Optical biostimulation effects on growth, and physiological, anatomical and antioxidant traits of Lupinus termis L. grown under drought stress induced by polyethylene glycol.

Limited research has been conducted on the application of brief exposure of light-emitting diode (LED) technology in seed priming to enhance early growth of legumes. This study aimed to evaluate whether priming of seeds with blue, red, or dual blue/red LEDs could promote early growth and drought tolerance in Lupinus termis L. A 4 × 4 factorial design (seed priming, drought) was conducted. Four concentrations of polyethylene glycol (PEG)-6000 were prepared at 0, 5, 10, and 20% to simulate drought stress. The vigor index increased by 29.97%, length by 34.61%, fresh weight by 85.63%, and total chlorophyl content by 50%, respectively, in seedlings germinated from unstressed seeds primed with red LED compared to control treatment. Also, red LED priming led to enhancements in root anatomical features, showing increases in root diameter and cortex thickness by 20.21% and 36.71%, respectively. In response to drought, priming with red LED resulted in the highest increase in the contents of total carbohydrates, proteins, flavonoids, and total antioxidant capacity by 75.29%, 69.32%, 30.06%, and 72.04%, respectively compared to the control seedlings. Our findings indicate that brief exposure of seeds to red or dual blue/red LEDs prior to sowing may enhance growth, stimulate antioxidant systems, and improve tolerance to drought stress.