Licorice root extract boosts Capsicum annuum L. production and reduces fruit contamination on a heavy metals-contaminated saline soil

Natural supplementations are used in agriculture nowadays not only for improving plant performance but also for reducing the contamination of plant edible parts. Two field trials were conducted to study the potential effects of licorice root extract (LRE; 0.5%) on performance, physio-biochemical components, antioxidant defense system, and contaminants concentrations of Capsicum annuum L. plants grown on a saline soil contaminated with heavy metals. LRE was applied in single (i.e., as rhizosphere application with drip irrigation water; -RA or as foliar spray; -FA) or in integration (i.e., LRE-RA + LRE-FA) treatment. The results showed that both single or integrative treatments significantly increased plant growth and yield, leaf concentrations of photosynthetic pigments, free proline, total soluble sugars, N, P, and K⁺, ratio of K⁺/Na⁺, and activities of CAT, POX, APX, SOD and GR, while significantly reduced contaminants; Na⁺, Cd, Cu, Pb and Ni concentrations in plant leaves and fruits on heavy metals-contaminated saline soil compared to the control (without LRE). Additionally, the integrative LRE-RA + LRE-FA treatment significantly exceeded both single treatments in this concern, which had been recommended for maximizing pepper plant performances with minimizing heavy metals in fruits on contaminated saline soils.