Abstract
Total dark respiration (vt), cytochrome pathway (veyt), alternative pathway (valt) and residual (vres) respiration were measured in Lemna gibba plants, by the use of pathway inhibitors. NaCN was used to inhibit veyt and SHAM (salicylhydroxamic acid) to inhibit valt. Residual respiration (vres) was about 5% of vt. The effect of high (100 Pa) and low (0 Pa) carbon dioxide partial pressure ([CO2]) on vt, veyt and valt was determined from both CO2 efflux and O2 uptake measurements. The higher [CO2] suppressed vt by about 30%. When respiration operated through the cytochrome pathway only, in the absence of valt, it was suppressed by about 12% as measured by the O2 uptake of submerged Lemna fronds or by about 40% as measured by CO2 efflux from floating fronds. The higher [CO2] treatment had only a small effect on respiration, when valt alone operated. There was no evidence of a specific suppression of the valt pathway by high [CO2]. Succinic dehydrogenase activity of the mitochondria of roots of Medicago sativum was reduced by 18%, when the mitochondria were pre-treated with 120 as compared to 34 Pa [CO2]. There was no such effect on cytochrome c oxidase activity of mitochondria under the same conditions. It is concluded that there is no evidence for the hypothesis that the high [CO2] suppression of respiration is a result of a CO2 effect on the non-phosphorylating alternative respiration pathway.
Original language | English |
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Pages (from-to) | 291-295 |
Number of pages | 5 |
Journal | Annals of Botany |
Volume | 76 |
Issue number | 3 |
DOIs | |
State | Published - Sep 1995 |
Keywords
- Alternative pathway
- Carbon dioxide
- Cyanide-insensitive pathway
- Cytochrome c oxidase
- Cytochrome pathway
- Lemna gibba
- Medicago sativum
- Respiration
- Succinic dehydrogenase