Germination of Anadenanthera colubrina seeds in abiotic stresses
Anadenanthera colubrina ((Vell.) Brennan) FABACEAE is a species with multiple uses (wood, coal, popular medicine and industry) and widely distributed in all brazillian territory. Its size ranges from 3 to 15 m in Caatinga, although in other ecosystems, such as the Altantic Forest it reaches 30m. The dehiscent legumes and seeds are mature by September (the end of dry season) and have an autocoric dispersion syndrome. Seeds are very thin, black, coin- shaped, non-dormant and germinate very quickly when in good conditions of water and temperatures (Dantas et al., 2014). This species is recommended for environmental restoration due to its fast growth and adaptation to poor and degraded soils. Moreover, it can also be used in urban forestry and landscape (Maia, 2012). The objective of this study was to evaluate the influence of environmental stresses on the germination of seed lots of A. colubrina from different harvest years (2012 to 2013) and provenances (Jutaí, Barro, Custódia, Brejo Santo). Prior to germination tests the seeds of about 10 % water content (Brasil, 2013) were macerated in a detergent solution for five minutes. 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. Or 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.