Improving Alkaline Stress Tolerance in Maize through Seed Priming with Silicon Nanoparticles: A Comprehensive Investigation of Growth, Photosynthetic Pigments, Antioxidants, and Ion Balance

Abstract

Abstract Silicon nanoparticles (Si NPs) have long been acknowledged for their ability to enhance plant defense against various biotic and abiotic stresses. Maize (Zea mays L.), among the plants known to accumulate Si NPs, is particularly vulnerable to alkaline stress. This study aimed to investigate the effects of different concentrations of Na2CO3 (0 and 75 mM) on maize seeds, along with varying levels of silicon nanoparticles (Si NPs) 0, 1.5 mM, and 3 mM over a 25-day period. The alkaline stress significantly impaired growth parameters, leaf relative water content (LRWC), and the concentrations of photosynthetic pigments, soluble sugars, total phenols, and potassium ions (K+), as well as the potassium/sodium ion (K+/Na+) ratio. However, this stress led to increased levels of soluble proteins, total free amino acids, proline, and sodium ions (Na+), and also elevated the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in the stressed plants. Conversely, applying silicon nanoparticles through seed-priming mitigated the growth impediments in stressed plants. This intervention resulted in improved LRWC, higher levels of photosynthetic pigments, soluble sugars, soluble proteins, total free amino acids, and potassium ions (K+). Moreover, Si NPs enhanced the activities of SOD, CAT, and POD enzymes. Si supplementation also led to decreased levels of proline and sodium ions (Na+), which in turn facilitated a more favorable adjustment of the K+/Na+ ratio in stressed plants.