Seed priming with vermicompost leachate, Ecklonia maxima extract-Kelpak® and smoke-water induce heat stress amelioration and growth in Vigna unguiculata L. seedlings

•Vigna unguiculata was primed with vermicompost leachate (VCL), Kelpak® (KEL), and smoke-water (SW) and sown under heat-stress.•VCL, KEL, and SW-priming optimized germination and growth under heat-stress.•Biostimulant-priming significantly increased seedling vigour index, shoot length, root length, leaf number, biomass and seedling area at 40 °C.•Potency of KEL and SW-priming increased with an increase in temperature.