The effects of hormonal chemicals and different genotypes on fruit growth of greenhouse-grown tomatoes (Lycopersicon esculentum Mill.) were examined. Continuous root application of 10nM N⁶-benzylaminopurine in Hoagland's nutrient solution to tomato seedlings of 'Fireball' and 'Red Cherry' significantly delayed anthesis of 'Fireball', but not 'Red Cherry'. Ovary diameter at anthesis, final fruit diameter, and fruit weight of both cultivars were unaffected. Irrespective of treatments, a significant positive correlation was obtained between ovary diameter at anthesis and final fruit diameter.

A single foliar application of 0.25mM or 0.37mM β-na-phthoxyaceticacid (βNOA) at the appearance of the first in florescence of ‘Fireball' significantly increased ovary diameter at anthesis, but had no effect on final fruit diameter. Flowers on the second inflorescence of tomato plants treated with 0.37mM βNOA had smaller ovary sizes at anthesis than those of untreated plants. Application of 0.125mM βNOA, and 1µM, 10µM, and 100µM gibberellin A₃ had no significant effect on ovary diameter at anthesis or final fruit diameter. A significant positive correlation was also shown between ovary diameter at anthesis and final fruit diameter of βNOA treated plants.

Among the twelve genotypes tested, significant correlations between ovary diameter at anthesis and final fruit diameter were found for 'Fireball', 'Michigan/Ohio Hybrid', and 'New Yorker'. The remaining genotypes showed no significant correlations between ovary diameter at anthesis and final fruit diameter. The average ovary diameter at anthesis (of all the genotypes) was significantly correlated with final fruit diameter, fruit weight, and locule number.