The potential for evolution of tolerance to sodium chloride, calcium chloride, magnesium chloride and seawater in four grass species

Abstract

To examine the contrasting genetic potentials of different species, wbich would allow or prevent the evolution of tolerance to naturally .saline environments, the growth of selected tolerant and normal lines o'i Af^rostis stolonifero L., A. capillciris L., /folnis lanatus L., and Loliiini perenne L., in NaCI, CaCl^, MgCl, and seawater solutions was examined.NaCl tolerant lines of all four species had significantly greater root growth in XaCl, CaCl, solutions, and seawater than unselected lines, hut in MgCl., only the NaCl tolerant lines of //. hiuatus had significantK-longer roots than the unselected line.Screening of seedlings in solution culture in all four species, tor tolerance to the same salt solutions, suggested that variability was available in each specie.s for enhanced tolerance to each salt. When the selected material wa.s tested as adults, the superior tolerance in response to increased seawater concentration remained for all lines in all species except those of A. capillnris and //. lanatus.The results suggest that all four species have genetic potential for the e\-olution of salt tolerance. The failure of some of these species to evolve salt tolerant populations in nature is likely to he due to other factors in naturally saline en\ ironments, for which the necessary adaptive genetic potential is lacking.

Tolerance of Grasses to Calcium Chloride, Magnesium Chloride and Sodium Chloride

“…4), indicating that most of the mechanisms of tolerance to excess MgCl 2 are different from those to excess CaCl 2 or NaCl. This was supported by the report that the NaCltolerant line had greater tolerance to excess MgCl 2 than did the unselected line in only one of the four grass species (Ashraf et al, 1989). In addition, low Ca 2+ concentration was suggested to cause subclinical growth depression in MgCl 2 -treated Eucalypts seedlings (Marcar and Termaat, 1990).…”

“…Likewise, grasses may share common physiological mechanisms conferring tolerance to both CaCl 2 and NaCl, which might explain the correlation between the tolerances to CaCl 2 and NaCl in this report. This idea is supported by reports that the NaCl-tolerant lines of four grass species or citrus cells had greater tolerance to excess CaCl 2 than did unselected lines (Ashraf et al, 1989;Ben-Hayyim et al, 1987). In the study of Citrus cells, internal K + concentration was suggested to play a key role in determining growth capacity in both increasing NaCl and CaCl 2 concentrations (Ben-Hayyim et al, 1987).…”

“…However, most of them have been concerned with sodium. By contrast, there are only a few reports about the tolerance to other cations, such as calcium and magnesium (Ashraf et al, 1989; Dvor v a k and Ross, 1986). For instance, Oizumi et al (1979) found calcium to be the main cation in soil with salt accumulation in a plastic greenhouse, and attempted the cultivation of grasses as a remedy for excessive salt accumulation.…”

“…Some reports have found coincidental tolerance (co-tolerance) to certain ions including Na + . Ashraf et al (1989) reported that NaCl-tolerant lines had greater root growth in CaCl 2 solutions than did unselected lines in each of the four grass species. In Medicago sativa L., the callus derived from NaClselected suspension cultures was more tolerant to the chlorides of alkali metals than the non-selected callus (Shah et al, 1993).…”

Adaptation to salinity inHordeum jubatum L. populations studied using reciprocal transplants

“…Variability in salt tolerance exists between and within plant species (Venables & Wilkins 1978), suggesting a genetic potential for the evolution of salt tolerant ecotypes (Ashraf et al 1989;Wu 1981). The existence of salt tolerant populations has been recognized in several species (e.g.…”