Atividade respiratória e metabolismo antioxidativo em raízes de plântulas de milho (Zea mays L.) submetidas ao estresse salino / Respiration activity and antioxidative metabolism in roots of maize (Zea mays L.) seedlings submitted to salt stress

AUTOR(ES)

Ricardo Marques Montanari

DATA DE PUBLICAÇÃO

2006

RESUMO

Tolerance to salt stress was studied in maize seedlings (Zea mays L.) cultivars AGN 3150, BR 106, BR 201, BR 206 and SHS 4040, grown in Hoaglands nutrient solution. Treatments with NaCl 50 and 100 mM led to a decrease in the biomass production and to an increase in the relative electrolyte leakage in the roots and shoots in all cultivars. However, the largest decrease in growth and electrolyte leakage were shown by cultivar BR 106 and the smallest ones by cultivar AGN 3150, lead them to be considered as the most sensitive and the most tolerant to salt stress, respectively. The effect of NaCl 100 mM was investigated by considering some components of the antioxidative metabolism and mitochondrial respiration in roots of the seedlings. The tolerant cultivar showed increased activities of the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione redutase (GR), as well as increase in ascorbate/dehydroascorbate ratio. The sensitive cultivar showed reduction in catalases (CAT) and GR activities as well as in ascorbate/dehydroascorbate ratio. The lipid peroxidation degree increased in roots and isolated mitochondria, only in the sensitive cultivar. In mitochondria isolated from the tolerant cultivar, NaCl treatment promoted an increase in the state 4 respiration rate and in the alternative pathway capacity. Additionally, salinity promoted a decrease in ADP/O and respiratory control ratios, indicating a lower coupling, likely due to an increase in alternative oxidase (AOX) activity. In sensitive cultivar, total respiration activity and the ADP/O ratio were strongly decreased, however the capacity of the alternative pathway was not altered. The NaCl treatment promoted decrease in the uncoupling protein (UCP) activity in the tolerant cultivar, but an increase it in the sensitive one occurred. These results suggest that the tolerant cultivar exhibits a larger efficiency in the reactive oxygen intermediates scavenging, as compared to the sensitive one. In addition, the high tolerance of cultivar AGN 3150 to the salt stress could be related to its high AOX capacity. A possible contribution of the UCP could not be confirmed from the results observed.

ASSUNTO(S)

metabolismo antioxidativo mitocondria fisiologia vegetal stress salino milho antioxidative metabolism salt stress mitochondria maize

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