Photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase in rice leaves from emergence through senescence. Quantitative analysis by carboxylation/oxygenation and regeneration of ribulose 1,5-bisphosphate

Amane Makino, T. Mae, K. Ohira

Research output: Contribution to journalArticlepeer-review

137 Citations (Scopus)

Abstract

Changes in gas-exchange rates during the life span of the leaves of rice (Oryza sativa L.) were analyzed quantitatively by measuring changes in the carboxylation/oxygenation and regeneration of ribulose 1,5-bisphosphate (RuBP) at photon fluence rates of 2000 (saturating) and 500 (subsaturating) μmol quanta·m-2·s-1 under ambient air conditions. The RuBP levels were always higher than the active-site concentrations of RuBP carboxylase (EC 4.1.1.39), irrespective of the irradiance supplied. Analysis of the CO2-assimilation rate as a function of intercellular CO2 concentration indicated that RuBP regeneration does not limit CO2 assimilation. The estimated RuBP-carboxylase/oxygenase activity in vivo was linearly correlated to the rate of CO2 assimilation at each level of irradiance. This enzyme activity was just enough to account for the rate of CO2 assimilation at the saturating irradiance and was 35% more than the rate of CO2 assimilation at the subsaturating irradiance. Analysis of the assimilation rate at subsaturating irradiance as a function of intercellular CO2 concentration indicated that a limitation caused by enzyme activation comes into play. The results indicate that the rate of CO2 assimilation in rice leaves under ambient air conditions is limited during their entire life span by the RuBP-carboxylation/oxygenation capacity.

Original languageEnglish
Pages (from-to)414-420
Number of pages7
JournalPlanta
Volume166
Issue number3
DOIs
Publication statusPublished - 1985 Nov 1

Keywords

  • Leaf (gas exchange during life)
  • Oryza (gas exchange)
  • Photosynthesis (gas exchange)
  • Ribulose-1,5-bisphosphate carboxylase/oxygenase
  • Senescence (leaf)

ASJC Scopus subject areas

  • Genetics
  • Plant Science

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