Effects of Indoleacetic Acid and Gibberellic Acid on Normal and Dwarf Tomatoes

Four normal tomato varieties and four dwarf strains homozygous for the genetic factor dd were studied. Indoleacetic acid (IAA) applied to the foliage of young plants gave no significant growth stimulation of either the normal or the dwarf type. When IAA was supplied to etiolated hypocotyl segments in straight growth tests, the only differential response was the greater sensitivity of one of the dwarf types. This sensitivity was not associated with the d locus. 2. Dwarf plants treated with gibberellic acid (GA) exceeded in height the untreated normal plants, but significant increases in growth occurred in all varieties treated, regardless of genotype. Two varieties, one dwarf and one normal, showed a significant sensitivity to GA at low concentrations which failed to stimulate the other varieties studied. 3. Light intensity was found to influence both the normal and the dwarf types similarly. In temperature studies the dwarf varieties appeared to be less responsive to temperature increases.