e-ISSN 1983-4063 - www.agro.ufg.br/pat - Pesq. Agropec. Trop., Goiânia, v. 49, e55341, 2019 Research Article Physiological quality of Urochloa brizantha seeds submitted to priming with calcium salts1 Elizena Cristina Gomes Ribeiro2, Rodrigo de Góes Esperon Reis2, Cesar Crispim Vilar2, Flavia Carolina Moreira Vilar2 ABSTRACT RESUMO Qualidade fisiológica de sementes deUrochloa brizantha submetidas a condicionamento com sais de cálcio Seed priming provides a variety of benefits, including seed invigoration and reduced dormancy. Urochloa brizantha O condicionamento fisiológico proporciona vários seeds are typically primed with difficult-to-acquire potassium benefícios, como melhoria no vigor das sementes e redução no grau nitrate (KNO3). In this sense, calcium salts stand out as an de dormência. Em sementes de Urochloa brizantha, geralmente, se alternative, but it is important to determine whether they provide utiliza nitrato de potássio (KNO3), que é de difícil aquisição. Nesse the same benefits as potassium nitrate. This study aimed to sentido, os sais de cálcio se destacam, mas é necessário verificar evaluate the physiological quality of U. brizantha seeds after se proporcionam os mesmos benefícios que o KNO3. Objetivou-se priming with calcium salts, and compare the results to those avaliar a qualidade fisiológica de sementes de U. brizantha após obtained with potassium nitrate. Seeds were submitted to condicionamento com sais de cálcio, em comparação a KNO3. priming with calcium nitrate [Ca(NO3)2] and calcium sulphate Utilizaram-se sementes submetidas a condicionamento fisiológico (CaSO4) at -0.55 MPa and -1.10 MPa, for 12 h and 24 h, and com nitrato de cálcio [Ca(NO3)2] e sulfato de cálcio (CaSO4) a potassium nitrate (KNO3) at -1.10 MPa for 12 h, as well as to -0,55 MPa e -1,10 MPa, por 12 h e 24 h, além de KNO3 a -1,10 MPa, no priming (control). A completely randomized design, with ten por 12 h, e sementes sem condicionamento (testemunha). Utilizou- treatments and four repetitions, was used. Priming promoted a se delineamento inteiramente casualizado, com dez tratamentos higher germination percentage and lower seed dormancy, with e quatro repetições. O condicionamento proporcionou menor a greater seedling emergence in a shorter time period. CaSO4 porcentagem de sementes dormentes e maior porcentagem de did not differ from KNO3 in shoot dry weight of seedlings, but germinação e de emergência de plântulas em menor tempo. O CaSO4 reduced the electrical conductivity of seeds. Calcium nitrate não diferiu do KNO3, quanto à massa seca da parte aérea de plântulas, and calcium sulfate show a promising potential for use in the e reduziu a condutividade elétrica das sementes. Nitrato e sulfato osmotic priming of Urochloa brizantha (BRS Piatã cultivar) de cálcio apresentam potencial promissor para serem utilizados seeds, since they are as efficient as potassium nitrate, as well no condicionamento osmótico de sementes de U. brizantha cv. as less costly and easier to purchase. Calcium sulfate priming BRS Piatã, visto que são tão eficientes quanto o KNO3, possuem at -0.55 MPa for 12 h, at 25 ºC, is recommended to replace the menor custo e têm maior facilidade de aquisição. Recomenda-se potassium nitrate solution. o condicionamento em solução de sulfato de cálcio a -0,55 MPa por 12 h, a 25 ºC, para substituir a solução de nitrato de potássio. KEYWORDS: Seed invigoration, calcium nitrate, calcium PALAVRAS-CHAVE: Envigoramento de sementes, nitrato de sulfate. cálcio, sulfato de cálcio. INTRODUCTION in Urochloa spp. seed production, consumption and exportation (Pereira et al. 2011). Grasses from the Urochloa (previously The demand for Urochloa spp. seeds has Brachiaria) genus have become increasingly increased considerably, largely due to the use of straw important in the Brazilian livestock breeding due to in no-tillage areas, providing benefits such as higher their use as pasture (Valle et al. 2009), accounting for biomass production, better soil coverage and slower about 80 % of the pasture seed market (Costa et al. decomposition, which suppress weeds and prevent 2011). As such, Brazil has become the global leader re-infestation (Timossi et al. 2007, Torres et al. 2008). 1. Received: Oct. 10, 2018. Accepted: May 30, 2019. Published: Jul. 09, 2019. DOI: 10.1590/1983-40632019v4955341. 2. Universidade do Estado de Mato Grosso, Faculdade de Ciências Agrárias, Biológicas e Sociais Aplicadas, Nova Xavantina, MT, Brasil. E-mail/ORCID: [email protected]/0000-0001-5955-7805, [email protected]/0000-0003-3656-664X, [email protected]/0000-0002-5415-6057, [email protected]/0000-0001-9589-7436. 2 E. C. G. Ribeiro et al. (2019) Urochloa spp. seeds do not germinate NAD(P)H to NAD(P)+ in the pentose-phosphate uniformly because of external structures that metabolic pathway (Hendricks & Taylorson 1974, inhibit gas diffusion and/or lead to undeveloped Cardoso et al. 2015). In the case of calcium sulfate, embryos (Munhoz et al. 2009, Binotti et al. 2014), studies have shown accelerated emergence and compromising the pasture implementation and decreased mortality in seeds planted in acidic soil contributing to its degradation (Lacerda et al. 2010). (Murata et al. 2008), likely due to the immobilization Studies aimed at overcoming seed dormancy of Al3+, the main problem in these soils. are indispensable in obtaining better quality seed This study aimed to evaluate the physiological lots with high germination and vigor. In this quality of Urochloa brizantha (BRS Piatã cultivar) respect, pre-germination treatments such as priming seeds after priming with calcium salts, and compare may reduce the percentage of dormant seeds, the results to those obtained with potassium nitrate accelerating germination and homogenizing the priming. seedling establishment (Abdoli 2014, Binotti et al. 2014, Cardoso et al. 2015, Paparella et al. 2015, MATERIAL AND METHODS Gebreegziabher & Qufa 2017, Batista et al. 2018, Pereira et al. 2018). The experiment was carried out at the Priming involves the partial moistening of Universidade do Estado de Mato Grosso, in Nova seeds, what helps to unlock the metabolic processes Xavantina, Mato Grosso state, Brazil, from October to that occur during the initial germination phases, December 2016. The Urochloa brizantha (BRS Piatã preventing radicle protrusion and maintaining seed cultivar) seeds were harvested in the 2015/2016 season. tolerance to desiccation (Paparella et al. 2015, Each treatment consisted of 20 g of seeds Ibrahim 2016). As a result, the seeds prepare for submitted to priming at 25 ºC, in solutions of calcium germination by restructuring membranes and nitrate [Ca(NO3)2] and calcium sulfate (CaSO4), at reorganizing metabolic systems, what favors a faster -0.55 MPa and -1.10 MPa, for 12 h and 24 h, and a uniform germination when conditions become more potassium nitrate (KNO3) solution at -1.10 MPa for favorable, or in adverse environments (Jisha et al. 12 h (Bonome et al. 2006), as well as no priming 2013, Ibrahim 2016, Batista et al. 2018). Osmotic (control). Each solution was prepared using the conditioning, or osmopriming, is a priming technique concentrations presented in Table 1, in order to obtain whereby seeds are soaked in a solution with low the desired osmotic potential. hydric potential, and water absorption occurs until The concentration of all solutions containing their internal hydric potential and that of the solution calcium salts and potassium nitrate were calculated are the same (Jisha et al. 2013, Hussian et al. 2014). using the Van’t Hoff’s equation (Hillel 1971): According to the scientific literature on seed Ψos = -iRTC, where Ψos is the osmotic potential of the priming, potassium nitrate (KNO3) has shown solution (MPa), i the isotonic coefficient, R the gas promising results in improving the physiological constant (0.0083 L MPa K-1 mol-1), T the temperature quality of several species (Anosheh et al. 2011, (K) and C the concentration (mol L-1). Entesari et al. 2012), including Urochloa brizantha The following equation was used to calculate (Bonome et al. 2006, Binotti et al. 2014, Cardoso et the isotonic coefficient (i): i = 1 + α(q - 1), where α al. 2015). In addition to osmotic priming, most studies is the degree of ionization (decimal) and q the total use other substances to boost seed germination and seedling establishment in the field, including Table 1. Solutes, osmotic potential and concentrations of solutions nutrients, growth regulators and biostimulants used for osmotic priming of Urochloa brizantha (BRS (Cardoso et al. 2015, Ramos et al. 2015, Pallaoro et Piatã cultivar) seeds. al. 2016, Batista et al. 2018). Calcium salts such as calcium nitrate Osmotic potential Concentration Solute -1 [Ca(NO ) ] and calcium sulfate (CaSO ) are an at 25 ºC (MPa) (g L ) 3 2 4 -0.55 17.5568 Ca(NO ) 4H O alternative to KNO3, can be easily purchased and 3 2 2 -1.10 35.1276 are less costly. Studies have found that priming -0.55 19.1816 CaSO 2H O using nitrates overcomes dormancy and increases 4 2 -1.10 38.3910 germination, since they act as oxidants, converting KNO3 -1.10 22.5308 e-ISSN 1983-4063 - www.agro.ufg.br/pat - Pesq. Agropec. Trop., Goiânia, v. 49, e55341, 2019 3 Physiological quality of Urochloa brizantha seeds submitted to priming with calcium salts 3 number of ions released during the ionization of a Emergence - quadruplicates of 50 seeds compound (mol). were planted in sand beds, with daily irrigation and Seeds from each treatment (20 g) were placed counting of emerged seedlings until 21 DAP, when in 500 mL plastic containers to which 150 mL of counting stabilized. The emergence percentage and priming solution were added in order to cover all average emergence time were calculated based on the seeds. The control seeds did not receive any the values obtained at counting (Labouriau 1983). pre-treatment. Next, the emerged seedlings were cut at the ground In order to prevent seed anoxia, all the level, placed in paper bags and dried in a ventilated solutions were aerated using silicone hoses connected oven (SOLAB, SL-102) at 65 ºC, until constant to an aquarium compressor (MINJINAG, NS 750).