Production of stigma exudate per flower of Petunia hybrida is about 200 μg. The effect of light, temperature, metabolic poison and emasculation on the production of the exudate at different ages of the bud has been studied. The presence of a thin film of water below the stigmatic exudate has been demonstrated. Physical properties of the exudate such as relative viscosity and surface tension have also been determined. Chemical analysis of the stigmatic fluid showed that it consists primarily of an oil, sugars and amino acids. No protein could be detected. It also contains no acid phosphatase.Behaviour of the pollen from its deposition on the stigmatic fluid until it germinates on the stigma surface has been studied in vivo and also with the aid of an "artificial stigma".The role of the stigmatic fluid in pollination has been determined.

A mature stigma of Petunia hybrida ready for pollination shows 4-6 large shining drops of the exudate along with numerous smaller ones. A developing style and stigma have a columnar tissue that flares at the top. In the stigma there can be distinguished a secretory and a storage zone. In the former, schizogenous cavities are formed which are filled with the exudate. The mode of formation and secretion of the drop has been studied with light and electron microscope. The nature of reserves has been studied histochemically.The exudation takes place in two stages. In the first stage, the epidermal and papillae cells release out the oily exudate upon rupture of the cuticle. The second phase of exudation begins with anthesis. The exudate from the schizogenous cavities is released between the epidermal cells. There are distinct loci on the stigma surface where more exudate is given out than at other places.

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