Seasonal characterization of antioxidant responses in plants of Ipomoea nil cv. Scarlet O'Hara

Abstract

Reactive oxygen species can be produced in leaf cells during normal aerobic metabolism or in a variety of exogenous factors, which may cause oxidative damage to plants, unless they have an efficient antioxidant defense system, consisting of enzymatic and non-enzymatic substances. This work raised the hypothesis that plants of Ipomoea nil cv. Scarlet O'Hara, a native species and ornamental vine of the tropics, might tolerate oxidative stress factors imposed by natural fluctuations in weather conditions through changes in the antioxidant profile.The objective of this study was to determine the variations in three leaf antioxidants in plants growing inside a greenhouse without air pollutants and exposed to varying meteorological conditions throughout the four seasons of the year and to observe if such variations are related to the oscillations in meteorological factors. Four experimental campaigns were carried out, one in each season of 2006. Each campaign lasted 28 days and started with 45 plants. Ascorbic acid (AA) concentrations and superoxide dismutase (SOD) and peroxidase (POD) activities were determined in leaves of five plants in nine sampling days of each campaign. The antioxidant responses oscillated throughout the year. The highest values were found during the spring. This seasonal antioxidant profile was associated to variations in temperature, relative humidity and global radiation. Plants of this cultivar may then tolerate oxidative stress naturally imposed by meteorological conditions. Keywords: climber plant, ascorbic acid, superoxide dismutase, peroxidase, meteorological factors. Caracterização sazonal de respostas antioxidativas em plantas de Ipomoea nil cv. Scarlet O'Hara ResumoAs espécies reativas de oxigênio podem ser produzidas em células de folhas durante o metabolismo aeróbico normal ou o sob uma diversidade de fatores exógenos que, por sua vez, podem causar danos oxidativos às plantas, a menos que estas tenham um eficiente sistema de defesa antioxidativo, formado por substâncias enzimáticas e não enzimáticas. Neste trabalho, levantou-se a hipótese de que as plantas de Ipomoea nil cv. Scarlet O'Hara, uma espécie trepadeira ornamental e nativa dos trópicos, podem tolerar fatores de estresse oxidativo imposto por oscilações naturais nas condições meteorológicas por meio de mudanças no perfil antioxidativo. Assim, este trabalho objetivou determinar as variações em três espécies antioxidantes foliares em plantas crescidas em casa de vegetação sob ar filtrado e expostas a condições meteorológicas variáveis ao longo das quatro estações do ano de 2006, bem como verificar se tais variações estão relacionadas às oscilações de fatores meteorológicos. Para tanto, realizaram-se quatro campanhas experimentais. Cada campanha durou 28 dias e começou com 45 plantas. Concentrações de ácido ascórbico (AA) e as atividades de superóxido dismutase (SOD) e peroxidase (POD) foram determinadas em folhas de cinco plantas distintas e retiradas da casa de vegetação em nove dias de amostragem de cada campanha. A...

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