219 Physiological Changes during Postharvest Life of Cut Sunflowers Anna Mensuali-Sodi 1 and Antonio Ferrante 2 1 Scuola Superiore S. Anna, Pz. Martiri della Libertà 33, Pisa, Italy 2 DIPROVE, via Celoria 2, University of Milano, Italy Keywords: Helianthus annuus, AOA, 8-HQS, citric acid, vase life, ethylene. Abstract The vase life of sunflowers (Helianthus annuus) is limited by early wilting of leaves and ray flowers. Vase life was positively correlated with stem length (5 days in 50 cm stems, 9 days in 70 cm stems). We also studied the vase life after a 24 h pulse treatment with a number of chemicals. It was significantly increased by treatment with 150 mg L -1 citric acid. Treatment with 10 μl L -1 ethylene reduced vase life and induced both flower bending and abscission of ray flowers. In contrast, 2 mM amino-oxyacetic acid (AOA), an ethylene inhibitor, reduced ethylene production but did not increase vase life. 8-Hydroxyquinoline (8-HQS) at 150 mg L -1 did not lengthen vase life. Vase life was reduced by treatment with 2% sucrose combined with either 150 mg L -1 citric or with 150 mg L -1 8-HQS. INTRODUCTION The sunflower is native to North America. In the early days, European invaders used this species for various purposes, including decoration. In recent years the consumer demand of cut sunflowers has been increasing, but little information is available on their senescence. Sunflower vase life is very variable, depending on the variety. It reportedly ranged from 4 to 13 days (Gast, 1995). Sunflowers of some cultivars may therefore need to be treated with preservative solutions for improve their vase life. A non-ionic detergent used as a pulse treatment (for 1 h) increased water uptake and the length of vase life in cut sunflowers stored for three days at 8°C prior to vase life (Jones et al., 1993). A lower storage temperature (0-1°C) both increased the length of vase life and reduced stem bending (Çelikel and Reid, 2002). Sunflowers have long stems when harvested, but the stems are cut several times during the distribution chain. This is done to avoid xylem occlusion in the basal stem end, and to adapt stem length to the use of the flowers in bouquets. The aim of the present work was to investigate the effects of stem length, of an ethylene inhibitor, ethylene, and biocides (alone or in combination with sucrose). Although sunflower is in Asteraceae, a family in which petal senescence is generally insensitive to ethylene, our preliminary trials indicated that ethylene had an effect on vase life. We therefore used ethylene-related treatments and measured ethylene production. MATERIALS AND METHODS Plant Material Cut sunflowers (Helianthus annuus L.) cv. Sunrich Orange were bought from the cooperative Geoflor (in Lucca, Italy) and transported to the laboratory in Pisa. In the laboratory flowers were selected for uniformity and stems were recut under water. The flowers were placed in deionised water. Experiments were performed in a controlled environment maintained at 20°C, 60% relative humidity and 15 μmol m -2 s -1 photosynthetically active quantum flux for 12 h day -1 , from cool-white fluorescent lamps. Flowers were cut to stem lengths of 50, 60 and 70 cm. Bottles, with and without flowers, were weighed daily. Data were used to calculate water uptake and fresh weight. Postharvest Treatments Control flowers were placed in vase solution containing distilled water. Treatments lasted 24 h and were 2 mM amino-oxyacetic acid (AOA; Sigma), 150 mg L -1 Proc. VIII th IS Postharvest Phys. Ornamentals Eds. N. Marissen et al. Acta Hort. 669, ISHS 2005