Hormonal changes during salinity-induced leaf senescence in tomato (Solanum lycopersicum L.).
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 F(v)/F(m) 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.
Groupe de Recherche en Physiologie Végétale, Université catholique de Louvain (UCL), Croix du Sud 5, boîte 13, B-1348 Louvain-la-Neuve, Belgium.
Michel Edmond
ME
Ghanem
Alfonso
A
Albacete
Cristina
C
Martínez-Andújar
Manuel
M
Acosta
Remedios
R
Romero-Aranda
Ian C
IC
Dodd
Stanley
S
Lutts
Francisco
F
Pérez-Alfocea
D000040:Abscisic Acid / Q000378:metabolism; D000598:Amino Acids, Cyclic / Q000378:metabolism; D002473:Cell Wall / Q000201:enzymology; D002734:Chlorophyll / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D018551:Solanum lycopersicum / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D054712:Salinity; D012964:Sodium / Q000378:metabolism; D043324:beta-Fructofuranosidase / Q000378:metabolism
D000598:Amino Acids, Cyclic; D003583:Cytokinins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D002734:Chlorophyll; C023863:1-aminocyclopropane-1-carboxylic acid; C030737:indoleacetic acid; D000040:Abscisic Acid; D012964:Sodium; D010088:Oxidoreductases; C019984:cytokinin oxidase; D043324:beta-Fructofuranosidase; D011188:Potassium