Die Wirkung von gibberellinsäure A3 und kinetin auf die bildung der photosynthesepigmente, lipochinone und anthocyane in Raphanus-keimlingen

Abstract

1. Gibberellic acid (GA 3 , 10 ppm) has a rather stimulating effect on germination, but decreases the synthesis of chlorophylls, carotenoids, plastidic benzoquinones, and anthocyanins in Raphanus-seedlmgs (Z 0 -plants). It is assumed that GA 3 inhibits the light induced formation of thylakoids. When applied to the 3 day old seedlings (Z 3 -plants) during the investigation period (5 days) GA 3 decreases the formation of carotenoids, isoprenoid benzoquinones, and anthocyanins, while chlorophyll synthesis is not affected. Thus the degree of inhibition of prenyl-lipid synthesis by GA 3 depends on the developmental stage of the Rapbanus -seedYmg. 2. In the Z 0 -plants GA 3 induces a change of metabolite flow in the biosynthesis chain of lipoquinones which yields more α -tocopherol (+ α -tocoquinone) and less plastoquinone-9 (+ hydroquinone). This is inverse to the metabolite flow during active thylakoid synthesis. Z 3 -plants do not show this effect. 3. Parallel to the inhibition of prenyl-lipid synthesis GA 3 decreases in the Z 0 - and Z 3 -plants the rate of prenyl-chain formation. The synthesis of C 20 -chains in chlorophylls, α-tocopherol, and α-tocoquinone, and of C 40 -chains (carotenoids) is earlier affected than that of C 45 -chains in plastoquinone-9. 4. Kinetin (2 ppm) at first retards germination and development of Rapbanus -plants for about 3 days. Thereafter kinetin induces an increased growth of the seedlings, which results in a promoted synthesis of chlorophylls, plastoquinone-9 (+ hydroquinone), and anthocyanins. Formation of α -tocopherol (+ α -tocoquinone) in turn is suppressed. The data on the chloroplast lipids are consistent with the assumption that kinetin induces a promoted thylakoid synthesis. 5. In Z 0 - and Z 3 -plants kinetin decreases the synthesis of carotenoids. This is, however, a normal process during increased thylakoid synthesis, where formation of chlorophylls and plastoquinone-9 preceds that of carotenoids. Concerning the prenyl chains kinetin produces the formation and incorporation of the C 45 -chains in plastoquinone-9 and of phytyl chains in chlorophylls, which leaves apparently less isoprenoid C 20 -precursors for α-tocopherol and carotenoid synthesis. 6. Kinetin promotes — similar to β -indolacetic acid (IAA) — the light-dependant synthesis of chloroplast lipids and anthocyanins, while GA 3 — similar to abscisic acid (ABA) — inhibits these light effects (fig.1). Thus kinetin, IAA and light have a synergistic influence on Raphanns-plants. GA 3 and ABA, in turn, are antagonists to the light induced changes of plant metabolism.