The relative proportions of the chloroplast pigments as influenced by different levels of iron and potassium supply

Abstract

1. Potato plants were grown in pot sand cultures at different levels of iron and potassium supply. Plants grown at the lowest level of iron developed iron deficiency chlorosis and potassium deficiency symptoms when maintained at the lowest level of potassium but not at the highest level. 2. Rapid procedures were developed for the extraction and estimation of chloroplast pigments from small samples of lamina—usually less than 1 g of fresh material. 3. The expression of pigment content on an area basis gave results which were in better agreement with visual observations than those expressed on either fresh or dry weight basis. 4. Both iron and potassium additions increased the chloroplast pigment content. Leaves exhibiting iron deficiency contained reduced quantities of all pigments per unit area of lamina. 5. A linear relationship existed between chlorophyll and carotene, chlorophyll and xanthophyll, and carotene and xanthophyll contents. 6. The results suggested that laminae completely deficient in chlorophyll would contain no carotene but might still contain xanthophyll. 7. The relative proportions of chlorophyll, carotene and xanthophyll do not remain constant under varying conditions of iron status. When iron is deficient the proportion of xanthophyll increased in relation to the chlorophyll and carotene contents.