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The major factors thought to control the distribution of associations on the sea cliffs in Britain are discussed in relation to the zonation of cliff vegetation, and some experiments to investigate the effects of these factors are described.The seeds 0fthe maritime cliff species are able to germinate in higher salinities than those of closely related inland species.Relative growth rates of maritime cliff species indicate stimulation at low salinities over non-saline conditions, and less reduction in growth at higher salinities than those of closely related inland species.Increasing salinity reduces both photosynthesis and dark respiration in Lavatera arborea. Mesophyll and stomatal resistances are increased while transpiration is reduced.The distribution of ions within Lavatera arborea grown at different salinities indicates differential accumulation between young leaves, old leaves and roots.

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This study was carried out to investigate the effect of refined petroleum products (diesel and gasoline, RPPs) on Sacciolepis africana (Hubb and Snowden). The parameters measured include number of leaves, plant height, biomass production, chlorophyll content index, leaf area and mineral nutrient content. The refined petroleum concentrations used were 0.2, 0.4, 0.6 and 0.8% (v/w). The results showed that leaf and biomass production, chlorophyll content index and mineral nutrients were significantly reduced (P<0.05) in S. africana when exposed to all concentrations of the RPPs for eight weeks. A gradual decrease in height of the test plant was also noticed. Leaf area was reduced as concentration increased. The effects were concentration and medium dependent. RPP of gasoline had more toxic effect on the test plant. The leaves of the test plant also showed signs of chlorosis and wilting. This study has been able to demonstrate that S. Original Research Articleafricana can play a role in phytoremediation at low levels of pollution and also that the test plant can act as a bio indicator of polluted water body. It is recommended that proper measures be put in place to prevent release of these products into the environment where it can adversely affect plants thus disrupting the ecosystem balance.