Suchergebnisse

The plant-parasitic nematodes Meloidogyne and Pratylenchus are the main nematode pathogens reducing sugarcane yield worldwide. Despite, defense responses to overcome the pathogen stresses through neutralizing cytotoxicity of reactive oxygen species (ROS) have been reported for a range of important crops and pathogens, few studies have been developed for sugarcane under nematode stress. The aim of this study was to evaluate responses of the antioxidant enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) at different density of Meloidogyne and Pratylenchus in a sugarcane replant field and in a ratoon crop. Evaluations based on nematode densities, plant growth parameters and SOD and APX activity at six (T6) and nine (T9) months after planting (Area 1) or cutting (Area 2 - ratoon crop). Pratylenchus abundance significantly decreased in Area 1, but not in Area 2. In contrast, Meloidogyne abundance increased through time in Area 1, but decreased in Area 2. In both areas, SOD activity decreased over time, but APX activity did not present significant fluctuation over time in Area 1, in contrast to the increase over time of APX activity in Area 2. Abundance of both nematodes correlated positively with number of tillers and negatively with height of stalks, besides the negative correlation between Pratylenchus and stalk diameter. This inverse correlation between the plant-parasitic nematode and stalk number was also demonstrated by the PCA. There was not significant correlation between the antioxidant enzymes and plant growth parameters or nematode abundance, except the positive correlation between SOD activity and number of tillers.

Aluminium (Al) toxicity in acid soils is a major abiotic stress that can limit plant production worldwide. Al toxicity directly inhibits root development and exacerbates oxidative stress in the plant. Sugarcane is mostly cultivated in tropical regions and is often exposed to phytotoxic concentrations of soil Al. In this study, our objectives were to evaluate nine sugarcane cultivars on their tolerance to Al in a hydroponic system, investigating the effects of 143µM {Al3+} on root growth and on activity of the antioxidant enzymes ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD). The screening method proposed was suitable for a rapid, reliable and reproducible procedure of the sugarcane cultivars. Exposure to Al for three days altered root growth and activity of enzymes of the nine sugarcane cultivars. However, the magnitude of the alterations varied significantly among cultivars. The cultivar RB928064 was classified as Al-tolerant and the cultivar RB835486 as Al-sensitive. Increases in enzyme activity after Al exposure varied from 4 to 46%, with average increases of 19% in APX, 20% in CAT, and 8% in SOD. The variations induced by Al in enzyme activity, however, did not correlate significantly with those variations induced by Al in the root growth.

<i>Background:</i> Reactive oxygen species, which are believed to play an important role in the aging process, are also found to be related to allergic skin diseases. Skin reactions to allergens are known to affect the antioxidant defense system such as antioxidant enzymes. <i>Objectives:</i> This study was conducted in order to investigate changes of the enzymatic antioxidant defense system in the lesional skin of allergic contact dermatitis (ACD) in vivo<i></i>and the influence of skin aging on the changes in the enzymatic antioxidant defense system. <i>Methods:</i> Diphenylcyclopropenone (DPCP) application was used to induce ACD in 10 volunteers under 30 years old and in 10 over 70 years old. Antioxidant enzyme assays were performed in 5 young volunteers and 6 elderly volunteers who showed a weakly positive reaction after DPCP application. The activities of catalase, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured in the lesional skin of ACD and in normal control skin. The differences between the two age-distinct groups were also compared and analyzed. <i>Results:</i> Compared with the control site, the DPCP-affected skin revealed a significantly lower catalase activity in both the young and the old groups. Reductions in cutaneous catalase activity were not different in the young and old skins. In contrast, SOD and GPx did not show any significant difference with respect to the presence of contact dermatitis or age. <i>Conclusion:</i> The catalase activity of human skin with ACD decreased in both young and old skins. These findings suggest that cutaneous catalase may play an important role in the pathophysiology of ACD.