Effects Of Plant Secondary Compounds Research Articles

487 Effects of plant secondary compounds found in Juniperus spp. on yearling Rambouillet wethers feedlot performance, carcass characteristics, adipose tissue fatty acid composition, and sensory panel traits.

487 Effects of plant secondary compounds found in Juniperus spp. on yearling Rambouillet wethers feedlot performance, carcass characteristics, adipose tissue fatty acid composition, and sensory panel traits.

Secondary compounds of Pinus massoniana alter decomposers' effects on Quercus variabilis litter decomposition.

A major gap to understand the effects of plant secondary compounds on litter decomposition in the brown food web is lack of information about how these secondary compounds modify the activities of soil decomposers. To address this question, we conducted an experiment where aqueous extracts and tannins prepared from Pinus massoniana needles were added to soils collected either from P. massoniana (pine soil) or Quercus variabilis (oak soil). Our objective was to investigate the cascading effects of the two compounds on isopod (Armadillidium vulgare) activity and subsequent change in Q. variabilis litter decomposition. We found that in pine soil, both aqueous extracts and tannins (especially at high concentrations) had positive effects on litter decomposition rates when isopods were present. While without isopods, litter decomposition was enhanced only by high concentrations of aqueous extracts, and tannins had no significant effect on decomposition. In oak soil, high concentrations of aqueous extracts and tannins inhibited litter decomposition and soil microbial biomass, regardless of whether isopods were present or not. Low concentrations of aqueous extracts increased litter decomposition rates and soil microbial biomass in oak soil in the absence of isopods. Based on our results, we suggest that the high concentration of secondary compounds in P. massoniana is a key factor influencing the effects of decomposers on litter decomposition rates, and tannins form a major part of secondary compounds. These funding particularly provide insight into form‐ and concentration‐oriented effects of secondary compounds and promote our understanding of litter decomposition and soil nutrient cycling in forest ecosystem.

Effect of Plant Secondary Compounds on Susceptibility of Insects to Entomopathogenic Microorganisms

Effect of Plant Secondary Compounds on Susceptibility of Insects to Entomopathogenic Microorganisms

Temperature affects insect outbreak risk through tritrophic interactions mediated by plant secondary compounds

Global warming may affect population dynamics of herbivorous insects since the relative impact of bottom‐up and top‐down processes on herbivore survival is likely to be influenced by temperature. However, little is known about the mechanisms by which warming could affect regulation of populations, particularly when indirect effects across trophic levels are involved. We quantified larval survival of the needle‐feeding European pine sawfly, Neodiprion sertifer, either protected from (caged) or exposed to natural enemies at three geographically separated localities in Sweden. The study shows that larval survival is affected by temperature but the direction of the effect is influenced by plant secondary compounds (diterpenes). The results suggest that survival of exposed larvae feeding on needles with high diterpene concentrations will decrease with increasing temperature, while larval survival on low diterpene concentration is less predictable with either no change or an increase with temperature. This food quality dependent response to temperature is probably due to diterpenes having a double‐sided effect on larvae; both a negative toxic effect and a positive anti‐predator defense effect. Increased temperature had also consequences at the population level; an established population model parameterized using data from the study to evaluate the influence of temperature and plant secondary compounds on the regulation of the sawfly predict that, depending on food quality, outbreak risks could both decrease and increase in a warmer climate. If so, effects of plant secondary compounds will play an increasing role for larval survival in a future warmer climate and temperature will, via multitrophic effects on larval survival, strongly influence how sawfly and other insect populations are regulated.

Effect of plant secondary compounds on in vitro methane, ammonia production and ruminal protozoa population

The objective of this study was to evaluate the potential of secondary plant metabolites from 38 sources to serve as antimethanogenic additives in ruminant diets. The effect of leaf tannins from these different plant sources on rumen fermentation, protozoal populations and methanogenesis was also studied. Samples (200 mg dry matter, DM) were incubated without and with polyethylene glycol (PEG)-6000 (400 mg DM) as a tannin binder during 24-h incubation in the in vitro Hohenheim gas system. In the leaf samples, total phenol (g kg(-1) DM) was maximum in Pimenta officinalis (312) followed by Oenothera lamarckiana (185) and Lawsonia inermis (105). Of the 38 samples, condensed tannins exceeded 4.0 g kg(-1) in only Alpinia galanga (7.50), Cinnamomum verum (4.58), Pelargonium graveolens (18.7) and Pimenta officinalis (23.2) and were not detected in seven samples. When the bioactivity of the leaf samples was assessed using the tannin bioassay, the percentage increase in the amount of gas produced during incubation of samples with the tannin-binding agent PEG-6000 over the amount produced during incubation without the tannin binder ranged from nil (zero) to 367%, with the highest being recorded with A. galanga leaves. The ratio of methane reduction per ml of total gas reduction was maximum with Rauvolfia serpentina (131.8) leaves, followed by Indigofera tinctoria (16.8) and Withania somnifera (10.2) leaves. Total and differential protozoal counts increased with added PEG in twenty-two samples, maximum being in Pimenta officinalis. Increased accumulation of total volatile fatty acids during incubation with added PEG-6000 was recorded, and the values ranged from zero to 61%. However, the increase was significant in only 11 of the 38 tannin sources tested indicating noninterference of tannin on in vitro fermentation of carbohydrates by the majority of samples tested. Conversely, in 26 of 38 plant sources, the leaf tannins reduced N-digestibility as evidenced by increased accumulation of NH3 -N with added PEG. Our study unequivocally demonstrated that plants containing secondary metabolites such as Rauvolfia serpentine, Indigofera tinctoria and Withania somnifera have great potential to suppress methanogenesis with minimal adverse effect of feedstuff fermentation. It was established that methanogenesis was not essentially related to the density of protozoa population in vitro. The tannins contained in these plants could be of interest in the development of new additives in ruminant nutrition.

The interplay between toxin-releasing β-glucosidase and plant iridoid glycosides impairs larval development in a generalist caterpillar, Grammia incorrupta (Arctiidae)

Herbivores with polyphagous feeding habits must cope with a diet that varies in quality. One of the most important sources of this variation in host plant suitability is plant secondary chemistry. We examined how feeding on plants containing one such group of compounds, the iridoid glycosides, might affect the growth and enzymatic activity in a polyphagous caterpillar that feeds on over 80 plant species in 50 different families. Larvae of the polyphagous arctiid, Grammia incorrupta, were reared exclusively on one of two plant species, one of which contains iridoid glycosides (Plantago lanceolata, Plantaginaceae) while the other does not (Taraxacum officinale, Asteraceae). Larval weight was measured on the two host plants, and midgut homogenates of last instar larvae were then assayed for activity and kinetic properties of β-glucosidases, using both a standard substrate, 4-nitrophenyl-β-d-glucose (NPβGlc), and the iridoid glycoside aucubin, one of the two main iridoid glycosides in P. lanceolata. Larvae feeding on P. lanceolata weighed significantly less and developed more slowly compared to larvae on T. officinale. While the larval midgut β-glucosidase activity determined with NPβGlc was significantly decreased when fed on P. lanceolata, aucubin was substantially hydrolyzed and the larval β-glucosidase activity towards both substrates correlated negatively with larval weight. Our results demonstrate that host plants containing high concentrations of iridoid glycosides have a negative impact on larval development of this generalist insect herbivore. This is most likely due to the hydrolysis of plant glycosides in the larval midgut which results in the release of toxic aglycones. Linking the reduced larval weight to the toxin-releasing action of an iridoid glycoside cleaving β-glucosidase, our results thus support the detoxification limitation hypothesis, suggesting fitness costs for the larvae feeding solely on P. lanceolata. Thus, in addition to the adaptive regulation of midgut β-glucosidase activity, host plant switching as a behavioral adaptation might be a prerequisite for generalist herbivores that allows them to circumvent the negative effects of plant secondary compounds.

Effects of Plant Secondary Compounds on Nutritional Carrying Capacity Estimates of a Browsing Ungulate

Abstract Carrying capacity estimates based on digestible protein (DP) and energy (DE) are useful in comparing effects of land management practices or the ability of different vegetation communities to support herbivores. Plant secondary compounds that negatively affect forage quality would be expected to change nutritionally based estimates of carrying capacity. We evaluated the effect of plant secondary compounds on nutritionally based carrying capacity estimates of white-tailed deer ( Odocoileus virginianus Zimmerman) in Tamaulipan thorn scrub of northern Mexico. Forage biomass, nutrient concentration, and tannin concentration (protein-precipitating capacity) were measured for 23 forage items during spring and summer in three replicate pastures. Nitrogen in phenolic amines was estimated for the two principal woody browse species in deer diets and was assumed to be unavailable for amino acid synthesis. Carrying capacity estimates were calculated based on three dietary concentrations of DP and DE. Nutritional carrying capacity estimates that accounted for antinutritional compounds were reduced 50 ± 6%, 28 ± 8%, and 0 ± 0% (mean ± SE) for diets of high, medium, and low DE concentration, respectively, compared to estimates from models that ignored the effects of these compounds. Accounting for effects of plant secondary compounds reduced DP-derived carrying capacity estimates 4 ± 3%, 47 ± 9%, and 9 ± 8% for diets with high, medium, and low concentrations of DP, respectively. High variation in percent reduction in carrying capacity estimates occurred because of site and seasonal variation in plant species composition and biomass, making application of a single correction factor to account for plant secondary compound effects on carrying capacity infeasible. Protein-precipitating capacity of tannins accounted for > 98% of the reductions in carrying capacity estimates based on DP. Our results clearly demonstrate the need to consider effects of tannins on ungulate carrying capacity estimates based on DP and DE. Estimates can be further refined by accounting for nonprotein nitrogen and other antinutritional compounds in all forage items.

A modified in vitro larvae migration inhibition assay using rumen fluid to evaluate Haemonchus contortus viability

Anthelmintic effects of plant secondary compounds may be occurring in the rumen, but in vitro larvae migration inhibition (LMI) methods using rumen fluid and forage material have not been widely used. Forage material added to an in vitro system can affect rumen pH, ammonia N, and volatile fatty acids, which may affect larvae viability (LV). Validating a LMI assay using rumen fluid and a known anthelmintic drug (Ivermectin) and a known anthelmintic plant extract (Quebracho tannins; QT) is important. Rumen fluid was collected and pooled from 3 goats, mixed with buffer solution and a treatment (1 jar/treatment), and placed into an anaerobic incubator for 16h. Ensheathed larvae (<3 months old) were then anaerobically incubated with treatment rumen fluid for 2, 4, or 16h depending on the trial. Larvae (n=15–45) were then transferred onto a screen (n=4–6 wells/treatment) within a multi-screen 96-well plate that contained treatment rumen fluid. Larvae were incubated overnight and those that passed through the 20-μm screen were considered viable. Adding dry or fresh juniper material reduced (P<0.05) pH, ammonia N, and isobutyric, butyric, isovaleric, and valeric acids, and increased (P<0.001) acetic, propionic, and total VFA. Including 4.5% (w/v) polyethylene glycol (PEG) in rumen fluid mixture with or without forage material reduced (P<0.01) LV. However, LV was similar at all PEG concentrations tested (0–2%, w/v; 89.4, 78.9, 76.5, 75.5, and 77.5% viable). Q. tannin concentrations from 0 to 1.2% (w/v) quadratically reduced (P<0.001) LV; 89.4, 65.5, 22.8, and 9.2%. Ivermectin concentrations from 0 to 15μg/mL quadratically reduced (P<0.001) LV; 90.2, 82.6, 73.6, 66.3, 51.9, 56.5, 43.5, 41.9, 29.3, and 19.9% viable, respectively. Effects of altering in vitro rumen fluid pH, ammonia N, and VFA and using PEG when evaluating LV need to be further investigated. In vitro rumen fluid assays using QT and Ivermectin resulted in decreased LV, validating the efficacy of this technique for measuring Haemonchus contortus larval viability.

How do herbivores trade-off the positive and negative consequences of diet selection decisions?

Herbivory is central to ecosystem function, and herbivores, through diet selection, exert a major influence on vegetation composition with consequent effects for associated fauna and human livelihoods. Understanding diet selection behaviour is therefore important to allow effective prediction of herbivore impacts on vegetation under different scenarios. Herbivores learn about foods by associating them with the positive postingestive effects of nutrients and the negative postingestive effects of toxins. However, the extent to which trade-offs are made between positive and negative effects, occurring simultaneously, and how this trade-off might be altered by the underlying nutritional status of herbivores are unclear. We investigated these effects using 36 goats, Capra hircus , half of which were on a low nutritional regime and half were moderately well fed. We offered three conifer species to the goats, on 3 consecutive days per week for 3 weeks. While the goats were consuming the conifers, they received one of three levels of a positive nutritional stimulus, simulating nutritional rewards, and one of three levels of a negative stimulus, simulating the effects of plant secondary compounds. Goats preferred conifers paired with positive effects and avoided those paired with negative effects in a dose-dependent way. Underlying nutritional status did not influence the response to the positive and negative postingestive effects. We conclude that diet choice in response to learning about postingestive effects represents a simple integration of the positive and negative consequences of consuming particular plants and that this balance is not greatly influenced by minor differences in nutritional status.

Effects of terpenes and tannins on some physiological and biochemical parameters in two species of phalangerid possums (Marsupialia : Phalangeridae)

The common brushtail possum (Trichosurus vulpecula) and the short-eared possum (T. caninus) are closely related but differ in several aspects of their life-history strategy, habitat and diet preferences. Both are generalist herbivores, but T. vulpecula consumes significant amounts of Eucalyptus spp. foliage, while T. caninus instead feeds mainly on Acacia spp. Eucalypt foliage is protected against herbivory by several classes of plant secondary compounds, including terpenes and tannins, while acacia foliage is protected mainly by tannins. We compared the responses of these two possum species to the addition of either sesquiterpenes or a hydrolysable tannin to a basal diet free of these compounds. In both species, sesquiterpenes tended to reduce food intake, and increased plasma concentrations of albumin and decreased concentrations of bicarbonate, the latter consistent with changes in acid–base balance. Tannic acid significantly depressed food intake in both species, and depressed plasma concentrations of total protein, albumin, glucose, sodium and chloride, consistent with dehydration. T. vulpecula increased urinary glucuronic acid excretion three-fold in response to dietary sesquiterpenes but there was no increase in T. caninus. T. vulpecula had five- to six-fold greater plasma concentrations of bilirubin, a potent antioxidant, than did T. caninus across all treatments. Results suggest that T. vulpecula can better withstand the detrimental effects of plant secondary compounds, consistent with its wider spectrum of foods and broader habitat preferences.

Ingestion of juniper foliage reduces metabolic rates in woodrat (Neotoma) herbivores

Ingestion of plant secondary compounds by herbivores is predicted to increase resting or basal metabolic rates. We tested this hypothesis with two species of woodrat herbivores, Neotoma stephensi and Neotoma albigula, consuming diets of juniper (Juniperus monosperma), which is rich in plant secondary compounds. In nature, N. stephensi specializes on juniper, whereas N. albigula consumes a variety of plant species including juniper. We measured resting metabolic rates (RMR) of woodrats on control, 25% juniper and a treatment containing the maximum tolerable dose of juniper (50% juniper for N. albigula and 70% juniper for N. stephensi). Ingestion of a juniper diet resulted in decreased RMR in both species of woodrats. We propose several potential mechanisms for metabolic depression of Neotoma on juniper diets. Our novel results underscore the need for more studies utilizing plant-based diets to determine the general effect of plant secondary compounds on metabolic rates of herbivores.

Soil consumption by Elephants might help to minimize the toxic effects of plant secondary compounds in forest browse

Soil consumption by Elephants might help to minimize the toxic effects of plant secondary compounds in forest browse

Soil consumption by Elephants might help to minimize the toxic effects of plant secondary compounds in forest browse

Soil consumption by Elephants might help to minimize the toxic effects of plant secondary compounds in forest browse

Robert Frost's Arthropods

ARTHROPODS HAVEA SPECIAL PLACE IN THE poetry of Robert Frost (18741963). In Frost's world, commonplace things, especially natural ones, take on cosmic meanings. He uses stone walls, birch trees, brooks, snowy woods, forks in a road, and a diversity of animals to raise universal questions about life and the nature of time and space. Frost uses arthropods as vehicles for raising philosophical issues. With arthropods as central characters, he constructs little scenes or natural history vignettes with themes that, when listed, look like a sylla bus of general entomology-plantinsect interactions, biological control/predation, cryptic coloration, resource utilization, effects of plant secondary compounds, and instinct and learning among many others. Although several dozen poems mention arthropods, only 17 of Frost's 347 poems are focused on insects, mites, or spiders 1, This fact, in itself, does not recommend Frost as poet laureate of entomology. However, humor and richness of those poems, their accuracy of detail, their thought-provoking themes as well as affection and respect with which he treats arthropods all recommend this great American poet's works to anyone who loves insects and their kin. For those of us who have chosen to dedicate our lives to arthropods, it is reinforcing to see insects and their kin respectfully and lovingly depicted and interpreted by artists, photographers, and poets. In this vein, I long have found Frost's treatment of arthropods a rewarding and thought-provoking experience that grows richer every time Ire-read works that I discuss here.

The effect of rumen adaptation to oxalic acid on diet choice by goats grazing a spinach/cabbage matrix

Adaptation of large herbivores to secondary plant compounds found in their food plants may influence their food choice. Plants, which are potentially toxic, may initially be avoided by herbivores but, following sampling and adaptation of detoxification pathways, herbivores may be able to exploit certain toxic plants without detrimental effects. Thus, adaptation of the rumen microbial population can protect the host animal from the toxic effects of plant secondary compounds. Oxalic acid is a plant component found at high concentrations in a range of food plants, such as Beta vulgaris L, and Rumex spp., commonly consumed by ruminants. It is readily degraded in the rumen by Oxalobacter formigenes following a period of adaptation (Allison and Reddy, 1984).

Choice of mixed diets by herbivores: the idiosyncratic effects of plant secondary compounds

Abstract Experiments were conducted to determine whether an unspecialized herbivore (the laboratory mouse) was capable of improved performance and increased microsomal detoxification when presented with multiple rather than single toxic diets. Mice presented with diets containing caffeine or rauwolfia alkaloids did not increase food consumption following a period of depressed food intake. These mice did not exhibit increased rates of detoxification through time. Mice presented with tannic acid diets increased their food intake through time, although this was not based on enhanced rates of microsomal detoxification. Mice presented with a choice of caffeine and rauwolfia, caffeine and tannic acid or rauwolfia and tannic acid diets ate from both food sources. Quantities of each toxic food eaten were dependent on the choice presented. Mice presented with dietary choices failed to ingest more food per unit time than mice presented with one of the toxic diets. These mice also failed to exhibit detoxification based increases in ingestion through time. Patterns of diet choice and mixing of diets appeared to result from the mice attempting to minimize the negative effects of individual toxins. Even gross patterns of weight gain, rates of ingestion and costs of detoxification appear unpredictable in the absence of information specific to the particular herbivore and the idiosyncratic physiologies of individual toxins. Interactions among toxins may have required generalist herbivores to evolve tolerances to and detoxification mechanisms for, highly select combinations of plant secondary compounds. Evolution in response to plant defences may provide a basis for interpreting niche definition and community structure of herbivorous mammals.