1829 AJCS 7(12):1829-1835 (2013) ISSN:1835-2707 Postharvest petal senescence of two cultivars of carnation flowers with different vase lives Asghar Ebrahimzadeh 1 , Silvia Jiménez-Becker 2* , Libia Acened Chaparro-Torres 3 , Juan Pablo Fernandez-Trujillo 3 , Maria Serrano-Mula 4 , Maria Teresa Lao-Arenas 2 1 Department of Horticultural Sciences, Faculty of Agriculture, University of Maragheh, Maragheh 55181-83111, Iran 2 Department of Crop Production, University of Almería (UAL), Ctra, Sacramento, s/n. La Cañada de San Urbano, s/n. 04120 Almería, Spain 3 Department of Agricultural and Food Engineering, Universidad Politécnica de Cartagena (UPCT), Paseo Alfonso XIII, 48. ETSIA. 30203 Cartagena (Murcia), Spain 4 Department of Applied Biology, Universidad Miguel Hernández (UMH) (Campus de Orihuela), Orihuela (Alicante), Spain *Corresponding author: sbecker@ual.es Abstract This work studies the influence of variations in free polyamines, 1-aminocyclopropane-1-carboxylic acid and ethylene, and their possible relationship, during the different development stages of two carnation cultivars (Dianthus caryophyllus L. cultivars Domingo and Famosa) with noticeable differences in vase life. A pre-treatment with ethylene or silver thiosulphate helped to verify the possible link between polyamines, ethylene biosynthesis and carnation vase life. The senescence periods in carnation petals, both untreated and treated with ethylene (1 ppm for 8 h) and silver thiosulphate (1 mM for 2 h), were studied at 21 o C and 60-70% relative humidity during eight different stages of senescence. ´Famosa´ (long-life cultivar) was associated with lower ethylene production and 1-aminocyclopropane-1-carboxylic acid concentration in petals compared with ´Domingo´ (short vase-life cultivar). The effects of pre-treatments with exogenous ethylene or silver thiosulphate were only evident in the short-life cultivar Domingo, in which ethylene production were increased or reduced, respectively. Silver thiosulphate reduced total ACC content during senescence in Domingo. The total polyamine content in Famosa (128-235 nmol g −1 FW) was lower than in Domingo (220-372 nmol g −1 FW). High free Putrescine and Spermidine concentrations were detected in earlier stages of flower senescence in the short vase-life cultivar. The high percentage of spermine in the petal tissue of ‘Famosa’ may inhibit ACC accumulation and ethylene prod uction, resulting in increased flower longevity. Keywords: Dianthus caryophyllus, ethylene production, exogenous ethylene, silver thiosulphate, putrescine, spermidine, spermine Abbreviations: ACC_1-aminocyclopropane-1-carboxylic acid, EP_ethylene production, ACC synthase_1-aminocyclopropane-1- carboxylic acid synthase, ACC_oxidase-1-aminocyclopropane-1-carboxylic acid oxidase, SAM_S-adenosyl methionine, Pas_polyamines Introduction Senescence in carnation flowers is associated with a climacteric-like increase in EP, although a degree of ethylene-independent flower senescence has also been reported (Shibuya, 2012). In petal tissue, ethylene is responsible for inducing many of the biochemical processes leading to programmed cell death, including the activation of senescence-related gene transcription (Lawton et al., 1990; Woodson et al., 1992; Shibuya, 2012). Before the ethylene burst, flowers produce a low constant rate of ethylene, but this is followed by a coordinated increase in the activities of ACC synthase and ACC oxidase (Peiser, 1986; Serrano et al., 1991; Tanase et al., 2008), which converts SAM into ACC which, in turn, is converted into ethylene. A long vase life in some carnation cultivars has been correlated with low expression, in the gynoecium and petals, of some genes of the Dianthus caryophyllus (DC) ACS and ACC oxidase (ACO) multigenic families (DC-ACS1, DC-ACS2 and DC-ACO1) (Tanase et al., 2008). Low sensitivity to ethylene is a common target to select carnation for breeding purposes (Onozaki et al., 2008). Endogenous ACC levels in different flower parts increase during senescence (Nichols et al., 1983). Exposure of isolated carnation petals, separated into upper and basal parts, to ethylene shows that most ethylene evolves from the basal part of the petals. The endogenous ACC content of the basal portion of senescing carnation petals is 3 to 5 times higher than that of the upper parts. During flower senescence, ACC is translocated from the basal part, where it is synthesized, to the upper part, where it is converted into ethylene (Overbeek and Woltering, 1990). It is reported that exogenous ACC treatments advance carnation senescence (Pun et al., 2001a). A degree of competition between PAs and ethylene, through their common precursor SAM (Valero et al., 2002), has been demonstrated, the balance between these two growth regulators being critical for retarding or accelerating the senescence process (Bouchereau et al. 1999; Valero, 2010). However, the effects of PAs on ethylene production vary greatly in different plant species and tissues and in the face of different treatments (Li