© 2007 Heron Publishing—Victoria, Canada
Polyphenols in the woody roots of Norway spruce and European beech reduce TTC
Anika K. Richter (1, 3), Emmanuel Frossard (2) and Ivano Brunner (1)
1. Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zuercherstr. 111, CH-8903 Birmensdorf, Switzerland / 2. Institute of Plant Science, Eschikon 33, CH-8315 Lindau, Switzerland / 3. Corresponding author (anika.richter@wsl.ch) / Received January 26, 2006; accepted March 17, 2006; published online October 2, 2006
Summary
A common method to determine the vitality of fine root tissue is the measurement of respiratory activity with triphenyltetrazolium
chloride (TTC). The colorless TTC is reduced to the red-colored triphenyl formazan (TF) as a result of the dehydrogenase activity
of the mitochondrial respiratory chain. However, measurements with woody fine roots of adult Norway spruce and European beech
trees showed that dead control roots had a high potential to react with TTC. High reactivity was found in boiled fine roots
and the bark of coarse roots, but not in the boiled wood of coarse roots. By sequential extraction of dried and ground adult
Norway spruce fine roots, reactivity with TTC was reduced by about 75% (water extraction), 93% (water/methanol extraction)
and 94% (water/acetone extraction). The water extract reacted with TTC in the same way as polyphenols such as lignin, catechin
and epicatechin. Boiling did not affect the extent to which fine roots of adult trees reduced TTC, whereas it greatly reduced
TTC reduction by seedling roots. Application of the TTC test to roots of spruce seedlings subjected to increasing drought
showed a progressive decrease in TTC reduction. The decrease in TTC reduction was paralleled by a reduction in O2 consumption, thus supporting the conclusion that for roots with a low polyphenol content the TTC test provides a valid assessment
of tissue vitality. Our results suggest, however, that the TTC test should not be applied to the fine roots of adult trees
because of their high content of polyphenolic compounds whose reaction with TTC masks changes in TTC reduction due to changes
in the respiratory capacity of the tissue.
Keywords:
Fagus sylvatica, fine root vitality, Picea abies, respiration, tannins, tetrazolium chloride.
