Harnessing light, defying salt: How photobiomodulation unlocks Maize's hidden potential

Salinity represents a significant abiotic stress that results from the excessive accumulation of salt ions in the soil, causing osmotic imbalances in plants and disrupting essential physiological processes. Among the proposed strategies that aimed at enhancing plant salt tolerance, the use of lasers has gained attention for their ability to promote plant growth by influencing cellular processes. Laser bio-stimulation induces short-term stress that triggers the production of antioxidants and bioactive compounds, functioning as adaptive mechanisms to support growth under challenging conditions. Though the impact of the laser priming on the biochemical and physiological factors associated with seed germination and plant development have been extensively investigated, the core inquiry remains: what mechanisms enable laser priming to enhance plant resilience against environmental stresses, particularly salt stress? Furthermore, how closely do the ideal characteristics of laser priming for seed growth and germination align with the optimal parameters for fostering resistance to such stresses? Accordingly, a study was undertaken to investigate the impact of laser priming parameters on seed development as well as the adaptive responses of maize (Zea mays L.) to salinity stress. The research focused on examining morphological, physiological, and biochemical in laser-primed maize seeds. The experiments evaluated the efficacy of seed priming using varying doses of laser irradiation at a wavelength of 660 nm, analyzing both germination efficiency and mitigation of salt stress-induced damage during germination and early seedling stages. Among irradiation dosages ranging from 0.3 to 3.0 J/cm², the dose of 0.73 J/cm² (intensity of 8.1 mW/cm² and irradiation duration of 90 s) significantly enhanced radicle length, Plumule height, and the seedling vigor index (SVI). Meanwhile, lower dosages of 0.29 and 0.48 J/cm² (corresponding to 3.2 mW/cm² intensity with respective irradiation durations of 90 and 150 s) demonstrated notable improvements in salinity resilience, as evidenced by the enhanced performance of salt-stressed maize seedlings derived from these treatments. Surface morphology and hydrophilicity analyses using scanning electron microscopy (SEM) and contact-angle (CA) measurements revealed that all laser treatments had no substantial effect on the physical attributes of the maize seed coat. Thermal evaluations indicated that the most effective laser treatments-relevant for both germination enhancement and salt tolerance-correlated with a temperature increase between 24.3 °C and 24.7 °C, reflecting variations of 1-1.4 °C. Ultimately, biochemical analyses confirmed that laser treatments effectively stimulated salt tolerance mechanisms in maize seeds exposed to salinity stress. These responses varied across different laser dosages, with each dosage activating distinct physiological pathways. The underlying principle is that laser priming alleviates the detrimental effects of salinity by eliciting tailored physiological responses from the seeds as part of their adaptation strategy.