Salinity in soil can affect Jatropha seedling metabolism, interfering with plant establishment. In this study, the effect of salinity on the mobilization of reserves during the development of Jatropha seedlings was tested. Two genotypes of Jatropha were used and three concentrations of NaCl were applied between the 4th and 8th days after germination. The effects of salinity on seedling growth, in terms of fresh and dry phytomass, ionic partition, and sugar quantification, starch, proteins, amino acids, and lipids were evaluated in cotyledon leaves, hypocotyls, and roots. There was an increase in the content of all classes of macromolecules analyzed in at least one of the organs. It is hypothesized that the hypocotyls acted as an accumulating organ of Na+. The accumulations of amino acids and protein in roots suggest that metabolic responses occurred in response to the ionic and osmotic effects of NaCl, although this accumulation did not appear to prevent biomass losses in seedlings. Furthermore, the findings of this study demonstrate that salinity inhibits the mobilization of lipids and carbon stocks from cotyledon leaves to the rest of the plant, and together with the synthesis of proteins and amino acids that occurred primarily in roots, contributed to response of these plants to salinity.

O presente estudo propõe definir as doses consideradas severa e moderada de NaCl utilizadas em ensaios experimentais de Jatropha curcas com até oito dias após a sementeira. Os resultados apresentados nesse estudo baseiam-se em indicadores fenológicos e fisiológicos para definir as doses de NaCl a partir do conceito de dose letal. A pesquisa foi realizada utilizando delineamento experimental inteiramente casualizado com fatorial formado por dois acessos (CNPAPM-X e CNPAPM-III) e cinco doses de NaCl (0; 50; 100; 150; 200 mM de NaCl). Avaliou-se a taxa de germinação, altura da plântula, diâmetro do caule, massa seca e o conteúdo de Na + , K + além da razão K + /Na + de folhas, caules e raízes. Evidenciou-se nas condições experimentais impostas que os acessos apresentaram distintos mecanismos de resposta aos stresses salinos. Obteve-se, ainda, como dose severa e moderada, padronizadas para ensaios de stresse salino em J. curcas com até 8 dias após a sementeira, as doses de 100 e 50 mM, respectivamente.

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