Effect of fire-derived chemicals on germination and seedling growth in Mediterranean plant species

The promoting effect of smoke-derived chemicals (e.g. karrikinolide and cyanohydrin) on germination in many plants from Mediterranean-type ecosystems such as South Africa and south-western Australia is well documented. However, very little is known about (1) the relative importance of different compounds and their possible interactive effects, (2) their role in enhancing seedling growth in wild plants, and (3) their effect on the germination of plants in the Mediterranean Basin. To fill these gaps in knowledge, we performed experiments to evaluate the effect of smoke water, karrikinolide, mandelonitrile (a cyanohydrin analogue), potassium nitrate and gibberellic acid on the germination and seedling growth of 37 species from the Mediterranean Basin. The results suggest that germination and/or seedling growth of 21 species are enhanced by at least one of the fire-derived chemicals. There were positive correlations between most of the compounds tested in terms of germination response, but synergetic and inhibitory effects were also detected. Stimulation of germination was most prominent in species with annual life cycles. Fire-derived chemicals were more effective in stimulating root growth than shoot growth. In conclusion, we provide novel evidence that the recruitment of different Mediterranean species may be enhanced by different smoke compounds, and that synergetic and inhibitory effects of chemical compounds are important in the germination ecology of plants.