Plant Science 167 (2004) 781–788 Polyamines and ethylene changes during germination of different plant species under salinity Pedro J. Zapata, Mar´ ıa Serrano, M. Teresa Pretel, Asunción Amorós, M. Ángeles Botella ∗ Div. Fisiolog´ ıa Vegetal, Escuela Politécnica Superior de Orihuela, Universidad Miguel Hernández, Ctra Beniel-Orihuela, Km 3.2, 03312 Orihuela (Alicante), Spain Received 14 November 2003; received in revised form 10 May 2004; accepted 12 May 2004 Available online 7 June 2004 Abstract The effect of salinity on germination percentage, seedling growth, ethylene production, respiration rate and polyamine levels was studied in different plant species: spinach (Spinacia oleracea L.), lettuce (Lactuca sativa L.), melon (Cucumis melo L.), pepper (Capsicum annum L.), broccoli (Brassica oleraceae L. var. Italica Plenk.), beetroot (Beta vulgaris L. var. crassa (Alef.) J. Helm.) and tomato (Lycopersicon esculentum Mill.). Seeds were germinated under control (NaCl 1 mM) and saline (100 or 150 mM NaCl) conditions. Generally, salinity decreased seedling fresh weight and germination percentage, spinach being the exception. The lowest effect of salinity on germination percentage was found with lettuce. Respiration rate increased with salinity in all species except spinach, while ethylene production increased in some species and decreased in others, as did free and total 1-aminocyclopropane-1-carboxylic acid (ACC). Polyamine levels changed with salinity, in most cases putrescine (Put) decreased while spermidine (Spd) and/or spermine (Spm) increased. That the ratio (Spd + Spm)/Put increased with salinity in all studied species would infer increased tolerance to salinity. Results obtained showed a general response by different plant species to salinity in relation to polyamine production, but not with regard to ethylene production. © 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Salinity tolerance; Germination; Ethylene; ACC; Putrescine; Spermine; Spermidine 1. Introduction Seed germination is a major factor limiting the establish- ment of plants under saline conditions [1]. The response to salinity during germination has been reported to be more complex than during plant growth because it depends on the availability of stored compounds [2]. Some plants that have been classified as salt sensitive, such as tomato and maize, can germinate under high concentrations of NaCl [3,4]. However, other tolerant species, such as cotton, are more sensitive during germination [5]. Consequently, the study of salt tolerance during germination, early and late growth of plants is important for determining saline limits at each developmental phase. Salt stress affects germination percentage, germination rate, and seedling growth in different ways depending on plant species. It has been found that germination percentage and growth of young seedlings were reduced with a high ∗ Corresponding author. Tel.: +34 966749684; fax: +34 966749678. E-mail address: mangeles.botella@umh.es (M. ´ A. Botella). NaCl concentration in beetroot [6]. Salinity caused a de- lay in germination and reduced germination percentage in different varieties of melon [7], and tomato [8]. In pepper, high osmotic concentrations lowered germination percent- ages and the latent period was longer [9]. Chartzoulakis and Klapaki, [10] with 100 and 150 mM NaCl, found similar re- sults. Previous work carried out by the authors of this paper with nine lettuce varieties showed that salinity delayed ger- mination and reduced growth of all studied cultivars [11]. Ethylene regulates a multitude of plant processes rang- ing from seed germination to organ senescence. The role of ethylene in germination remains unclear. Some authors have indicated that ethylene production is a consequence of seed germination. Others consider ethylene production to be required for germination [12–14]. Its involvement in plant responses to a variety of biotic and abiotic stresses is well known [15]. It has been suggested that this hormone and abscisic acid may modulate the physiological effects in- duced by salinity [16]. More specifically, increases in ethy- lene production during germination under saline conditions have been reported in different species such as rice, wheat, 0168-9452/$ – see front matter © 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2004.05.014