Die wirkung von β-indolessigsäure auf die bildung der chloroplastenpigmente, plastidenchinone und anthocyane in Raphanus-keimlingen

Abstract

Summary 1. IAA induces an enhanced synthesis of chlorophylls, carotenoids and lipophilic benzoquinones, which is due to an increased thylakoid synthesis. 2. IAA causes a general, increased synthesis of the products of the shikimic acid pathways. This applies to the precursors of the benzoquinone nucleus (homogentisic acid) and to the phenylpropane formation, as it is indicated by the enhanced benzoquinone- and anthocyan-(in part) synthesis. 3. In the biosynthesis chain of lipophilic benzoquinones IAA causes a change of the metabolite flow, which yields more plastoquinone-9 (+ plastohydroquinone-9) and less α-tocopherol (+ α-tocoquinone). IAA affects the biosynthesis on the level of homogentisic acid, which in presence of IAA reacts more with the isoprenoid solanesyl-chain (C45) and less with the phytyl-chain (C20). 4. IAA also increases the proportion of the oxidized benzoquinones plastoquinone-9 and α-tocoquinone. 5. IAA promotes the prenyl-synthesis that is the sum of isoprenoid side chains of chlorophylls, benzoquinones, and carotenoids (C20-, C45-, C40-isoprenoid structures) and leads to an increased synthesis of all isoprenoid chloroplast-lipids such as chlorophylls, carotenoids, and lipoquinones. This specific IAA effect is obtained in both cases: by application of IAA during germination or to the three day old seedling. 6. The promotion of the synthesis of the isoprenoid chloroplast-lipids by IAA is in principle visible throughout the investigation period (8 days). The Z0-plants show, however, on the third day an additional specific increase in chlorophyll synthesis with a concomitant decreased formation of carotenoids and α-tocopherol. It is concluded that this IAA effect is due to the increased requirement of phytylpyrophosphate for the chlorophyll synthesis, which leaves less geranyl-geranyl-pyrophosphate for carotenoid and α-tocopherolformation. 7. The known light-induced change of benzoquinone synthesis in etioplasts (more plastoquinone-9-, less α-tocopherol formation) and other light effects are enhanced by IAA in a synergistic way. The synergism between light and IAA is discussed.