Salinity from NaCl changes the nutrient and polyphenolic composition of basil leaves

Abstract

Abstract Decreasing availability and rising costs of high quality water for irrigation, results in more frequent use of saline water sources in many crop production systems. The effect of salinity on biomass yield has been the focus of most salinity studies with basil, and a few studies have reported how salinity influences basil polyphenolic composition. Two basil cultivars [Ocimum basilicum L. ‘Sweet Broadleaf’ (SB) and ‘Siam Queen’ (SQ)] were grown hydroponically for 71 d with four different concentrations of NaCl (no NaCl, Low, Moderate, and High) to determine whether the phenolic and elemental composition of leaves is altered by salinity. Salinity in the hydroponic solution reached as high as 20\u2009dS\u2009m-1 at the highest NaCl level. Salinity had no influence on leaf color or plant mortality and minimal leaf necrosis occurred during the experiment. Compared with controls, NaCl decreased leaf biomass only at the highest salinity level. Salinity increased K concentrations in leaves, and plants generally excluded Na from leaves except at the highest NaCl level. Levels of salinity that altered basil leaf polyphenolic and nutrient composition were lower than those that influenced yield (leaf biomass). In both cultivars, salinity increased leaf concentrations of certain caffeic acid derivatives, caftaric acid, cinnamyl malic acid, and feruloyl tartaric acid and decreased concentrations of chicoric acid. In SB, salinity increased leaf concentrations of the two of the major polyphenolics in basil leaves, quercetin-rutinoside and rosmarinic acid. In contrast, salinity decreased concentrations of rosmarinic acid in SQ leaves. Effects of salinity on leaf concentrations of elements other than Na, Cl, K, and Mg, were not directly related to effects of salinity on polyphenolics. Salinity levels that do not influence biomass yield in basil may negatively impact yield of certain polyphenolics important to quality.