Caracterização bioquímica parcial de sementes, plântulas, e calos cultivados de Calotropis Procera expostos à ação de campo magnético

Abstract

ABSTRACT Magnetic field (MF) is a natural component of the environment and affects living organisms with intensities between 25μT and 65μT, depending on different geographic locations. However, it can act as an abiotic stressor. There are reports in the literature about the effects of magnetic fields on plants, most of the studies with species of agronomic importance. In this project, the effect of exposure to MF (5 days) was characterized, in biochemical terms, with seeds, callus and seedlings of Calotropis procera (Apocynaceae), a species of laticiferous plant that has therapeutic potential. C. procera seeds were exposed to MF and analyzed before sowing. C. procera were germinated under MF (2 mT) or exposed to MF and then germinated, this MF being generated by a Helmholtz coil. Seedlings and callus were exposed to MF and then analyzed. Exposure to MF reduced seed germination time and increased germination rate. This was accompanied by increased fresh and dry matter. Antioxidant enzymes activity: such as CAT, POX, and APX were altered in seeds after exposure to MF. The increase in the levels of hydrogen peroxide and malondialdehyde were indicators of oxidative stress. DNA integrity was not altered, while the cell density, amount of soluble protein and DNA increased, in relation to control treatment. Proteomics/bioinformatics analyses corroborated these data. Overall, these observations indicated oxidative stress in seeds submitted to MF. However, this did not affect seed germination. On the contrary, it improved germination performance in terms of time and proportion. This study indicates that exposure to MF induces an intriguing balance between oxidative stress (potentially harmful) and accelerated germination (desired effect) of seeds. Such effects can be technologically appreciated for the production of seedlings, mainly of recalcitrant seeds of important agronomic species. Seedlings and callus also had growth favored by exposure to MF, with higher concentration of photosynthetic pigments and lower lignin content in the callus. Exposure to MF provided faster growth and development of C. procera and this observation seems to be associated with a redox condition favorable to the activation of cellular metabolism, indicated by an increase in the content of DNA, soluble proteins and a differential increase in proteins involved in cellular metabolic activities, typical of growth