Photosynthesis, Biomass Production, Nutritional Quality, and Flavor-Related Phytochemical Properties of Hydroponic-Grown Arugula (Eruca sativa Mill.) ‘Standard’ under Different Electrical Conductivities of Nutrient Solution

Abstract

Arugula (Eruca sativa) is cultivated using hydroponic techniques in greenhouses to fulfill high year-round demand, but its nutrient management in hydroponic production has not yet been standardized, potentially leading to limited quality and productivity. Aiming to address this issue, we investigated the effect of electrical conductivity (EC) on yield, nutritional and phytochemical properties of arugula. The model cultivar arugula ‘Standard’ was grown at four different EC levels (1.2, 1.5, 1.8, and 2.1 dS·m−1). Our results indicated photosynthetic properties, SPAD, leaf area, yield and dry weight increased with increasing EC from 1.2 to 1.8 dS·m−1. Foliar nutrient content increased with higher EC, but nutrient solution with 2.1 dS·m−1 showed a significant decline in N, Ca and most of the micronutrients including Fe, Zn, Mo, Cu, B and Mn. Total glucosinolates, total chlorophyll and total carotenoids concentrations increased with increasing EC. In addition, total anthocyanin content was highest in plants grown in EC 1.2 and 2.1 dS·m−1, demonstrating a stress response when grown in extreme EC levels. Our results further indicated a rapid accumulation of nitrate with higher EC, potentially detrimental to human health. This research demonstrated the optimal EC range would be 1.5 to 1.8 dS·m−1 for arugula in hydroponic production systems based on yield, quality criteria and human health considerations.