Polyamines and ethylene changes during germination of different plant species under salinity

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. (C) 2004 Elsevier Ireland Ltd. All rights reserved.