caa a22 4500 605480621 CHVBK 20210128100416.0 cr unu---uuuuu 210128e20150901xx s 000 0 eng 10.1007/s11099-015-0116-3 doi (NATIONALLICENCE)springer-10.1007/s11099-015-0116-3 Differential blockage of photosynthetic electron flow in young and mature leaves of Arabidopsis thaliana by exogenous proline [Elektronische Daten] [I. Sperdouli, M. Moustakas] Responses of the photosynthetic electron transport system of chloroplasts to exogenous proline application were evaluated in young and mature leaves of Arabidopsis thaliana plants under optimal growth conditions. Exogenous proline application (10 mM) during the 4th week of growth increased proline accumulation in young leaves more than in mature leaves, and possibly due to its degradation producing NADPH, decreased significantly the ratio of NADP+/NADPH in both leaf types compared with controls (without proline). However, the ratio of NADP+/NADPH remained significantly higher in the young leaves, suggesting lower proline degradation which resulted in less reduced plastoquinone pool than that in the mature leaves, under both low light [130 μmol(photon) m−2 s−1] and high light [1,200 μmol(photon) m−2 s−1] treatments. The young leaves seemed to adjust nonphotochemical fluorescence quenching in order to maintain a better PSII quantum yield. We concluded that under optimal growth conditions exogenous proline results in overreduction of the plastoquinone pool and blockage of photosynthetic electron flow due to accumulation of NADPH. We suggest that optimum concentrations of proline are required for optimal PSII photochemistry. The Institute of Experimental Botany, 2015 chlorophyll fluorescence nationallicence electron transport rate nationallicence leaf age nationallicence reactive oxygen species nationallicence AL : actinic light nationallicence AOI : area of interest nationallicence Chl : chlorophyll nationallicence ETR : electron transport rate nationallicence F0, Fm : minimal and maximal chlorophyll a fluorescence of the dark-adapted state nationallicence F0′, Fm′ : minimal and maximal chlorophyll a fluorescence of the light-adapted state nationallicence Fs : steady-state photosynthesis at a given actinic light nationallicence Fv/Fm : potential (maximal) quantum yield of PSII photochemistry nationallicence HL : high light nationallicence LL : low light nationallicence ML : mature leaves nationallicence NPQ : nonphotochemical quenching nationallicence P5C : Δ1-pyrroline-5-carboxylate nationallicence P5CDH : Δ1-pyrroline-5-carboxylate dehydrogenase nationallicence P5CR : Δ1-pyrroline-5-carboxylate reductase nationallicence P5CS : Δ1-pyrroline-5-carboxylate synthase nationallicence PDH : proline dehydrogenase nationallicence PQ : plastoquinone nationallicence Pro : proline nationallicence qP : photochemical quenching coefficient nationallicence ROS : reactive oxygen species nationallicence YL : young leaves nationallicence ΦPSII : actual (effective) quantum yield of PSII photochemistry nationallicence Sperdouli I. Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece aut Moustakas M. Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece aut Photosynthetica The Institute of Experimental Biology of the Czech Academy of Sciences 53/3(2015-09-01), 471-477 0300-3604 53:3<471 2015 53 11099 https://doi.org/10.1007/s11099-015-0116-3 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s11099-015-0116-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sperdouli I. Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece aut NATIONALLICENCE 700 1- Moustakas M. Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece aut NATIONALLICENCE 773 0- Photosynthetica The Institute of Experimental Biology of the Czech Academy of Sciences 53/3(2015-09-01), 471-477 0300-3604 53:3<471 2015 53 11099