Does Pollination Induce Corolla Abscission of Cyclamen Flowers by Promoting Ethylene Production?

Abstract

AUSTRACF MATERIALS AND METHODSVery low ethylee production rates were measured in nonpoilinated Cyclame persum Mill flows, aod o change in production was observed dring the whoie lfe spa of the flower until death. Normal senscence was accompnd by a gradul discolotion aod loss of turgor followed by wilting. Polliation induced a dramatic i emin ethylene evoluon, culmatg in a peak 4 days after pollinatio, and a of the corolla on that day. Silver-thioslfate, an inhibitor of ethylene acton, had no effect on longevity of unpollinated flowers, but completely nullified the effect of polliation on corolla abscio. (2,3,10). Some species, however, are not sensitive to ethylene, and their leaves or flowers will not drop in response to exposure to ethylene (2, 10).The longevity of flowers is generally much shorter than that of leaves. Flowers may be generally divided into two distinct groups as to the cause for the termination of their life: (a) those showing a gradual change in composition ofthe corolla with age, loss of turgor, and final wilting; and (b) those in which the life ofthe flower is terminated by the abscission ofthe corolla, when it is still fully turgid (10, 15). In both groups ethylene production, and senescence or abscission are accelerated in pollinated flowers. It is, therefore, generally assumed that pollination-induced senescence and abscission are mediated by the increased ethylene production and exposure of the flowers to endogenous ethylene (6,(10)(11)(12).In the present study we examine the role of ethylene and pollination in controlling senescence and abscission ofcyclamen flowers, and if corolla abscision is regulated solely by the pollination-induced ethylene production. were grown from seeds in 15-cm pots using standard greenhouse production methods. Intact flower buds were tagged when they were still in a downward position, and again on the day when at least 4 of the 5 corolla lobes were folded upward. This stage was considered as the opening stage (day 0). In experiments using cut flowers, flowers were harvested on d 3 or 4, since the scape of flowers harvested earlier than this often bent when placd in water (A. H. Halevy, H. C. Kohl and A. M. Kofranek, unpublished data).Ethylene Prodution and Expwosure to Ethyle. On the opening day a group of 60 flowers was pollinated 3 times, while the rest ofthe flowers were unpollinated. Each day 15 pollinated and 15 unpollinated flowers were harvested and placed in DI.3 Ethylene production by the flowers was determined by sealing 3 flowers in a 0.5-L Mason jar fitted with a sampling port and measuring the accumulated ethylene after 1 h by GC.The effect of ethylene and flower age on time to senescence was examined by harvesting petagged flowers of different ages, placing them for 24 or 48 h in flowing air streams containing 0, 1, 10, and 50 1Al1-' ethylene, and evaluating their longevity in DI under conditions described below.Determintion of ACC Content in Pollen. Five samples of pollen were collected from flowers in the greenhouse. Each sample was collect...

Interorgan Translocation of 1-Aminocyclopropane-1-Carboxylic Acid and Ethylene Coordinates Senescence in Emasculated Cymbidium Flowers

“…It may therefore be concluded that the transported signal is not ACC but, rather, ethylene itself may be translocated or the lip may become more sensitive to ethylene following emasculation. The latter would meet our expectations as the existence of (mobile) ethylene-sensitivity factor(s) has also been suggested in cyclamen, petunia, and carnation flowers (7,9,13,19).…”

“…decanoic acid and octanoic acid, were isolated from eluates of pollinated Petunia styles (19). In Cyclamen flowers, pollination-induced corolla abscission was ascribed to the action of a pollination-induced ethylene-sensitivity factor as abscission in pollinated flowers could be prevented by silver thiosulphate whereas it could not be induced by ethylene or ACC in nonpollinated flowers (7). Similarly, such a mobile ethylene-sensitivity factor was suggested to be produced in the lower portion of the carnation petal (13).…”

Role of Ethylene in the Senescence of Isolated Hibiscus Petals

“…Ethylene production by AOA-treated petals was not detected (level of sensitivity : 0.010 1u/L) throughout the 32-h experiment (Fig. 3) 10 Ml/L ethylene as described under "Materials and Methods." After 2 h, petals were transferred to distilled H20 for the remainder of the experiment.…”

“…The sensitivity of flowers to ethylene varies greatly among plant species (9,10). In general, there is a gradual increase in the flower's sensitivity to ethylene with increasing age (5, 9, 13, 18).…”

Molecular Mechanisms of Petal Senescence in Ornamental Plants

“…The effect of pollination can be blocked by treatment with ethylene action inhibitors, and exogenous ethylene treatment accelerates senescence in these flowers. Flowers of other plants such as cyclamen senesce in response to ethylene only when pollinated (Halevy et al, 1984). It should be noted here that patterns of petal senescence can vary even within species but are specific to cultivars.…”