The response of barley to salinity stress differs between hydroponic and soil systems

Abstract

Many studies on salinity stress assume that responses in hydroponics mimic those in soil. However, interactions between the soil solution and the soil matrix can affect responses to salinity stress. This study compared responses to salinity in hydroponics and soil, using two varieties of barley (Hordeum vulgare L.). The responses to salinity caused by high concentrations of Na+ and Cl– were compared to assess any consistent differences between hydroponics and soil associated with a cation and an anion that contribute to salinity stress. Concentrated nutrient solutions were also used to assess the effects of osmotic stress. The effects of salinity differed between the hydroponic and soil systems. Differences between barley cultivars in growth, tissue moisture content and ionic composition were not apparent in hydroponics, whereas significant differences occurred in soil. Growth reductions were greater under hydroponics than in soil at similar electrical conductivity values, and the uptake of Na+ and Cl– was also greater. The relative importance of ion exclusion and osmotic stress varied. In soil, ion exclusion tended to be more important at low to moderate levels of stress (EC at field capacity up to 10 dS m–1) but osmotic stress became more important at higher stress levels. High external concentrations of Cl– had similar adverse effects as high concentrations of Na+, suggesting that Cl– toxicity may reduce growth. Fundamental differences in salinity responses appeared between soil and solution culture, and the importance of the different mechanisms of damage varies according to the severity and duration of the salt stress.

Impact of ancestral wheat sodium exclusion genes Nax1 and Nax2 on grain yield of durum wheat on saline soils

“…The other is that soil is a very different ionic medium from solution culture. A clay soil can influence Na + and Clavailability and can result in different growth responses (Tavakkoli et al 2010). There is, therefore, the need to confirm the usefulness of results found in controlled environments in the typical soils and ambient conditions that occur in grain production fields.…”

22Na influx is significantly lower in salt tolerant groundnut (Arachis hypogaea) varieties

“…This has been primarily due to the fact that several studies have shown a lack of correlation between the ability to exclude Na and the overall tolerance of a genotype (Genc et al 2007). It is evident that a combination of different mechanisms (exclusion, extrusion, compartmentation and cellular tolerance) are responsible, and not solely ion exclusion or ion extrusion (Tavakkoli et al 2010).…”

“…More recently (Almansouri et al 1999), a study has shown that expression of this two-phase response, initially suggested (Munns et al 1995), as a simplistic explanation for genetic differences in salt tolerance of wheat cultivars, was even influenced by how the salt stress was imposed; whether sudden or progressive. More recently, it has been observed (Tavakkoli et al 2010) that the expression of differences in these two components amongst barley cultivars is also influenced by what kind of system was used, whether a hydroponic system or a soil system. The concept of exclusion ability of genotypes being the primary determinant of salt tolerance has itself come in for re-evaluation.…”

“…Such an approach has been widely followed (Almansouri et al 1999) by others. Four salt tolerant and three salt susceptible cultivars were identified in both solution and soil culture (experiment I and II respectively) based on set of well established physiological traits; used extensively in salt stress screening (Almansouri et al 1999;Tavakkoli et al 2010). Based on the results of experiment I and II only two distinct contrasting varieties differing in salt tolerance was taken for 22 Na uptake studies (experiment III).…”

Genetic diversity and association analysis among Egyptian barley (Hordeum vulgare L.) genotypes with different adaptations to saline conditions analyzed by SSR markers

“…Reduction in growth with increased salinity levels might be due to limited supply of metabolites to young growing tissue as a result of either metabolic disturbance or low water uptake along with toxic effects of sodium Adjel et al (2013). High external concentrations of Cl -had similar adverse effects as high concentrations of Na + , suggesting that Cl -toxicity may reduce growth Tavakkoli et al (2010). Fundamental differences in salinity responses appeared between soil and solution culture, and the importance of the different mechanisms of damage varies according to the severity and duration of the salt stress Ehsan et al (2010).…”