Physiology and biochemistry of the stigmatic fluid of Petunia hybrida

Abstract

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.

Expression of the Arabidopsis HMG2 gene, encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase, is restricted to meristematic and floral tissues.

“…In many plant species, the stigmatic surface is covered by a chemically complex exudate that provides a favorable environment for pollen adhesion and germination (Konar and Linskens, 1966;Knox, 1984). Although the chemical composition of these exudates has not been established, the detection of GUS expression driven by the HMG2 promoter in the stigma secretory cells suggests that they may contain isoprenoid compounds or derivatives.…”

The Composition of Stigmatic Exudate from Lilium longiflorum

“…Exudate fractions were incubated in 0.1 M sodium phosphate (pH 6.5) with Pronase (10 mg, volume 1 ml, 37 C, 20 hr). After inactivating the Pronase (10 min, 100 C) and after cooling, Pectinol R-10 (10 mg) and disodium EDTA (1 mg) were added, and the incubation was continued for another 6 hr at 37 C. Pectinol was then inactivated (10 min,'100 C), and the solution was centrifuged. The precipitate was discarded, and residual protein in the supernatant solution was removed by passage through a Dowex-50 H+ ion exchange column.…”

“…This sheath is poorly understood regarding both composition and function. Recently, Konar and Linskens (10) reviewed the literature related to stigmatic exudate. They found no consistent pattern for the composition of stigmatic exudate among various plant species.…”

The plant stigma exudate

“…This extracellular fluid, the so-called stigma exudate, mostly contains water, sugars, lipids and proteins, 1 but other compounds such as phenols, amino acids, ROS/ RNS and Ca 2+ ions are also present in measurable amounts. [2][3][4][5] The picture of the stigma secretome remains fragmentary and only a few proteins have been identified and characterized so far. [6][7][8] In a recent publication, we performed a largescale protein profiling study of the stigma exudate in two plant species, namely Eastern lily (Lilium longiflorum) and olive (Olea europaea), that substantially differ in their taxonomical position, pistil morphology and anatomy, ecology and cultivation purposes.…”