Effects of hypoxia on respiration and the onset of senescence in cut carnation flowers (Dianthus caryophyllus L)

Oxygen concentrations ranging between 1.62 and 5.01 kPa O-2 reduced the rate of CO2 evolution in cut carnation flowers (Dianthus caryophyllus L.) and, more importantly, delayed the onset of senescence. The suppressive effects of low O-2 on respiration could not be ascribed to the restriction of mitochondrial terminal oxidases. An O-2 concentration of 2.02 kPa totally suppressed the onset of the climacteric rise in CO2 evolution and increased the vase life of flowers twofold over that of flowers treated with STS, indicating that the retarding effects of hypoxia on the onset of senescence transcend its inhibitory effects on the action of C2H4. Hypoxia diminished the effects of exogenously applied C2H4 on the rate of CO2 evolution and appeared to retard the rate at which the usual morphological symptoms associated with petal senescence occurred. Rapid wilting, concomitant with the climacteric, was a facet of C2H4 action and coincided with a decrease in water uptake. The latter could not be ascribed to the obstruction of vascular bundles but rather to the inability of petals to absorb water. It is suggested that the sudden increase in water loss may be the result of an C2H4-induced increase in hydraulic conductivity of the petals. (C) 1997 Elsevier Science B.V.