The effect of mucilage removal on germination percentages and velocity (Timson's index) was studied for five Arabian desert species (Lavandula subnuda, Lepidium aucheri, Boerhavia elegans, Plantago ciliata and Plantago amplexicaulis) under two photoperiods (0, 12 h of light daily) and three thermoperiods (night/day temperatures of 15/25, 20/30 and 25/35 °C). Mucilage presence increased water uptake in all species, and was associated with higher germination percentages in L. subnuda, B. elegans and P. ciliata, but not L. aucheri and P. amplexicaulis. Germination velocity response to mucilage presence was mixed, being increased in L. aucheri and reduced in L. subnuda. In all species germination was increased by light and affected...