Germination of Myracrodruon urundeuva seeds in abiotic stresses
Myracrodruon urundeuva Allemão (Anacardiaceae), a native species to the Caatinga with wide distribution in all South America, shows the potential to survive wide climatic variations. The objective of this study was to evaluate the influence of environmental stresses on the germination of seed lots of M. urundeuva from different harvest years (2010 to 2013) and biomes (Caatinga, Pantanal and Cerrado). Prior to germination tests the diaspores of about 10 % water content (Brasil, 2013) were macerated in a detergent solution for five minutes. Seeds of M. urundeuva were extracted from fruits using aluminium sieves and surface sterilized in sodium hypochlorite (2.5%) for three minutes, rinsed thoroughly with tap water and treated with captan fungicide (3mL fungicide/1L seeds). All germination tests were performed in a totally randomized design, during 14 days with four replicates of 25 seeds sown in transparent germination boxes onto two layers of blotting paper moistened either with water, polyethylene glycol 6000 (PEG) or sodium chloride (NaCl) solutions in a volume corresponding to 2.5 times the weight of the paper (Brasil, 2013). Seeds were incubated on blotting paper moistened with water at eight constant temperatures from 5 oC to 50 oC (with intervals of 5 oC), with a 12 h photoperiod. To create data for a hydrotime model, seeds were incubated at 25 oC, with a 12 h photoperiod, on blotting paper moistened with seven PEG or NaCl solutions from 0 MPa (pure distilled water) to -1.1 MPa (equivalent to 444 mmol L-1 NaCl and 30 dS m-1) (Villela, 1991). Seed germination was evaluated twice a day during 14 days, until no germination was observed for at least 5 days. Seeds were considered germinated when radicle emergence was ≥ 1mm in length. Data consists of the average germination of 3 replications of 50 seeds as a function of time.