relationship of the three major steps in protein synthesis - replication, transcription and translation - with the three major events associated with seedling morphogenesis: radicle protrusion, radicle elongation, and plumule protrusion. This was accomplished through the use of selected inhibitors of replication, transcription, and translation. Results suggest that a) radicle emergence is regulated by translation but is independent of replication and transcription; b) the translational regulation of the above event is mediated through preformed (i.e., long-lived) m-RNAs; c) radicle elongation following its emergence and plumule emergence are regulated by all three components of protein synthesis; d) radicle length data obtained in laboratory investigations are a better predictor than radicle number (i.e., germination percentage) of seedling emergence potential under field conditions.