Protein-precipitating Tannins Research Articles

Exogenous naringenin improved digestible protein accumulation and altered morphology via VrPIN and auxin redistribution in Vigna radiata.

Naringenin exposure altered auxin redistribution via VrPIN1 leading to morphological alterations and significantly reduced the protein precipitable tannins that further enhanced the protein accumulation and bioavailability. Flavonoid exposure is known to affect the antioxidant profile of legumes. However, a detailed study evaluating the effect of flavonoid naringenin on morphology and biochemical profile of legume is lacking. The present study is a novel report of improved in planta protein bioavailability and antioxidant potential of legume mungbean on naringenin exposure. The quantitative evaluation revealed significant protein accumulation (64-122μg/g FW) on naringenin exposure. Further, an increase in protein solubility and digestibility compared to control was evident. Naringenin mediated altered α-amylase activity improved the mungbean seed germination rate. Naringenin induced auxin redistribution and altered PIN formed transcript expression reduced lateral root density and increased stem length that was subsequently reverted on exogenous indole acetic acid application. Naringenin enhanced polyphenolic accumulation and improved the antioxidant potential of mungbean. Additionally, the responsiveness of the early gene of the flavonoid biosynthetic pathway, Chalcone isomerase to naringenin concentration was revealed indicating a probable feedback regulation. Further, the presence of alternate liquiritigenin biosynthesis was also evident. The present study, thus reveals the probable potential of phytochemical naringenin towards agricultural sustainability in the changing environmental conditions.

Effects of pruning on the concentration of secondary metabolites in Colophospermum mopane leaves

Colophospermum mopane, commonly known as mopane, produces secondary metabolites during the growing season. However, there is still insufficient knowledge on the quantity of secondary metabolites and the effect of browsers on the concentration of secondary metabolites. A pruning experiment was conducted in the Musina Nature Reserve, Limpopo province, South Africa, to simulate the effect of browsers on the concentration of secondary metabolites in mopane leaves. The twigs from 40 selected experimental mopane trees were pruned back 50 mm from their tips using a hand shear. The total amount of leaf and shoot biomass removed from branches of selected experimental trees was less than 10%. Three independent samples composed of seven mopane leaves per 40 mopane trees were randomly collected from the canopies of experimental and control trees per sampling event. The dried leaves from each three independent samples were then mixed separately and a pooled sample of 10 g per treatment per sample cycle (55 d) was used for determination of total phenols (TP), condensed tannins (CT) and protein-precipitating tannins (PPT). Results showed that <10% pruning does not have an effect on the amount of secondary metabolites in the mopane leaves. The concentration of TP, CT and PPT increased during leaf flush in October and then declined as the leaves matured and aged. It is concluded that the amount of secondary metabolites in mopane leaves is not dependent on <10% pruning, but appeared to be associated with leaf growth stages. The ability of mopane to produce secondary metabolites has implications on the seasonal diet composition and distribution of browsers in mopane woodland.

Leaf litter diversity positively affects the decomposition of plant polyphenols

Leaf litter decomposition is closely linked to nutrient cycling and driven by environmental conditions, species-specific leaf chemistry, and here in particular by polyphenols composition. However, not much attention has been paid on the decomposition of polyphenols themselves. We hypothesized that phenolics and tannin decomposition rates are species-specific and positively affected by litter species richness. Leaf litter of three Chinese tree species was exposed to field decomposition conditions, aggregated in mixtures of different species richness (1-, 2-, 3-species mixtures). We sampled litter five times over the course of 171 days, calculated species-specific total phenolics and total protein precipitable tannin decomposition rates, assessed changes in polyphenol composition using HPLC, and tentatively identified compounds by LC-ESI-MS/MS. Leaf litter richness effects on phenolics and tannin decomposition rates were positive, except for Sapindus-specific tannins, and differed between leaf litter species. Decomposition duration changed polyphenol compositions, and significantly interacted with leaf litter species richness with increasing effects of litter richness with time. Litter diversity effects on polyphenol decomposition are crucial for whole leaf litter decomposition. The contrasting dependencies of phenolics and tannin decomposition rates on leaf litter richness may provide explanations for equivocal results in leaf litter mixture experiments.

Glucose, fructose and sucrose increase the solubility of protein–tannin complexes and at high concentration, glucose and sucrose interfere with bisulphite bleaching of wine pigments

Wines were modified with increasing sugar concentrations and decreasing tannin concentrations and analysed by a combination of protein precipitation and bisulphite bleaching. Increasing sugar concentration decreased the precipitation of tannin and protein-precipitable polymeric pigments (PPP). The use of a hydrogen bond disruptor (urea) to reduce protein–tannin and protein–pigment complex formation showed that the effect of sugar concentration occurred by increasing the solubility of the tannin–protein complex, not by interfering with protein–tannin complex formation. By increasing the solubility of pigment–protein complexes, non-protein-precipitable polymeric pigments (nPPP) appeared to increase. There was also an increase in total polymeric pigments at each tannin concentration with increasing glucose and sucrose concentration, indicating that sugar concentration might also affect bisulphite bleaching of wine pigments. While a significant effect of sugar concentration on tannin–protein complex solubility was observed, these effects were greatest at sugar concentrations far in excess of normal wine making conditions. Under normal wine making conditions, sugar concentration will have a negligible effect on protein-precipitable tannin, PPP and nPPP concentrations.

Influence of Geographic Origin on the Sensory Characteristics and Wine Composition of Vitis vinifera cv. Cabernet Sauvignon Wines from Australia

The current study explores the relationship between sensory characteristics and wine composition of Cabernet Sauvignon wines in relation to Australian geographical indications (GIs). Descriptive sensory analysis was conducted to characterize the sensory attributes of commercially produced Cabernet Sauvignon wines from the Barossa Valley, Clare Valley, Coonawarra, Frankland River, Langhorne Creek, Mount Barker, Margaret River, McLaren Vale, Padthaway, and Wrattonbully GIs. Canonical variate analysis using the significant sensory attributes demonstrated that each GI could be distinguished from the others. A recently developed analytical method was used to analyze over 350 volatile compounds in the wines assessed, and measures of the major nonvolatile components were also determined. Compositional results were analyzed using partial least squares discriminant analysis to identify candidate components that were unique to certain GIs, including 2-isobutyl-3-methoxypyrazine, menthone, isomenthone, carvacrol, δ-octalactone, <i>p</i>-methylacetophenone, <i>m</i>-dimethoxybenzene, protein-precipitable tannin, and monomeric anthocyanins. Results demonstrate that Australian Cabernet Sauvignon wines have common sensory attributes related to geographic origin. The work also identifies a number of candidate components that are related to individual GIs which warrant further investigation. The study is the first to explore the concept of regionality in Cabernet Sauvignon wines from Australia.

Impact of exogenous tannin additions on wine chemistry and wine sensory character

Tannins are an important part of wine quality and are frequently added during winemaking. Tannin additives and their impact on wine are poorly documented. This work sought to characterize a range of enological tannins and their contribution to wine quality. Enological tannins were analysed for protein precipitable tannins and iron reactive phenolics. One tannin product was added to a Merlot wine during barrel ageing, at a range of concentrations from 60 to 300 mg/l. Condensed and hydrolysable tannins were added to Cabernet Sauvignon wine post-pressing at a recommended and excessive rate. Wines were analysed for anthocyanin, small and large polymeric pigment, precipitable tannin, iron reactive phenolics and sensory character. Enological tannins contained 12–48% tannin and recommended additions had little impact on wine tannin. High tannin additions were readily measured in the wines and were discriminated in sensory analysis with lower intensities of most parameters except brown colour, bitterness and earthy character. Recommended addition rates are too low to impact the measured tannin concentration of Merlot and Cabernet Sauvignon wines from Washington (USA). High enological tannin additions had a measureable impact on final wine had a negative impact on sensory character. Tannins are added to wines for a range of reasons and represent one of many input costs in an industry increasingly seeking efficiencies in response to global economic circumstances, over-supply and an ongoing price point squeeze. This research suggests many tannin additions may be unjustified and have limited or negative impacts on quality.

Effect of heat treatment on antinutrients and precaecal crude protein digestibility in broilers of four tropical crop seeds

SummaryFour tropical crop seeds, namely Vigna unguiculata (Cowpea), Mucuna pruriens, Manihot esculenta and Centrosema pubescens were thermally processed for 1 h at 100 °C and analysed for their antinutritional factors (ANF). Four hundred and forty‐eight 1‐day‐old broilers were used to determine the effect of heating the seeds on their precaecal crude protein (CP) digestibility. Total phenols, protein precipitable tannins and l‐dopa were higher in the mucuna and centrosema seeds and diets than in the vigna and manihot seeds and diets. Phytic acid was of similar occurrence in all the raw seeds. Heat treatment resulted in reduction in all the ANF in the seeds. Precaecal CP digestibility, feed intake and growth rate were significantly (P &lt; 0.01) increased in the heat‐treated mucuna and centrosema diets. There was no significant effect on the digestibility of CP, feed intake and growth rate in birds on the vigna and manihot diets owing to heat treatment of the seeds. The results showed that heating improved the nutritive quality of mucuna and centrosema seeds but was not of significant advantage with vigna and manihot seeds when used at levels of up to 150 g kg−1 in diets.

Variability in feed quality between populations of Acacia saligna (Labill.) H. Wendl. (Mimosoideae)—implications for domestication

Due to its favorable agronomic traits, Acacia saligna has the potential to be used as a perennial forage crop in the agricultural regions of southern Australia. The feed quality of populations from across the natural range of A. saligna was examined using in vitro and spectroscopic methods. The mean feed quality of A. saligna was found to be low in comparison to other forage species commonly used in southern Australia, this was due primarily to low dry matter digestibility (DMD) and high protein precipitable tannin (PPT) levels. The content of crude protein (CP) and fibre were both moderate, and the content of essential minerals was found to meet the basic requirements for sheep, with the exception of phosphorus. There was a significant level of variation in fodder quality between the sampled populations. The feed qualities of some populations were found to approach or exceed what is desirable for a livestock feed. The results showed that A. saligna has the potential to produce feed of an acceptable quality. Further development of the species as a crop requires the detailed characterisation of the variation. Some of the variation in feed quality was correlated with genetic variation in the species, and was poorly correlated with known environmental variation. It may therefore be genetically controlled, suggesting that the feed quality of A. saligna could be improved through selection and breeding.

Measuring Phenolics in the Winery

Phenolics are a widely recognized, fundamental quality component of grapes and wines. They are responsible for key wine properties, including color, bitterness, astringency, and longevity. Although many methods are available for measuring grape and wine phenolics, few are suited for rapid, routine analyses in a winery laboratory setting. All current published methods that are within the economic realm of routine winery use require a spectrophotometer. This review concentrates on the spectrophotometric methods designed to measure different phenolic components in grapes and wines, including tri-stimulus, total phenolics, protein precipitable tannins, and color components.

Leaf chemistry of woody plants in relation to season, canopy retention and goat browsing in a semiarid subtropical savanna

Abstract It is assumed that the phytochemistry of browse species protects their biomass and nutrients against herbivory. In this study we were primarily interested in (i) seasonal and phenology‐related variations in leaf chemistry, and (ii) chemistry‐related variations in the feeding behaviour of domestic goats. Such knowledge would guide management‐orientated modelling of browse–browser interactions in seasonal, subtropical zones where goats are abundant. The browse species studied were typical of semiarid savannas in southern Africa: Grewia occidentalis L. (Tiliaceae), Scutia myrtina (Burm. f) Kurz (Rhamnaceae), Diospyros lycioides Desf. ssp. lycioides (Ebenaceae), Rhus longispina Eckl. and Zeyh. (Anacardiaceae), Ehretia rigida (Thunb.) Druce (Boraginaceae) and Acacia karroo Hayne (Mimosoideae). Nitrogen (N), phosphorus (P), condensed tannins (CT), protein‐precipitating tannins (PPT), total phenols (TP), cellulose and lignin concentrations were estimated for each species during the late dormant and early growing seasons. N, P, CT and TP were elevated during the growth season, while cellulose, lignin and PPT decreased. Unlike cytoplasm contents, which varied seasonally, cell wall and vacuole contents varied both seasonally and among species. Except that seasonal variation in N of deciduous species was greater than that of evergreen species, leaf phenology was not related to variations in forage quality. Short‐term intake rates were not related to primary metabolite concentrations, but were positively related to secondary metabolites. Elevated intake rates of putative defences were concluded to be side‐effects of attempts by goats to increase nutrient intake rate, indicating tolerance of chemical defences. Without support for the hypothesis that chemical defences are correlated to canopy retention, we propose an alternative hypothesis, that defences are distributed among woody plants in semiarid, subtropical savannas according to shoot morphology because it affects the vulnerability of plant parts to browsers.

Vegetation and deer response to mechanical shrub clearing and burning

Prescribed burning is a recommended maintenance treatment following mechanical treatments of south Texas brushlands, but it is unknown whether it is preferable to additional mechanical treatments to improve habitat for white-tailed deer (Odocoileus virginianus Raf.). We tested the hypotheses that prescribed burning of aerated (top-growth removal of woody plants) plots during late summer would decrease protein-precipitating tannins in browse, increase forb biomass, and increase deer utilization compared to a second aeration. Ten patches of brush, ranging in size from 2.8-8.1 ha, were aerated during spring 1999. In late summer 2000, maintenance treatments were applied; 5 patches were burned and 5 were aerated a second time. Standing crop, nutritional quality, and tannin concentrations (browse only) of deer forages were estimated. Deer tracks crossing bulldozed lanes surrounding each patch were counted to estimate deer use. Standing crop of browse, forbs, grass, succulents, protein-precipitating tannins in browse, and track density did not differ between treatments. Based on deer use and forage biomass response, burning and a second aeration 16-17 months following an initial aeration appear to have similar effects on habitat characteristics and use of cleared patches by white-tailed deer. Because of lower cost, we recommended prescribed burning as a maintenance treatment of aerated shrublands.

Vegetation and deer response to mechanical shrub clearing and burning

Abstract Prescribed burning is a recommended maintenance treatment following mechanical treatments of south Texas brushlands, but it is unknown whether it is preferable to additional mechanical treatments to improve habitat for white-tailed deer (Odocoileus virginianus Raf.). We tested the hypotheses that prescribed burning of aerated (top-growth removal of woody plants) plots during late summer would decrease protein-precipitating tannins in browse, increase forb biomass, and increase deer utilization compared to a second aeration. Ten patches of brush, ranging in size from 2.8–8.1 ha, were aerated during spring 1999. In late summer 2000, maintenance treatments were applied; 5 patches were burned and 5 were aerated a second time. Standing crop, nutritional quality, and tannin concentrations (browse only) of deer forages were estimated. Deer tracks crossing bulldozed lanes surrounding each patch were counted to estimate deer use. Standing crop of browse, forbs, grass, succulents, protein-precipitating tan...

Influence of thorns and tannins on white-tailed deer browsing after mowing

We used caged and uncaged plants to compare shoot growth, biomass, spinescence, nutrient, and tannin content of blackbrush acacia ( Acacia rigidula Benth.), honey mesquite ( Prosopis glandulosa Torr.), and spiny hackberry ( Celtis pallida Torr.) 6 and 12 weeks after mowing, and estimated white-tailed deer ( Odocoileus virginianus Raf.) use of sprouts of each species stripped of spines and unstripped. Blackbrush acacia grew slowly and had more thorns, protein-precipitating tannins, and fiber than honey mesquite or spiny hackberry. Spiny hackberry, a shrub adapted to fertile sites, grew slower and was more physically defended than honey mesquite but lower in tannins than blackbrush acacia, and was the most palatable to deer of the three species. Thorn removal did not alter palatability of the three species to deer.

Yield and nutritive quality of sericea lespedeza ( Lespedeza cuneata) and little bluestem ( Schizachyrium scoparium) exposed to ground-level ozone

Sericea lespedeza ( Lespedeza cuneata cv. Interstate 76) and little bluestem ( Schizachyrium scoparium cv. Aldous) were raised from seed in a glasshouse, transplanted into 5.7-l pots and placed into open-top chambers (OTC) on 6 June 1999. Following a 7-day adjustment period, each of six OTCs (duplicate OTCs per treatment) was ventilated with either air that had been carbon-filtered (CF) to remove ambient ozone (O 3); non-filtered (NF), representative of ambient air; or enriched to twice-ambient O 3 concentration (2X). Primary-growth forage was harvested on days 7, 32, 46, 59 and 72 following the start of fumigation, and regrowth forage from the first primary-growth harvest was harvested on days 36, 54 and 72 following the start of fumigation. Dry matter (DM) yield of either forage species did not differ among treatments except in the final regrowth period when yield of sericea lespedeza was greater for the NF than 2X O 3 treatment. In vitro DM digestibility (IVDMD) and concentrations of crude protein (CP), soluble phenolics (SP) and condensed tannins (CT) in primary-growth sericea lespedeza did not differ between treatments, but NF primary-growth forage had higher concentration of protein-precipitating tannins (PPT) than did 2X primary-growth forage. Concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) were higher in NF and 2X than in CF primary-growth sericea lespedeza. Similarly, concentrations of NDF and ADL were higher, and IVDMD was lower for NF and 2X than for CF regrowth sericea lespedeza. Concentrations of ADF and ADL were lower, whereas IVDMD, in vitro NDF digestibility (IVNDFD) and concentrations of CP and SP were greater, in CF than in NF and 2X primary-growth little bluestem. Percentages IVDMD and IVNDFD and concentrations of CP and SP in NF primary-growth little bluestem were greater than those in forage exposed to 2X O 3 treatment. No significant differences were observed among treatments in percentages IVDMD and IVNDFD, or concentrations of cell wall constituents or SP in little bluestem regrowth. Nutritive quality of little bluestem was decreased by <2%, and that of sericea lespedeza by ∼7% as a result of increased concentrations of cell wall constituents and decreased in vitro digestibility of NF and 2X compared with CF forages. Results indicate that existing and projected O 3 levels can drive alterations in forage quality of select warm-season forages sufficient to have nutritional and economic implications for their utilization by ruminant herbivores.

Leaf chemical changes induced in Populus trichocarpa by enhanced UV-B radiation and concomitant effects on herbivory by Chrysomela scripta (Coleoptera: Chrysomelidae).

To assess the potential impact of enhanced ultraviolet-B (UV-B) radiation over two trophic levels, we monitored key leaf chemical constituents and related changes in their concentration to dietary preference and performance of a specialist insect herbivore. Ramets of Populus trichocarpa Torr. & Gray (black cottonwood) were subjected to near zero (0X), ambient (1X) or twice ambient (2X) doses of biologically effective UV-B radiation (UV-B(BE)) in a randomized block design using either a square-wave (greenhouse) or a modulated (field) lamp system. After a 3-month treatment period, apparent photosynthesis was determined in situ and plants were harvested for biomass determination. Leaf subsamples were analyzed for nitrogen, sulfur, chlorophylls, UV-absorbing compounds and protein-precipitable tannins. Effects of changes in these constituents on feeding by Chrysomela scripta Fab. (cottonwood leaf beetle) were determined by (1) adult feeding preference trials and (2) larval growth rate trials. Enhanced UV-B(BE) radiation had minimal effects on photosynthesis, growth, leaf area and biomass distribution. In the greenhouse study, concentrations of foliar nitrogen and chlorophylls increased, but tannins decreased slightly in young leaves exposed to enhanced UV-B(BE) radiation. There were no significant effects on these parameters in the field study. The concentration of methanol-extractable foliar phenolics increased in plants grown with enhanced UV-B(BE) radiation in both the greenhouse and field studies. In feeding preference trials, adult C. scripta chose 2X-treated tissue almost twice as often as 1X-treated tissue in both greenhouse and field studies, but differences were not statistically significant (P = 0.12). In the field study, first instar larvae grown to adult eclosion on 2X-treated leaves had a significant (P < 0.001) reduction in consumption efficiency compared with larvae grown on 1X-treated leaves. We conclude that effects of enhanced UV-B(BE) radiation at the molecular-photochemical level can elicit significant responses at higher trophic levels that may ultimately affect forest canopy structure, plant competitive interactions and ecosystem-level processes.

Evaluation of the seeds of selected lines of three Lathyrus spp for β‐N‐oxalylamino‐L‐ alanine (BOAA), tannins, trypsin inhibitor activity and certain in‐vitro characteristics

AbstractSixty eight lines comprising 36 Lathyrus sativus, 16 L cicera and 16 of L ochrus were analysed for crude protein (CP), the neurotoxin β‐N‐oxalylamino‐ L‐alanine (BOAA), protein precipitable tannin (PPT), catechin equivalents (CE), and trypsin inhibitor activity (TIA). Randomly chosen lines from each of the species were also evaluated for other chemical and in‐vitro characteristics including neutral detergent fibre (NDF), acid detergent fibre (ADF), in‐vitro dry matter and in‐vitro organic matter digestibilities (IVDMD, IVOMD), respectively.The species with the lowest and highest CP were L cicera(295.39 ± 18.69 g kg−1 DM) and L sativus(324.99 ± 13.40 g kg−1 DM), respectively. BOAA concentration, also, was least in L cicera (1.26 ± 0.18 g kg−1 DM) and highest in L sativus(5.63 ± 0.43 g kg−1 DM). There were higher intraspecies variations in BOAA levels among L sativus and L cicera than in L ochus genotypes. On average, BOAA levels in L ochrus and L sativus were about four to five times higher than those in L cicera. The PPT level in L sativus(4.54 ± 0.31 g kg−1 DM) was similar to that in the other species. However, there were some lines without detectable PPT in all the species. CE, which detects simple flavonoids as well as condensed tannins, was no more than 6.10 g kg−1DM in any accession, except in L ochrus in which CE ranged from 14.07 g kg−1 to 28.50 g kg−1 DM. There were high variabilities between and within species in CE values as shown by the high coefficients of variation. Mean TIA in all the L sativus lines (18.16 ± 2.38 g kg−1 DM) was similar to that in L ochrus and about twice the levels in L cicera. The coefficients of variation ranged from 10.93% in L ochrus to 17.13% in L sativus. The ash, organic matter and NDF content of the lines did not differ significantly. However, the ADF, IVDMD and IVOMD differed significantly (P &lt; 0.05) between the species. The IVDMD and IVOMD of L cicera (88.55 ± 0.80% and 85.53 ± 0.85%, respectively) were significantly lower (P &lt; 0.05) than in the other species. Seed weight correlated significantly (P &lt; 0.05) with CE and TIA in both L sativus and L ochrus while CP correlated significatly (P &lt; 0.01) with TIA in both L sativus and L cicera with respective r values of 0.70 and −0.75.

Nutritional and antinutritional characteristics of selected Vicia genotypes

Mature seeds of Vicia narbonensis (91 lines), Vicia sativa (23 lines), Vicia ervilia (16 lines) and Vicia palaestina (16 lines) were evaluated for crude protein (CP), protein precipitable tannin (PPT), vanillin-HCl catechin equivalent (CE) and trypsin inhibitor activity (TIA). Other chemical and in vitro characteristics measured included ash, organic matter (OM), neutral detergent fibre (NDF), acid detergent fibre (ADF), in vitro organic digestibility (IVOMD) and in vitro dry matter (DM) digestibility (IVDMD). Crude protein content ranged from 264.38 ± 6.34 g kg −1 DM in V. ervilia to 341.87 ± 8.55 g kg −1 DM in V. palaestina with all species showing little intraspecies variability. The DM, OM and ash contents of all the lines were similar. However, the ADF and NDF values for V. narbonensis were significantly ( P < 0.05) higher than those of the other species. Mean IVDMD and IVOMD values of the species also differed significantly ( P < 0.05). The higher IVDMD (90.95%) and IVOMD (88.30%) values of V. ervilia paralleled the relatively lower ADF and NDF values. PPT was mainly restricted to V. narbonensis while none was detected in any of the lines of either V. sativa or V. ervilia. Tannin expressed as CE was no more than 8.27 g kg −1 in any of the species and seven of the 91 lines of V. narbonensis had no detectable CE levels. There was considerable intraspecies variability in CE as indicated by the high coefficients of variation (CV), which ranged from 17.48% in V. palaestina to 68.99% in V. sativa. In comparison with most conventional legumes, TIA values were generally low in all the species, ranging from 0.36 g kg −1 DM in selection IFLVP 2524 to 5.00 g kg −1 DM in IFLVS 2560. Values for TIA in V. palaestina were particularly low (0.51 ± 0.13 g kg −1 DM) and a CV of 25.86% suggests that selection for lower inhibitor levels is possible. Seed weight was significantly ( P < 0.05) correlated with CE in both V. sativa and V. palaestina, while CP was weakly negatively correlated ( r = −0.48) with TIA among the V. sativa genotypes. There was no significant relationship between seed weight and TIA in any of the species investigated.

Regrowth and tannin production in woody and succulent karoo shrubs in response to simulated browsing.

Allocation of carbon to chemical defences has often been suggested to be a direct response to browsing or grazing by herbivores. This study quantitatively compares total polyphenol and tannin production in response to simulated browsing of three karoo shrubs in order to test this induced defence hypothesis. The three species studied responded to browsing either by rapid regrowth or by increasing polyphenol production in the remaining tissues. The patterns did not follow any phylogenetic relationships but were weakly associated with the palatability of each species. The highly palatable deciduous species Osteospermum sinuatum, which is capable of rapid regrowth, showed no or very low levels of constitutive and browsing-induced total polyphenols, condensed tannins and protein-precipitating tannins. The evergreen sclerophyllous species Pteronia pallens showed a limited regrowth capacity and had intermediate levels of polyphenols, while the evergreen succulent species Ruschia spinosa showed almost no regrowth over the study period. R. spinosa contained the highest constitutive and browsing-induced levels of polyphenols, condensed tannins and protein-precipitating tannins. In two of the species more than one anti-herbivore defence feature co-occur. P. pallens foliage contains both hepatotoxins and polyphenols while R. spinosa has both structural (spines) and chemical defences. Responses of karoo shrubs to simulated browsing are interpreted as the result of passive alterations in plant chemistry rather than as an active defence response to herbivores.

The critical condition of hutias in Cuba: V. Berovides Alvarezz & A. Comas Gonzalez, Oryx, 25(4), 1991, pp 206–208

We used caged and uncaged plants to compare shoot growth, biomass, spinescence, nutrient, and tannin content of blackbrush acacia (Acacia rigidula Benth.), honey mesquite (Prosopis glandulosa Torr.), and spiny hackberry (Celtis pallida Torr.) 6 and 12 weeks after mowing, and estimated white-tailed deer (Odocoileus virginianus Raf.) use of sprouts of each species stripped of spines and unstripped. Blackbrush acacia grew slowly and had more thorns, protein-precipitating tannins, and fiber than honey mesquite or spiny hackberry. Spiny hackberry, a shrub adapted to fertile sites, grew slower and was more physically defended than honey mesquite but lower in tannins than blackbrush acacia, and was the most palatable to deer of the three species. Thorn removal did not alter palatability of the three species to deer.

Ruffed grouse feeding behavior and its relationship to secondary metabolites of quaking aspen flower buds

Quaking aspen (Populus tremuloides Michx.) staminate flower buds and the extended catkins are primary food resources for ruffed grouse (Bonasa umbellus). Winter feeding observations indicate that ruffed grouse select specific trees or clones of quaking aspen to feed in. Flower buds and catkins of quaking aspen were analyzed for secondary compounds (tannins, alkaloids, and phenolics) that might cause ruffed grouse to avoid trees with high levels of these compounds. Coniferyl benzoate, a compound that has not been previously found in quaking aspen, exists in significantly higher concentrations in buds from trees with no feeding history as compared to ruffed grouse feeding trees. Aspen catkins were also significantly lower in coniferyl benzoate than buds from the same tree. Ruffed grouse feeding preference was not related to the tannin or total phenolic levels found in buds or catkins. Buds from feeding trees had higher protein levels than trees with no feeding history; however, catkins did not differ from buds in protein concentration. The high use of extended catkins in the spring by ruffed grouse is probably due to a lower percentage of bud scale material in the catkin as opposed to the dormant bud. Bud scales contain almost all of the nontannin phenolics in catkins and dormant buds. A feeding strategy where bud scales are avoided may exist for other bird species that feed on quaking aspen. Dormant flower buds are significantly lower in protein-precipitable tannins than catkins and differ in secondary metabolite composition from other aspen foliage.