Estádios de maturação de frutos, secagem e armazenamento de sementes de tabaco

Abstract

The tobacco farming is dependent on seedlings transplanting originated from seeds and therefore the economic viability of culture is closely linked to the seeds quality. The objective of this study was to evaluate the influence of harvest point and drying methods on the tobacco seeds quality during storage. Seeds of cultivars CSC 439 and CSC 444, were evaluated separately. The experimental design was a factorial RBD with additional treatment (3x2x4) + 4, ie, 3 maturation stages, 2 drying methods and 4 storage periods, and an additional for each season, using three blocks. Fruits were classified into three maturity stages (E1, E2, E3) according to specific staining: fruits with at least 50% brown color and totally green stalk (E1); totally brown fruits and until 50% of stalk with the same color (E2); totally brown fruits and stalk, since that still firmly attached to the plant (E3). The selected fruits were separated into two parts, half were subjected to pre-drying process and the other half not. The fruits not submitted to pre-drying were placed in dryer with forced air ventilation (2.5 m/s) with a temperature of 35 °C, until the seeds have reduced moisture to values around 8%. The pre-drying consisted in permanence of fruits in dryer with forced ventilation (2.5 m/s) at room temperature until the time when the seeds have reached close moisture to 20%. After pre-drying, it was proceeded drying with forced air ventilation (2.5 m/s) with a temperature of 35 °C, until the seeds reduced the moisture to values around 8%. Physiological and vigor analysis tests were performed throughout the storage period: germination percentage, first count of germination, germination velocity index, electrical conductivity, initial plants stand, final plants stand, germination speed index, leaves/plant counting of number, shoot length of plants, plant dry matter. The tests were performed punctually at the times zero, 2, 4 and 6 months of storage.