The net photosynthetic rate (Pn), stomatal conductance (Gs), and intercellular
CO2 concentration (Ci) of leaves on ‘Fuji’ apple trees were measured with a
portable photosynthetic system (CIRAS-2,PP Systems, UK). Measurements were
conducted between 9:00 and 11:00 am on 10 June at a saturating light flux (1100
mol s−1 m−2),a relative humidity of 70%, a leaf temperature of 28 ± 2◦C and ambient
atmospheric CO2 levels (385 ± 23 mol mol−1). Ten leaves were measured on the
middle of selected shoots for each Zn deficiencycategory.