Effect of lumichrome on seed germination of four legumes and three non-leguminous crops

Abstract

Lumichrome is a novel multitrophic signal molecule produced by rhizobia and plants that affects many physiological functions including seedling growth, root respiration, photosynthetic rates, leaf stomatal conductance and transpiration in several plant species. The effect of lumichrome on seed germination of four legumes (Rooibos, cowpea, Bambara groundnut and Kersting's bean), and three non-leguminous crops (traditional pumpkin, makataan and spinach), was investigated. All seeds were surface-sterilized and treated for 2 h with either of three levels of lumichrome (0, 5 or 50 nM). Seed germination (two replicates of ten seeds per crop) was done under sterile conditions using 9 cm-plastic petri dishes and Whatman No. 1 filter paper discs moistened with sterile distilled water. Treating legume seeds with nanomolar concentrations of lumichrome enhanced the seed germination percentage and rate of germination of Kersting's bean seeds, but not those of cowpea when compared to the control. Similarly, no significant differences in seed germination were recorded for Rooibos and Bambara groundnut, however, 9 days after treatment with lumichrome, slight stimulation of seed germination was observed for Rooibos and Bambara groundnut soaked in 5 nM lumichrome, compared to their respective controls. In response to nanomolar concentrations of lumichrome, non-leguminous crops also responded differently. A low nanomolar concentration of lumichrome (5 nM) significantly (p<0.05) affected the seed germination of spinach compared to control. The optimum seed germination percentage for makataan (53%) and the least seed germination percentage for traditional pumpkin (2%) were recorded for the 50 nM lumichrome treatment compared to control. In conclusion, nanomolar concentrations of lumichrome enhanced seed germination of both legumes and non-leguminous crops in addition to its known stimulating effect on seedling growth and development in both monocots and dicots.