ABSTRACT
All groups of phenols are found in glandular hairs and epithelium of many plant species (Roshchina and Roshchina, 1989; 1993). They may be concentrated in the vacuolar space of the trichomes as water-soluble glycosides of flavonols and anthocyanins, but their lipophilic aglycons usually are excreted out of the cell in oil and resinous secretions. A lot of phenols, mainly, flavonols are found in buds of woody plants (Wollenweber, 1984; Wollenweber et al., 1987; 1991). Kaempferol is
secreted by pistil stigma, when the flower is ready for fertilization (Vogt et al., 1994). The roots of many plants secrete and excrete various phenolic compounds (Rao, 1990). Some phenols when released in the cell wall form polymers, as it is seen for lignins. Aromatic acids. Aromatic acids are mainly derivatives of amino acids - phenylalanine and tryptophan, and usually have one benzene ring. Components of the cell wall include ferulic acid and carbohydrate esters in many plants (Hartley, 1973) which may fluoresce. Blue-green fluorescence is related to ferulic acid as a main fluorophore of epidermis (Morales et al., 1996; 1998). The phenomenon in particular was studied well in the family Gramineae by the use of ultra-violet fluorescence microscopy (Harris and Hartley, 1976). Chlorogenic, ferulic and caffeic acids solved in ethanol may fluoresce in blue with maxima at 450-460 nm. Aromatic acids and their derivatives may be included in many mixtures of plant secretory products (Roshchina and Roshchina, 1989; 1993). Polymeric phenols* Polymeric phenols - lignins of cell walls (formed by earlier secreted monomers) often demonstrate blue lightening in ultra-violet light (Zobel and March, 1993). Among products secreted through the cell wall is hydrogen peroxide which induces the accumulation of insoluble fluorescent material on the surfaces of cell walls of living coleoptyl segments (Schopfer, 1996). W hen polymeric material containing phenolic components (cinnamic acid derivatives) accumulates in the cell walls, H20 2 takes part in formation of phenolic cross-links, the fluorescence of the surface increases and becomes bright greenish-yellow. The peroxidasecatalyzed polymerization of the pollen sporopollenin also needs H 20 2 (Scott, 1994), and the pattern of light emission during the process of pollen development (Roshchina et al., 1997a) may be related with the peroxidation reactions.
