Condensed tannins in the tissue culture of sainfoin (Onobrychis viciifolia Scop.) and birdsfoot trefoil (Lotus corniculatus L.)

Two forage legumes, birdsfoot trefoil (Lotus corniculatus L.) and sainfoin (Onobrychis viciifolia Scop.), containing condensed tannins in their leaves and stems were used as source material to study condensed tannins in tissue culture. More protoplasts were isolated from mesophyll tissue of a low tannin-containing strain of birdsfoot trefoil than from a high tannin-containing strain, but more tannin-filled protoplasts were observed in the latter. Growth rates of leaf explant-derived callus tissue were greater for the high-tannin than for the low-tannin strain. In sainfoin, callus cultures from leaf explants produced numerous tannin-filled cells by 21 days. Explants from sainfoin cotyledons and roots, tissues which normally do not contain tannins, also formed callus with tannin-filled cells in 21 days but in almost every case, a cytokinin was required for tannin formation to occur. The occurrence of tannin-filled cells in callus from root and cotyledon explants was variable and genotype specific. These results show that endogenous tannins can affect protoplast isolation and possibly callus growth in birds-foot trefoil, and that the formation of condensed tannins in sainfoin callus culture can be influenced by a growth regulator.Abbreviations BAP benzylaminopurine - KIN kinetin - NAA naphthaleneacetic acid - PAR photosynthetically active radiation Contribution no. 920 of Agriculture Canada Research Station, 107 Science Cres., Saskatoon, Saskatchewan, Canada S7N OX2     

Impact of increasing levels of condensed tannins from sainfoin in the grower–finisher diets of entire male pigs on growth performance,carcass characteristics,and meat quality

Sainfoin is a protein-rich legume with an ideal amino acid profile and therefore could partly replace soybeans in the diets of growing pigs. However, sainfoin also contains a non-negligible amount of condensed tannins (CTs), which can act as antinutritional factors. Bioactive plant compounds, like hydrolysable tannins, have been suggested to be suitable in entire male (EM) production, as they impair the development of accessory sex glands and, by that, reduce boar taint compound levels without negatively impacting growth. It is unknown whether, similar to hydrolysable tannins, CTs from sainfoin reduce the incidence of boar taint without impacting growth performance, carcass traits, and meat quality. For the experiment, 48 Swiss Large White EM were assigned within litter to one of four grower (25–60 kg BW) and finisher (60–105 kg BW) diets supplemented with 0 (T0), 5 (T5), 10 (T10), and 15% (T15) sainfoin meal, respectively. The four diets were designed to be isocaloric and isoproteic. Increasing the dietary sainfoin level had no negative effect on growth performance or the carcass characteristics. Despite leading to a similar feed intake between the treatment groups, increasing the dietary sainfoin levels tended (P ≤ 0.08) to reduce the number of feeder visits but increased the time spent at the feeder as well as the feed intake per visit during the finisher period. By increasing sainfoin intake, the levels of C18:3n-3 and long-chain homologs linearly increased (P < 0.01) in the backfat and intramuscular fat (IMF), whereas in the backfat, but not the IMF, the 18:2n-6 levels decreased (P < 0.01). The latter triggered a greater (P < 0.01) desaturation rate (C18:1n-9/C18:0) of the saturated fatty acids, resulting in a greater (P < 0.01) proportion of monounsaturated fatty acid. Apart from a linear decrease (P = 0.02) in the androstenone levels in the longissimus thoracis (LT), increasing the sainfoin intake had no effect on the level of boar taint in the LT and backfat. As determined by the elevated correlation coefficient, skatole and indole levels, but not androstenone levels, in the adipose tissue seem to be reliable proxies for their respective levels in LT and, therefore, in pork. In conclusion, sainfoin is a suitable homegrown protein source for grower finisher pigs and can be included at up to 15% in the diet to replace 7% of soybean in a diet without producing any noteworthy effects on growth, whereas the impact of CTs on boar taint was limited.     

Effects of sainfoin (Onobrychis viciifolia) extract and monomers of condensed tannins on the association of abomasal nematode larvae with fundic explants

Tannin-rich forages offer an alternative to anthelmintic chemicals to control gastrointestinal nematodes. However, the mode of action of such bioactive plants still needs to be assessed. Previous studies have shown that extracts of tannin-rich plants interfere with the first phase of host invasion, i.e., the exsheathment of infective larvae (L3s). In the current study, we examined the hypothesis that exposure to tannins could also affect the second phase of larval establishment, i.e., the tissue association/penetration of the exsheathed L3s into the digestive mucosae. An in vitro direct challenge technique using fundic explants was applied in this study. The main parasite model was Haemonchus contortus. The objectives were to verify: (i) whether a modification of the association/penetration of L3s with the mucosae occurred after contact with sainfoin extract; (ii) whether this is a dose-dependent phenomenon; (iii) whether tannins were responsible for these effects; (iv) whether these effects were dependent on the parasite species; and (v) how the biochemical structure of tannins might influence these effects. Following 3 h contact with sainfoin extract at 1,200 μg/ml, the penetration of exsheathed L3s of H. contortus and Teladorsagia circumcincta into fundic explants was significantly reduced. Moreover, a dose–response relationship was found for H. contortus. For both nematodes, the changes were totally alleviated after addition of polyvinyl polypyrrolidone, an inhibitor of tannins, to the sainfoin extract, suggesting that tannins play a major role in the observed effects. Comparison of results obtained with different monomers of condensed tannins confirms a relationship between structure and activity, the prodelphinidin monomers and galloyl-derivatives being more effective than the procyanidin monomers. Combined with the delay or the inhibition of larval exsheathment previously shown, these effects could explain how tanniniferous plants reduce the establishment of infective larvae in small ruminants.     

Effect of feeding dehydrated and ensiled tanniferous sainfoin (Onobrychis viciifolia) on nitrogen and mineral digestion and metabolism of lambs

The effects of tanniferous sainfoin on digestion and metabolism have been investigated in 12 lambs in an incomplete cross-over design (n = 6). Effects of condensed tannins (CT) were evaluated by comparing dehydrated and ensiled sainfoin treated with and without polyethylene glycol (PEG). Dehydrated and ensiled grass-clover mixtures served as controls. The lambs were fed the treatment diets, including a mineral supplement, for 21 d. During the last 7 d excreta, rumen fluid and blood were sampled. The CT of sainfoin decreased rumen fluid ammonia concentration (p < 0.001) and increased the plasma concentration mainly of essential amino acids (p < 0.001). Body retention of phosphorus, calcium and magnesium was lower with sainfoin compared to PEG-treated sainfoin (p < 0.05). Sainfoin without PEG resulted in lower digestibilities of organic matter and neutral detergent fibre than sainfoin with PEG and the grass-clover mixture (p < 0.001). Ensiling of sainfoin led to the lowest N-retention. In conclusion, the reduction in ruminal ammonia and urine-N losses by sainfoin CT did not improve N-retention.     

Extractability and biological activity of tannins from various tree leaves determined by chemical and biological assays as affected by drying procedure

Leaf samples of Juglans regia (walnut), Rhus typhina (sumach), Aesculus hippocastanum (chestnut) and Salix alba (willow) were either freeze dried or oven dried and the amount of tannins was determined by two chemical assays (Folin Ciocalteau and ferric chloride method). In addition, the biological activity of these tannins was determined by their protein precipitation capacity and by a bioassay based on the incubation to the leaves in vitro in buffered rumen fluid with and without polyethylene glycol. Generally, oven drying is recognised to decrease the extractability and/or the biological activity of tannins. Our results however do not indicate a general decrease in extractability of tannins due to oven drying. The effects observed were plant specific with negative effects of oven drying in walnut and willow leafs, positive effects in chestnut leaves and no effects were observed for the sumach. No negative effects of oven drying were detected for the biological activity of the tannins. The specific protein precipitation capacity was nearly identical for the freeze dried and the oven dried tannins. Oven drying however decreased the solubility of the cell contents and the plant cell wall, which led to changes in fermentation end products, but the biological activity of the tannins was not negatively affected by the oven drying. Although some differences in the extractability and activity of the individual plant species were observed, we conclude from this work that the drying procedure has no negative effect on the biological activity of the tannins examined.     

In vivo and in situ measurements of the digestive characteristics of sainfoin in comparison with lucerne fed to sheep as fresh forages at two growth stages and as hay

In vivo and in situ digestive characteristics of sainfoin (Onobrychis viciifolia L., a tannin-rich forage) and lucerne (Medicago sativa L., a tannin-free forage) were compared to evaluate the effects of condensed tannins (CT) and growth stage (vegetative v. early flowering) in experiment 1. In experiment 2, the hays of the two forages, harvested at early flowering, were compared. Ingestibility, organic matter digestibility (OMD) and nitrogen (N) retention were measured in sheep fed sainfoin and lucerne fresh forages and hays. The loss of dry matter (DM) and N from polyester bags suspended in the rumen, abomasum and small intestine was also measured using rumen fistulated sheep and other intestine fistulated sheep. Nitrogen content was lower in sainfoin than in lucerne. Content of CT in sainfoin decreased with growth stage (3.5 to 2.5 g CT/kg DM) and was lower for sainfoin hay (0.6 g CT/kg DM). Ingestibility and OMD did not differ between fresh-fed forage species. Total N tract digestibility in vivo was much lower for sainfoin than for lucerne fresh forages (mean value 0.540 v. 0.721, P < 0.001) and for sainfoin hay than lucerne hay (0.464 v. 0.683, P < 0.001). In both species, N digestibility was not altered by growth stage. The rumen degradation of N was lower in sainfoin than in lucerne, resulting in a lower proportion of N intake excreted in urine. The intestinal digestibility of sainfoin was also lower than that of lucerne, resulting in a higher N excretion in faeces. Hence the efficiency of N utilisation by sheep (ENr) was similar (mean value 0.205 and 0.199 g N retained/g N intake for fresh sainfoin and lucerne, respectively). The coefficient of N retention by the animal was higher for sainfoin at the vegetative stage than for all the other forages. Nitrogen degradability in the rumen determined by the nylon bag technique (DegN) was lower for sainfoin than for lucerne when forages were studied both fresh (mean value 0.608 and 0.818, respectively) and as hays (0.631 and 0.767). The efficiency of forage N digestion (ENd) was higher for sainfoin at the vegetative stage. Compared with lucerne, sainfoin greatly increased the in situ estimate of forage N escaping the rumen but decreased its intestinal digestibility.     

Photosynthesis, Water Relations, Temperature and Canopy Structure as Factors Influencing the Growth of Sainfoin (Onobrychis viciifolia Scop.) and Lucerne (Medicago sativa L.)

Measurements of the growth of sainfoin and lucerne were madein the field after cutting on 31 May 1977. Sainfoin reacheda total above-ground dry weight of 408 g m^–2 over thegrowing period of 48 days compared with 598 g m^–2 in lucerne.Final leaf area indices (LAIs) were 2.8 in sainfoin and 6.1in lucerne. The specific leaf areas (SLAs) for sainfoin wereapproximately half those of lucerne throughout the regrowthperiod. The maximum rates of leaf appearance were 0.12 leavesper day in sainfoin and 0.85 leaves per day in lucerne. Themaximum mean rate of plant extension growth for lucerne of 2.12mm h^–1 occurred during the night, whereas, in sainfointhe maximum rate of 1.72 mm h^–1 occurred during the day. Measurements of extinction coefficients for PAR ranged from0.45 to 0.89 in sainfoin and from 0 42 to 0.57 in lucerne. Asthe lucerne crop increased in size leaf water potentials andsolute potentials became more negative. In sainfoin leaf waterpotentials remained remarkably high throughout the growth period,solute potentials decreased and turgor potentials increased.The stomatal conductances of the two species were similar. The photosynthetic capacities and rates of dark respirationper unit leaf area in both species were similar. The rate ofcanopy ‘gross’ photosynthesis at 295 W m^–2was always greater in lucerne than in sainfoin. This was largelya matter of differences between the species in LAI, althoughat higher LAIs the more erect structure of lucerne leads toa better utilization of photosynthetically active radiation. Onobrychis vicifolia Scop, sainfoin, Medicago sativa L., lucerne, photosynthesis, water relations, temperature, canopy structure     

Effects of artificial grassland establishment on soil nutrients and carbon properties in a black-soil-type degraded grassland

Despite a growing knowledge of nutrient limitation for mangrove species and how mangroves adapt to low nutrients, there is scant information about the relative importance of N:P ratio and leaf phenolics variability in determining nutrient conservation. In this study, we evaluated possible nutrient conservation strategies of a mangrove Rhizophora stylosa under nutrient limitation. 1. The leaf nutrient concentrations of R. stylosa changed with season, with the highest N concentration in winter and the highest P concentration in spring for both mature and senescent leaves. Leaf N and P concentrations decreased significantly during leaf senescence. Based on N:P ratios R. stylosa forest was N-limited. Accordingly, the nitrogen resorption efficiency (NRE) was significantly higher than phosphorus resorption efficiency (PRE) for the R. stylosa leaves during leaf senescence. The NRE and PRE both reached the highest in the autumn. Average N and P concentrations in the senescent leaves were 0.15% and 0.06% for R. stylosa, respectively, indicating a complete resorption of N and an incomplete resorption of P. There was a significant negative correlation between nitrogen resorption proficiency (NRP) and NRE, meanwhile phosphorus resorption proficiency (PRP) and PRE correlation was also highly significantly. 2. R. stylosa leaves contained relatively high tannin level. Total phenolics, extractable condensed tannins and total condensed tannins contents increased during leaf senescence, and changed between seasons. The lowest concentrations of total phenolics, extractable condensed tannins and total condensed tannins occurred in summer, total phenolics concentrations were inversely related to nitrogen or phosphorus concentrations. 3. Our results confirmed that resorption efficiency during leaf senescence depends on the type of nutrient limitation, and NRE was much higher than PRE under N-limited conditions. R. stylosa forest developed several nutrient conservation strategies in the intertidal coastline surroundings, including high nitrogen resorption efficiency, low nutrient losses and high tannins level.     

Light as a regulator of structural and chemical leaf defenses against insects in two Prunus species

Light is a key factor influencing competition between species, and the mechanisms by which trees overcome insect outbreaks can be associated with alternation of the leaves structure, which then prevent or promotes their susceptibility to herbivores. It was predicted that leaf tissue anatomy would likely be different in sun and shade leaves, with a gradual decline of leaves resistance coupled with reduction of accessible light. We quantified anatomical patterns and the distribution of defence compounds (phenols, total tannins, catechol tannins) within heavily grazed leaves of Prunus padus, native in Europe and Prunus serotina, an invasive to Central Europe. Both species were strongly attacked by folivorous insects when shrubs grew in the shade. In the sun, however only P. padus leaves were grazed, but P. serotina leaves were almost unaffected. We identified that anatomical characteristics are not linked to different P. padus and P. serotina leaf vulnerability to insects. Furthermore, the staining of defence compounds of P. serotina leaves grown in full sun revealed that the palisade mesophyll cells had a higher content of phenolic compounds and catechol tannins. Thus, our results indicate that a specific distribution of defence compounds, but not the anatomical relationships between palisade and spongy mesophyll, may be beneficial for P. serotina growth outside its natural range. The identified pattern of defence compounds distribution is linked to a lower susceptibility of P. serotina leaves to herbivores, and is associated with its invasiveness. This likely reflects that P. serotina is a stronger competitor than P. padus, especially at high sunlit sites i.e. gaps in the forest.     

Condensed tannins of cotton leaves

Some primitive races of cotton (Gossypium hirsutum) are almost immune to spider mites. These strains contain condensed tannins of about 20% of dry wt. The tannins accumulate in leaves and their concentration increases in successive leaves until about the 10th true leaf. The upper leaves maintain this quantity until early fall. The condensed tannins give a moderate astringency to the leaf, and are mixed polymers hydrolysing in acidic digests to 1 part cyanidin and 4 parts delphinidin.     

Tannins from four commonAcacia species of Texas and Northeastern Mexico

The amount of tannins present inAcacia berlandierii, A. farnesiana, A. greggii andA. rigidula, 4 common species of the southwestern United States and northern Mexico, was determined. Bark samples of the 4 species were extracted with water, 80% methanol, and 70% acetone. Of these, 70% acetone proved to be the most efficient solvent. Tannins were determined by Folin-Denis analysis for total phenolic materials, followed by precipitation with casein or hide powder. The hidepowder method was modified to facilitate handling of smaller samples. Results of tannin determination by casein and hide-powder precipitation methods gave comparable results. The amount of tannins present in leaves, bark, wood, and immature fruits of samples of these species was then determined by the same analytical methods. In most instances, bark and immature fruits had the highest percentage of tannins (5–15%) and wood was much lower (less than 1%). Leaves had intermediate values.     

Purification and thermal dependence of glutathione reductase from two forage legume species

Alfalfa (Medicago sativa L.) and sainfoin (Onobrychis viciifolia Scop.) are forage legumes that differ in their responses to high and low temperature stresses. Thermal limitations on the function of glutathione reductase (EC 1.6.4.2) could adversely affect the ability of the plant to cope with adverse temperatures. Our objectives were to (a) purify glutathione reductase from `Cimarron' alfalfa and `PI 212241' sainfoin and (b) investigate the intraspecies variation in the thermal dependency of glutathione reductase from each of three cultivars of alfalfa and two cultivars and an introduction of sainfoin. Glutathione reductase was purified 1222-and 1948-fold to a specific activity of 281 and 273 units per milligram of protein, from one species each of alfalfa and sainfoin, respectively. The relative molecular mass of the protein was approximately 140 kilodaltons with subunits of 57 and 37 kilodaltons under denaturing conditions. The activation energies were approximately 50 kilojoules per mole for both species. Over a 5 to 45°C temperature gradient, large variation among species and genotypes within species was found for: (a) the minimum apparent Michaelis constant (0.6-2.1 micromoles of NADPH), (b) the temperature at which the minimum apparent Michaelis constant was observed (10-25°C), and (c) the thermal kinetic windows (6-19°C width). Future studies will focus on relating the thermal dependence of the Michaelis constant of the glutathione reductases and plant growth rates and forage quality of these species throughout the growing season.     

Influence of condensed tannins from Brazilian semi-arid legumes on ruminal degradability,microbial colonization and ruminal enzymatic activity in Saanen goats

The present study aimed at determining the influence of condensed tannins present in the Brazilian legume species Mimosa hostilis, Mimosa caesalpinifolia and Bauhinia cheilantha on ruminal degradability, microbial colonization and enzymatic activity. Polyethylene glycol (PEG) was used to reduce the astringency and concentration of soluble condensed tannins. Four ruminally-cannulated Saanen goats (60 ± 8 kg BW) were fed, in two experimental periods, with a hay diet based on the studied legumes treated or non-treated with PEG. Voluntary intake, microbial colonization, DM, CP, NDF, and ruminal degradability of PEG treated and non-treated forage leaves, as well as pH, ammonia and 1,4 β-endoglucanase activity of the rumen content were evaluated. Astringency and soluble tannin concentration of the studied legumes were reduced by approximately 70% and 50%, respectively, with PEG treatment. Average DM intake was higher for the treated diet (16.76 g DM/kg BW/day against 13.06 g DM/kg BW/day). Percentile values for degradation parameters and for potential and effective degradabilities of DM, CP and NDF were also affected by the tannins, but at different intensities. Electron microscopic observations of ruminally-incubated legume leaves showed a more effective microbial colonization of PEG-treated leaves for all legume species. A decrease in pH and an increase in ammonia concentration and in endoglucanase activity in the ruminal content was also observed for PEG-treated diets at all sampling periods. Condensed tannins of the studied legume species have influenced the adhesion conditions, colonization and enzymatic activity of the microbial ecosystem, and consequently the ruminal degradation of the different dietary fractions. For this reason, the reduction in condensed tannin would be of great importance to improve the nutrition of ruminant feeding of these species.     

Ultrastructural changes in the third-stage, infective larvae of ruminant nematodes treated with sainfoin (Onobrychis viciifolia) extract

Plants rich in condensed tannins are an alternative to chemical anthelmintics to control gastrointestinal nematodes (GINs) in ruminants. Previous functional studies have shown that sainfoin extracts affect the two forms of infective larvae (L3), ensheathed and exsheathed. However, the mechanisms of action remain unknown. The aim of this study was thus to compare ultrastructural changes in ensheathed and exsheathed L3 of two GIN species after in vitro contact with sainfoin extracts using transmission electron microscopy. The main changes identified were an alteration of the hypodermis, the presence of numerous vesicles in the cytoplasm and degeneration and/or death of muscular and intestinal cells. The changes suggested similar and nonspecies-specific lesions in the two nematode species. Comparison of the modifications found in the ensheathed vs. exsheathed L3s revealed different locations of the main cellular changes depending on the larval form. It is hypothesized that these spatial differences in lesions are mainly influenced by the presence of the sheath which favors contact between the active compounds and either the cuticle or the digestive tract. Overall, our observations suggest that the functional changes observed in the biology of GIN L3s after contact with sainfoin extracts are mediated through a direct mode of action, i.e. different interactions between the bioactive plant metabolites and the nematode structure depending on the route of contact.     

Pathogenicity of Two Populations of Meloidogyne hapla Chitwood on Alfalfa and Sainfoin

The pathogenicity of two populations of the northern root-knot nematode, Meloidogyne hapla Chitwood, population 1 (P1) from alfalfa and population 2 (P2) from sainfoin, was studied on both alfalfa and sainfoin for 25 weeks. Alfalfa and sainfoin plants inoculated with P2 had significantly (P ≤ 0.05) higher mortality than plants inoculated with P1. Plant stands over all weeks for the uninoculated control, P1, and P2 were 90.5, 78.5, and 64.0% for alfalfa and 84.5, 51.0, and 41.0% for sainfoin, respectively. The increased virulence of P2 was again shown when means of plant species were combined (inoculation × week of count interaction). Plants inoculated with P2 had significantly higher mortality than either those inoculated with P1 or the uninoculated control beginning at week 7 and continuing through week 25. Plant stands over species at 25 weeks for the uninoculated control, P1, and P2 were 82.5, 29.0, and 18.0%, respectively. Sainfoin was significantly more susceptible to either population than alfalfa (plant species × week of count interaction). Separation between species first occurred after week 7 and continued until week 25. Percentages of plants remaining for alfalfa and sainfoin were 61.5 and 25.0 after 25 weeks. Significantly higher reproduction occurred in the alfalfa plants remaining after 25 weeks in P2 than in P1. Mean number of eggs per root system were 60,371 for P1 and 104,438 for P2, a difference of 42%. The results of this study indicate a need for breeders to adequately sample nematode populations present in the intended area of cultivar use and to design screening procedures to account for population pathogenicity variability.     

How life history affects threat status: Requirements of two Onobrychis-feeding lycaenid butterflies, Polyommatus damon and Polyommatus thersites, in the Czech Republic

Comparisons of related species differing in conservation status may offer insights into causes of species declines. We studied egg-laying patterns and landscape occupancy of two sympatric lycaenidae butterflies inhabiting xeric grasslands, vulnerable Polyommatus thersites and critically endangered Polyommatus [Agrodiaetus] damon, both developing on sainfoin, Onobrychis spp. Females of bivoltine P. thersites oviposit on host plant leaves at a relatively low height (??20 cm), in both spring (May?CJune) and summer (July?CAugust) generations. Females of univoltine P. damon (July?CSeptember) oviposit to senescing inflorescences, in significantly higher heights (>30 cm), and the species is hence vulnerable to summer mowing or grazing. On a landscape scale, both species tended to occur at sites with diverse sward management, including temporarily unmanaged patches. In addition, P. damon occurred only in the proximity of other occupied sites. The study documents that grassland management must respect the needs of the most vulnerable species, and because these needs are seldom known, it must maintain a high diversity of conditions within individual sites.     

Contributions to the botany and nutritional value of some wild amaranthus species (Amaranthaceae) of Nuevo leon,Mexico

Seeds and plants of Amaranthus have been a source of food for many cultures in the world. Some species can be found as weeds or growing wild under severe climatic and soil conditions, but their potential as food sources has not been studied. The objective of this work was to study the nutritional quality of four wild species ofAmaranthus,A. retroflexus (AR),A. viridis (A V),A. palmeri (AP) andA. blitoides (AB) as potential sources of vegetable greens. Histochemical studies showed higher levels of starch in leaves of AR and AB, moderate amounts of tannins in all leaves, high protein concentration in stems and leaves, and moderate amounts of alkaloids in all tissues of AV and AB. Antinutritional factors (nitrates, oxalates, cyanogenic glycosides, tannins and phytates) were quantified in plants at the preflowering stage, but only nitrates were found at levels (0.34-2% dw) above those generally considered as safe, but at similar levels found in spinach. No cyanogenic glycosides were detected in any species. Bromatologic analysis of whole or different plant parts at preflowering and maturity (mature seeds) showed that mature whole plants or individual sections can be recommended as animal feed since they contain high levels of protein (20.6-24.7% whole plant, 25.3-32.9% leaves) and soluble carbohydrate (>40%).Amaranthus plants could be best consumed as vegetables at the preflowering stage. At this stage, the highest protein concentrations were found in leaves (22.8-27.8%), while the remaining chemical composition was very similar to that found in other food vegetables. The four species showed similar chemical compositions, and had no detrimental chemicals which would deter their use as vegetable foods. Organoleptic taste preference studies would best indicate the stage at which the plant should be harvested for human consumption.     

Astringent tannins of Viburnum and Hydrangea species

The tannins of the leaves of Viburnum and Hydrangea species consist of proanthocyanidins only, but in each genus the range is very wide. In several species of Hydrangea the proanthocyanidins are of the A type, otherwise they are mostly tri- or tetrameric B type. Tannin content is correlated with evolutionary advancement, the more advanced and more widely dispersed species having the less. Species with most tannin occur in E. Asia and E. N. America, but species with little or no tannin are present in both areas. The occurrence in both genera of globose inflorescences with sterile flowers is correlated neither with morphological nor with chemical characters.     

Tannin allocation in blackbrush (Coleogyne ramosissima)

Blackbrush (Coleogyne ramosissima) is a spinescent shrub occurring in nearly monospecific stands in the southwestern United States. Winter browsing by domestic goats stimulates spring twig production by blackbrush plants. Current season's twigs produced by older branches growing on the outer edges of the plant canopy (terminal branches) contained 2.37 times more tannins than did older twigs. Within blackbrush plants, current season's twigs on terminal branches contained 1.34 times more tannins than did current season's twigs on sprouts and younger branches (basal branches). When analysed separately, current season's terminal twigs contained 1.47 times more tannins than did leaves, while current season's basal twigs contained 1.10 times more tannins than did leaves. Phytochemicals, mainly phenolics, in blackbrush reduce its risk of being over-utilized by domestic herbivores, and the occurrence and distribution of tannins in blackbrush lend support to hypotheses dealing with secondary compounds as plant defences.     

乌桕叶片及其乳汁中酚类物质比较分析

大戟科乌桕（Triadica sebifera）是我国南方重要的经济和绿化树种。分析了乌桕叶片乳汁中单宁和类黄酮的含量,并与叶片中单宁和类黄酮的含量进行对比。研究发现,在乳汁和叶片中共同检测到的2种单宁和2种类黄酮物质,它们在叶片中的浓度远远高于乳汁中的浓度。这表明乌桕中的单宁和类黄酮这类防御物质主要存在于叶片中。乌桕各种群间单宁与类黄酮含量都有显著差异,这可能是不同种群所处的生态环境以及面临植食昆虫的不同而导致的。