This enabled us to measure the PAR value, its maximum, and to calculate the total input and to obtain average values of PAR for each treatment during canopy development. The total PAR input of any leaf was calculated as a sum of incident PAR (in mols of photons per unit area per second) between the appearance of the leaf and the time of performing photosynthesis and fluorescence measurements and the HL treatment. The middle part of mature leaves of barley (which was measured) was almost in a horizontal position; hence, the measured values of PAR almost fully

corresponded to light intensities incident on leaves. Measurement of photosynthetic parameters Barley plants were transferred to the laboratory for photosynthesis (CO2 fixation) measurements buy C646 at different light intensities (to provide light response curve; see “Introduction” section), for rapid light curves of ChlF (see below),

and for ChlF induction curves that provided information on the photochemical efficiency of PSII, among other parameters (see “Discussion” section, for details). “Results” section describes the protocol for studying the effect of HL. Measurements were done on fully expanded penultimate leaves. 1. Light response curve of photosynthesis was measured using CIRAS-2 gas analyzer (PP Systems, USA). CO2 find more concentration was fixed PKC412 mouse at ~370 μmol CO2 mol air−1; the sample temperature was 25 °C;

PAR light intensities were 100, 300, 600, 900, and 1200 μmol photons m−2 s−1, given at an interval of 15 min Pyruvate dehydrogenase for each light increment.   2. Rapid light curves for fluorescence were made as described by White and Critchley (1999). Parameters of modulated ChlF were measured using Mini-PAM Fluorimeter (Walz, Germany) with PAR intensity of 152, 246, 389, 554, 845, 1164, 1795, and 2629 μmol photons m−2 s−1 (internal halogen lamp). The measured and calculated parameters of ChlF are shown in Table 1. Table 1 Measured and calculated chlorophyll fluorescence parameters Parameters Name and basic physiological interpretation Measured or computed inputs for calculation of the key fluorescence parameters  F, F′ Fluorescence emission from dark- or light-adapted leaf, respectively  F 0 Minimum fluorescence from dark-adapted leaf (PSII centers open); F 0 was not corrected for PSI fluorescence, and for the possible presence of reduced QB that could produce some reduced QA in darkness.