The effect of Cd²⁺ on the biosynthesis of chlorophyll in leaves of barley

Abstract

The effect of cadmium on the biosynthesis of chlorophyll has been investigated in the leaves of dark‐grown seedlings of barley ( Hordeum vulture L. cv. Proctor). Cd2+ inhibited the production of chlorophyll by affecting 1) the synthesis of 5‐aminolacvulinic acid and 2) the protoehlorophyllide reductase ternary complex with its substrates. Cd2+ had no effect on the constituent enzymes that catalyse the synthesis of free protoehlorophyllide from 5‐aminolaevulinic acid. The results obtained are consistent with Cd2+ inhibiting the formation of chlorophyll by reacting with essential thiol groups in both the protochlorophyllide reductase protein and the enzyme(s) involved in the light dependent synthesis of 5‐aminolaevulinic acid.