INTRODUÇÃOO girassol (Hellianthus annuus L.) é cultivado em várias partes do mundo, atingindo, em 2012, a produção mundial de 37 milhões de toneladas, em área de, aproximadamente, 25 milhões de hectares (Factfish 2013). ABSTRACT RESUMOA importância da cultura do girassol, no mundo, deve-se ao óleo de excelente qualidade que se extrai de suas sementes e aos grãos in natura que são consumidos na alimentação humana, de diversas formas. Além disto, o girassol pode ser utilizado para outras finalidades, como a produção de flores ornamentais, farelo para a alimentação de animais, forragem e si-1. Trabalho recebido em maio/2013 e aceito para publicação em maio/2014 (nº registro: PAT 24430).

Salinity is one of the main limiting factors for crop growth. The metabolic responses to salt stress are variable and depend on species characteristics. This study aimed to select sunflower genotypes tolerant to salt stress and evaluate some mechanisms of salt tolerance in two contrasting (salt-tolerant and salt-sensitive) genotypes. In the first assay, the biomass production and the accumulation of Na+ and K+ in 26 sunflower genotypes were evaluated. Genotypes AG963, AG967, AG972, BRS321, BRS324, H251, H360 and H863 showed lower biomass production and were characterized as salt-sensitive and the genotypes BRS323, Catisol, EXP11-26, EXP44-49, EXP60050, EXP887, HLA860HO and Olisun 5 showed higher biomass production and were considered salt-tolerant. The high K+ content and the low Na+ content in the leaves were the ion traits related to salt tolerance and can be used in sunflower breeding programs for this purpose. In the second assay, the plants of salt-tolerant BRS323 had lower Na+ and Cl- contents and higher levels of K+ than plants of salt-sensitive AG967. A better homeostasis in the mechanisms of transport, distribution and accumulation of inorganic solutes in conjunction with a more efficient osmoregulation mechanism through the synthesis of organic solutes may, at least in part, explain the greater salt-tolerance of BRS323 genotype in comparison to AG967.