Oxidative Stress and Antioxidants in Tomato (Solanum lycopersicum) Plants Subjected to Boron Toxicity

• Published in: Annals of botany 2007-10, Vol.100 (4), p.747-756
• Main Authors: Cervilla, Luis M, Blasco, Begoña, Ríos, Juan J, Romero, Luis, Ruiz, Juan M
• Format: Article
• Language: English
• Subjects: antioxidant enzymes; Antioxidants; Antioxidants - metabolism; ascorbate; Ascorbic Acid - metabolism; Barley; Biomass; Boron; Boron - pharmacology; Boron toxicity; Enzymes; glutathione; Glutathione - metabolism; Hydrogen Peroxide - metabolism; Leaves; lipid peroxidation; Lycopersicon esculentum; Lycopersicon esculentum - drug effects; Lycopersicon esculentum - growth & development; Lycopersicon esculentum - metabolism; Malondialdehyde - metabolism; Original; Oxidative Stress; Plant growth; Plant Leaves - drug effects; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant physiology; Plants; Reactive oxygen species; Solanum; tomato
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1093/aob/mcm156

BACKGROUND AND AIMS: Boron (B) toxicity triggers the formation of reactive oxygen species in plant tissues. However, there is still a lack of knowledge as to how B toxicity affects the plant antioxidant defence system. It has been suggested that ascorbate could be important against B stress, although existing information is limited in this respect. The objective of this study was to analyse how ascorbate and some other components of the antioxidant network respond to B toxicity. METHODS: Two tomato (Solanum lycopersicum) cultivars ('Kosaco' and 'Josefina') were subjected to 0·05 (control), 0·5 and 2 mM B. The following were studied in leaves: dry weight; relative leaf growth rate; total and free B; H₂O₂; malondialdehyde; ascorbate; glutathione; sugars; total non-enzymatic antioxidant activity, and the activity of superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, ascorbate oxidase and L-galactose dehydrogenase. KEY RESULTS: The B-toxicity treatments diminished growth and boosted the amount of B, malondialdehyde and H₂O₂ in the leaves of the two cultivars, these trends being more pronounced in 'Josefina' than in 'Kosaco'. B toxicity increased ascorbate concentration in both cultivars and increased glutathione only in 'Kosaco'. Activities of antioxidant- and ascorbate-metabolizing enzymes were also induced. CONCLUSIONS: High B concentration in the culture medium provokes oxidative damage in tomato leaves and induces a general increase in antioxidant enzyme activity. In particular, B toxicity increased ascorbate pool size. It also increased the activity of L-galactose dehydrogenase, an enzyme involved in ascorbate biosynthesis, and the activity of enzymes of the Halliwell-Asada cycle. This work therefore provides a starting point towards a better understanding of the role of ascorbate in the plant response against B stress.