ABSTRACT
Table 1.3 demonstrates the lower fluorescence intensity of cell walls from Allium cepa in comparison with other parts of the cell. The fluorescence of the cell wall also depends on the excited light wavelength: when it was excited by blue or violet lights the emission maximum shifted to longer wavelengths. For instance, the cell walls of stomata guard cells in the leaf of Solidago canadensis L. fluoresce weakly in blue, when they were radiated by UV-light 360-380 nm, whereas at the excitation by violet 420 nm or blue 440 nm, green-yellow fluorescence with maxima 530-535 nm was seen in Fig. 1.8 (see also colour Fig. 4 in Appendix 2). Bright luminescence is especially peculiar to stomata chink formed by two guard cells. Plasmalemma. The plasma membrane produces NAD(P)H and dependent products, therefore the pyridine nucleotides fluoresce in blue at 460 nm. Perhaps, other components could fluoresce, for instance, plasma membrane of cyanobacteria Anacystis nidulans contains a small fluorescent pool of both carotenoids and protochlorophyllide - chlorophyllide (Peschek et al., 1989). The contribution of plasmalemma in the summed cellular blue fluorescence is also possible due to the NADH formation and other redox reactions (Dahse et al., 1989). More complex protochlorophyll participation in the red emission was described for some blue-green bacteria (Peschek et al., 1989) and may be assumed for other chlorophyllproducing organisms. Cytoplasmic structures. The contribution of internal content of the secretory cell to the total fluorescence also relates to the transparency of epidermal cells. The actinic ultra-violet light easily penetrates through them and excites the luminescence of the secretion located both in periplasmic space and within a cell, as well as luminescence of cellular organelles. The fluorescence of the secondary metabolites of the secretion has been described above. The light emission of microsomes, mitochondria, chloroplasts may be caused by the production of NAD(P)H and flavins. The fluorescence of carotenoids mainly, chlorophyll, prevails in a total luminescence of the chloroplasts (Vogelmann, 1993). Chlorophyll may greatly contribute to total cellular luminescence. In some cases, it is an indicator. For instance, immature pollen without completely formed sporopollenin of exine (in anthers) is transparent for ultra-violet light and the 680 nm fluorescence maximum of chlorophyll is seen clearly (Roshchina et al., 1997b). Chloroplasts were found directly in spermia of pollen from Lupinus luteus (Ruhland and Wetzel, 1924).
