Photorespiration rate in mungbean (Vigna radiata (L.) Wilczek) leaves: A further estimation from the quantum yield at photosystem (2)
1999
Hirao, K. (Kyushu Univ., Fukuoka (Japan)) | Kubota, F. | Yoshimura, Y. | Tokuda, S. | Saitou, K.
Photorespiration rates (PR) in peeled (PL, without epidermis) and nonpeeled (NL) leaves of mungbean (Vigna radiata (L.) Wilczek) were estimated from electron transport situations at photosystem II using the chlorophyll fluorescence quenching diagnosis. The number (k1) of electron equivalents required to produce 9 mol adenosine 5'-triphosphate (ATP) for fixing 1 mol 002 was experimentally determined 4.62. Also the number (k2) of electrons required for releasing 1 mol CO2 in photorespiration was estimated 7.44 or 9.49 on the assumption that 14.5 or 18.5 mol ATP was consumed for 1 mol CO2 releasing, respectively. The simultaneous equations were constructed with the parameters of k1, k2 and related elements to calculate PR, and the mutual relationships in energy balance among PR, gross photosynthetic rate (Pg), total photosynthetic rate (TC, TC=PR+Pg) and PR ratio (PR/TC) were discussed. The value of PR, 1.75 or 2.05/mu-mol m(-1) s(-1), in PL was estimated corresponding to k2=7.44 or 9.49 in a light intensity of 300 mu-mol m'2 s'1 PPFD, and PR/TO was 18.2 or 20.6%, respectively. The estimation by chlorophyll fluorescence quenching diagnosis may give a more reasonable value of PR as compared with the PR obtained by the subtraction method (PR==Pg measured in 2% [O2] air-Pg measured in 2% [O2] air)
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