Affiliation: | a Departament d'Ecologia, Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08028-, Barcelona, Spain b Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona Diagonal 645, 08028-, Barcelona, Spain |
Abstract: | The rates of respiratory O2 uptake have been studied in leaves, stems and whole shoots of several freshwater plants: 6 angiosperms, 2 bryophytes and one alga. For angiosperm leaves, rates varied widely with species (30–142 μmol O2 (gDW)−1 h−1), were correlated with chlorophyll content and were higher than those of the stems (13–71 μmol O2 (gDQ)−1 h−1). The rates for the shoots of bryophytes (53–66 μmol O2 (gDW)−1 h−1) and for the alga Cladophora glomerata (L.) Kütz. (96 μmol O2 (gDW)−1 h−1) were slightly higher than those of most angiosperm stems, but lower than those for most leaves. These plants had a significant cyanide-resistant respiration, suggesting the existence of an alternative pathway to the “classic” cytochrome system. This pathway was found to be active in all the species studied, as judged by responses to a specific inhibitor, SHAM (salicylhydroxamic acid). Measurement of electron-transport system (ETS) activity showed that there is a large electron-transport capacity which is not normally used by respiration in vivo. |