Seed Dormancy Responses of Sponge Gourd (Luffa cylindrical L.) to Different Silver Nanoparticle Concentrations

Sponge gourd (Luffa cylindrica L.) is an economically important cucurbitaceous crop valued for both its edible immature fruits and fibrous mature gourds. Seed dormancy, low viability, and poor vigour frequently limit uniform seedling establishment. Nanopriming with silver nanoparticles (AgNPs) offers a potential strategy to enhance seed physiological quality through improved water uptake, enzymatic activation, and microbial suppression. This study evaluated the effects of different AgNP concentrations (10, 20, 30, 40, and 50 ppm) on seed viability and vigour in L. cylindrica under laboratory conditions, using a Completely Randomized Block Design with four replications. Seeds were soaked in AgNP solutions for two hours, air-dried, and assessed for germination percentage, shoot and root length, seedling biomass, and vigour indices following International Seed Testing Association protocols. Seedling data were collected at 7 days after sowing by carefully uprooting seedlings, blotting excess moisture, and measuring growth parameters with a digital caliper and precision balance to ensure accuracy and uniformity. Results indicated a significant concentration-dependent response, with 40 ppm AgNPs achieving the highest germination (90.0%), shoot length (3.41 cm), fresh weight (7.40 g), dry weight (0.69 g), and vigour index II (62.35), while root length peaked at 10 ppm (7.54 cm). Performance declined at 50 ppm, suggesting phytotoxic effects at higher doses. The observed benefits of moderate AgNP levels may result from enhanced water imbibition, membrane permeability modulation, reactive oxygen species (ROS) signalling, and suppression of seed-borne pathogens, collectively promoting metabolic activation and seedling growth. The findings support the potential of moderate AgNP concentrations (10–40 ppm), particularly 40 ppm, to improve early seedling establishment in sponge gourd, with a bell-shaped dose–response pattern typical of nanoparticle–plant interactions. Field validation and biochemical assays are recommended to elucidate underlying mechanisms.