CHLOROPHYLL FLUORESCENCE IN in vitro CULTIVATED APPLE

Abstract

Chlorophyll fluorescence is a useful tool because it allows the interpretation of the aspects related to the photosynthesis. The aim of this study was to examine the use of the fluorescence as an indicator of the photosynthetic efficiency of rootstock (Malus domestica - cv M9) cultivated in vitro. The explants (nodal sections with two lateral buds) were kept in growth chamber with 16 hours light and PF of 15 µmol m^-2s^-2. The plants were kept for 55 (T1) and 90 (T2) days, and the plants with 55 days were transferred to PF of 150 µmol m^-2s^-2 for 2 h before the determination (T3). The leaves were maintained in the dark for 15 minutes for determining the parameters of the dark adapted state. Then the leaves were submitted to the actinic light for 5 minutes for the determination of the parameters of the light adapted state. It was observed that T2 presented higher values of F_m; F_v/F_m and F_v/F_o, and lower F_o/F_m. The coefficients q_N and NPQ were higher in T2, indicating higher energy dissipation in non-photochemical processes; q_P did not differ between the treatments T2 and T3. Comparison of the quenching coefficients between T1 and T3 indicates that the in vitro culture conditions for T1 imposes limitations in the biochemical phase.