JXB Advance Access published online on June 23, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern153
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Hormonal changes during salinity-induced leaf senescence in tomato (Solanum lycopersicum L.)
1Groupe de Recherche en Physiologie Végétale, Université catholique de Louvain (UCL), Croix du Sud 5, boîte 13, B-1348 Louvain-la-Neuve, Belgium
2Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Campus Universitario de Espinardo, PO Box 164, E-30100 Murcia, Spain
3Departamento de Biología Vegetal–Fisiología Vegetal, Facultad de Biología, Universidad de Murcia, Campus Universitario de Espinardo, E-30100 Murcia, Spain
4Departamento de Mejora Vegetal, Estación Experimental ‘La Mayora’ (EELM), Consejo Superior de Investigaciones Científicas (CSIC), E-29750 Algarrobo-Costa, Málaga, Spain
5Department of Biological Sciences, The Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
To whom correspondence should be addressed. E-mail: alfocea{at}cebas.csic.es
Leaf senescence is one of the most limiting factors to plant productivity under salinity. Both the accumulation of specific toxic ions (e.g. Na+) and changes in leaf hormone relations are involved in the regulation of this process. Tomato plants (Solanum lycopersicum L. cv Moneymaker) were cultivated for 3 weeks under high salinity (100 mM NaCl) and leaf senescence-related parameters were studied during leaf development in relation to Na+ and K+ contents and changes in abscisic acid (ABA), cytokinins, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and the auxin indole-3-acetic acid (IAA). Na+ accumulated to a similar extent in both leaves 4 and 5 (numbering from the base of the plant) and more quickly during the third week, while concurrently K+ contents sharply decreased. However, photosystem II efficiency, measured as the Fv/Fm ratio, decreased from the second week of salinization in leaf 4 but only at the end of the third week in the younger leaf 5. In the prematurely senescent leaf 4, ABA content increased linearly while IAA strongly decreased with salinization time. Although zeatin (Z) levels were scarcely affected by salinity, zeatin-riboside (ZR) and the total cytokinin content (Z+ZR) progressively decreased by 50% from the imposition of the stress. ACC was the only hormonal compound that increased in leaf tissue coincident with the onset of oxidative damage and the decline in chlorophyll fluorescence, and prior to massive Na+ accumulation. Indeed, (Z+ZR) and ACC contents and their ratio (Z+ZR/ACC) were the hormonal parameters best correlated with the onset and progression of leaf senescence. The influence of different hormonal changes on salt-induced leaf senescence is discussed.
Key words: Abscisic acid, 1-aminocyclopropane-1-carboxylic acid, indole-3-acetic acid, plant hormones, salt stress, senescence, sodium chloride, tomato (Solanum lycopersicum L.), zeatin, zeatin-riboside
* These authors contributed equally to this work.
Received 19 February 2008; Revised 30 April 2008 Accepted 8 May 2008
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