Nano-copper sulfate mediated alleviation of salt stress: Optimizing elemental homeostasis and nutrient ratios in tomato

Salt stress represents a critical constraint to agricultural productivity worldwide, necessitating innovative approaches for crop resilience enhancement. This study investigated the ameliorative effects of nano-copper sulfate (nano-CuSO₄) on salt-stressed plants, examining elemental composition changes in two tomato (Solanum lycopersicum L.) varieties (Pant Tomato3: PT3 and Hisar Arun: HA) under graduated NaCl stress (25-100 mM) and nano-CuSO₄ treatments (5-100 ppm). Results demonstrated that nanoparticle treatments significantly improved plant performance under salt stress. Treatment T14 (100 mM NaCl + 10 ppm nano-CuSO₄) emerged as the most effective for PT3 variety, enhancing Ca (+7.55 %), K (+11.57 %) and Cu (+3.14 %), along with improvement in K/Na (+6.60 %) and Ca/Na (+2.75 %) ratios. For HA variety, T17 (100 mM NaCl + 50 ppm nano-CuSO₄) proved most effective, increasing Ca (+7.76 %), K (+11.79 %) and Cu (+3.09 %) with superior ratio improvements (K/Na +8.93 %, Ca/Na +4.89 %). The morphological analysis demonstrated that 10 ppm nano-CuSO₄ (T6) consistently optimized plant architecture, enhancing plant height by 20.4 % and 15.1 % in PT3 and HA respectively, while increasing branching by 7.2 % and 24.0 %. The reproductive performance data revealed that nano-CuSO₄ treatments accelerated flowering by up to 10.5 % in PT3 and 8.6 % in HA, counteracting salt-induced delays and promoting early reproductive development. Critical findings revealed that nano-CuSO₄ application effectively counteracted salt-induced ionic imbalances, with treatments T13-T17 working best. The study provides compelling evidence for nano-CuSO₄ as a precision agriculture tool for salt stress mitigation, offering variety-specific treatment protocols for optimized crop performance under saline conditions.