Action of bicarbonate and Photosystem 2 inhibiting herbicides on electron transport in pea grana and in thylakoids of a blue‐green alga

Jack J.S. van Rensen, Willem Vermaas

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

Bicarbonate (or carbon dioxide) is required for electron transport in isolated broken pea chloroplasts. The site of action of the bicarbonate ion is between the primary electron acceptor of Photosystem 2, Q, and the plastoquinone pool. After trypsin treatment the Hill reaction with ferricyanide does not require bicarbonate. Photosystem 2 inhibiting herbicides act also at this site. Therefore, a possible interaction of bicarbonate and these herbicides in their effect on photosynthetic electron transport was studied. The reciprocal of the Hill reaction rate in CO2‐depleted chloroplasts was plotted against the reciprocal of added bicarbonate concentration in the absence and in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), 2‐methoxy‐4,6‐bis (ethylamino)‐1,3,5‐triazine (simeton) or 4,6‐dinitro‐o‐cresol (DNOC). From these Lineweaver‐Burk plots we concluded that DCMU and simeton inhibit both bicarbonate binding and Vmax. There is a purely competitive inhibition of bicarbonate binding by DNOC. We suggest that DNOC may exert its inhibition of electron transport by removing bicarbonate from its binding site. In isolated thylakoid membranes of Synechococcus leopoliensis we did not find a bicarbonate effect nor inhibition by DNOC after Q, indicating that in the thylakoids of this blue‐green alga the binding site for bicarbonate and DNOC between Q and plastoquinone is absent.

Original languageEnglish (US)
Pages (from-to)106-110
Number of pages5
JournalPhysiologia Plantarum
Volume51
Issue number1
DOIs
StatePublished - 1981
Externally publishedYes

Keywords

  • bicarbonate
  • Chloroplast
  • electron transport
  • mechanism of action of herbicides
  • Synechococcus
  • trypsin

ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Plant Science
  • Cell Biology

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