Resilient mechanism of strigolactone (GR24) in regulating morphological and biochemical status of maize under salt stress

Strigolactones (SLs), relatively recent plant growth regulators, bolster plant resilience in challenging environmental conditions and augment signaling networks. Salinity, a well-established abiotic stressor, threatens global crop cultivation and productivity. We hypothesized that the synthetic SL analogue GR24 could alleviate salinity stress in maize by reducing oxidative damage and enhancing various growth and physiological attributes. To explore this hypothesis, we subjected two maize hybrids, PB-ProA-2018 and PB-ProA-2019, to seed priming with three GR24 concentrations (non-soaked, water-soaked, 0.001, 0.01, 0.1 mg/L) for 16 h. Seeds were then germinated in sand culture under two salt stress levels [ 0 (Control) and 100 mM NaCl] and nourished with Hoagland's nutrient medium. Salt stress significantly stunted maize growth attributes. The pre-soaking seed treatment with 0.01 mg L-1 GR24 demonstrated a significant enhancement in plant growth metrics, yielding a 31.3% increase in root length and a 62% augmentation in total leaf area per plant, in comparison to non-soaked yet stressed plants. Salt stress led to increased activities of catalase and peroxidase, along with higher levels of leaf ascorbic acid, malondialdehyde, H2O2, glycine betaine, and free proline, compared to control seedlings. Pre-soaking with 0.01 mg L-1 GR24 further upregulated superoxide dismutase (SOD) by 29.6%, peroxidase (POD) by 68.3%, catalase (CAT) by 25%, ascorbic acid by 23.1%, free proline by 42.3%, and total phenolics content by 13%, compared to stressed counterparts. Notably, the 0.01 mg L-1 GR24 concentration exhibited superior efficacy in mitigating salt stress effects, with PB-ProA-2019 outperforming PB-ProA-2018 among the maize hybrids. These findings advance our understanding of