EFFECTS OF INTERSPECIFIC POLLINATION ON STYLAR ETHYLENE PRODUCTION AND FLOWER LONGEVITY IN PETUNIA HYBRIDA

In petunia cross and self pollination are known to reduce flower longevity to less than 70% of that of the unpollinated control.
Pollen from related species, capable of tube growth in petunia stigmas caused similar reduction in flower life.
When foreign pollen tubes did not penetrate the stigma, varying effects on corolla longevity were noticed.
Irradiation-killed petunia pollen, however, was unable to significantly accelerate wilting.

Upon pollination with different pollen species, excised styles produced various amounts of ethylene, ranging from 0.1 to 8.9 nl/h/style (measured from the 2^nd to the 7^th h after pollination). The amount of ethylene produced did not correlate with the rate of wilting.
Neither was the endogenous ACC content in the different pollen species correlated with the level of pistillate ethylene production.
Thus, apart from ACC, other substances leak from pollen and induce stylar ethylene synthesis.
Furthermore no correlation could be established between pollen ACC content and accelerated flower wilting, although coincidentally, the Solanaceae pollen tested, had extremely high ACC contents, grew into the stigma, and caused accelerated wilting.

Eluates from a few pollen species accelerated wilting when applied onto the stigma in physiological concentrations.
Applied more concentrated, these eluates caused early ethylene synthesis and rapid wilting.
The neutral (sugar) fraction particularly, and the amino acid fraction to a lesser extent, were shown to have this wilting-inducing property.
Sucrose, the main component in the neutral fraction, but also glucose, fructose and mannitol were effective in concentrations ranging from 0.2–0.6 mg/stigma.
Application of IAA to the stigma at concentrations sufficiently high to cause senescence of Cymbidium flowers (10 nmol) did not stimulate wilting or ethylene production.
The common free amino acid in pollen, proline, was equally ineffective.

We conclude that a high pollen ACC content is not required for stylar ethylene production and flower wilting, but that these processes can be accelerated due to the leakage of a mixture of other substances from pollen.

III International Symposium on Postharvest Physiology of Ornamentals

F.A. Hoekstra, G.Ch. van Roekel

https://doi.org/10.17660/ActaHortic.1986.181.12