Cellular basis of the effects of gibberellin and the pro gene on stem growth in tomato

Tomato (Lycopersicon esculentum Mill.) plants homozygous for the mutant pro gene, exhibiting the distinctive procera phenotype, appeared virtually identical to gibberellic acid (GA₃)-treated isogenic normal plants. The pro gene and GA₃ caused analogous increases in internode length, and in the length and number of cells in the outer cell layers of each internode. Internode number was also increased by pro and GA₃ over the period of the experiment. Despite their greater length, the internodes of GA₃-treated and pro plants reached their final size within a time period similar to that of internodes of untreated normal plants. The pro mutant itself was responsive to GA₃, especially in the seedling stage, but the proportional increase in height seen in the later stages of growth was less than that of normal plants.Abbreviations GA gibberellin - GA₃ gibberellic acid - LSD least significant difference