Condicionamento fisiológico e pelotização de sementes de tabaco

Abstract

Tobacco seeds are very small (approximately 0.75 x 0.53 x 0.47 mm) and, for this reason, they are pelletized for commercialization, which facilitates sowing. However, the pellet may affect germination due to the barrier formed by the coating, making the emission of the radicle, water absorption and gas exchange with the environment difficult. Thus, all of the stages and procedures adopted in pelletizing must be monitored, seeking to obtain quality seeds. The physiological conditioning of the seeds may be an alternative before the pelletizing process, seeking to reduce the negative effect of the coating in germination speed. In addition to promoting the increase in germination speed of the seeds, the conditioning also allows a more synchronized germination, resulting in a uniform stand. The treatment may improve seed development, allowing the seeds to sever the coating in a quick and uniform manner. In order to verify the influence of the pellet in germination and emergence of the tobacco seeds, we evaluated different phases of the pelletizing process, investigating the factors which affect their quality. To adapt the physiological conditioning methodology, we evaluated the following factors: temperature (15 and 25 oC), soaking time (24; 48 hours) and conditioning medium (water, PEG-6000, KNO3, PEG-6000 + KNO3 and the combination of each medium with gibberellic acid (GA3)). In order to verify the relations between the conditioning and the germination of the pelletized seeds, after adapting the best invigorating methodology, we evaluated the physiological quality of the tobacco seeds, submitted to hydro-conditioning and pelletized. We concluded that the evaluated pelletizing process does not influence the quality of the tobacco seeds, but delays the germination process. The physiological conditioning in water at 25 oC, for 24 hours positively affects the germination and emergence of nude and pelletized tobacco seeds.