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Differential effects of Na+, Mg2+, K+, Ca2+ and osmotic stress on the wild type and the NaCl-tolerant mutants stl1 and stl2 of Ceratopteris richardii

Vogelien, D.L., Hickok, L.G., Warne, T.R.
Plant, cell and environment 1996 v.19 no.1 pp. 17-23
salt tolerance, Ceratopteris, salinity, magnesium chloride, osmotic pressure, calcium, mutation, magnesium, sodium, potassium, sodium chloride, mutants, inorganic ions
In order to identify physiological components that contribute to salinity tolerance, we compared the effects of Na+, Mg2+ and K+ salts (NaCl, Na2SO4, MgCl2, MgSO4, KCl and K2SO4), Ca2+ (CaSO4), mannitol and melibiose on the wild type and the single-gene NaCl-tolerant mutants stl1 and stl2 of Ceratopteris richardii. Compared with gametophytic growth of the wild type, stl2 showed a low level of tolerance that was restricted to Na+ salts and osmotic stress. stl2 exhibited high tolerance to both Na+ and Mg2+ salts, as well as to osmotic stress. In response to short-term exposure (3 d) to NaCl, accumulation d K+ and Na+ was similar in the wild type and stl1. In contrast, stl2 accumulated higher levels of K+ and lower levels of Na+. Ca2+ supplementation (10 mol m-3) ameliorated growth inhibition by Na+ and Mg2+ stress in wild type and stl1, but not in stl2. In addition, under Na+ stress (175 mol m-3) wild type, stl1 and stl2 gametophytes maintained higher tissue levels of K+ and lower levels of Na+ when supplemented with Ca2+ (1.0 mol m-3). stl2 gametophytes were extremely sensitive to K+ supplementation. Growth of stl2 was greater than or equal to that of the wild type at trace concentrations of K+ but decreased subtantially with increasing K+ concentration. Supplementation with K+ from 0 to 1.85 mol m-3 alleviated some of the inhibition by 75 mol m-3 NaCl in the wild type and in stl1. In stl2, growth at 75 mol m-3 NaCl was similar at 0 and 1.85 mol m-3 K+ supplementation. Although K+ supplementation above 1.85 mol m-3 did not alleviate inhibition of growth by Na+ in any genotype, stl2 maintained greater relative tolerance to NaCl at all K+ concentrations tested.