Leaf chlorophyll content and its relation to the intracellular localization of iron

Abstract Chlorophyll contents of leaves of sugar beets undergoing Fe stress have been shown to be correlated positively with leaf Fe concentration (Plant Physiol. 1980 65:114–120). In the present work, the nature of this quantitative relationship was explored by determining the amounts of leaf Fe associated with whole chloroplasts (isolated nonaqueously) and with EDTA‐washed chloroplast lamellae. The results show that leaf chlorophyll content was quantitatively related to the leaf content of chloroplast Fe and to the leaf content of chloroplast lamellar Fe. Nonaqueously isolated chloroplasts accounted for 79 and 73 percent of the Fe of leaves of Fe sufficient and Fe deficient plants, respectively. The Fe content of EDTA‐washed chloroplast lamellae constituted 58 percent of leaf Fe in control plants; this increased to 75 percent in Fe deficient plants. In contrast with the view that chlorophyll contents may be correlated with a “biochemically active fraction” of leaf Fe (e.g. water or acid soluble fractions), these results imply that chlorophyll content is quantitatively related to the bound Fe content of the chloroplast lamellae. In addition, we postulate that Fe deficiency may reduce chlorophyll and lamellar Fe contents concomitantly by retarding the formation of new thylakoids, of which chlorophyll and Fe are integral constituents, rather than by diminishing chlorophyll synthesis per se.