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 .