This type of spectrophotometer has proven ideally suited for detailed analysis of flash-induced absorbance changes at 515–520 nm (electrochromic shift) (Joliot and Delosme 1974; Joliot

and Joliot 1989; Joliot et al. 2004), as well as of cyt b6f (Joliot and Joliot 1984, 1986, 1988) and of C-550 (Joliot and Joliot 1979). A first portable version for measurement with leaves was introduced by Kramer and Crofts 1990, which has been further developed over the past 20 years AUY-922 (see below). A different kind of approach for measuring in vivo absorbance changes was taken by Klughammer et al. (1990), which was based on the Pulse-Amplitude-Modulation (PAM) method previously developed for measurements of chlorophyll fluorescence in natural daylight and assessment of various quenching

parameters by the saturation pulse method (Schreiber 1986; Schreiber et al. 1986). This approach employs continuous trains of 1 μs ML pulses generated by light emitting diodes (LED), the frequency of which can be adjusted over a wide range (depending on the rate of the investigated changes), and a special pulse signal amplifier. The original spectrophotometer (Klughammer et al. 1990; Klughammer this website 1992) featured 16 independent monochromatic LED ML sources equipped with narrow band interference filters (530–600 nm), with the various wavelengths being sequentially pulsed at high-repetition rate. While the time resolution (1 ms) of this type of Kinetic LED Array Spectrophotometer (KLAS) cannot cope with that of the Joliot-type device (30 μs), the KLAS displays the practical advantage of absorbance being https://www.selleckchem.com/btk.html measured quasi-simultaneously at 16 wavelengths. In this way, changes can be measured continuously under close to natural conditions of illumination, during dark-light or light–dark induction and in the steady-state, very similar to chlorophyll fluorescence, rendering this device particularly suited for in vivo studies. The absorbance changes can be deconvoluted into the specific contributions of cyt f, cyt b-563, cyt b-559, and C550, as well as of changes caused

6-phosphogluconolactonase by the electrochromic shift at 515–520 nm, “light scattering” around 535 nm and zeaxanthin at 505 nm (Klughammer et al. 1990; Klughammer 1992; Heimann 1998). So far practical applications of the KLAS have been quite limited, as only few prototypes were built by the authors (Ch.K. and U.Sch.) (for some examples of application see e.g., Klughammer and Schreiber 1993; Miyake et al. 1995; Heimann and Schreiber 1996; Klughammer et al. 1998; Aronsson et al. 2008; Miyake 2010; Takagi et al. 2012). A conceptually similar spectrophotometer allowing near-simultaneous measurements of absorbance changes at up to four different wavelengths was introduced by Avenson et al. (2004a) and described in more detail by Hall et al. (2012).