Showing papers on "Bark published in 2014"

Bark functional ecology: evidence for tradeoffs, functional coordination, and environment producing bark diversity

Abstract: The causes underlying bark diversity are unclear. Variation has been frequently attributed to environmental differences across sites. However, variation may also result from tradeoffs and coordination between bark's multiple functions. Bark traits may also covary with wood and leaf traits as part of major dimensions of plant variation. To assess hypotheses regarding tradeoffs and functional coordination, we measured bark traits reflecting protection, storage, mechanics, and photosynthesis in branches of 90 species spanning a wide phylogenetic and environmental range. We also tested associations between bark, wood, and leaf traits. We partitioned trait variation within species, and within and across communities to quantify variation associated with across-site differences. We observed associations between bark mechanics and storage, density and thickness, and thickness and photosynthetic activity. Increasing bark thickness contributed significantly to stiffer stems and greater water storage. Bark density, water content, and mechanics covaried strongly with the equivalent wood traits, and to a lesser degree with leaf size, xylem conductivity, and vessel diameter. Most variation was observed within sites and had low phylogenetic signal. Compared with relatively minor across-site differences, tradeoffs and coordination among functions of bark, leaves, and wood are likely to be major and overlooked factors shaping bark ecology and evolution.

Flavan-3-ols in Norway Spruce: Biosynthesis, Accumulation, and Function in Response to Attack by the Bark Beetle-Associated Fungus Ceratocystis polonica

Abstract: Proanthocyanidins (PAs) are common polyphenolic polymers of plants found in foliage, fruit, bark, roots, rhizomes, and seed coats that consist of flavan-3-ol units such as 2,3-trans-(+)-catechin and 2,3-cis-(–)-epicatechin. Although the biosynthesis of flavan-3-ols has been studied in angiosperms, little is known about their biosynthesis and ecological roles in gymnosperms. In this study, the genes encoding leucoanthocyanidin reductase, a branch point enzyme involved in the biosynthesis of 2,3-trans-(+)-flavan-3-ols, were identified and functionally characterized in Norway spruce (Picea abies), the most widespread and economically important conifer in Europe. In addition, the accumulation of flavan-3-ols and PAs was investigated in Norway spruce saplings after wounding or inoculation with the fungal pathogen Ceratocystis polonica, which is vectored by bark beetles (Ips typographus) and is usually present during fatal beetle attacks. Monomeric and dimeric flavan-3-ols were analyzed by reverse-phase high-pressure liquid chromatography, while the size and subunit composition of larger PAs were characterized using a novel acid hydrolysis method and normal phase chromatography. Only flavan-3-ol monomers with 2,3-trans stereochemistry were detected in spruce bark; dimeric and larger PAs contained flavan-3-ols with both 2,3-trans and 2,3-cis stereochemistry. Levels of monomers as well as PAs with a higher degree of polymerization increased dramatically in spruce bark after infection by C. polonica. In accordance with their role in the biosynthesis of 2,3-trans-(+)-flavan-3-ols, transcript abundance of Norway spruce LEUCOANTHOCYANIDIN REDUCTASE genes also increased significantly during fungal infection. Bioassays with C. polonica revealed that the levels of 2,3-trans-(+)-catechin and PAs that are produced in the tree in response to fungal infection inhibit C. polonica growth and can therefore be considered chemical defense compounds.

Bark traits and life-history strategies of tropical dry- and moist forest trees

Abstract: Summary 1. Bark is crucial to trees because it protects their stems against fire and other hazards and because of its importance for assimilate transport, water relationships and repair. We evaluate size-dependent changes in bark thickness for 50 woody species from a moist forest and 50 species from a dry forest in Bolivia and relate bark thickness to their other bark characteristics, species life-history strategies and wood properties. 2. For 71% of the evaluated species, the allometric coefficient describing the relationship between bark thickness and stem diameter was significantly <1 (average 074; range 038–120), indicating that species attain an absolute increase in bark thickness with increasing stem diameter but invest relatively less in bark thickness at larger diameters. 3. We hypothesized that in response to more frequent fires, dry-forest species should have thicker barked trees. Contrary to this prediction, dry- and moist-forest tree species were similar in allometric bark coefficients and bark thickness. 4. In both forest types, about 50% of the species never developed bark thick enough to avoid fire damage to their vascular cambia. Recent increases in fire frequency and extent may therefore have potentially large effects on the composition of these forests. 5. Within each forest, coexisting species displayed a diversity of bark investment strategies, and bark thickness of trees 40 cm stem diameter varied up to 15-fold across species (ranging from 1 7t o 257 mm). 6. In both forests, sapling bark thickness was positively related to adult stature (maximum height) of the species, possibly because trees of long-lived species are more likely to experience fire during their life span, whereas for species that are characteristically small or short-lived, it may not pay off to invest heavily in bark and they may follow a resprouter strategy instead. Sapling bark thickness was not related to species’ shade tolerance. 7. Bark and wood traits were closely associated, showing a trade-off between species with tough tissues (high densities of bark and wood) on the one hand vs. species with watery tissues (high water contents of bark and wood) and thick bark on the other hand. 8. Species with different bark investment strategies coexist in both the moist and the dry tropical forest studied. Bark and wood fulfil many functions, and the observed trade-offs may reflect different plant strategies to deal with fire, avoidance and repair of stem damage, avoidance and resistance of drought stress, and mechanical stability.

Pine Bark and Green Tea Concentrated Extracts: Antioxidant Activity and Comprehensive Characterization of Bioactive Compounds by HPLC–ESI-QTOF-MS

Abstract: The consumption of polyphenols has frequently been associated with low incidence of degenerative diseases. Most of these natural antioxidants come from fruits, vegetables, spices, grains and herbs. For this reason, there has been increasing interest in identifying plant extract compounds. Polymeric tannins and monomeric flavonoids, such as catechin and epicatechin, in pine bark and green tea extracts could be responsible for the higher antioxidant activities of these extracts. The aim of the present study was to characterize the phenolic compounds in pine bark and green tea concentrated extracts using high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC–ESI-QTOF-MS). A total of 37 and 35 compounds from pine bark and green tea extracts, respectively, were identified as belonging to various structural classes, mainly flavan-3-ol and its derivatives (including procyanidins). The antioxidant capacity of both extracts was evaluated by three complementary antioxidant activity methods: Trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC). Higher antioxidant activity values by each method were obtained. In addition, total polyphenol and flavan-3-ol contents, which were determined by Folin–Ciocalteu and vanillin assays, respectively, exhibited higher amounts of gallic acid and (+)-catechin equivalents.

Antioxidant activities of ethanol extracts and fractions of Crescentia cujete leaves and stem bark and the involvement of phenolic compounds

Abstract: Antioxidant compounds like phenols and flavonoids scavenge free radicals and thus inhibit the oxidative mechanisms that lead to control degenerative and other diseases The aim of this study was to investigate the antioxidant activity in vitro, total phenolic and flavonoid contents in ethanol extracts and fractions of Crescentia cujete leaves and stem bark Crescentia cujete leaves and bark crude ethanol extract (CEE) and their partitionates petroleum ether (PEF), chloroform (CHF), ethyl acetate (EAF) and aqueous (AQF) were firstly prepared Different established testing methods, such as 1, 1-diphenyl-2-picryl hydrazyl (DPPH) radical, ferric reducing power (FRP), and total antioxidant capacity (TAC) assays were used to detect the antioxidant activity Further, the total yield, total phenolic (TPC) and total flavonoid contents (TFC) of CEE and all the fractions were determined Ethanol extracts of both leaves and stem bark were also subjected to preliminary phytochemical screening to detect the presence of secondary metabolites, using standard phytochemical methods (Thin layer chromatography and spray reagents) Phytochemical screening of crude ethanol extract of both leaves and stem bark revealed the presence of steroids, flavonoids, saponins, tannins, glycosides and terpenoids All the fractions and CEE of leaves and bark exhibited antioxidant activities, however, EAF of leaves showing the highest antioxidant activity based on the results of DPPH, FRP and TAC assay tests The above fraction has shown the significant DPPH scavenging activity (IC50 = 878 μg/ml) when compared with standard ascorbic acid (IC50 =768 μg/ml) The TAC and FRP activities increased with increasing crude extract/fractions content The TPC (37123 ± 1577 mg GAE/g extract) and TFC (14464 ± 582 mg QE/g extract) of EAF of leaves were found significantly higher as compared to other solvent fractions for both leaves and bark TPC were highly correlated with the antioxidant activity (R2 = 09268 and 08515 in DPPH test for leaves and bark, respectively) The results of the study show that leaves of C cujete possesses significant free radical scavenging properties compared with stem bark and a clear correlation exists between the antioxidant activity and phenolic content

Smooth bark surfaces can defend trees against insect attack: resurrecting a ‘slippery’ hypothesis

Abstract: Summary 1. Smooth bark on trees and shrubs was historically hypothesized to be an anatomical defence against epiphytic vegetation and phytophagous insects. This hypothesis has fallen from favour, yet no clear tests of bark texture as a defence against insects have been published. 2. We tested the smooth bark defence hypothesis using bark beetles specialized in attacking pine trees as model insects, and Pinus flexilis (limber pine) – a widespread tree that can have both smooth and rough bark surfaces on the same stem – as the model tree. We investigated the effects of bark texture on the locations of bark beetle attacks on trees with a combination of field surveys and experiments in the Colorado Rocky Mountains, USA. 3. Bark beetle attacks were overwhelmingly located on rough bark surfaces and virtually absent from smooth bark. Increasing proportional coverage by smooth bark was negatively related to bark beetle attacks per square metre of bark surface. Experimental tests of bark beetles’ ability to grip smooth versus rough bark revealed that bark beetles have difficulty gripping and quickly fell from smooth bark but not from rough bark. 4. Smooth bark was negatively related to increasing tree size, but our models indicated that even partial coverage by smooth bark on a tree’s trunk can significantly reduce total bark beetle attacks – this reduction likely improves tree fitness as bark beetles must aggregate to overcome tree defences. 5. Synthesis. Our results indicate that smooth bark on trees can act as an anatomical defence against insects by reducing their ability to grip a tree’s surface – even for insects specialized in attacking tree stems. Similar to other forms of anti-insect defence (i.e. secondary chemistry, leaf toughness), smooth bark appears to be influenced by plant ontogeny whereby younger trees have greater defences than older trees. Understanding the adaptive significance of bark texture will require continued field and genetic study. Nevertheless, our results revealed that smooth bark texture increases tree resistance to phytophagous insects calling for the resurrection and vetting of the smooth bark defence hypothesis.

Outer bark thickness decreases more with height on stems of fire-resistant than fire-sensitive Floridian oaks (Quercus spp.; Fagaceae).

Abstract: UNLABELLED • PREMISE OF THE STUDY In ecosystems maintained by low-intensity surface fires, tree bark thickness is a determinant of fire-survival because it protects underlying tissues from heat damage. However, it has been unclear whether relatively thick bark i S: maintained at all heights or only near the ground where damage is most likely.• METHODS We studied six Quercus species from the red and white clades, with three species characteristic of fire-maintained savannas and three species characteristic of forests with infrequent fire. Inner and outer bark (secondary phloem and rhytidome, respectively) thicknesses were measured at intervals from 10 to 300 cm above the ground. We used linear mixed-effects models to test for relationships among height, habitat, and clade on relative thickness (stem proportion) of total, inner, and outer bark. Bark moisture and tissue density were measured for each species at 10 cm.• KEY RESULTS Absolute and relative total bark thickness declined with height, with no difference in height-related changes between habitat groups. Relative outer bark thickness showed a height-by-habitat interaction. There was a clade effect on relative thickness, but no interaction with height. Moisture contents were higher in inner than outer bark, and red oaks had denser bark than white oaks, but neither trait differed by habitat.• CONCLUSIONS Quercus species characteristic of fire-prone habitats invest more in outer bark near the ground where heat damage to outer tissues is most likely. Future investigations of bark should consider the height at which measurements are made and distinguish between inner and outer bark.

Individual vulnerability factors of Silver fir (Abies alba Mill.) to parasitism by two contrasting biotic agents: mistletoe (Viscum album L. ssp. abietis) and bark beetles (Coleoptera: Curculionidae: Scolytinae) during a decline process

Abstract: In recent decades, there have been increasing reports of forest decline, especially in Mediterranean forest ecosystems. Decline in tree vitality is usually due to complex interactions between abiotic factors and biotic agents that attack weakened trees. Estimating dendrometrical characteristics [basal area increment (BAI), age at DBH from tree ring counting, social status, height, and diameter], tree health status, and a competition index, we investigated the individual vulnerability of a French declining silver fir forest to both mistletoe (Viscum album L. ssp. abietis) and bark beetles (Pityophthorus pityographus Ratz., Pityokteines vorontzovi Jac., and Pityokteines spinidens Reitt.). BAI was negatively correlated with both mistletoe infection (via mistletoe biomass) and bark beetle attack (number of insects per square meter), but there was evidence of divergence in tree choice between two groups of parasites. Mistletoe preferentially infected isolated and dominant trees that showed higher past growth rates than non-infected ones. Conversely, bark beetles mainly attacked defoliated and preferably declining trees with diameter (DBH) lower than 44.5 cm and slower past growth. While successive severe drought periods are thought to greatly weaken southern silver fir populations, mistletoe and bark beetles may contribute actively to their decline processes as inciting and contributing factors, respectively.

Impact of environmental variables on the isolation, diversity and antibacterial activity of endophytic fungal communities from Madhuca indica Gmel. at different locations in India

Abstract: A total of 1,897 isolates of endophytic fungi from Madhuca indica Gmel., representing 40 morphologically distinct fungal taxa were obtained from 2,700 segments of stem, bark and leaf from three different locations (Loc 1, Loc 2 and Loc 3) in Uttar Pradesh, India. Out of 40 taxa, 28 were identified microscopically and the remaining 12 by molecular methods. Coelomycetes (62.41 %) were the most prevalent fungal group followed by hyphomycetes (28.89 %) and ascomycetes (8.70 %). Colonisation frequency (CF) was greater in stem (82.55 %) than in leaf (65.00 %) and bark (63.22 %). Due to the dominance of a few taxa, species richness and Shannon and Simpson diversity indices were lower in stem than in leaf and bark at each location. Interestingly, less rainfall and lower temperatures disfavoured the overall colonisation of fungal endophytes at Loc 2. The stem samples from all locations were very similar in their endophytic composition, whereas bark and leaf samples showed differences. The dominant endophytic fungi isolated were Phomopsis sp. 1 (9.185 %), and Colletotrichum gloeosporioides (7.00 %). Principal component analysis showed 55 % tissue specificity with 51.08 % maximum variance. Antibacterial activity revealed that 58.33 % endophytic fungi were active against at least one or more bacterial pathogens, whereas the crude extract of five endophytic fungi inhibited the growth of five or more than five (50 %) of the pathogens tested. This report illustrates the value of having an adequate sample size from different tissues and different locations for species and chemical diversity in search of novel natural products.

Spatial variations in non-structural carbohydrates in stems of twelve temperate tree species

Abstract: The radial, axial and inter-specific variations in concentrations and contents of non-structural carbohydrates (NSC) in stems were investigated for 12 Chinese temperate tree species. These species had contrasting leaf phenology (evergreen and deciduous) and wood types (non-, ring- and diffuse-porous wood). For each species, we sampled bark (periderm and phloem), outer wood (light-colored) and inner wood (dark-colored) at four heights along the stem (stump, breast height, crown base and mid-crown). Concentrations of total NSC (TNC, sum of sugars and starch), sugars and starch were much higher in bark than those in wood. On average, contents of sugars and starch accounted for 48 and 52 % of the TNC, respectively, and contents of TNC in bark, outer wood, and inner wood accounted for 34, 38, and 28 % of the stem total, respectively. Bark was the major pool of sugars in the stem (accounting for 50 % of the stem total on average), while outer wood was the major pool of starch (41 %). The concentration of sugars varied axially for all the conifers but did not for the broadleaved species. Mean concentrations of TNC, sugars and starch in stem varied by more than twofold among the species. However, there were no significant differences in these values for the species groups with different leaf phenology or wood types. Ignoring the radial, axial and inter-specific variations in NSC in stem would introduce large bias in estimating NSC storage at tree or ecosystem levels.

Yield of stilbene glucosides from the bark of young and old Norway spruce stems

Abstract: Bioactive stilbene glucosides are the major constituents of the acetone extracts of the phloem and bark of Norway spruce (Picea abies (L.) Karst.) trees. We studied their variation patterns across phloem and bark within the stems of Norway spruce. The total yields of stilbene glucosides (astringin, isorhapontin, and piceid) from trees were estimated. Bark samples were collected from young (18 years-old) and older trees (37 years-old), representing age and size typical for energy wood harvesting and the first commercial thinning, respectively. Different bark layers of younger trees had 10%–63% lower average amount of stilbene glucosides than the bark layers of older trees. The inner bark had the highest mass fraction of stilbene glucosides (2.7%–4.8% of dry weight (d.w.)) and the outermost bark showed the lowest amount (0.4%–1.2% d.w.). Axially along the stem, the highest amount of stilbene glucosides was found at the stem base in the young trees (average over bark zones 2.1% d.w.) and at the breast height and the base of the living crown in the older trees (average over bark zones 3.6% d.w.). Astringin and isorhapontin yielded the highest amounts, while the share of piceid was the smallest. The total yield of stilbene glucosides was dependent on the bark biomass, and positively correlated with total wood and bark volume. The basal stem was the most valuable stilbene source in both younger and older trees. The bark of Norway spruce from the first commercial thinnings, especially of butt and middle logs, can provide feasible source for high-value extracts.

In situ decomposition of northern hardwood tree boles: decay rates and nutrient dynamics in wood and bark

Abstract: The decomposition of coarse woody debris contributes to forest nutrient sustainability and carbon (C) balances, yet few field studies have been undertaken to investigate these relationships in northern hardwood forests. We used a paired-sample approach to study the decomposition of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Erhr.), and yellow birch (Betula alleghaniensis Britt.) boles at the Hubbard Brook Experimental Forest in New Hampshire. Mass loss over 16 years followed a first-order exponential decay pattern with half-lives ranging from 4.9 to 9.4 years in bark and from 7.3 to 10.9 years in wood. Nitrogen (N) and phosphorus (P) concentrations increased significantly during decomposition, resulting in sharp decreases in C:N and C:P ratios. We did not, however, observe significant net increases in the amount of N or P stored in decomposing boles, as reported in some other studies. Calcium (Ca) concentration decreased by up to 50% in bark but more than doubled in wood of all species. The retention of Ca in decomposing wood helps maintain Ca pools in this base-poor ecosystem. Together, the exponential model for mass loss and a combined power-exponential model for changes in nutrient concentrations were able to simulate nutrient dynamics in decomposing boles after clear-cutting in an adjacent watershed.

Stem Wood and Bark Extracts of Delonix regia (Boj. Ex. Hook): Chemical Analysis and Antibacterial, Antifungal, and Antioxidant Properties

Abstract: In the present study, the fatty acid components of the wood, bark, and essential oil of wood from Delonix regia as well as its antibacterial, antifungal, and antioxidant properties were investigated for the potential ability to control plant and human pathogens. Myristic acid was found to be a major fatty acid in the wood and bark of Delonix regia, comprising 10.77% of wood and 9.63% of bark. According to the GC-MS results, naphthalene derivatives were detected in the essential oils from the wood samples. Heptadecane and acyclic hydrocarbons were found in a high percentage (14.05%). Methanol: chloroform (1:1 v/v) wood extract showed effective activity against Bacillus subtilis, Sarcina lutea, and Staphylococcus aureus, where the bark extract was most active against Escherichia coli. The essential oil showed good antibacterial activity against Pectobacterium carotovorum. The bark extract showed the maximum percentage inhibition of fungal mycelial growth against Penicillium selerotigenum (70.37%) and Paecilomyces variotii (77.78%), and the essential oil showed moderate inhibition against Aspergillus nigra (44.44%). The total antioxidant activity of essential oil, stem wood, and stem bark extract was 84.34%, 80.33%, and 70.21%, respectively.

Mites associated with bark beetles and their hyperphoretic ophiostomatoid fungi

Abstract: The role that mites play in many ecosystems is often overlooked or ignored. Within bark beetle habitats, more than 100 mite species exist and they have important impacts on community dynamics, ecosystem processes, and biodiversity of bark beetle systems. Mites use bark beetles to access and disperse among beetle-infested trees and the associations may range from mutualistic to antagonistic, and from facultative to obligate. Many of these mites are mycetophagous, feeding on ophiostomatoid fungi found in beetle-infested trees and carried by bark beetles. Mycetophagous mites can affect the evolution and ecology of ophiostomatoid fungi and thus impact bark beeHe-fungal associations and beetle population dynamics. In this chapter, we provide an overview of the known associations of bark beetles and mites and discuss how these associations may impact the interaction between beetles and fungi, and the evolution and ecology of ophiostomatoid fungi.

The protective role of bark against fire damage: a comparative study on selected introduced and indigenous tree species in the Western Cape, South Africa

Abstract: The objective of this study was to compare the protective role of bark against fire for three selected indigenous and five exotic species in the Western Cape, South Africa. Bark thickness, compass direction, stem diameter at breast height, bark moisture content and relative height of the sample in the stem were tested for their effect on heat insulation capacity of bark. Trees were felled and heating experiments were conducted at 400 oC on fresh billets with intact bark. Time to heat the cambium to lethal 60 oC was determined. Statistical analysis based on correlation, multi-model inference and multiple regression revealed no significant influence of compass direction and diameter at breast height. Heat resistance was mainly determined by bark thickness, to a lesser degree by moisture content. In several species relative height at the stem modulated the bark thickness effect. Higher up the stem bark of the same thickness offered less protection against heat. Significant species-specific differences in heat resistance were apparent in the results, which could not be explained by bark thickness thus indicating further need for research in scrutinising these factors, which might help to explain the relative higher fire tolerance of certain species compared to others.

Antileishmanial Potential of Tropical Rainforest Plant Extracts.

Abstract: A total of 115 different plant extracts from our collection, representing 96 plant species, have been evaluated for in vitro antileishmanial activity against L. amazonensis promastigotes. In addition, the extracts were screened for cytotoxic activity against BALB/c mouse macrophages in order to assess a selectivity index. Crude extracts that showed a selectivity index (CC50 for macrophage / IC50 for promastigotes) ³ 5 or with IC50 < 12.5 μg/mL against promastigotes, a total of 28 extracts, were further screened for anti-amastigote activity. A total of 25 extracts showed promising activity against L. amazonensis promastigotes with low cytotoxic activity. Ten of these extracts showed selectivity indices, (CC50 for macrophages / IC50 for amastigotes) greater than 10 and are considered "hits", worthy candidates for further phytochemical exploration: Conostegia xalapensis methanol bark extract, Endiandra palmerstonii bark extract, Eugenia monteverdensis acetone bark extract, Eugenia sp. "fine leaf" acetone bark extract, Exothea paniculata chloroform bark extract, Mallotus paniculatus ethanol bark extract, Matelea pseudobarbata ethanol extract, Quercus insignis ethanol bark extract, Sassafras albidum dichloromethane bark extract, and Stemmadenia donnell-smithii acetone bark extract.

Analysis of Essential Oils from Cassia Bark and Cassia Twig Samples by GC-MS Combined with Multivariate Data Analysis

Abstract: Cinnamomum cassia is one of several species of Cinnamomum which has been widely used as a spice. In this study, the chemical profiles of its bark and twig were characterized by gas chromatography-mass spectrometry (GC-MS) and multivariate data analysis. Principle component analysis (PCA) and orthogonal projection to latent structures discriminate analysis (OPLS-DA) of GC-MS data provided a clear separation between those samples. The result obviously showed that the metabolome of cinnamon bark (CB) and cinnamon twig (CT) is different, and the corresponding loading S-plots revealed that the differential metabolites between the essential oils of CB and CT were trans-cinnamaldehyde, trans-anethole, α-cubebene, γ-muurolene, γ-amorphene, δ-cadinene, (−)-calamenene, and o-methoxycinnamaldehyde. Our study demonstrates that the combination of GC-MS spectrum and multivariate data analysis can be applied to identify essential oils from different parts of C. cassia.

Determination of Tannins of Three Common Acacia Species of Sudan

Abstract: The objective of this study is to analyze and compare tannins of three common Acacia species of Sudan, since vegetable tannins are important in leather industry. Acacia nilotica and Acacia seyal samples were collected from Sunt Forest in Khartoum State, while Acacia senegal samples were collected from the Debabat Forest in South Kordofan State. Bark samples from bulk collections of the three Acacia species were extracted with boiled deionized water. The amount of tannins present in these bulk samples was determined by Folin-Denis method for total phenolic materials, followed by precipitation with hide-powder. The difference between the amount of phenolic materials present before and after addition of hide-powder represents the amount of tannins present. The percentage of tannins in the leaves, bark, and mature and immature fruits of collections of individuals of Acacia species was estimated; mature and immature fruits of Acacia nilotica contain tannins (22.15% and 22.10%, resp.). The leaves of Acacia nilotica and Acacia seyal contain tannins (11.80% and 6.30%, resp.). The barks of Acacia seyal, Acacia nilotica, and Acacia senegal contain tannins (12.15%, 10.47%, and 3.49%, resp.).