Perfil fisiológico e bioquímico de três variedades de cana-de-açúcar (Saccharum spp.) durante a aclimatização

Abstract

The cultivation of sugarcane in Brazil has notoriety for contributing significantly to the economy. The micropropagation is a tool for tissue culture plants to produce on a large scale genetically identical to the mother plant in a relatively short time compared with the conventional spread, environmental, and controlled aseptic conditions. The acclimatization stage is considered critical by large losses of micropropagated material, caused by the changing environment of the laboratory plants for greenhouses. Objective was to evaluate plants of varieties sugarcane RB931011 , RB92579 and RB98710 in different acclimatization conditions. These varieties were micropropagated in temporary immersion bioreactor (BIT) and acclimatized in a greenhouse whose structural roofing material consisted of milky plastic (PL), half of the area covered in association with black mesh shade (MS) (70% shading ). The plants were subjected to full sun (SP), after 30 days in the greenhouse. The acclimatization period under PL and MS was 15 days. The three varieties were planted in the substrate Carolina Soil® in volumes of 55 cm3 and 95 cm3, establishing the following treatments : T1 (RB931011 - 55 cm3), T2 (RB931011 - 95 cm3), T3 (RB92579 - 55 cm3), T4 (RB92579 - 95 cm3), T5 (RB98710 - 55 cm3) and T6 (RB98710 - 95 cm3). Every 15 days were evaluated: number of leaves (NF), plant height (AP) and percentage of plants with tillers (% P). At the end of the experimental period were determined: dry shoot weight (MSa) and roots (MSr), percentage of survival (S%), leaf area (AF), high water content (CHR), stomatal density, activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT), content of malondialdehyde (MDA) and hydrogen peroxide. The experimental design was completely randomized in a 2x3 factorial design with 20 replications. Each replicate was represented by one plant per pot. The RB92579 and RB98710 varieties showed more robustness reaching the largest biometric medium and higher survival rate in the acclimatization. The largest volume of substrate provided better average height, dry weight, leaf area and lower SOD activity after 45 days of acclimatization, highlighting the influence of stress reduction and balance in plants. The substrate volume of 95 cm3 is the most suitable for acclimatization and plant production of sugarcane.