2.5 Photosynthetic pigment content, photosynthesis, and
chlorophyll fluorescence
Photosynthetic pigments were extracted with 80% acetone for 48 h and
observed by spectrophotometry based on Arnon (1949). Net photosynthesis
(Pn) and stomatal conductance (GS) were
assessed with a CIRAS-3 portable photosynthesis system (CIRAS, Amesbury,
MA, USA).
The apple plants were kept in darkness for 30 min before measuring their
chlorophyll fluorescence. The FV/Fm ratio was
measured by placing fully expanded leaves on an Imaging-Pam Chl
fluorimeter (Walz, Effeltrich, Germany), then determining chlorophyll
fluorescence parameters with Imaging WinGegE software.