Lignification process

Finally, it should be noted that the structure of the DHP varies greatly depending on the polymerization conditions employed. Additionally, the yield and chemical and physical properties of these DHP preparations differ substantially from protolignin. Further improvements in simulation of the lignification process are therefore needed, and the radiotracer method can be employed as one approach to solve such problems. 

Thus ferulic acid, which is not in vivo a natural substrate for peroxidases involved in lignification processes, can be oxidized not only in vitro but also in situ, i.e., in the normal, biological environment of the enzyme. Furthermore, the oxidation seems to be limited to the walls of lignifying cells. This restricted localization has been described only in the case of syringaldazine, a synthetic substrate closely related to cinnamic compounds... 

Finally, there were recently isolated an optically active phenolic compound, dehydrodiconiferyl alcohol (2,3-dihydro-2-(4-hydroxy-3-methoxyphenyl)-5-(3-hydroxypropenyl) - 7-methoxy - 3-benzofuranyl-methanol) (70),192 and a complex 2,3-dihydro-2-phenylbenzofuran, hordanatin A, an antifungal factor 193 it has recently been synthesized,194 and may play a part in the lignification process. 

Different histochemical tests have been used for peroxidase identification. Benzidine (4.33) has been used as a staining reagent, as well as guaiacol (4.34) and pyrogallol (4.35). However, until the 1970s, no reliable methods were known that allowed a sharp discrimination between oxidase and peroxidase activities (Maehly and Chance, 1954). Harkin and Obst (1973) reported the syringaldazine (4.36) histochemical test for peroxidase. This test permitted the proof of exclusive peroxidase participation in the lignification process. 

The following conclusions can be made with regard to current knowledge of the lignification process 1) strict enzymatic control leading to the final product apparently does not occur and 2) both regulatory processes controlling its deposition and structure in situ are poorly understood. 

Takabe K, Fukazawa K, Terashima N, Fukushima K (1987) Lignification process of hardwoods xylem elements by UV microspectrophotometry. Proc 32nd Jpn Lignin Symp, Fukuoka, Japan, 1-4... 

Several studies have been conducted for the separation of hemicellulose from different plant byproduct with different methods of isolation. Lignification process conducted among others by NaOH in 70% ethanol, chlorine, sodium hypochlorite and 30% H2O2. Isolation of hemicellulose used alkaline compounds such as KOH and NaOH with various concentrations, whereas HCl and 90% ethanol is used for the purification of hemicellulose [39,40,57]. 

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