The number of counts in the peak channels are 28, 156, and 2028, respectively The fluorescence decay traces of isolated chloroplasts have also been measured with FLIM and are compared to those of leaf tissue (Fig. 4). The in vivo fluorescence kinetics of chloroplasts are similar to those of the isolated chloroplasts for the first 170-ps part of the trace. There is a small discrepancy in the middle part of R788 cost the trace, but overall the traces are nearly identical. The chloroplasts were isolated with percoll and are smaller in size (not shown) than the chloroplasts in leaves.

Fig. 4 Room temperature fluorescence decay traces (measured with FLIM). The chloroplasts in Alocasia ABT-888 solubility dmso wentii are excited with TPE at 860 nm and detected with a bandpass filter centered at 700 nm with a bandwidth of 75 nm. Round open circles are isolated chloroplasts (in vitro) with an average lifetime of 180 ps. Black squares correspond to chloroplasts in leaves (in vivo) with an average lifetime of 212 ps In order to try to distinguish between PSI and PSII in the microscopic images, the difference in fluorescence lifetimes between the two photosystems has been increased by closing the reaction centers of PSII by vacuum infiltration of Arabidopsis thaliana with 0.1 mM

DCMU in 20 mM Hepes, 5 mM NaCl, and 5 mM MgCl2 buffer with pH 7.5. The average lifetime for the leaf infiltrated with DCMU is 1.3 ns (Fig. 5) whereas for “”normal”" leaves the average lifetime is 290 ps. Both photosystems are separated

in space and have substantially different lifetimes in the presence of DCMU (Lukins et al. 2005; Pfündel 1998; Zucchelli et al. 1992) because the average lifetime of PSI with antenna complexes is reported to be ~60 ps (Croce et al. 2000; van Oort et al. 2008) and that of closed PSII is ~1.5 ns (Zucchelli et al. Clomifene 1992). This is visible in the traces and images of the chloroplasts of Alocasia wentii in Fig. 6. The GSK2118436 solubility dmso expectation is that pixels with more grana stacks have a higher intensity compared to pixels with relatively more stroma lamellae (Spencer and Wildman 1962). In Fig. 6a, the fluorescence kinetics of 10 high-intensity pixels (white) are compared with those of 10 low-intensity pixels (grey). The 10 high- and low-intensity pixels have 623 (266,342) and 541 (195,833) counts in the peak (and total number of fluorescence counts), respectively. The global fitting results with linked lifetimes and independent amplitudes are τ 1 = 116 ps (53.3, 59.6%), τ 2 = 1,027 ps (35.1, 29.5%), and τ 3 = 3,957 ps (11.6, 10.9%). The first amplitude for each lifetime refers to the high-intensity pixels and the second amplitude, to the low-intensity pixels. The first lifetime of 116 ps probably reflects a mixture of PSI and open PSII reaction centers (Broess et al.