Chin J Plan Ecolo ›› 2014, Vol. 38 ›› Issue (10): 1110-1116.doi: 10.3724/SP.J.1258.2014.00105
• Research Articles •
KANG Hua-Jing1,2,3,4*, LI Hong4, QUAN Wei4, and OUYANG Zhu1,2,3**
Aims Despite the increasing attention given to the rate of mitochondrial respiration under light (Rd), considerable confusion persists over whether mitochondrial respiration in the dark (Rn) is inhibited by light and whether Rd is affected by light intensity. The objective of this study is to test the hypotheses: 1) Rn is not inhibited by light; 2) the rate of Rd changes with light intensity; and 3) the photosynthetic refixation of CO2 produced by Rn accounts for the apparent disparity between Rd and Rn.
Methods In the present study, 0.02 mol·mol–1 O2 (i.e. 2% O2) was used to saturate Rn and to inhibit photorespiration (Rp). By using combined gas exchange measurements and a low O2 (2% O2) method, the post-illumination CO2 release rate of Rn, photosynthetic rate (Pn) in response to photosynthetically active radiation (PAR) in 2% O2 at either 380 or 0 μmol·mol–1 CO2, of C3 (Triticum aestivum and Glycine max) and C4 (Zea mays and Amaranthus hypochondriacus) plants, were measured.
Important finding Rn was not inhibited by light. At 2% O2 and 0 μmol·mol–1 CO2, the measured parameters could be used to accurately estimate Rd when CO2 concentration was set for 0 μmol·mol–1. Rd decreased with increasing light intensity. Although Rd was lower in the dark, this could be accounted for by photosynthetic re-fixing of respiratory CO2. For all plants tested, CO2 recovery rates increased with increasing light intensity (from 50 and 2 000 μmol·m–2·s–1).
KANG Hua-Jing, LI Hong, QUAN Wei, and OUYANG Zhu. Causes of decreasing mitochondrial respiration under light in four crops[J].Chin J Plan Ecolo, 2014, 38(10): 1110-1116.
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