Physiology and biochemistry of the stigmatic fluid of Petunia hybrida.

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.