INHIBITION OF SPINACH CHLOROPLAST PHOTOPHOSPHORYLATION AND ELECTRON TRANSPORT BY SELECTED NATURAL PRODUCTS | ||
| Journal of Plant Protection and Pathology | ||
| Article 1, Volume 31, Issue 1, January 2006, Pages 411-418 PDF (2.59 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jppp.2006.235147 | ||
| Author | ||
| Shafika A. EI-Kassabany, | ||
| Pesticide Central Laboratory, Agriculture Research Center, Sabahia, . Alexandria, Egypt. | ||
| Abstract | ||
| The effects of the biflavonoid crassifolin (1), the flavonoid tephrobotin, the Annnonaceous acetogenins squamocin (3), and buliatacin (4) were investigated on different photosynthetic activities in isolated spinach chloroplasts. The results indicated that compounds 1-4 inhibited both ATP synthesis and uncoupled electron transport. In addition, s~uamocin (3), and bullatacin (4) enhanced basal electron flow and light-activated Mg + -ATPase. Therefore, acetogenins 3, and 4 behave as uncouplers and Hill reaction inhibitors. Compounds 1, and 2 inhibited basal electron flow and did not affect light-activated Mg2+ -ATPase. All the compounds induced a concentration-dependent inhibition of photophosphorylation. Natural products 1-4 did , not affect photosystem I (PSI) activity but they inhibited photosystem II (PSII) electron flow. The study of the partial PSII reactions from H20 to OCPIPox, H20 to SiMo and diphenykarbazide OPC to OCPIP established that the site of inhibition was at the oxygen-evolving complex (OEC). | ||
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