caa a22 4500 397522843 CHVBK 20180308164637.0 cr unu---uuuuu 161202e199509 xx s 000 0 eng 10.1093/jxb/46.special_issue.1439 doi (NATIONALLICENCE)oxford-10.1093/jxb/46.special_issue.1439 Decarboxylation of primary and end products of photosynthesis at different oxygen concentrations [Elektronische Daten] [Tiit Pärnik, Olav Keerberg] A radiogasometric method for the determination of the rates of intracellular decarboxylation of primary and end products of steady-state photosynthesis in the light has been worked out. On the basis of oxygen dependence of the CO2 evolution, two types of decarboxylation, oxygenase (photorespiration) and oxidase (dark respiration), have been distinguished. Oxygenase decarboxylation is linearly dependent on O2 concentration in the range from 0 to 210 mmol mol−1, which is characteristic of the oxygenation of RuBP, the ratelimiting reaction of the glycolate cycle. Oxidase decarboxylation is saturated at relatively low O2 concentration (of about 15 mmol mol−1), similar to the oxidative reactions associated with glycolysis and the Krebs cycle. In the C3 plants (tobacco, wheat, barley) we have studied, primary products were decarb-oxylated predominantly via the oxygenase mechanism; the oxidase component was 3-15% of the total rate of the decarboxylation of primary photosynthates in the light. The oxygenase mechanism was also involved in the decarboxylation of end products of photosynthesis. The rate of this component exceeded by 3 to 5 times the rate of oxidase decarboxylation of end products in the light. It has been suggested that compounds derived from the degradation of end products of photosynthesis are incorporated into the reductive pentose phosphate cycle and, via the cycle, into the glycolate cycle where they are decarboxylated. In this way, four components of plant leaf respiration in the light may be distinguished according to the substrates and mechanisms of decarboxylation. In the dark, only one of them, oxidase decarboxylation of end products, is functioning. The rate of this component has been shown to be partially suppressed by light. © 1995 Oxford University Press Environmental Interactions nationallicence Photorespiration nationallicence dark respiration nationallicence decarboxylation nationallicence primary products of photosynthesis nationallicence end products of photosynthesis nationallicence Pärnik Tiit Institute of Experimental Biology, Estonian Academy of Sciences, EE3051 Harku, Estonia aut Keerberg Olav Institute of Experimental Biology, Estonian Academy of Sciences, EE3051 Harku, Estonia aut Journal of Experimental Botany Oxford University Press 46/special_issue(1995-09), 1439-1477 0022-0957 46:special_issue<1439 1995 46 exbotj https://doi.org/10.1093/jxb/46.special_issue.1439 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/jxb/46.special_issue.1439 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pärnik Tiit Institute of Experimental Biology, Estonian Academy of Sciences, EE3051 Harku, Estonia aut NATIONALLICENCE 700 1- Keerberg Olav Institute of Experimental Biology, Estonian Academy of Sciences, EE3051 Harku, Estonia aut NATIONALLICENCE 773 0- Journal of Experimental Botany Oxford University Press 46/special_issue(1995-09), 1439-1477 0022-0957 46:special_issue<1439 1995 46 exbotj Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford