Physiological homeostasis, yield, and sugar profile of salt-stressed sugar beet plants as influenced by nano-structured mixture of zinc, boron, and molybdenum application

Abstract

Sugar beet is a key industrial crop valued for its sucrose content, but its yield and sugar profile are greatly affected by soil salinity. In this study, we introduce novel nano-structured zinc (Zn), boron (B), and molybdenum (Mo) mixture designed to mitigate the adverse effects of salt stress. While individual nano-micronutrient applications have been investigated, the potential of combined nano-micronutrient formulations still need to be clarified. A two-season field experiments evaluated the effect of a nano-structured Zn, B, and Mo (MMNPs) mixture on salt-stressed sugar beet. Treatments included applied once (MMNPs1) or twice (MMNPs2) applications of MMNPs, their bulk counterparts (MMB1 or MMB2), and a control treatment (CK). Physiological traits, yield attributes, and sugar profile were assessed. The findings of this study pointed out that application of MMNPs2 and MMB2 treatments improved growth, photosynthetic efficiency, productivity, and juice quality compared with CK, MMNPs1, and MMB1, with MMNPs2 showing the greatest effects. Relative to CK, MMNPs2 increased net assimilation rate, absolute crop growth rate, taproot dry weight, taproot length, and taproot diameter by 3.87-, 6.14-, 1.98-, 1.24-, and 1.20-fold, respectively. It also enhanced chlorophyll a by 78.3%, chlorophyll b by 163.1%, carotenoids by 50.4%, Fv/F₀ by 19.7%, Fv/Fm by 3.6%, and the photosynthetic performance index by 77.7%. The MMNPs2 treatment yielded the highest sugar content and lowest non-sugar impurities. Briefly, foliar applying a nano-structured Zn, B, and Mo mixture at 165 mg L⁻¹ twice during the growth development is an effective strategy to maintain high sugar yield and quality in nutrient-deficient, sandy, salt-affected soils.