Germinação e vigor de sementes de urucu

Abstract

This research was carried out to evaluate the germination and vigor of annatto seeds (Bixa orellana L.) during maturation, collecting samples 70, 77, and 84 days after anthesis (DAA). The research consisted of two phases: first, seed samples of each harvest were submitted to different treatments: (i) mechanical scarification; (ii) thermotherapy (70°C in water bath) for 1, 2, and 3 min; (iii) prechilling at 3°C during seven days, using distilled water or KNO3 solution to moist the paper towel, and untreated intact seeds (control). In the second phase, seed samples (70, 77, and 84 DAA) were submitted to accelerated aging (AA) (42°C, 100% relative humidity) for 0, 12, 24, 36, 48, 60, 72, 84, and 96 hours. In both phases, seeds were sub sampled for evaluation. The germination of intact seeds collected 70, 77, and 84 DAA was 51, 53, and 16%, respectively, and thermotherapy was the only treatment that significantly altered it. Although hindering the germination of seeds collected 70 DAA, thermotherapy for 1 and 3 minutes enhanced germination in seeds collected 84 DAA (62 and 55%, respectively). In intact seeds, the germination rate (GR) of seeds collected 84 DAA (0.51) was significantly lower than in seeds collected 70 (1.90) and 77 DAA (2.32). However, thermotherapy significantly increased GR for seeds collected at 84 DAA (1.65, 3.03, 1.83, respectively for 1, 3, and 5 minutes of immersion), which suggests the occurrence of dormancy after the alleged physiological maturation point (84 DAA). For seeds collected 70 DAA, accelerated aging (AA) up to 96 hours did not interfered in germination. For seeds collected 77 and 84 DAA, germination decreased as exposure time to AA increased. Seeds collected 70 DAA had the highest proportion of regular seedlings.