Salinity and pH stress on Lolium multiflorum Lam. germination

Direct spreading on agricultural lands of olive mill wastewaters (OMWs) may represent an environmentally friendly disposal method. In the olive oil-producing Mediterranean regions OMWs spreading on soil represents a simple and cheap alternative to detoxification techniques that result in final waste discharge into natural water bodies (Barbera et al., 2013). Additionally, because these regions are characterized by serious deficiencies in water availability and soil organic matter, the reuse of OMWs could be particularly beneficial (Piotrowska et al., 2006) and may contribute to a more sustainable agricultural system. However, the agronomic use of OMWs is limited by some constraints, such as oil and grease (Amaral et al., 2008; Ouzounidou et al., 2008), high salinity, acidity, and phenolic compounds content (Hanifi e El Hadrami, 2008) that exert an antimicrobial action (Obied et al., 2005) and a phytotoxic effect. Many authors (El Hadrami et al., 2004; Isidori et al., 2005) studied OMWs polyphenol phytotoxic effects, but only few (Pierantozzi et al. 2011) the effects of salinity and acidity on seed germination. High levels of lethality or seed germination inhibition of Lactuca sativa L. induced by OMWs were attributed by Pierantozzi et al. (2011) not only to polyphenols content, but also to acid pH, salts and other organic compounds. Positive effects of pH enhancement on seed germination had been reported by Suthar et al. (2009). In a previous research (unpublished data), the addition of Ca(OH)2 to activated charcoal (AC), determined a pH raise in the OMWs solutions and a significant enhancement on Lolium seed germination up to 79% as compared to the effects of AC alone (43%). With this in mind, on five Lolium multiflorum cultivars, a research was carried out to study the effects on germination of two levels of salinity induced by two different salts, and two pH. Twelve-month-old seeds of Lolium multiflorum Lam. cvs. Jolly, Barmultra, Furore, Mowester and Mythos were used for the experiment. The studied treatments are listed in table 1. The two levels of salinity stress and one pH value (4.5) were similar to the range of salinity and pH frequently encountered in OMWs. pH was raised to 7.5 to simulate the pH determined by the addition of calcium hydroxide to the system OMWs + activated charcoal. pH was adjusted to the studied values by 0.1 N HCl or 0.1 N KOH. pH (Hanna instruments mod. pH 211) and Electrical Conductivity (EC) (Conductivity Meter Jenway mod. 4200) were evaluated for each solution at the beginning of the germination trial. On average of the other studied factors germination ranged from 54% (cv. Barmultra) to 92% (cv. Mythos). Irrespective of the studied cultivars, salinity and pH levels did not exert significant effects on final germination. When the same levels of salinity were induced by CaCl2 no significant increases in germination were detected. Our result confirms what reported in literature that Lolium is a species moderately tolerant to saline conditions (Maas, 1986). Moderate levels of NaCl affected dormancy and germination percentages and delayed the germination of this plant, but are not deleterious (Alonzo et al., 1999). Moreover Marcar (1987) reported that the adverse effect of NaCl in Italian ryegrass concerned the ability of the seed to start rather than to complete germination as a consequence of the difficulty of the seed to absorb water under high osmotic pressure (Guerrier, 1986), rather than to the NaCl toxicity. Irrespective of the other studied factors, cv. Furore showed the highest root length (2.3 mm) as compared to the cvs. Mowester (2.0 mm) and Barmurtra (1.9 mm). All the studied treatments significantly decreased root length (Figure 1) as compared to the germination in distilled water at pH