Hawkesbury Campus;
Australia;
Western Sydney Univ;
Australian Natl Univ;
Res Sch Biol;
Locked Bag 1797;
Canberra;
ARC Ctr Excellence Translat Photosynth;
Penrith;
NSW 2751;
Hawkesbury Inst Environm;
ACT 2601;
关键词：
Chlorophyll fluorescence;
Mehler reaction;
Photosystem;
Oxygen exchange rate;
Electron transport rate;
C-4 photosynthesis;
Respiration;
期刊名称：
Photosynthesis Research: An International Journal
i s s n：
0166-8595
年卷期：
2021 年
149 卷
1/2 期
页 码：
171-185
页 码：
摘 要：
Alternative electron fluxes such as the cyclic electron flux (CEF) around photosystem I (PSI) and Mehler reaction (Me) are essential for efficient photosynthesis because they generate additional ATP and protect both photosystems against photoinhibition. The capacity for Me can be estimated by measuring O-2 exchange rate under varying irradiance and CO2 concentration. In this study, mass spectrometric measurements of O-2 exchange were made using leaves of representative species of C-3 and C-4 grasses grown under natural light (control; PAR similar to 800 mu mol quanta m(-2) s(-1)) and shade (similar to 300 mu mol quanta m(-2) s(-1)), and in representative species of gymnosperm, liverwort and fern grown under natural light. For all control grown plants measured at high CO2, O-2 uptake rates were similar between the light and dark, and the ratio of Rubisco oxygenation to carboxylation (V-o/V-c) was low, which suggests little potential for Me, and that O-2 uptake was mainly due to photorespiration or mitochondrial respiration under these conditions. Low CO2 stimulated O-2 uptake in the light, V-o/V-c and Me in all species. The C-3 species had similar V-o/V-c, but Me was highest in the grass and lowest in the fern. Among the C-4 grasses, shade increased O-2 uptake in the light, V-o/V-c and the assimilation quotient (AQ), particularly at low CO2, whilst Me was only substantial at low CO2 where it may contribute 20-50% of maximum electron flow under high light.
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