ARTICLES RIA / Vol. 44 / N.º 1 Physical purity and germination of caryopses of Chloris gayana Kunth and Panicum coloratum L. harvested from plants grown in an alkaline-sodium soil GARCÍA, M.D.1; PESQUEIRA, J.1; OTONDO, J.2 ABSTRACT The objective of the study was to evaluate physical purity, germination percentage (G) and germination velocity (GV) of caryopses of Chloris gayana cv. Finecut (Cg) and Panicum coloratum cv. Klein Verde (Pc) collected from plants grown in an alkaline-sodic soil (pH = 9.8, ECe = 0.69 dS m-1, EPS = 26.2%). To compare G of both species, 50 caryopses (n= 5) were incubated in deionized water. To evaluate G res- ponses to salinity and alkalinity, an experiment with completely randomized design and factorial structure (n= 4) of two species x four concentrations of Na+-salts (25, 50, 100 and 150 mM) x two pHs (6 and 10) was per- formed. Treatments consisted in combinations 1:1 of NaCl + SO4Na (pH= 6) and Na2CO3 + NaHCO3 (pH= 10): 25mMpH6 (control); 25mM-pH10; 50mM-pH6; 50 mM-pH10; 100mM-pH6; 100mM-pH10; 150mM-pH6 and 150mM-pH10. Samples of the natural-dispersal material from panicles of Cg and Pc contained (mean ± SEM; % of total weight): caryopses covered by glumes (53 ± 2.6; 41.3 ± 4.6), isolated caryopses (1.4 ± 0.6; 10.3 ± 1.95), empty caryopses (32.9 ± 2.4; 22.7 ± 2.4) and inert materials (12.5 ± 2.2; 25.7 ± 2.1). Caryopses of Cg and Pc incu- bated in water showed similar values (mean ± SEM, in %) of G (96.5 ± 2.4 and 89.2 ± 3.6) and GV (54.7 ± 7 and 51.7 ± 5.5). In the presence of salt 25 mM, the increment of pH from 6 to 10 did not inhibit G of Cg (94.4 ± 2.55 and 90.7 ± 3.7) or Pc (93.9 ± 2.2 and 92.95 ± 1.9). Incubation in 50mM-pH=10 inhibited G of Pc (33.2 ± 4.7) but not G of Cg (93.5 ± 3.3). The solution 100mM-pH=10 inhibited more the germination of Pc (2.5 ± 1.5) than that of Cg (66.35 ± 5.5), and 150mM-pH10 strongly inhibited germination of both species, Cg (3.5 ± 1.5) and Pc (0 ± 0). In solutions with pH = 6, the G of Cg and Pc was not affected up to 100 mM of salt, but 150 mM induced decreases of 25 % and 20 % of G, respectively, in relation to that observed in 25mM-pH=6. The increment of pH also affected more GV of Pc than that of Cg. GV of both species responded in a similar way to increases of salinity in neutral (pH= 6) solutions. The GV of the caryopses incubated in 50mM-pH=6 did not differ from their respective controls. From 50 mM, each increase of salt concentration induced the decrease of GV of both species, relative to their respective controls. Keywords: salinity, alkalinity, megathermic forage poaceae, germination velocity. 1Universidad Nacional de Lomas de Zamora, Facultad de Ciencias Agrarias, Ruta 4 km 2 (1836) Llavallol, Buenos Aires, Argentina. 2Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria (EEA) Cuenca del Salado, (7130) Chasco- mús, Buenos Aires, Argentina. Correo electrónico: [email protected] Received September 19, 2016 // Accepted August 15, 2017 // Published online April 3, 2018 Pureza física y germinación de cariopses de Chloris gayana Kunth y Panicum coloratum L. cosechados de plantas cultivadas en un suelo alcalino-sódico April 2018, Argentina 5 INTRODUCTION 2015; Avaca et al., 2015) and have a moderate tolerance to frost (Jones, 1969, Pesqueira et al., 2016). For these, they According to estimates of FAO / UNESCO, the global are an interesting fit to plant in the Salado’s basin. area affected by salinity and alkalinity exceeds 900 million hectares (Wicke et al., 2011). For example, in the province P. coloratum cv. Klein verde and C. gayana cv. Finecut of Buenos Aires about 7 million ha (24% of the province’s were planted in 2012, in the Integrated Experimental Farm surface) are occupied by soils with hydrohalomorphism of Chascomús (Buenos Aires). Soil pH= 9.8; ECe= 0.69 dS problems (Miaczynski, 1995), the vast majority of which are m -1 and ESP= 26.2%. The emergence and biomass pro- located in the Cuenca del Salado [Salado’s Basin]. duction of P. coloratum and C. gayana were similar (Oton- do et al., 2014) the year of implantation. After three years, Among the soils that predominate in this basin are the P. coloratum cv. Klein produced 36% more biomass than Natracualfs and typical Natralcuols, that in the province co- the average of the natural grassland, Thinopyrum ponticum ver more than 4.7 million ha (@ 15.66% of the total area). (Podp.) Liu & Wang and C. gayana (Pesqueira et al., 2015). These soils have a low-permeability clay horizon, with a high content of sodium salts (Miaczynski, 1995). There con- The flowering of P. coloratum is very heterogeneous, with ditions generate a restrictive soil environment for germina- seeds that mature irregularly and are dormant at the time tion and growth of most plant species, especially when the of dispersion. The type of reproduction is mainly by seeds, mentioned factors are combined in the same soil (salinity, which completely lose dormancy 6 months after post-matu- alkalinity and flooding or drought). ration (Petruzzi and Stritzler, 2003). C. gayana propagates vegetatively via stolons, flowering is concentrated in the There are numerous studies on the effects of salinity on first half of autumn and produces large numbers of seeds the plant germination and growth, but there is little informa- with high germinative power, which favors reseeding and tion on the effects of alkalinity. In recent years,there has been rapid soil cover (Avila et al., 2012) . an increase in the number of studies on the effects of alkalini- ty on germination of seeds, growth and metabolism of plants. However, under the cultivation conditions of the plots in Chascomús, new seedlings of C. gayana and P. coloratum In these studies, the pH of the nutrient solution are not observed during the spring-summer coverage eva- has normally been alkalized and stabilized by adding luations, despite the fact that established plants produce Tris(hydroxymethyl)aminomethane buffer (which allows to abundant seeds every summer (data not shown). completely separate the pH from the salt concentration) (Singh et al., 2002; Avaca et al., 2015), or by combining The environment in which the parent plant grows can affect different proportions and concentrations of sodium bicarbo- different characteristics of the seeds, such as production, nate and sodium carbonate (which generates solutions with weight, viability, and dormancy level, to give some examples different levels of alkalinity and salinity) (Guo et al., 2010; (Fenner, 1991). Young and Evans (1981) observed that the Li et al., 2010). emergence and growth of Elymus cinereus (Scribn. & Merr.) A. Löve seedlings in a saline - alkaline soil was better from These investigations have shown that the alkaline sodium seeds obtained from plants that had grown in a non-alkaline salts (NaHCO3 and Na2CO3) produce a more damaging soil, when compared to plants grown in a saline-alkaline soil. effect on the plants than equimolar concentrations of neutral salts (NaCl and Na2SO4). For example, seed germination However, Koyro and Eisa (2008) observed that Cheno- was more inhibited in the presence of alkaline salts than podium quinoa Willd. plants grown in nutrient solutions neutral salts in Medicago sativa L. (Li et al., 2010), Leymus containing NaCl 100, 300 or 500 mM produced seeds with chinensis (Trin.) Tzvelev (Ma et al., 2015), Medicago rutheni- higher germination speed in saline media than seeds ob- ca (L.) Sojak, (Guan et al., 2009), Chloris virgata Sw. (Lin et tained from plants grown in nutrient solutions without the al., 2015), Triticum aestivum L. (Guo et al., 2010), Sorghum addition of NaCl. bicolor (L.) Moench (Zhao et al., 2014), Panicum virgatum L. To date, no data has been published on the quality attri- (Lui et al., 2014), Chloris gayana Kunth y Panicum coloratum butes (purity, germination potential, and germination rate) L. (García et al., 2015), Setaria viridis (L.) P. Beauv. (Guo et of the seeds produced by C. gayana and P. coloratum al., 2011), Helianthus annuus L. (Liu et al., 2010), and diffe- plants grown on alkaline-sodium soils. rent grass species (Zhang and Rue, 2014), to name some. The objectives of this study were to evaluate the physical Panicum coloratum L. and Chloris gayana Kunth are purity, final germination (G) and germination velocity (GV) subtropical perennial Poaceae characterized by a high bio- of Chloris gayana cv. Finecut (Cg) and Panicum coloratum mass production, with an adequate nutritional value to sa- cv. Klein Verde (Pc) cariopses harvested from plants grown tisfy the requirements of the cattle breeding herd (Avila et in an alkaline-sodium soil. al., 2012). The implantation of C. gayana and P. coloratum led to an increase in the productivity when compared to the natural community of halophytes, although their nutritional MATERIALS AND METHODS quality is lower (Otondo, 2011). Plant material They are also tolerant to drought (Ghannoum, 2009, Pon- sens et al., 2010), salinity (Ribotta et al., 2013), short pe- Dispersion units (caryopses covered by glumes and glu- riods of flooding (Imaz et al., 2015), alkalinity (García et al., mella) harvested from Chloris gayana cv. Finecut (Cg) and GARCÍA, M.D.; PESQUEIRA, J.; OTONDO, J. ARTICLES RIA / Vol. 44 / N.º 1 Panicum coloratum cv. Klein Verde (Pc) plants growing in a The dishes were stored 26 days under an alternating typical Natracualf soil with pH= 9.8, electrical conductivity of regime of 12 h of light / 12 h of darkness at temperatu- the aqueous extract, ECe = 0.69 dS m-1 and exchangeable res (mean ± SEM, ºC) of 28.00 ± 0.14 and 23.04 ± 0.08, sodium percentage, ESP= 26.2%.