Aqueous smoke and karrikin influence seed germination of Amaranthus dubius in varying light, temperature and osmotic stress conditions

Abstract

Amaranthus dubius is a green leafy vegetable that contributes significantly to food and nutrition security in sub-Saharan Africa. We explored the influence of plant-derived aqueous smoke and karrikin on Amaranthus dubius seed germination under varying environmental conditions. Final germination percentage, germination index, mean germination time, coefficient of velocity of germination and germination rate index were measured in a completely randomized design consisting of smoke-water and karrikin treatments with four replications. Light conditions significantly influenced germination of Amaranthus dubius seeds, with constant dark and constant light conditions stimulating the greatest and least response, respectively. High temperatures favored the best seed germination response, irrespective of smoke-water or karrikin treatments. The optimum temperature for seed germination of 35 °C suggests high tolerance to heat stress conditions. Decrease in water potential significantly reduced germination irrespective of seed treatments with aqueous smoke and karrikin solutions. However, aqueous smoke seemed to have mitigated drought stress under moderate water potential (-0.15 MPa). The capacity of Amaranthus dubius seeds to germinate under high temperatures and seed treatment with aqueous smoke could extend its cultivation in heat-prone and moderately dry environments, thus broadening the food base in such environments.