Superação de dormência e germinação de sementes de marcela (Achyrocline 12 satureioides) (Lam) DC (Asteraceae)

Abstract

The objective of this study was to evaluate different methods of dormancy overcoming and optimal germination conditions for marcela seeds, aiming at the standardization of the germination test for this species. Seeds of marcela plants harvested in the municipalities of Pelotas (Cascata district) and Arroio do Padre were used, totaling nine collection points. After harvesting the plants, the chapters were manually separated, and these were set to dry in an oven with air circulation at 28 °C for seven days. Subsequently, we proceeded with the manual threshing to obtain the seeds and their size separation, in sieves. The work was conducted at Seed Analysis Didactic Laboratory – FAEM / UFPel, and conducted different studies, divided into three chapters. The first one was responsible for identifying the initial physiological quality and, afterwards, 34 different treatments for overcoming seed dormancy were tested, among cold conditions, hydroconditioning and high temperatures, besides a control treatment. With the results of the first chapter, the second aimed to evaluate the overcoming of dormancy using the cold, using temperature of 10 °C and 5 °C under different conditions, being conducted in a factorial scheme, with Factor A: seed condition (stratification, dried seeds and hydroconditioning); and Factor B: cold exposure period (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 days). For chapters one and two, we used the germination test with evaluations performed at 7, 14 and 21 days after the start of the germination test (DAITG). In chapter three the best conditions of the germination test for marcela seeds were evaluated using germitest type paper (roll paper) and Gerbox type boxes (on paper) as substrate, with 21 DAITG evaluation. The experiment was conducted in a factorial scheme, with Factor A: germination temperature (20, 25, 30 and 20-30 °C); and Factor B: amount of water in the substrate (2.0, 2.5 and 3.0 times the weight of dry paper). It was concluded that overcoming dormancy of Marcela (Achyrocline satureioides) seeds, evaluated by germination at 7, 14 and 21 DAITG, is effective when using stratification methods at 10 °C for six days. In addition, the constant temperature of 20 °C to conduct the germination test is ideal, with substrate, between paper or paper, moistened with 2.0 to 3.0 times its dry weight, being evaluated at 21 DAITG.