Abbreviations: ABS/CS -absorption flux per CS; ABS/RC -absorption flux (exciting PS II antenna of Chl a molecules) per RC; AQY -apparent quantum yield; BRs -brassinosteroids; CEF -cyclic electron transport around PS I; ci -intercellular CO2 concentration; CS -cros section; E -transpiration rate; EBR -24-epibrassinolide; ETo/CS -electron transport flux per CS; ETo/RC -electron transport flux (further than QA -) per RC; ETR -electron transport rate; Fm -maximal fluorescence yield; Fo -minimal fluorescence yield; Fv/Fmmaximal quantum yield of PS II photochemistry; gs -stomatal conductance; Mo -approximated initial slop (in ms -1 ) of the fluorescence transient normalized on the maximal variable fluorescence Fv; NPQ -nonphotochemical quenching coefficient; OEC -oxygen-evolving complex; OJIP curve -Chl a fluorescence transient; PIABS -performance index for energy conservation from photons absorbed by PS II until the reduction of intersystem electron acceptors; Pm -maximum P700 oxidation; PN -net photosynthetic rate; PN,max -maximum net photosynthetic rate; PPFD -photosynthetic photon flux density; PS I -photosystem I; PS II -photosystem II; qP -photochemical quenching coefficient; RC/CS -density of QA-reducing PS II RCs per CS; RCs -PS II reaction centers; ROS -reactive oxygen species; TRo/CS -trapped energy flux per CS; TRo/RC -trapped energy flux (leading to QA reduction) per RC; VJ -relative variable fluorescence at the J-step; WK -normalized relative variable fluorescence at the K step; Y(I) -effective photochemical quantum yield of PS I; Y(II)effective PS II quantum yield; Y(NA) -quantum yield of non-photochemical energy dissipation of reaction centers due to PS I acceptor side limitation; Y(ND) -quantum yield of non-photochemical energy dissipation in reaction centers due to PS I donor side limitation; Y(NPQ) -quantum yield of regulated energy dissipation; Y(NO) -quantum yield of nonregulated energy dissipation; φEo -quantum yield for electron transport (ET); φPo -maximum quantum yield for primary photochemistry; Ψo -probability that a trapped exciton moves an electron into the electron transport chain beyond QA -.