The susceptibility of soil enzymes to inhibition by leaf litter tannins is dependent on the tannin chemistry, enzyme class and vegetation history

Abstract

SummaryBy inhibiting soil enzymes, tannins play an important role in soil carbon (C) and nitrogen (N) mineralization. The role of tannin chemistry in this inhibitory process, in conjunction with enzyme classes and isoforms, is less well understood.Here, we compared the inhibition efficiencies of mixed tannins (MTs, mostly limited to angiosperms) and condensed tannins (CTs, produced mostly by gymnosperms) against the potential activity of b-glucosidase (BG), N-acetyl-glucosaminidase (NAG), and peroxidase in two soils that differed in their vegetation histories.Compared with CTs, MTs exhibited 50% more inhibition of almond (Prunus dulcis) BG activity and greater inhibition of the potential NAG activity in the gymnosperm-acclimatized soils. CTs exhibited lower BG inhibition in the angiosperm-acclimated soils, whereas both types of tannins exhibited higher peroxidase inhibition in the angiosperm soils than in gymnosperm soils. At all of the tested tannin concentrations, irrespective of the tannin type and site history, the potential peroxidase activity was inhibited two-fold more than the hydrolase activity and was positively associated with the redox-buffering efficiency of tannins.Our finding that the inhibitory activities and mechanisms of MTs and CTs are dependent on the vegetative history and enzyme class is novel and furthers our understanding of the role of tannins and soil isoenzymes in decomposition.

Monoterpenes and higher terpenes may inhibit enzyme activities in boreal forest soil

“…In present study, colophony and abietic acid showed a correlation between the decrease in activity and the precipitation of an enzyme. A similar mechanism was already shown for tannins, which inhibit enzymes by creation of complexes with them (Schimel et al, 1998;Adamczyk et al, 2009;Triebwasser et al, 2012); however, sometimes only minor decrease in activity was observed after complexation (Juntheikki and Julkunen-Tiitto, 2000).…”

Climate Influences the Content and Chemical Composition of Foliar Tannins in Green and Senesced Tissues of Quercus rubra

“…Along with the total quantity of tannins, climate influenced both the monomer composition and mean degree of polymerization of tannins, the two parameters that are seldom investigated despite their regulatory influence on the potential biological reactivity of tannins (Zucker, 1983; Kraus et al, 2003b; Tharayil et al, 2011; Triebwasser et al, 2012). Reactivity of CT is a function of the hydroxylation pattern of the B-ring, and tannins with trihydroxy B-rings (PD) are more reactive than those with dihydroxy B-ring (PC).…”

“…Alternatively, the greater chain-length and higher proportion of PC units would have resulted in lower extractability of tannins from the leaf tissues, resulting in the observed lower content of tannins in Wet treatments. Also, the Wet treatments, despite a lower content of CTs, have a higher percentage of HTs, which have a higher enzyme inhibition capacity compared to CTs (Triebwasser et al, 2012). Thus, overall, the leaves formed under Wet treatments would have a similar herbivore deterrence contributed by tannins, despite a lower content of CTs in the tissue.…”

“…Tannins in senescent leaves can account for up to 25% leaf dry weight (Kraus et al, 2003b) and thus can be a major form of carbon reaching the belowground ecosystems. Tannins in senescent tissues also retain their ability to complex with proteins (Hagerman et al, 1998) and inactivate soil enzymes (Triebwasser et al, 2012), which could hinder soil N mineralization (Hättenschwiler and Vitousek, 2000; Kraus et al, 2003a; Adamczyk et al, 2013; Tharayil et al, 2013). Thus, environmental conditions that exist during plant growth, by regulating the production of tannins in green tissues, can influence carbon and nitrogen cycling in soils.…”

“…Tannins can be broadly classified into condensed tannins (CTs) and hydrolysable tannins (HTs; Kraus et al, 2003a), with gymnosperms and monocots producing primarily CTs, and dicots able to produce either HTs or CTs alone or as mixtures (Bate-Smith, 1977; Haslam, 1988; Kraus et al, 2003a; Triebwasser et al, 2012). Condensed tannins, also known as proanthocyanidins, are polymers of flavan-3-ols such as catechin and gallocatechin (Xie and Dixon, 2005).…”