The role of light and water in the establishment of mullein (Verbascum sinaiticum and V. fruticulosum) in a gravel wadi bed

Verbascum sinaiticum and V. fruticulosum became established side by side in an erratically flooded gravel bed of the Zin Basin in the Negev Highlands. In the laboratory, mass and uniform germinating V. sinaiticum seed lots enhanced germination of less alert seeds from the same or closely related species if the seeds were germinated in clusters in the same petri-dish. Potassium nitrate (50-100 mM) delays and inhibits germinability in light-requiring seeds, probably due to a gradual change in osmolarity. The causal event described here results in a unique niche which enables the establishment of distinctly different biennial and perennial mullein species. -from Authors