Regulation of Senescence in Carnation (Dianthus caryophyllus) by Ethylene

Abstract

Carnation (Dianthus caryophyllus) flowers were exposed to 2^i/l ethylene and examined at intervals to determine the time course of wilting, decrease in water uptake, and increase in ionic leakage in response to ethylene. A rapid decrease in water uptake was observed about 4 hours after initiating treatment with ethylene. This was followed by wilting (in-rolling of petals) about 2 hours later. Carbon dioxide inhibited the decline in water uptake and wilting and this is typical of most ethylene-induced responses. Ethylene did not affect closure of stomates. Ethylene enhanced ionic leakage, as measured by efflux of 36CI from the vacuole. This was judged to coincide with the decrease in water uptake. Gassing flowers with propylene initiated autocatalytic ethylene production within 2.4 hours. Since the increase in ethylene production by carnations preceded the increase in ionic leakage and the decline in water uptake by several hours, it is apparent that the change in ionic leakage does not lead to the initial increase in ethylene production as reported (Hanson and Kende 1975 Plant Physiol 55:663-669) in morning glory but may explain the autocatalytic phase of ethylene production.The association of ethylene with senescence of flowers is widely recognized and carnation flowers have been thoroughly examined in this respect (13). As the cut flower approaches senescence, a dramatic rise in the rate of ethylene production occurs followed soon after by wilting of the petals. Senescence can be hastened by as little as 30 nl/l of ethylene (2, 15). The events taking place between the rise in ethylene production, or exposure to ethylene, and the development of visual symptoms remain obscure. Lieberman et al. (11) over-all length, and placed individually in 20-ml vials. Flowers were obtained from a local grower and experiments were begun on the day of harvest. Four flowers in a 10-liter desiccator with a CO2 scrubber (NaOH solution) comprised a treatment. Flowers were exposed to ethylene at 21AI/I for 0, 3, 6, 9, or 12 hr, after which they were ventilated with ethylene-free air at a rate of 100 ml/min for the remainder of the experiment. Flowers were observed at 1-hr intervals to determine the onset of wilting symptoms as judged by in-rolling of petals.Effect of Ethylene on Rate of Water Uptake. Cut flowers were fitted into a specially designed glass sphere in which the flower bud was maintained in the desired gas atmosphere while the stem was connected to a potometer (5) and water uptake was measured at 30-min intervals. The flowers were ventilated continuously with 2 ,ul/l ethylene in dry air or with ethylene-free at a flow rate of 40 ml/min.Effect of Ethylene on Stomatal Aperture of Carnation Sepals. Flowers were cut to 10 cm over-all length and treated with ethylenie in desiccators as described above. Flowers were removed at 3-hr intervals from each of four desiccators and the sepals were excised, frozen in liquid N2, and freeze-dried. Sections (4 x 4 mm) were sputter-coated with gold and the surface was observed ...

Physiological Changes Accompanying Senescence in the Ephemeral Daylily Flower

“…1). By the time the climacteric had passed (hour 24), the whole flower had wilted and the ends of the petal had started to fray with onset ofautolysis, a sequence ofevents resembling those seen in carnation and other flowers (1,18). Such a climacteric has often been interpreted as one of the physiological responses to autocatalytic ethylene production (15,18).…”

“…By the time the climacteric had passed (hour 24), the whole flower had wilted and the ends of the petal had started to fray with onset ofautolysis, a sequence ofevents resembling those seen in carnation and other flowers (1,18). Such a climacteric has often been interpreted as one of the physiological responses to autocatalytic ethylene production (15,18). But unlike carnation, the daylily flower produces little ethylene during senescence, and its senescence is not affected by ethylene or ethylene inhibitors (16; M. Lay-Yee, personal communication), resembling some leaves in this respect (25).…”

Ethylene Enhances Water Transport in Hypoxic Aspen

“…Several studies on the effects of exogenous ethylene on stomatal movements demonstrated differential responses between the examined species (Taylor and Gunderson, 1986; Woodrow et al, 1988; Gunderson and Taylor, 1991; Abeles et al, 1992). Exogenous ethylene is known to increase membrane permeability in petal cells (Mayak et al, 1977; Borochov and Woodson, 1989); however, its impact on cell-to-cell water transport has not been thoroughly examined.Water transport across intact higher plant cell membranes occurs predominantly through water channels (aquaporins; Chrispeels et al, 1997). Aquaporins are located in root cell membranes (Chrispeels and Maurel, 1994) at a high density (Johansson et al, 1998).…”

“…Several studies on the effects of exogenous ethylene on stomatal movements demonstrated differential responses between the examined species (Taylor and Gunderson, 1986;Woodrow et al, 1988;Gunderson and Taylor, 1991;Abeles et al, 1992). Exogenous ethylene is known to increase membrane permeability in petal cells (Mayak et al, 1977;Borochov and Woodson, 1989); however, its impact on cell-to-cell water transport has not been thoroughly examined.…”

Autoinhibition of Ethylene Production in Citrus Peel Discs

“…Autocatalysis of ethylene production is a common feature of ripening in climacteric fruits (1,6,9) and some other senescing tissues (11), in which an increased synthesis ofethylene is triggered by exposure to ethylene above a threshold level (1,6). Several reports, however, have demonstrated autoinhibition of ethylene production (12,14,15,20,21).…”