Chlorophyll absorption

The identification of xanthophylls in vivo is a complex task and should be approached gradually with the increasing complexity of the sample. In the case of the antenna xanthophylls, the simplest sample is the isolated LHCII complex. Even here four xanthophylls are present, each having at least three major absorption transitions, 0-0, 0-1, and 0-2 (Figure 7.4). Heterogeneity in the xanthophyll environment and overlap with the chlorophyll absorption add additional complexity to the identification task. No single spectroscopic method seems suitable to resolve the overlapping spectra. However, the combination of two spectroscopic techniques, low-temperature absorption and resonance Raman spectroscopy, has proved to be fruitful (Ruban et al., 2001 Robert et al., 2004). 

As we indicated in Chapter 4 (Section 4.1 D), both the quantity and the quality of radiation change as a function of depth in water wavelengths near 500 nm penetrate the deepest. For instance, only about 10% of the blue and the red parts of the spectrum penetrate to a depth of 50 m in clear water, so chlorophyll is not a very useful light-harvesting pigment below that depth (see Fig. 5-3 for a chlorophyll absorption spectrum). Changes in the spectral quality (relative amounts of various wavelengths) with depth can affect the... 

Action spectra can be used to show the wavelengths of light that make photosynthesis work. If we compare this to chlorophyll absorption spectrum, we see they are a good match. This implies chlorophyll is the main pigment in photosynthesis (Fig. 13.6). 

Maximum chlorophyll absorption Species differentiation and assessment of vegetation vigour... 

The chlorophyll absorption spectrum shows the lack of absorption in the green wavelengths. 

Effects of chilling pretreatment on chlorophyll absorption species and Chi—protein complexes... 

In Calvin s view, in the organized and oriented system containing chlorophyll, absorption of light liberates an electron. As depicted in Fig. 28, water is on one side of the photobattery and the disulphide form of thioctic acid on the other. Electrons move towards the thioctic acid layer and the sites which are left empty are immediately filled up by electrons coming... 

Chlorophyll absorption spectra - http //commons.wikimedia.org/ wiki/File Chlorophyll ab spectra-en.svg... 

Visible radiation is required in both cases and the region of the. spectrum utilized corresponds with that of chlorophyll absorption. 

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