• 'O ••• ALO'. PI .... PII,sjO.", © 1997 by Gustav Fischer Verlag, Jena Effects of Spermine on Ethylene Biosynthesis in Cut Carnation (Dianthus caryophyl/us L.) Flowers During Senescence MYEONG MIN LEE, SUN HI LEE, and Ky YOUNG PARK* Department of Biology, Yonsei University, Sinchon, Seoul 120-749, Korea (M.M.L., S.H.L.); Department of Biology, Sunchon National University, Sunchon, Chonnam 540-742, Korea (K.Y.P.) Received August 1, 1996 . Accepted December 10, 1996 Summary To investigate the relationship between polyamine and ethylene during senescence of cut carnation (Dianthus caryophyllus L.) flowers, we studied the effects of spermine on ethylene biosynthesis. Spermine delayed the senescence of cut carnation flowers and reduced ethylene production, endogenous l-aminocy- clopropane-l-carboxylic acid (ACe) content, and the activities and transcript amounts of ACC synthase and ACC oxidase in petals. Methylglyoxal bis-(guanylhydrazone) (MGBG), an inhibitor of polyamine biosynthesis, elevated ethylene production, increased activities and amounts of transcripts for ACC syn- thase and ACC oxidase, and shifted the climacteric pattern of ethylene production ahead by 1 day. How- ever, endogenous ACe content was not increased in the petals of MGBG-treated flowers because of the high activity of ACC oxidase. Spermine also inhibited MGBG-induced ethylene production by decreasing the activities and amounts of transcripts for ACC synthase and ACC oxidase. The accumulation of tran- scripts for ACC synthase and ACC oxidase in MGBG-treated and in climacteric control petals was corre- lated with the increase of these enzyme activities. By comparing ethylene production with the changes of endogenous polyamine levels from control and MGBG- or spermine-treated petals during the entire incubation period, it was suggested that endogenous polyamines possibly suppress ethylene production. Key words: ACC synthase, ACC oxidase, carnation flower, ethylene, MGBG, polyamine, spermine. Abbreviations: ACC = l-aminocyclopropane-l-carboxylic acid; OJ = deionized water; gFw = gram fresh weight; MGBG = methylglyoxal bis-(guanylhydrazone); SAM = S-adenosylmethionine; SAMOC = S-ade- nosylmethionine decarboxylase. Introduction Ethylene, a plant hormone, regulates many aspects of plant growth and development (Yang and Hoffman, 1984), and its own biosynthetic enzyme activity with positive or negative mode (Schierle et al., 1989). In carnation flowers the onset of senescence is associated with a sharp increase in ethylene pro- duction similar to the climacteric of many fruits (Yang and Hoffinan, 1984). Ethylene biosynthesis is regulated by an autocatalytic mode (Park et al., 1992). * Correspondence. J Plant Physiol. Vol. 151. pp. 68-73 (1997) Polyamines and ethylene share a common precursor, S- adenosylmethionine (SAM), but the physiological effects of polyamines and ethylene on senescence and fruit ripening are the opposite of each other (Fuhrer et al., 1982; Winer and Apelbaum, 1986). Biosynthesis of polyamine was inhibited by ethylene in pea seedlings (lcekson et al., 1985), while it was increased by ethylene and auxin in tobacco suspension cells (Park and Lee, 1994). The fact that the ale tomato geno- type delays ripening and enhances long keeping properties has been correlated with an increase in the level of putrescine. The cellular contents of polyamines were high in active grow- ing cells, but low in senescing cells concomitant with an