caa a22 4500 477100996 CHVBK 20180405111541.0 cr unu---uuuuu 170330e19960401xx s 000 0 eng 10.1007/BF00262645 doi (NATIONALLICENCE)springer-10.1007/BF00262645 Oxygen-dependent electron transport and protection from photoinhibition in leaves of tropical tree species [Elektronische Daten] [Catherine Lovelock, Klaus Winter] The roles of photorespiration and the Mehlerperoxidase pathway in sustaining electron transport and protection from photoinhibition were studied in outer canopy leaves of two species of tropical trees: the drought-deciduous Pseudobombax septenatum (Jacq.) Dug. and the evergreen Ficus insipida Willd. Ficus had a higher photosynthetic capacity than Pseudobombax and also a greater capacity for light-dependent electron transport under photorespiratory conditions (in the absence of CO2). As a consequence, in the absence of CO2, Ficus was able to maintain a largely oxidized electron-transport chain at higher photon flux densities than Pseudobombax. Under the same light conditions, photoinhibition (reduction in Fv/Fm) was always greater in Pseudobombax than Ficus, was increased when leaves were exposed to 2% O2 in nitrogen compared to 21% O2 in CO2-free air, but was not increased by the absence of CO2. Rates of electron transport due to the Mehler-peroxidase pathway (assessed in 2% O2 in nitrogen) ranged between 16-40 μmol · m−2·s−1 in both species. As the dry season approached and Pseudobombax neared leaf senescence there was a decline in the capacity for photorespiratory flux to maintain electron transport in Pseudobombax, but not in Ficus. Ratios of light-dependent electron transport to net CO2 fixation for Pseudobombax, Ficus and two other species in the field, Luehea seemannii Tr. & Planch, and Didymopanax morototoni (Aubl.) Dec. & Planch., ranged from 6.2 (Ficus) to 16.7 (Pseudobombax). High in-situ rates of photorespiration combined with the decreased capacity of Pseudobombax for photorespiratory flux as the dry season approached indicates a decreased capacity to protect against photooxidative damage. This may contribute to the promotion of leaf senescence in Pseudobombax during the transition from wet to dry season. Springer-Verlag, 1996 Electron transport (oxygen dependent) nationallicence Photoinhibition nationallicence Tropical tree species nationallicence Fv/Fm : ratio of variable to maximum chlorophyll a fluorescence nationallicence NPQ : nonphotochemical fluorescence quenching nationallicence PFD : photon flux density nationallicence QA : primary electron acceptor of PSII nationallicence Lovelock Catherine Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Republic of Panamá aut Winter Klaus Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Republic of Panamá aut Planta Springer-Verlag 198/4(1996-04-01), 580-587 0032-0935 198:4<580 1996 198 425 https://doi.org/10.1007/BF00262645 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00262645 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Lovelock Catherine Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Republic of Panamá aut NATIONALLICENCE 700 1- Winter Klaus Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Republic of Panamá aut NATIONALLICENCE 773 0- Planta Springer-Verlag 198/4(1996-04-01), 580-587 0032-0935 198:4<580 1996 198 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer