Most crops in saline environments are negatively affected in their rate of growth. This effect is attributed either to osmotic causes or to ion toxicity depending on the plant species, salt composition and salt concentration. Species of the Chenopodiaceae family are considered to be resistant to this type of stress. Two cultivars of quinoa (Chenopodium quinoa Willd.), an ancestral crop from the Andes of South America with a high nutritional value are evaluated for tolerance to saline stress by calorimetric experiments of seed germination carried out at 24.7 degrees C in NaCl, KCl, Na2SO4, K2SO4 and Na2CO3 solutions. Also, 0.1 mM HgCl2 was used in combination with the salts to evaluate the possible existence of channels blocked by the mercurial reagent involved in the transport of ions. Results indicate that seeds of cv. Robura are less tolerant to saline stress than are seeds of cv. Sajama with a tolerance limit for seeds of the former cultivar of 100 mM NaCl. Above this concentration there is an apparent expression of proteins bearing -SH groups that block influx of NaCl, which are inhibited by 0. 1 mM HgCl2. (c) 2004 Elsevier B.V. All rights reserved.