Effects of Aqueous Smoke and Nitrate Treatments on Germination of 12 Eastern Mediterranean Basin Plants

Determining the relative role of various cues on seed germination in Mediterranean plants is important to understanding their response to variable conditions. We studied germination responses of 12 eastern Mediterranean Basin species (Alyssum caricum, A. minus, Carthamus dentatus, Daucus broteri, D. carota, Hypericum aviculariifolium, Muscari comosum, Onopordum caricum, Rumex crispus, Sarcopoterium spinosum, Silene vulgaris, Smyrnium rotundifolium) to different smoke and nitrate concentrations in laboratory. Smoke treatments resulted in significant increase in germination of D. carota, O. caricum, and S. spinosum, but had a negative effect on germination of Hypericum aviculariifolium. Of the 12 studied species, five showed significant improvement in germination after at least one of the nitrate treatments compared with the control. In total, smoke and nitrate treatments significantly increased the germination percentage in six of the 12 studied species. All the species that have smoke- and/or nitrate-stimulated germination were propagule-persisters (P+), able to recruit after fire. The results reveal that both smoke and nitrate improve germination of Mediterranean species. Our results also suggest the presence of species-specific germination response to smoke and nitrate in Mediterranean plants.