Petal water stress precedes increase of ethylene production in senescence of STS-treated sweet pea

Sweet pea (Lathyrus odoratus L.) has wide range of flower color and great fragrance; however, its short vase life limits commercial potential. Our previous study revealed glucose treatment extends the vase life of cut sweet pea flowers by the improved water uptake (Hirose et al., 2020). The vase life of cut flowers in sucrose or glucose solution was 7 days and 9 days, respectively. However, the detailed mechanism how glucose improved water uptake and/or extends the vase life are still unclear. Cut flowers of fragrant sweet pea variety ‘Sweet pink’ treated with STS were kept in 40 g L^‑1 (117 mM) sucrose or 21 g L^‑1 (117 mM) glucose solutions, both with 200 mg L^‑1 8-HQS and kept at 23°C, 70% relative humidity, under 20-40 µmol m^‑2 s^‑1 photon flux density and 12 h photoperiod in a growth chamber. Water potential and osmotic potential of petals were measured using psychrometer and turgor pressure was calculated from these values. Ethylene production of florets was also measured using gas chromatography. Turgor pressure has no significant difference between treatments. Glucose treatment kept high water potential throughout the vase period in petals. While sucrose treatment decreased water potential of petals from 2 days after harvest and increased ethylene production at 6 days after harvest. These results showed the decrease of water potential of petals was followed by the increase of ethylene production of florets in sucrose treatment. Increased ethylene production is often regarded as the trigger of flower senescence, however it also thought to be a result of flower senescence. We conclude that glucose treatment kept high solution uptake and subsequent water condition of petals was improved, consequently vase life of cut flowers was extended.