CO2 gas exchange rates (CER) in a peeled leaf (PL) and nonpeeled leaf (NL) of mungbean (Vigna radiata (L.) Wilczek) were measured in a saturating light intensity to identify their responses to CO2 concentrations ([CO2]) and leaf temperatures. The CER of PL was regarded as an indicator for the photosynthetic potential in mesophyll. When measured at 35 °C, CER was enhanced by peeling the epidermis, whereas it was less effective at 25 °C and almost not effective at 15 °C. In [CO2]-CER response curves, CER of PL had a highest plateau in 500 to 1,000μmolmol-1 [CO2] at 35 °C, whereas at both 25 and 15 °C CER showed a peak in 500μmolmol-1 [CO2]. When measured in the air of 20% O2 concentration ([O2]) in a light intensity of 300μmolm-2s-1 photosynthetically photon flux density (PPFD) at 25 °C, the CO2 quantum yield (ΦCO2) in PL was higher than that in NL, whereas the photosystem II (PSII) quantum yield (Φe) was a little lower in PL. The number (k) of electron equivalents required to fix 1 mol CO2 was greatly increased in NL due to the increased photorespiration. In 2% [O2] k of PL was 4.62, which was a little larger than a theoretical minimum (k=4). From the relationships between k, CER and adenosine 5′-triphosphate (ATP) required for photosynthesis, the rates of photorespiration were estimated in different environments.
|Number of pages||10|
|Journal||Journal of the Faculty of Agriculture, Kyushu University|
|Publication status||Published - Feb 1999|
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences (miscellaneous)