Dl. Vogelien et al., DIFFERENTIAL-EFFECTS OF NA-STRESS ON THE WILD-TYPE AND THE NACL-TOLERANT MUTANTS STL1 AND STL2 OF CERATOPTERIS-RICHARDII(, MG2+, K+, CA2+ AND OSMOTIC), Plant, cell and environment, 19(1), 1996, pp. 17-23
In order to identify physiological components that contribute to salin
ity tolerance, we compared the effects of Na+, Mg2+ and K+ salts (NaCl
, Na2SO4, MgCl2, MgSO4, KCl and K2SO4), Ca2+ (CaSO4), mannitol and mel
ibiose 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, st12 showed a low level of tolerance that was restr
icted to Na+ salts and osmotic stress. st12 exhibited high tolerance t
o both Na+ and Mg2+ salts, as well as to osmotic stress. In response t
o short-term exposure (3 d) to NaCl, accumulation of K+ and Na+ was si
milar in the wild type and stl1. In contrast, stl2 accumulated higher
levels of K+ and lower levels of Na+. Ca2+ supplementation (1.0 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, sil1 and stl2 gametophytes maintained higher tissue lev
els of K+ and lower levels of Na+ when supplemented with Ca2+ (1.0 mol
m(-3)). stl2 gametophytes were extremely sensitive to K+ supplementat
ion. Growth of st12 was greater than or equal to that of the wild type
at trace concentrations of K+ but decreased substantially with increa
sing 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 t
ype 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 ab
ove 1.85 mol m(-3) did not alleviate inhibition of growth by Na+ in an
y genotype, stl2 maintained greater relative tolerance to NaCl at all
K+ concentrations tested.