Chlorophyll fluorescence of the second apical, fully developedleaves of 3-week-old in vitro shoots was measured using OS5p Mod-ulated Fluorometer (Opti-Sciences, USA). Chlorophyll fluorescencewas measured both in dark-adapted and in light-adapted samplesusing dark-adapted Fv/Fmtest for the determination of maximumquantum yield and light adapted yield of photosynthetic efficiencyof PSII for the determination of effective quantum photochemicalyield, respectively.