Adaptabilidade fisiológica ao estresse abiótico induzida pela aplicação de priming in vitro em plantas de cana-de-açúcar

Abstract

During all phenological phases, the plants are under the effects of environmental variations and to survive stressful conditions, they use antioxidant defense mechanisms, able to regulate the excess reactive oxygen species. Preconditioning techniques (priming), consisting of prior exposure to a stressor agent can stimulate the antioxidative defense mechanisms and promote more efficient responses, when the plant was again subjected to a stress cycle. The thesis has been conducted with the aim to describe the redox state of varieties of sugarcane micropropagation in temporary immersion bioreactor system (BIT) and submitted to in vitro priming with sodium chloride (NaCl), aiming to promote the rustification and preconditioning to salt stress and water, through analysis of growth and biochemical responses. Two experiments, which originated three scientific articles were performed. In the first, planting sugarcane variety RB867515 halopriming received treatments with 100 mM NaCl during in vitro culture in BIT and were subsequently subject to gradual salt stress in the greenhouse. In the second, plants of the variety RB98710 were preconditioned with halopriming in vitro (25 mM NaCl), submitted to treatments gradual salt stress with posterior irrigation without NaCl and evaluation of recovery. In the third, they were also performed treatments halopriming (25 mM de NaCl) with the variety RB98710, with subsequent submission of plants to salt and water stress. In the first article, preconditioning for 24 hours to afforded a better development of the plants of the variety RB867515 during salt stress. Has preserved the growth of plants, prevented the buildup of toxic ions and contributed to maintenance of the hydrogen peroxide levels (H2O2). In the second article, the priming favored the growth parameterswhile keeping the buildup of plant biomass and tillering, providing tolerance to salinity variety RB98710. In the third article, the treatment of priming stimulated the of enzymes activity of superoxide dismutase and catalase, which avoided lipid peroxidation and H2O2 accumulation, but it is not preserved the growth of plants in saline stress conditions. There was also no effect of priming to water stress, this caused reduction in plant growt, increase in content of H2O2 and lipid peroxidation.