New applications for an old lignified element staining reagent

The use is reported of Mirande's reagent in epifluorescence microscopy which permits a clear distinction between cellulosic and lignified tissues. Homogeneous Prespermatophytae and gymnosperm xylem appeared entirely green with Mirande's reagent under ultraviolet excitation, whereas heteroxyled angiosperm wood showed a mixed pink and blue-green colour. This coloration was due to the fluorescence of cellulose, since certain elements in dicotyledonous wood (parenchyma, fibres, xylem rays) are not entirely lignified. Monocotyledonous (Poaceae) lignin showed an intense blue fluorescence due to hydroxycinnamic acids bound to the cell wall. The method showed that lignification occurs first in the middle lamella, and later in the secondary wall of xylem cells. In addition, this staining technique proved useful in the study of lignin and suberin deposition in response to various stress factors.

Les esters de l'acide caféique dans la chimiotaxinomie des Teucrium de la section polium (Lamiaceae)

Several species of the genus Teucrium section polium from the mediterranean region are difficult to identify because of their wide morphological variability. The relationship between the morphological variations and the distribution of caffeic acid esters was studied. The results show that the taxonomic value of these markers is different depending on the nature of the molecule. Ecological factors interfere with the presence of verbascoside (diglycoside) more than they do with those of stachyoside and T2 (triglycosides). The presence of these latter molecules confirms the close relationship between T. polium subsp. polium and T. capitatum. The stachyoside present in T. polium subsp. polium also allows the distinction, in overlapping areas, of intermediary forms to T. aureum subsp. aureum, in which it is absent. Poliumoside is a specific marker for the polium section. It is never found in the other sections, where it is replaced by teucrioside and chlorogenic acid.