Fruit growth and pseudoembryo development affected by uniconazole, an inhibitor of gibberellin biosynthesis, in pat-2 and auxin-induced parthenocarpic tomato fruits

Abstract Morphological changes during the development of pseudoembryos in parthenocarpic fruits of the genetic parthenocarpic tomato cultivar, ‘Severianin’, were observed. Pseudoembryos that originated from division of the innermost integument cells were formed in the ovule cavity. These cells were highly stained with toluidine blue O and actively divided until 20 days after anthesis. Uniconazole, an inhibitor of gibberellin biosynthesis, applied at anthesis decreased the setting ratio of fruits and inhibited the development of pseudoembryos. Uniconazole applied at 3 days after anthesis inhibited fruit growth entirely and suppressed pseudoembryo development. Gibberellin treatment at 2 days after uniconazole treatment reversed the inhibitory effect of uniconazole on fruit growth and pseudoembryo development in ‘Severianin’. The inhibitory effect of uniconazole on fruit growth and pseudoembryo development in auxin-induced fruits of ‘Kyouryoku-Kyokkou’, a commercial cultivar without genetic parthenocarpy, was weaker than that in ‘Severianin’. Application of gibberellin also reversed the inhibitory effect of uniconazole in this cultivar. Well-developed pseudoembryos were always observed in the well growing fruit in both cultivars. These results indicate that the development of pseudoembryos is closely related to the growth of parthenocarpic fruit.