INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS. III. INHIBITORS OTHER THAN TANNINS

We obtained considerable evidence in earlier work that inhibition of nitrification begins during old-field succession and increases to a maximum in the climax (Rice and Pancholy, 1972, 1973). Moreover, we found that tannins and tannin derivatives appear to be important inhibitors of nitrification. In the present project, other potential phenolic inhibitors of nitrification were identified in acetone extracts of entire plants of most herbaceous species and leaves of tree species important in an intermediate stage of succession and the climax in three vegetation types in Oklahoma. Attempts were made also to identify potential inhibitors in acetone extracts of soil from the top 15 cm of the oak-pine climax. Seventeen potential inhibitors were identified from the eleven important species of plants surveyed. These were mostly phenolic acids and flavonoids, but one coumarin compound, scopolin, was found in high amounts in several species. The potential inhibitors were most common in green tops or green leaves, but roots, dead tops (of previous year), and dead leaves had high amounts of some compounds. Caffeic and ferulic acids were prominent in dead leaves or dead tops, and one flavonoid, myricetin, occurred in sizeable amounts in dead tops of Sorghastrum nutans. The aglycones of most of the compounds were tested against nitrification in soil suspensions, and all completely inhibited oxidation of NH⁺₄ to NO⁻₂ by Nitrosomonas at concentrations as low as 10⁻⁶ to 10⁻⁸ M. Oxidation of NO⁻₂ to NO⁻₃ by Nitrobacter, however, was affected much less severely by these inhibitors. The greater resistance of Nitrobacter is not significant biologically because inhibition of the first step carried out by Nitrosomonas effectively inhibits the entire process of nitrification. The 3-glucoside of quercetin, isoquercitrin, inhibited the activity of Nitrosomonas completely at the same concentration as quercetin. We found a compound in large quantities in the oak-pine climax soil which appeared in all tests to be a flavonoid aglycone, but we were never able to identify it to our satisfaction. This substance was extremely inhibitory to germination and seedling growth of ‘Crimson Giant’ radish seeds. These have hard seed coats and germinate very rapidly so most inhibitors do not affect their germination at all. It is likely that some, if not all, of the nitrification inhibitors identified may be important in inhibition of nitrification in the later stages of succession and in the climax along with the tannins.     

INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS

Three plots representing two stages of old-field succession and the climax were selected in each of three vegetation types in Oklahoma: oak-pine forest, post oak-blackjack oak forest, and tall grass prairie. Soil samples from the 0–15 and 45–60 cm levels were analyzed every other month for 1 yr for exchangeable ammonium nitrogen and for nitrate. On alternate months numbers of Nitrosomonas and Nitrobacter were determined in the 0–15 cm level. The amount of ammonium nitrogen was lowest in the first successional stage, intermediate in the second successional stage, and highest in the climax stand. This trend was remarkably consistent throughout all sampling periods, all vegetation types, and both sampling levels in the soil. The amount of nitrate was highest in the first successional stage, intermediate in the second successional stage, and lowest in the climax stand in both sampling levels, all vegetation types, and virtually all sampling periods. The numbers of nitrifiers were high in the first successional stage, generally, and decreased to a very low level in the climax. In fact, there was often no Nitrobacter in the climax stands. These results indicate that the nitrifiers are inhibited in the climax so that ammonium nitrogen is not oxidized to nitrate as readily in the climax as in the successional stages. Evidence from other geographic areas and vegetation types strongly supports this conclusion. This would certainly appear to be a logical trend in the evolution of ecosystems because of the increased conservation of nitrogen and energy. The ammonium ion is positively charged and is adsorbed on the negatively charged colloidal micelles, thus preventing leaching below the depth of rooting. On the other hand, nitrate ions are negatively charged, are repelled by the colloidal micelles in the soil, and thus readily leach below the depth of rooting or are washed away in surface drainage. There is growing evidence also that many plant species can use ammonium nitrogen as effectively or more so than nitrate nitrogen. If ammonium nitrogen is used directly, this eliminates four chemical steps because nitrogen which is oxidized to nitrite and then to nitrate must be reduced back to nitrite and then to ammonium nitrogen before it can react with keto-acids in the formation of amino acids. The two reduction reactions require considerable expenditure of energy.     

ALLELOPATHIC INHIBITION OF NITRIFICATION AND NITRIFYING BACTERIA IN A PONDEROSA PINE (PINUS PONDEROSA DOUGL.) COMMUNITY

The dynamics of ponderosa pine (Pinus ponderosa Dougl.) stands in western North Dakota were studied to determine the influence of plant-produced chemicals on nitrification rates and competitive interactions within the stands. Ponderosa pine accounted for more than 98% of all tree and shrub stratum stems in this climax community. Low levels of nitrate-nitrogen relative to ammonium-nitrogen and low numbers of Nitrosomonas and Nitrobacter in the soils indicated that nitrification rates were low. Inhibition of nitrification is often attributed to low soil pH in coniferous forests, but the slightly alkaline soils in this study (pH 7.25–7.75) suggested that another factor caused the low nitrification. Evidence obtained suggested that the reduction in nitrate synthesis was due to the production and subsequent transfer to the soil of secondary plant chemicals that were toxic to Nitrosomonas. Chemical inhibitors of nitrification, including caffeic acid, chlorogenic acid, quercitin, and condensed tannins, were found in extracts from ponderosa pine needles, bark, and A horizon soils. These extracts proved to be toxic to soil suspensions of Nitrosomonas causing reductions of from 68–93% of the control. These findings indicate that climax ponderosa pine communities minimize the conversion of ammonia-nitrogen to nitrate-nitrogen by chemically inhibiting nitrification.     

COMPARATIVE INHIBITION OF NITRIFIERS AND NITRIFICATION IN A FOREST COMMUNITY AS A RESULT OF THE ALLELOPATHIC NATURE OF VARIOUS TREE SPECIES

Inhibition of nitrification and nitrifiers was significantly variable under different tree species in the same forest ecosystem. Nitrate nitrogen was always lower than ammonium nitrogen when compared under each species. On the other hand, low numbers of Nitrosomonas and Nitrobacter showed an inverse relationship with large amounts of ammonium in most samples. Aforementioned variation is due to the variable tree litter under different species, which in turn produces inhibitors of nitrification and nitrifiers. Inhibition of nitrification in natural ecosystems increases the amounts of ammonium nitrogen thus resulting in a conservation of energy, if plants utilize such nitrogen directly.     

Inhibition of Nitrogen-Fixing and Nitrifying Bacteria by Seed Plants: VI. Inhibitors from Euphorbia supina

Euphorbia suinna occurs in the pioneer weed stage of succession in abandoned fields in several midwestern states of the United States. It was previously found to be very inhibitory to several test strains of nitrogen-fixing and nitrifying bacteria and to several associated seed plants. The present project was concerned wilh the identification of the chief inhibitors produced by that species, using appropriate column and paper chromatographic techniques, and by tests of bacterial inhibition employing the diffusion technique on solid media. Three hydrolyzable tannins were consistently isolated from extracts of the species. All three tannins and purified reagent tannic acid from at least two commercial sources yielded ellagic acid, gallic acid, and glucose on hydrolj'sis by acid or tannase. All yielded one or more additional phenolics which were not identified. The tannins from E. supina were all slightly different from each other and from commercial reagent tannic acid as indicated by different Rf's on paper, elution sequence from polyamide columns, and relative amounts of glucose, ellagic acid and gallic acid produced on hydrolysis.     

Tree resistance to Lymantria dispar caterpillars: importance and limitations of foliar tannin composition

The ability of foliar tannins to increase plant resistance to herbivores is potentially determined by the composition of the tannins; hydrolyzable tannins are much more active as prooxidants in the guts of caterpillars than are condensed tannins. By manipulating the tannin compositions of two contrasting tree species, this work examined: (1) whether increased levels of hydrolyzable tannins increase the resistance of red oak (Quercus rubra L.), a tree with low resistance that produces mainly condensed tannins, and (2) whether increased levels of condensed tannins decrease the resistance of sugar maple (Acer saccharum Marsh.), a tree with relatively high resistance that produces high levels of hydrolyzable tannins. As expected, when Lymantria dispar L. caterpillars ingested oak leaves coated with hydrolyzable tannins, levels of hydrolyzable tannin oxidation increased in their midgut contents. However, increased tannin oxidation had no significant impact on oxidative stress in the surrounding midgut tissues. Although growth efficiencies were decreased by hydrolyzable tannins, growth rates remained unchanged, suggesting that additional hydrolyzable tannins are not sufficient to increase the resistance of oak. In larvae on condensed tannin-coated maple, no antioxidant effects were observed in the midgut, and levels of tannin oxidation remained high. Consequently, neither oxidative stress in midgut tissues nor larval performance were significantly affected by high levels of condensed tannins. Post hoc comparisons of physiological mechanisms related to tree resistance revealed that maple produced not only higher levels of oxidative stress in the midgut lumen and midgut tissues of L. dispar, but also decreased protein utilization efficiency compared with oak. Our results suggest that high levels of hydrolyzable tannins are important for producing oxidative stress, but increased tree resistance to caterpillars may require additional factors, such as those that produce nutritional stress.     

Protein-binding capacity of microquantities of tannins

The physiological effect of tannins is studied in terms of their protein-binding or precipitation capacity. A number of assays based on binding of hemoglobin or bovine serum albumin (BSA) and subsequent determination of unbound protein in supernatant or tannin in a protein-tannin complex are available but with various limitations. These methods are unable to estimate protein-binding capacity, if the quantity of tannin available is low. In the method reported here, tannins or other phenolics were applied on chromatography paper and reacted with BSA and unbound BSA was washed off. The protein in the tannin-protein complex was measured spectrophotometrically after staining with Ponceau S. It required microquantities of sample. Using this method the protein-binding capacity of total leaf extract and hydrolyzable and condensed tannins of Quercus incana, Q. semecarpofolia, and Q. dilatata was determined. The protein binding capacities of ellagic acid and quercetin (microgram BSA/mg) were 297.3 and 78.0, respectively.     

Effects of hydrolyzable and condensed tannin on growth and development of two species of polyphagous lepidoptera: Spodoptera eridania and Callosamia promethea

Summary The effects of tannins on survival, growth, and digestion were compared in two polyphagous species of Lepidoptera (one, the southern armyworm, a forb-feeder; and the other, the promethea silkmoth, a tree-feeder). Two different types of tannins (hydrolyzable and condensed) were incorporated into artificial basal diets in order to determine whether or not differential survival and growth would result between the forb feeder, which normally does not encounter tannins in its natural diet, and the tree-feeder, whose host species include many tanniniferous plants from several different families.Neonate larvae of the forb-feeding armyworms exhibited significantly suppressed 10-day growth rates at all tannin concentrations tested (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0% of wet weight) for both the hydrolyzable and the condensed tannin compared to the control diet, however no dose-effect was detectable. In contrast, there were no detectable differences in neonate survival or growth through the first 10 days for the tree-feeding promethea silkmoth larvae fed diets with either tannic acid or quebracho tree condensed tannin.In order to determine the physiological mechanisms of action of these tannins against armyworms, we conducted detailed physiological bioassays of biomass and nitrogen utilization by penultimate instar larvae. Standard gravimetric feeding studies with both tannic acid and the quebracho tree condensed tannin demonstrated that reduced relative growth rates (RGR's) of Spodoptera eridania Cram. were due to the suppressed relative consumption rates (RCR's) and decreased conversion efficiencies (ECD's) rather than due to digestibility-reduction (as reflected by approximate digestibility, AD). As with the neonate larval growth rate suppression, there were no detectable dose responses at the different concentrations of tannic acid (0.25, 0.50, 0.75, 1.00, 2.50, and 5.0 percent) and condensed tannins from quebracho (0.25, 0.50, 0.75, 1.0, and 2.5 percent) in our penultimate instar studies.     

Biotransformation of hydrolysable tannin to ellagic acid by tannase from Aspergillus awamori

Madhuca indica, locally known as mahua in India is a multipurpose tree species. Mahua, particularly bark contains a significant amount of hydrolysable tannin (17.31%) which can be utilized for ellagic acid production through biotransformation. In the present study, mahua bark utilized not only as a raw material for tannase production but also for ellagic acid a well-known therapeutic compound. After prior confirmation of hydrolysable tannin content in bark, it has been supplemented, as a substrate for tannase production through solid state fermentation of Aspergillus awamori. Tannase production, as well as biodegradation of the hydrolysable tannin reached a maximum at 72?h of incubation time. The optimum conditions for tannase production are solid to liquid ratio of 1:2, 35?°C, pH 5.5 and 72h incubation time which resulted 0.256?mg/mL of an extract of ellagic acid. Maximum tannase activity of 56.16?IU/gds at 35?°C and 72h of incubation time is recorded. It seems that tannase production and biotransformation of hydrolysable tannins using bark powder of mahua can be considered as an appropriate alternative to the existing procedures of ellagic acid production.     

EFFECTS OF H ION ON ECOLOGICAL SYSTEMS: EFFECTS ON HERBACEOUS BIOMASS,MINERALIZATION, NITRIFIERS AND NITRIFICATION IN A FOREST COMMUNITY

The effects of H ion were studied by lowering the soil pH in a deciduous forest. Increased H⁺ burden significantly reduced the dry mass of herbaceous vegetation. Increased H⁺ significantly mobilized Ca (226%) and Mg (244%) to the deeper soil profile, thus reducing uptake of those nutrients by intact vegetation. Moreover, the low pH also had a drastic impact on nitrifiers and nitrification. The 70% reduction in NO^-₃-N was directly related to the reduction in numbers of Nitrosomonas (91%) and Nitrobacter (100%). Ammonium N also declined under H⁺ stress, indicating a reduction in N-mineralization process. It was hypothesized that increased H⁺ stress in deciduous forests may deplete major nutrients, mobilize micronutrients, reduce soil microbial populations and decrease plant biomass. Thus a deciduous forest may evolve into a nutrient-poor soil ecosystem and may shift toward a “semi-podzol ecosystem.”     

Effect of adhesion to particles on the survival and activity of Nitrosomonas sp. and Nitrobacter sp.

The adhesion of Nitrosomonas sp. and Nitrobacter sp. cells isolated from fishpond sediment to different solid particles was studied. Nitrosomonas and Nitrobacter cells rapidly attached to particles of bentonite, calcium carbonate, amberlite, and fishpond sediment, however they did not adhere to phenyl-sepharose beads. The nitrifying activity of attached bacteria was greater than the activity of freely suspended cells or the activity of cells which have been detached from CaCO₃ particles. The enhancement in the nitrifying activity was rapid and was already observed within the first hour after attachment (which equals only 1/24 to 1/50 of the generation time of Nitrosomonas sp. or Nitrobacter sp. In addition, the survival of the attached bacteria under both anaerobic and under aerobic incubation was extended to weeks, compared to only a few days for the free cells. The presence of substrate (ammonia or nitrite) during the anaerobic incubation period was found not to affect the survival time of the bacteria. Finally, it was found that the attachment of Nitrosomonas and Nitrobacter cells to CaCO₃ particles affected the dispersal and sinking rate of these particles.     

THE BIOCHEMISTRY OF NITRIFYING MICROORGANISMS

• 1 Biological nitrification is mediated primarily by two genera of bacteria, Nitrosomonas and its marine form Nitrosocystis, oxidizing ammonia to nitrite, and Nitrobacter, converting nitrite into nitrate. These are chemoautotrophic organisms since they usually derive their energy for growth by oxidizing these inorganic nitrogen compounds and their carbon from carbon dioxide, carbonates or bicarbonates.
• 2 The morphology and structure of these Gram-negative bacteria studied by electron microscopy show numerous intracellular membranes reminiscent of those in photosynthetic bacteria and blue-green algae. These structures may therefore be associated with the production of ATP.
• 3 The bacteria are difficult to grow in pure cultures in sufficient amounts for biochemical work since their generation time is around 10 hr. and the yields are only about one hundredth of those obtained with heterotrophic bacteria. Thus in continuous cultures great care must be taken to avoid ‘wash-out’ of the cells. Since Nitrosomonas and Nitrosocystis produce copious amounts of nitrous acid, which would eventually retard growth, pH stat units are used to titrate the cultures continuously with a solution of sodium carbonate, to hold the pH around 7–8.
• 4 The respiratory chain which is associated with cell membranes, contains flavin, quinones and many cytochromes linking to oxygen as a terminal acceptor. In Nitro-somonas-Nitrosocytis hydroxylamine is oxidized by the electron transfer chain and in Nitrobacter nitrous acid is utilized. The ammonia-oxidizing system, which in Nitrosomonas probably resides near the cell surface, does not appear to survive cell breakage. During the oxidation of hydroxylamine and nitrous acid by the respiratory chains, a phosphorylation occurs but the P/O ratios around 0–30 are low. There is little energy reserve material in the cells, possibly β-hydroxybutyrate and some metaphosphates and as soon as the oxidative processes are impaired the cells cease dividing.
• 5 Chemoautotrophic bacteria have a novel way of producing reduced nicotinamide adenine dinucleotide (NADH). This involves a reversal of electron flow from reduced cytochrome c to nicotinamide adenine dinucleotide (NAD) that is energy-dependent, thus requiring adenosine triphosphate.
• 6 Reductase enzymes, nitrate, nitrite and hydroxylamine reductases in Nitrobacter and nitrite and hydroxylamine reductases in Nitrosomonas, have been described. They appear to be readily extracted in soluble form and are probably assimilatory enzymes since ¹⁶N labelled nitrate, nitrite and hydroxylamine respectively in Nitrobacter and the last two in Nitrosomonas are readily incorporated into cell nitrogen. It has been suggested that a particulate nitrate reductase in Nitrobacter is coupled to the synthesis of adenosine triphosphate but adequate experimental evidence for this concept has not been produced.
• 7 Some recent observations with Nitrobacter suggest that it grows on acetate, deriving all its energy and carbon skeletons from this source but the mean generation time for the bacterium is unchanged. Under these conditions the carbon dioxide fixing enzymes of the pentose pathway are suppressed. This then is a case of facultative chemoautotrophy but there is no increase in the biosynthesis of the TCA enzymes. Whether this is a widespread phenomenon in other chemoautotrophic bacteria remains to be established. If this does prove to be the case it would aid their survival in a variety of habitats and extend their distribution in soils and seas.
• 8 The carbon dioxide fixing enzymes of the pentose pathway are found in the soluble parts of the cells. The major route is via the carboxydismutase system with only a small incorporation via the phosphoenolpyruvate carboxylase enzyme. Enzymes of the tricarboxylic acid cycle have low activities compared with those in heterotrophs and this overall slow metabolism, rather than the lack of a specific enzyme such as NADH oxidase, may well account for the slow growth of these bacteria. Although there is very active glutamic dehydrogenase in Nitrosomonas that utilizes ammonia, the enzyme has a very small activity in Nitrobacter. This poses a problem of the route of incorporation of nitrite nitrogen into cell nitrogen in the latter bacterium.
• 9 A few heterotrophic fungi have been described which oxidize ammonia to nitrate but their activity is small compared with that of the nitrifying bacteria.
• 10 It is concluded that the nitrifying bacteria which have many novel biochemical features not met with in other organisms merit further study.

     

Tannins from mimosoid legumes of Texas and Mexico

The percentage of tannins in leaves, bark, wood, and immature fruits of several species of Acacia and related mimosoid legumes from the southwestern U.S. and Mexico, along with a few from Costa Rica and Argentina, was determined by a modified hide powder procedure and by precipitation with casein. The relative percentages of hydrolyzable and condensed tannins were determined by the iodate and the vanillin-HCl methods, respectively. Gallotannins of selected samples were also determined by the rhodanine method. Although the amount of total tannins was similar for the first two methods, values for condensed tannins by the vanillin-HCl method were frequently two to four times greater than the total tannin values.     

Hydrolyzable tannins as “quantitative defenses”: Limited impact against Lymantria dispar caterpillars on hybrid poplar

The high levels of tannins in many tree leaves are believed to cause decreased insect performance, but few controlled studies have been done. This study tested the hypothesis that higher foliar tannin levels produce higher concentrations of semiquinone radicals (from tannin oxidation) in caterpillar midguts, and that elevated levels of radicals are associated with increased oxidative stress in midgut tissues and decreased larval performance. The tannin-free leaves of hybrid poplar (Populus tremula × P. alba) were treated with hydrolyzable tannins, producing concentrations of 0%, 7.5% or 15% dry weight, and fed to Lymantria dispar caterpillars. As expected, larvae that ingested control leaves contained no measurable semiquinone radicals in the midgut, those that ingested 7.5% hydrolyzable tannin contained low levels of semiquinone radicals, and those that ingested 15% tannin contained greatly increased levels of semiquinone radicals. Ingested hydrolyzable tannins were also partially hydrolyzed in the midgut. However, increased levels of semiquinone radicals in the midgut were not associated with oxidative stress in midgut tissues. Instead, it appears that tannin consumption was associated with increased metabolic costs, as measured by the decreased efficiency of conversion of digested matter to body mass (ECD). Decreased ECD, in turn, decreased the overall efficiency of conversion of ingested matter to body mass (ECI). Contrary to our hypothesis, L. dispar larvae were able to maintain similar growth rates across all tannin treatment levels, in part, because of compensatory feeding. We conclude that hydrolyzable tannins act as “quantitative defenses” in the sense that high levels appear to be necessary to increase levels of semiquinone radicals in the midguts of caterpillars. However, these putative resistance factors are not sufficient to decrease the performance of tannin-tolerant caterpillars such as L. dispar.     

Soil chemical properties as related to forest succession in a highland area in north-east Tasmania

The relationship between vegetational type and a number of soil chemical factors was examined in secondary successions from fire-maintained eucalypt/grass to climax rainforest communities growing on uniform granitic soil parent material. Canonical variates analysis, which utilized the following variables: pH; loss on ignition; total N, P, K, Ca, and Mg; cation exchange capacity and exchangeable Ca, K, and Mg; and potentially mineralizable N, revealed close overall similarity between surface soils of adjacent types, and significant differences among those of types distant from each other in the successional sequences. Exchangeable Ca, mineralizable N, total N. P, and Mg, and pH all differed significantly among soils of the vegetational types. However, the only identifiable gradients in soil properties that were detected within a successional sequence were in total and mineralizable N, which tended to increase, and pH, which generally tended to decrease with progression towards the climax vegetation. Nitrification was promoted by the presence of Acacia dealbata and apparently inhibited by the presence of Leptospermum lanigerum; it was more rapid in soils beneath late successional vegetation than in those from climax vegetation or early stages of succession, and was inhibited in soil from old (> 200 years) grassland. It was concluded that differences among soils in chemical composition and rates of mineralization of N were due to differences in species composition of the vegetational types that they carried for the time being.     

Oligomeric hydrolyzable tannins from Monochaetum multiflorum

Four hydrolyzable tannins, nobotanins Q, R, S, and T, were isolated from the aqueous acetone extract of the dried leaves of Monochaetum multiflorum (Melastomataceae), a plant indigenous to Colombia. Their dimeric and tetrameric structures were elucidated by spectral and chemical methods. Eight known hydrolyzable tannin monomers and eight ellagitannin oligomers characteristic of melastomataceous plants were also characterized as tannin constituents of the plant.     

Carabid beetle (Coleoptera: Carabidae) assemblages in the intermediate successional stage after Mt. Bandai eruption of 1888: Effects of environmental variables on carabid beetles in the Urabandai area

We studied carabid beetle assemblage structure and species diversity in an intermediate successional stage (seral) forest established in areas affected by the 1888 eruption of Mt. Bandai and a climax forest that had not been affected by the eruption at the Urabandai area, Fukushima Prefecture, Japan. In total, 2,131 carabid beetles representing 31 species were collected using pitfall traps without bait. A comparison of carabid beetle assemblages between the two forest types revealed that the number of species observed was comparable, but their abundance was greater in the seral forest. The assemblage structure clearly differed between the two forest types. In the seral forest, forest generalists, such as Synuchus arcuaticollis and Pterostichus prolongatus, along with forest specialists including Carabus vanvolxemi and Pterostichus asymmetricus, were collected. In the climax forest, forest generalists, such as Synuchus cycloderus and Carabus albrechti tsukubanus, were more abundant than forest specialists. This suggests that the current seral forest in the Urabandai area possesses environmental variables that enable the coexistence of both forest specialist and generalist beetle species. A redundancy analysis showed that six species from the genera Synuchus and Pterostichus were associated with high canopy openness and high understory vegetation cover, whereas species recorded only in the climax forest were associated with deep litter. Therefore, it seems likely that carabid beetles in the Urabandai area were affected by these three environmental variables.     

Gallotannin production in cell cultures ofCornus officinalis Sieb. et Zucc.

Gallotannin mixtures composed of tri-, tetra- and pentagalloylglucoses were produced by callus and suspension cultures ofCornus officinalis Sieb. et Zucc. The content of the main tannin, 1,2,3,6-tetragalloylglucose, was 36 times that of the intact fruits. The other three tannins, 1,2,6-trigalloyl-glucose, 1,2,3,4,6-pentagalloyl-glucose, and 6-digalloyl-1,2,3-trigalloyl-glucose, were isolated and identified with the authentic specimens. The ratios of the amounts among these tannins were not changed much during the culture period, and by the differences in the combination of plant growth regulators in the medium. Tannin production was stimulated by 6-benzyladenine, whereas cell growth required 2,4-dichlorophenoxyacetic acid or 1-naphthaleneacetic acid. Light irradiation appears to have inhibited tannin production in the cell cultures.     

Microbial production of ellagic acid and biodegradation of ellagitannins

In the last years, tannin biodegradation has been the subject of a lot of studies due to its commercial importance and scientific relevance. Tannins are molecules of low biodegradation and represent the main chemical group of natural anti-microbials occurring in the plants. Among the different kinds of tannins, ellagitannins represent the group less studied manly due to their diversity and chemical complexity. The general outline of this work includes information on tannins, their classification and properties, biodegradation, ellagic acid production, and potential applications. In addition, it describes molecular, catalytic, and functional information. Special attention has been focused on the biodegradation of ellagitannins describing the possible role of microbial enzymes in the production of ellagic acid.     

Tannins in nutrient dynamics of forest ecosystems - a review

Tannins make up a significant portion of forest carbon pools and foliage and bark may contain up to 40% tannin. Like many other plant secondary compounds, tannins were believed to function primarily as herbivore deterrents. However, recent evidence casts doubts on their universal effectiveness against herbivory. Alternatively, tannins may play an important role in plant–plant and plant–litter–soil interactions. The convergent evolution of tannin-rich plant communities on highly acidic and infertile soils throughout the world, and the intraspecific variation in tannin concentrations along edaphic gradients suggests that tannins can affect nutrient cycles. This paper reviews nutrient dynamics in forest ecosystems in relation to tannins. Tannins comprise a complex class of organic compounds whose concentration and chemistry differ greatly both among and within plant species. Because the function and reactivity of tannins are strongly controlled by their chemical structure, the effects of tannins on forest ecosystem processes are expected to vary widely. Tannins can affect nutrient cycling by hindering decomposition rates, complexing proteins, inducing toxicity to microbial populations and inhibiting enzyme activities. As a result, tannins may reduce nutrient losses in infertile ecosystems and may alter N cycling to enhance the level of organic versus mineral N forms. The ecological consequences of elevated tannin levels may include allelopathic responses, changes in soil quality and reduced ecosystem productivity. These effects may alter or control successional pathways. While a great deal of research has addressed tannins and their role in nutrient dynamics, there are many facets of tannin biogeochemistry that are not known. This lack of information hinders a complete synthesis of tannin effects on forest ecosystem processes and nutrient cycling. Areas of study that would help clarify the role of tannins in forest ecosystems include improved characterization and quantification techniques, enhanced understanding of structure-activity relationships, investigation of the fate of tannins in soil, further determination of the influence of environmental factors on plant tannin production and decomposition, and additional information on the effects of tannins on soil organisms.