Occurrence of 'flower browning' of cut Gypsophila paniculata L. and its prevention by harvesting at bud stage

Abstract

Inflorescences of Gypsophila paniculata L. 'Bristol Fairy', harvested with 30% of their buds open, were held in deionized water and kept at 20, 23, 26, or 29 °C. Petals of flowers held at 20 °C became translucent and desiccated, although the floret shape remained unchanged. When the inflorescences were kept at 23 °C or higher, the petals of open florets turned brown, wilted and inrolled into calyxes; commercially the phenomenon is called 'flower browning'. Following a pulse of 0.2 mM silver thiosulfate (STS), a continuous supply of 4% sucrose and 0.26 mM 8-hydroxyquinoline sulfate (8-HQS) to bud-cut inflorescences not only enhanced bud opening but also inhibited the occurrence of 'flower browning' even under an inductive stress of 25 °C. Days between bud-cutting, when the terminal floret had just open, to the marketable stage with 30% of open buds, were 5 and 3 at 20 and 25 °C, respectively. Light intensity of 15.0 W · m-2 during the forcing period for bud opening after harvest was desirable for getting marketable inflorescences with good quality and long vase life. The rate of respiration by cut inflorescences increased exponentially with increasing temperature; the respiration rate at 20 °C was c. 210 μmol CO2 · hr-1 · 100 gfw-1 (Q10 =1.5). At 25 °C, a severe decrease in sugar content of florets occurred on cut inflorescences. On days 2 and 4, glucose and fructose contents per floret at 25 °C were one-half to one-third of those at 20 °C; whereas sucrose content was almost one-fourth. Application of sucrose helped maintain a high soluble sugar level in florets which may contribute to prevent petals from wilting and browning even under inductive temperature conditions. Bud-cut inflorescences treated with STS could be stored with their stem base in a solution containing sucrose and 8-HQS at 1 °C for 4 weeks without lowering cut-flower quality and longevity.