Histochemical & Biochemical Differences Between Lignin-Like Materials in Phleum pratense L.

Abstract

Differences have been observed among the lignins of mature tissues of elongated 1st internodes, the upper internodes or sheaths, and the blades of timothy. Three types of lignin-like compounds are postulated; 1 associated with the metaxylem, the other 2 with sclerenchyma cells. The type found in the sclerenchyma of the blade differs from that found in the rest of the plant. These lignin-like substances differ in the relative time of differentiation of the functional groups giving positive phloroglucinol and chlorine-sodium sulfite tests, in the position and height of the peak in the long wave length portion of the ionization difference spectrum, in the ratio of the amount of chromophore absorbing at this peak and the amount of free phenolic groups reacting with benzoquinoneimine reagent, and in the quantity of ether soluble components in the acidified alkaline extracts containing the lignin. The most important of the ether soluble compounds identified are p-hydroxycinnamie and ferulic acids, p-hydroxybenzaldehyde, vanillin, and syringaldehyde. The lack of an adequate definition of lignin, and the dependency of the detection of the amount of lignin on the analytical test used are discussed.