2.4 Leaf chlorophyll fluorescence measurements
In 2019, diurnal change in PSII functionality was detected using Plant Efficiency Analyzer (Pocket-PEA , Hansatch Instrument, King’s Lynn, Norfolk, UK). Three first fully expanded leaves in each type of seedling were randomly selected at jointing (August 7), heading (September 8) and grain filling stages (September 24), respectively. The central part of the selected leaves was dark-adapted for 0.5 hour using leaf clips before measuring at predawn, 7:00, 9:00, 11:00, 13:00, 15:00, 17:00 and 19:00. On the day of observation during each growth period, the dawn time was 4:57, 5:19 and 5:29, and the dark time was 19:24, 18:46 and 18:24, respectively. The temperature and PPFD at each observation time were shown in Fig.1. The saturating light pulse 3500 µmol m-2s-1 was applied in Pocket PEA .