Tolerância à salinidade em manjericão sob cultivo hidropônico

Abstract

The aim of this work was to evaluate the effect of salt stress on physiological and biochemical aspects of basil genotypes differing in salt tolerance. The research was performed in three stages. In the first stage the biomass production and the inorganic solutes accumulation in the basil were evaluated under increasing concentrations (0, 20, 40, 60 or 80 mM) of NaCl in the nutrient solution. Plant height, leaf number, stem diameter and biomass production decreased with salinity. The levels of Cl- and Na+ increased in all plant parts and K+ levels decreased in the stem and roots and increased in the leaves. In the second stage, biomass production, pigments content, membrane integrity percentage (PIA) and relative water content were evaluated in six basil genotypes under two salt levels (0 or 80 mM NaCl). The pigments and the relative water content were not good indicators of salinity tolerance. The ‘Toscano folha de alface’ genotype (TFA) presented higher accumulation of K+ and less accumulation of Na+ in the leaves. The biomass production and the PIA were good indicators of salinity tolerance in basil, thus, based on biomass reduction of the stressed plants, the TFA genotype was considered as salt- tolerant and the ‘Gennaro de menta’ (GM) as salt-sensitive. In the third stage the TFA and GM genotypes were cultivated under the same conditions as the previous one, and the harvests were realized at 8, 16, 24 and 32 days of stress. Inorganic (Na+, Cl-, K+), organic (soluble carbohydrates, free amino acids, free proline and soluble proteins), chlorophylls, carotenoids and essential oils contents were evaluated. Salinity increased the levels of Cl- and Na+ in all parts of the plant, while that of K+ increased in the leaves and decreased in the stem and roots, however no differences were observed among the genotypes, suggesting that inorganic solutes were not good indicators of salt tolerance. Salt stress did not induce substantial changes in the carbohydrates and soluble protein contents of both genotypes, but increased the free amino acids in the leaves and roots of the TFA genotype, suggesting a role of these compounds in the tolerance of basil to salinity. Proline increased in the leaves and roots of both genotypes. The salinity increased the pigments content only in the GM genotype, showing no relation with the salt tolerance in the studied genotypes. Salt stress increased the oil content in the GM genotype and decreased in the TFA, however the TFA showed higher productivity when compared to the GM.