Effects of Previous Pollination and Stylar Ethylene on Pollen Tube Growth in Petunia hybrida Styles

The effect of ethylene on the growth rate of pollen tubes in styles of Petunia hybrida was examined. Apart from its strong inhibition of pollination-induced ethylene synthesis, aminoethoxyvinylglycine, placed on the stigma, did not impede tube growth. The inhibitors of the action of ethylene, silver thiosulfate and 2,5-norbornadiene, were similarly ineffective. Application of the ethylene precursor, 1-amino-cyclopropane-1-carboxylic acid, onto the stigma at different intervals prior to pollination evoked synthesis of ethylene, but was without effect on tube growth. However, prepollination (by 24 hours) with Nicotiana tabacum pollen, significantly enhanced tube growth of Petunia pollen. This enhancement was not counteracted by the pretreatment of stigmas with aminoethoxy-vinylglycine. It is concluded that the ethylene associated with pollination is without effect on pollen tube growth in the style, but that other pollination-induced factors may lead to an acceleration of growth.