Fig 5. Light induction curves of transient Chl fluorescence (A) and JIP-test results (B).

Data were determined in the first true leaves of cucumber seedlings under different root-zone (RZ) temperature and PEG treatments. RC/ABS: Q_A reducing RCs per PSII antenna Chl; TR_o/ABS: maximum quantum yield for primary photochemistry; ET_o/TR_o: efficiency/probability that an electron moves further than Q_A⁻; ET_o/ABS: quantum yield for electron transport; RE_o/ET_o: efficiency/probability with which an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side; RE_o/ABS: quantum yield for reduction of end electron acceptors at the PSI acceptor side; PI_ABS: performance index (potential) for energy conservation from photons absorbed by PSII to the reduction of intersystem electron acceptors; PI_total: performance index (potential) for energy conservation from photons absorbed by PSII to the reduction of PSI end acceptors. Lines and values are the averages of four individual measurements with four different seedlings.