For determination of ROS scavenging capacity, the H2O2 content of lime plants under EMF stress was estimated. H2O2 content was always significantly lower under EMF stress throughout the experiments until performed here (Figure 6). This result is in contrast to the obtained result on MDA content (Figure 5). Lower content of H2O2 might be a result of the significantly higher induction of the activities of antioxidant enzymes in the lime plants under EMF stress. Several authors have described the overproduction of toxic oxygen forms with aging in plants [37, 38]. It is known that ROS can cause peroxidation of membrane fatty acids [39]. In turn, these oxidized fatty acids may give rise to the propagation of peroxidation resulting in membrane damage.

In a recent report, Lacan and Baccou [40, 41], besides supporting that ROS are involved in the ripening and senescence events in nonnetted muskmelon fruit, also showed that the observed delay in senescence in the long-storage life variety Clipper is closely linked to the very low free radical induced membrane lipid peroxidation in comparison with that of the short-storage life variety Jerac. These data explain the EMF-improved ability to scavenge free radicals, leading to a delay in senescence and alterations in membrane integrity, as demonstrated by the growth and survival responses. Furthermore, these results suggest that, under specific conditions, it takes the combined action of more than one antioxidant to provide an increased resistance to oxidative stress and lengthened survival in plants. This is in agreement with some previous reports [42, 43].

Figure 6Effect of EMF on H2O2 content in healthy and infected plants of Citrus aurantifolia. Vertical bars indicate mean �� SE of three replicates. Different letters indicate significant differences (P < 0.05).4. ConclusionsThe obtained result show that 10KHz EMF field can simulate the growth rate of healthy and infected lime plants. Moreover, it seems that EMF field could reduce the intensity of Witches' broom disease in infected trees and this effect could probably be due to the reduction of phytoplasma in plant tissues. This study provides an initial understanding of the response of infected lime plants to EMF stress, which is important for future studies aimed at developing strategies for struggle against phytoplasma and Witches' broom disease in lime plants.AcknowledgmentsThe financial support of this research was provided partly by College of Science, University of Tehran and partly by Engineering Research Institute.
In higher plants, salinity GSK-3 can provoke alterations in the metabolism of proteins and nucleic acids, photosynthesis and respiration [1�C3].