Effect of pollination or treatment with growth regulators on levels of extractable hormones in tomato ovaries and young fruits

Levels of extractable free indolyl-3-acetic acid (IAA), gibberellin-like substances (GA's), and abscisic acid (ABA) were analysed in tomato ovaries ( Lycopersicon esculentum Mill.) before pollination as well as in fruits 5 and 10 days after pollination or treatment with growth regulators to induce parthenocarpic fruit development. Growth regulators applied were a naphthoquinone (bendroquinone), an auxin (4-CPA), a morphactin (CME), and a benzothiadiazole (DU).
The initial high levels of ABA (2.7 μg/g dry weight) in unpollinated ovaries decreased to one third or less after 5 and 10 days. In contrast levels of IAA increased from 80 up to 180 ng/g dry weight. Activity of GA's could be detected only in young fruits but not in unpollinated ovaries.
The possible relevance of these findings for tomato fruit-set is discussed.