NA AND K ACCUMULATION AND SALT TOLERANCE OF ATRIPLEX-CANESCENS (CHENOPODIACEAE) GENOTYPES

Sixteen accessions of the xerohalophyte, Atriplex canescens (Pursh.) N utt., differing in tendency to accumulate Na or K in leaf tissues, wer e compared for salt tolerance in a greenhouse study. Plants were grown along a salinity gradient from 72 to 2017 mol/m(3) NaCl measured in t he root zone. Growth rates (RGR) were negatively affected by salinity for all accessions. Initial leaf levels of Na (measured before exposin g plants to saline solutions) were positively correlated with subseque nt RGR's of accessions on the salinity gradient (r = 0.60 - 0.88, P < 0.05 across salinity levels), whereas initial leaf K levels were negat ively correlated (r = -0.68 to -0.85, P < 0.01 across salinity levels) . Varieties linearis (S. Wats.) Munz and grandidentatum Stutz & Sander son had greater tendency for Na accumulation, lower tendency for K, an d higher growth rates on saline solutions than var. occidentalis (Torr . & Frem.) Welsh & Stutz accessions. Within var. occidentalis accessio ns, RGRs were negatively correlated with initial leaf levels of K but not Na. Postexposure leaf Na and K levels were not strongly correlated with RGR's. All accessions responded to salinity by increasing their uptake of Na, which is the primary mechanism of osmotic adjustment to salinity in this species. It is suggested that differences in tendency to accumulate Na or K among A. canescens genotypes are related to the ir specialization for saline or xeric habitats, respectively.