Roles of ethylene and 1‐aminocyclopropane‐1‐carboxylic acid in pollination and wound‐induced senescence of Petunia hybrida flowers

Normal senescence of Petunia hybrida L. (cv. Pink Cascade) was associated with a 10‐fold increase in their ethylene production. Soon after pollination wounding of the stigma of detached flowers there was a burst of ethylene production by the gynoecium, which reached a maximum after 3 h. A subsequnt more gradual rise in ethylene production by the flowers was accompanied by blueing, wilting, and senescence of the corolla. Treatment with 1 μl ethylene 1⁻¹ accelerated the onset of senescence as measured first by color change and then by wilting of the corolla. These changes were further accelerated by using older flowers or higher concentrations of ethylene. Senescence was also hastened by supplying 1‐aminocyclopropane‐1‐carboxylic acid (ACC) through the flower pedicel. Petunia pollen contained high concentrations of ACC (300 nmol g⁻¹); treatment of stigmas with ACC (1 mM) caused a 4‐fold increase in their ethylene production. Senescence, whether natural or hastened by pollination or piercing, was delayed by treating the flowers with the anionic silver thiosulfate complex.