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Department of Botany, Faculty of Science, P.O. Box: 2455, King Saud University, Riyadh 11451, Saudi Arabia

ABSTRACT

The role of d-aminolevulinic acid (ALA) as a rate-limiting intermediate in chlorophyll (Chl( synthesis in angiosperms is well known. The results indicate that ALA can be accumulated to a maximum during the light-induced greening of 7/8 day-old etiolated barley leaves. The highest formation of ALA was observed using 20 mM levulinic acid (LA) and at this concentration of the competitive inhibitor. Chl synthesis was partially blocked (60 to 68 %). At 100 mM LA, however. a net loss of ALA as well as Chl occurred and this was followed by an eventual cessation of ALA accumulation and the complete inhibition of Chl production. The study suggests that some of the adverse effects of LA on the Chl pathway could be minimized by using low concentrations of LA.