Note that the light intensity is relatively low, which may lead to an altered antenna composition as compared to that of plants grown under high-light conditions. Alocasia was grown at room temperature with alternating 16 h of light at a light intensity of 10–15 μE m−2 s−1 and 8 h of darkness. For closing the reaction centers of PSII in leaves, vacuum infiltration was performed with 0.1 mM DCMU, 20 mM Hepes, 5 mM NaCl, and 5 mM MgCl2 buffer with pH 7.5. Isolation of chloroplasts: Alocasia wentii leaves were ground in semi-frozen buffer 1 (0.45 M sorbitol, 20 mM Tricine, 10 mM EDTA, 10 mM NaHCO3, and

0.1% BSA, pH 8.4) using a blender for 5-s, and then filtrated through eight layers of cheesecloth and centrifuged at 3,000 × g for 20 s at 4°C. The supernatant was Protein Tyrosine Kinase inhibitor discarded and the pellet washed with buffer 2 (0.3 M Sorbitol, 20 mM Tricine, 5 mM SC79 in vitro MgCl2, and 2.1 mM EDTA, pH 7.4). The collected resuspended chloroplasts were put on 50% Percoll/50% buffer 3 (0.6 M Sorbitol, 20 mM Tricine,

and 5 mM MgCl2, pH 7.6) and centrifuged at 3,500 × g for 10 min at 4°C. The supernatant was disposed, and the pellet was diluted in buffer 2 before measuring. Results and discussion It has been demonstrated that FLIM can be a noninvasive tool (Holub et al. 2000; Lukins et al. 2005) for measuring Chl a fluorescence lifetimes in plants and algae which can then be correlated to the response PDK4 of the photosynthetic apparatus to, for instance, the effect of dehydration. However,

measurements so far have only been performed under high-light conditions at the maximum fluorescence level (FM) in which PSII reaction centers are closed and average lifetimes were found to be 1.7 ns ± 0.2 ns (Holub et al. 2000) and 611 ps (Lukins et al. 2005), indeed corresponding to lifetimes of PSII with (selleck products partially) closed reaction centers. With the FLIM setup used in the present study it is possible to measure under low-light conditions. In Fig. 2 two images with 1,024 pixels are presented, showing Alocasia wentii chloroplasts. The fluorescence images illustrated in the figure are intensity-based, whereas the fluorescence kinetics has been obtained for each pixel and has been analyzed with a combination of SPCimage2.3 software (Becker & Hickl) and home-built software using a exponential decay model (Digris et al. 1999; Mullen et al. 2007; Novikov et al. 1999). The fitted chloroplast fluorescence lifetimes and amplitudes averaged over all the pixels of Fig. 2b are as follows: τ 1 = 59.5 ps (44.1%), τ 2 = 205 ps (35.3%) and τ 3 = 588 ps (20.6%). Without further experiments and knowledge, it is not possible to assign the lifetimes to processes in PSI and PSII. The amplitudes are expected to depend strongly on the excitation and detection wavelength. A complicating factor at this stage is the fact that the two-photon absorption spectra of all the relevant pigments are not known.