Salt tolerance in wild Hordeum species is associated with restricted entry of Na⁺ and Cl⁻ into the shoots
2005
Garthwaite, Alaina J. | Bothmer, Roland von | Colmer, Timothy D.
Eight wild Hordeum species: H. bogdanii, H. intercedens, H. jubatum, H. lechleri, H. marinum, H. murinum, H. patagonicum, and H. secalinum, and cultivated barley (H. vulgare) were grown in nutrient solution containing 0.2 (control), 150, 300, or 450 mol m⁻³ NaCl. In saline conditions, the wild Hordeum species (except H. murinum) had better Na⁺ and Cl⁻ 'exclusion', and maintained higher leaf K⁺, compared with H. vulgare. For example, at 150 mol m⁻³ NaCl, the K⁺:Na⁺ in the youngest, fully expanded leaf blades of the wild Hordeum species was, on average, 5.2 compared with 0.8 in H. vulgare. In H. marinum grown in 300 mol m⁻³ NaCl, K⁺ contributed 35% to leaf [Psi][subscript [pi]], whereas Na⁺ and Cl⁻ accounted for only 6% and 10%, respectively. By comparison, in H. vulgare grown at 300 mol m⁻³ NaCl, K⁺ accounted for 19% and Na⁺ and Cl⁻ made up 21% and 25% of leaf [Psi][subscript [pi]], respectively. At 300 mol m⁻³ NaCl, glycinebetaine and proline together contributed almost 15% to [Psi][subscript [pi]] in the expanding leaf blades of H. marinum, compared with 8% in H. vulgare. Decreased tissue water content under saline conditions made a substantial contribution to declines in leaf [Psi][subscript [pi]] in the wild Hordeum species, but not in H. vulgare. A number of the wild Hordeum species were markedly more salt tolerant than H. vulgare. H. marinum and H. intercedens, as examples, had relative growth rates 30% higher than H. vulgare in 450 mol m⁻³ NaCl. Hordeum vulgare also suffered up to 6-fold more dead leaf material (as a proportion of shoot dry mass) than the wild Hordeum species. Thus, several salt-tolerant wild Hordeum species were identified, and these showed an exceptional capacity to 'exclude' Na⁺ and Cl⁻ from their shoots.
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