2.6 Determination of photosynthetic parameters
The CIRAS-3 portable photosynthesis system (CIRAS, Amesbury, MA, USA)
was used to determine the Pn and Gs. For
each measurement, data were collected from six fully mature leaves of
different seedlings. Before measuring chlorophyll fluorescence, the
apple plants were kept in darkness for 30 minutes. To measure
FV/FM ratio, fully expanded leaves were
placed on a modulated chlorophyll fluorescence imaging system from Walz
(Effeltrich, Germany).