Estresse oxidativo em trigo causado por diferentes disponibilidade de fósforo em solução hidropônica / Oxidative stress in wheat caused by different availabilities of phosphorus in hidroponics

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2011

RESUMO

Phosphorus (P) is one of the most important nutrients for plant growth. However, it is known that its availability is often hampered by the presence of chelating substances in the soil, which turns it unavailable. In order to study the oxidative stress caused by different concentrations of P in two cultivars of wheat, Toropi (tolerant) and Anahuac (sensitive to P deficiency), seedlings were grown under hydroponic conditions with 0 ¿M, 100 ¿M, 500 ¿M e 1000 ¿M de KH2PO4, after 10 days of treatment, roots and shoots were collected. The activity of antioxidative enzymes, catalase (CAT), glutathione reductase (GR) and ascorbate peroxidase (APX) were analyzed, the content of ascorbic acid (AsA) and non-protein thiols (NPSH) chlorophyll A, B and carotenoids were quantified. Oxidative stress was verified by the content of malonaldehyde (MDA), which assesses the levels of lipid peroxidation, also hydrogen peroxide and superoxide were quantified. Toropi and Anahuac showed differences in the production of reactive oxygen species when exposed to phosphorus deficiency. There was an increase in the production of H2O2 in the shoot of Anahuac, and of superoxide for Toropi when P availability was increased. Lipid peroxidation was found to be much higher in the leaves of Toropi, especially in the extreme conditions of P, on the other hand, in the roots only Anahuac showed increase in lipid peroxidation with increase in P availability. It is possible that very low levels of reactive oxygen species (ROS) in the roots, due to the P starvation, negatively affect root growth of Anahuac. The content of chlorophyll B and carotenoids were similar and the chlorophyll A content was constant. The AsA content was far greater in the roots than in the leaves for both cultivars and a similar pattern of NPSH production was observed. The results suggest that increase in P availability, induces ROS production, which is counteracted by increased activity of antioxidant enzymes, GR and APX, and higher content of carotenoids and chlorophyll B in Toropi. Anahuac responded to the oxidative stress caused by higher P availability by increasing catalase activity, but not efficiently, since the levels of lipid peroxidation also increased.

ASSUNTO(S)

trigo estresse oxidativo fosforo solo

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