Changes in Growth and Activity of Enzymes Involved in Nitrate Reduction and Ammonium Assimilation in Tomato Seedlings in Response to NaCl Stress

• Published in: Annals of botany Vol. 99; no. 6; pp. 1143 - 1151
• Main Authors: Debouba, Mohamed, Maâroufi-Dghimi, Houda, Suzuki, Akira, Ghorbel, Mohamed Habib, Gouia, Houda
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.06.2007; Oxford Publishing Limited (England)
• Subjects: Amino Acid Oxidoreductases - metabolism; amino acids; enzyme activity; Enzymes; glutamate dehydrogenase; glutamates; INVITED REVIEW; Leaves; nitrate reductase; Nitrate Reductase - metabolism; Nitrates; Nitrates - metabolism; nitrogen metabolism; plant growth; Plant physiology; Plant roots; plant tissues; Plants; Quaternary ammonium compounds; Quaternary Ammonium Compounds - metabolism; roots; saline water; salt stress; Salts; Seedlings; Seedlings - drug effects; Seedlings - growth & development; Seedlings - metabolism; sodium chloride; Sodium Chloride - pharmacology; Solanum lycopersicum; Solanum lycopersicum - drug effects; Solanum lycopersicum - growth & development; Solanum lycopersicum - metabolism; stress response; Table salt; Time Factors; tomatoes; water use; NaCl stress, nitrate reduction; Ammonium assimilation, growth
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1093/aob/mcm050

BACKGROUND AND AIMS: In Tunisia, salt water is largely used for tomato irrigation. In this work, a study was made of the changes in the nitrate reduction and ammonium assimilation into amino acids in tomato seedlings under salinity in order to providee further insight into the salt effects on plant growth. METHODS: Ten-day-old tomatoes (Solanum lycopersicum) were subjected to 100 mM NaCl stress, and nitrogen metabolism in leaves and roots was studied. KEY RESULTS: The concentrations of Na⁺ and Cl⁻ rapidly increased in the leaves and in the roots following exposure of tomato seedlings to NaCl stress. In contrast, the NO₃⁻ concentrations were lowered first in the roots and later in the leaves. From 5 to 10 d of treatment, salt ions provoked a decrease in the dry weight and an increase in the NH₄⁺ concentrations in the leaves. Inhibition was observed in the leaves for the activities of nitrate reductase (NR, EC 1·6·6·1), ferredoxin-dependent glutamate synthase (Fd-GOGAT, EC 1·4·7·1) and deaminating glutamate dehydrogenase (NAD-GDH, EC 1·4·1·2). NaCl affected these enzyme activities less in the roots than in leaves. This was in accordance with the pronounced decrease of dry weight by salt in leaves compared with that in the roots. CONCLUSIONS: NaCl stress effects on growth, metabolite concentrations and enzyme activities depended on the duration of salt treatment and the plant tissue.