Parthenocarpic tomato fruits can be produced by -

Parthenocarpy is the development of a fruit without fertilisation; such fruits are seedless.
Normally the growth of the ovary into a fruit is stimulated by the auxins and gibberellins produced by the developing seeds after fertilisation.
If the unpollinated flowers are sprayed with low concentrations of auxins (such as IAA or NAA) and gibberellic acid, the ovary is stimulated to grow into a fruit without fertilisation.
This is how parthenocarpic (seedless) tomato fruits are produced.
Simply removing the androecium (emasculation) prevents self-pollination but does not make the ovary develop.
Vernalisation promotes flowering, and phenylmercuric acetate is an antitranspirant that closes stomata.
So parthenocarpic tomatoes are produced by treating the plants with low concentrations of gibberellic acid and auxins.