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Defence Compounds (defence + compound)
Selected AbstractsInfluence of atmospheric carbon dioxide enrichment on induced response and growth compensation after herbivore damage in Lotus corniculatusECOLOGICAL ENTOMOLOGY, Issue 3 2002Alain Bazin Abstract 1. Plant growth and chemical defence compounds in four Lotus corniculatus genotypes exposed to factorial combinations of ambient and elevated carbon dioxide, and herbivory by caterpillars of Polyommatus icarus were measured to test the predictions of the carbon/nutrient balance hypothesis. 2. Shoot and root biomass, allocation to shoots versus roots, and carbon-based defence compounds were greater under elevated carbon dioxide. Pupal weight of P. icarus was greater and development time shorter under elevated carbon dioxide. 3. Herbivory decreased shoot growth relative to root growth and production of nitrogen-based defence (cyanide). Young leaves contained more defence compounds than old leaves, and this response depended on carbon dioxide and herbivory treatments (significant interactions). 4. Genotype-specific responses of plants to carbon dioxide and herbivory were found for the production of cyanide. Furthermore, maternal butterfly-specific responses of caterpillars to carbon dioxide were found for development time. This suggests the existence of genetic variation for important defence and life-history traits in plants and herbivores in response to rising carbon dioxide levels. [source] Nitrogen fertilization effects on Myzus persicae aphid dynamics on peach: vegetative growth allocation or chemical defence?ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2010Marie-Hélène Sauge Abstract Plant nitrogen (N) fertilization is a common cropping practice that is expected to serve as a pest management tool. Its effects on the dynamics of the aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) were examined on young peach [Prunus persica (L.) Batsch (Rosaceae)] trees grown under five N treatments, ranging from N shortage to supra-optimal supply for growth. Aphid population increased over time at the three intermediate N levels. It remained stable at the lowest N level and decreased at the highest N level. Four weeks after the start of infestation, the number of aphids displayed a parabolic response to N level. The relationships between N status and parameters of plant vegetative growth (stem diameter) or biomass allocation (lateral-total leaf area and root-shoot ratio) were consistent with responses proposed by models of adaptive plasticity in resource allocation patterns. However, the variation in plant growth predicted aphid population dynamics only partially. Whereas aphid number was positively correlated with plant N status and vegetative growth up to the intermediate N level, it was negatively correlated with plant N status above this level, but not with vegetative growth. The concentrations of primary and secondary (plant defence-related) metabolites in the plant shoots were modified by N treatments: amino acids (main nutritional resource of aphids) and prunasin increased, whereas chlorogenic acid decreased with increasing N availability. Constitutive changes in plant chemistry in response to N fertilization could not directly explain the reduced aphid performance for the highest N level. Nevertheless, the indirect effect of N on the induction of plant defence compounds by aphid feeding warrants further investigation. The study focuses on the feasibility of handling N fertilization to control M. persicae in orchards, but findings may also be relevant for our understanding of the physiological relationships between the host's nutritional status and the requirements of the insect. [source] Foraging by fearful frugivores: combined effect of fruit ripening and predation riskFUNCTIONAL ECOLOGY, Issue 6 2006J. M. FEDRIANI Summary 1Plant defensive compounds and predation risk are main determinants of herbivore foraging, though empirical studies have seldom measured the combined effects of these two factors. By considering the interaction between the herb Helleborus foetidus and its main fruit and seed predator, the Wood Mouse Apodemus sylvaticus, we evaluated whether the defensive role against seed predators of compounds present in H. foetidus unripe fruits holds across a micro-landscape that differs in foraging costs (i.e. predation risk). 2First, we used standardized food patches that simulated fruiting H. foetidus plants to ascertain fruit preferences of captive mice. Then, by means of field experiments, we assessed the combined effects of fruit ripening and predation risk on foraging by free-ranging mice. 3Captive mice avoided plants with unripe fruit and avoided consuming unripe fruits within a particular plant. Free-ranging mice also avoided unripe fruits in safe microhabitats (rocky substrate), but not in risky microhabitats (bare ground) where few fruits were consumed. This unexpected result may be driven by predation risk experienced by mice foraging on H. foetidus fruits, and/or plant defensive compounds acting in a dose-dependent manner. 4Frugivorous mice responded to both chemical defences present in unripe H. foetidus fruits as well as to predation cost though such response was sequential. Plant defence compounds appeared to play a part in mouse foraging only after mice selected low predation risk microhabitats. 5Our study indicates that both digestive and ecological factors influence foraging decisions, which in turn affects pressures exerted by herbivores on plant populations. [source] Trade-offs between the shade-avoidance response and plant resistance to herbivores?FUNCTIONAL ECOLOGY, Issue 6 2005Tests with mutant Cucumis sativus Summary 1Plants exhibit adaptations to many stresses, including light competition and herbivory. The expression of these traits may interact negatively, potentially instigating a trade-off. 2We employed a combination of genetically altered Cucumis sativus varieties and phenotypic manipulations to test for trade-offs in field experiments. The different genetic lines of C. sativus were altered in their phytochrome-mediated shade responses and the production of terpenoid defence compounds. 3Cucumber plants constitutively expressing the shade-avoidance response had 93% more herbivory by specialist beetles compared with wild types. The long-hypocotyl mutants also produced leaves with fewer trichomes, greater toughness and a higher carbon to nitrogen ratio (C : N) than wild types. Plants lacking defensive cucurbitacins had 23% longer internodes than the cucurbitacin-producing line. 4We then manipulated the plant phenotype by artificially imposing neighbours' shade on plants with and without cucurbitacins. As expected, plants responded to shade by growing longer hypocotyls and first internodes, but few trade-offs were found between plant line and shade treatment and, although herbivory levels were very low, there was a trend towards reduced damage on shaded plants. 5The use of genetically altered plant lines provided strong evidence for the trade-off hypothesis, while phenotypic manipulations did not support the hypothesis. [source] Intraclonal variation in defence substances and palatability: a study on Carex and lemmingsOIKOS, Issue 3 2004Kari Anne Bråthen Clonal sedges consist of integrated ramets at different development stages. Many of these sedges are important food for herbivores, yet differences in herbivore preferences and defence allocation between ramet development stages have not previously been evaluated. In this study we investigated intraclonal ramet variation in level of plant defence and nutrient compounds and intraclonal ramet preferences by lemmings (Lemmus trimucronatus) in field samples of a rhizomatous sedge (Carex stans). Plant defence was measured as the level of proteinase inhibitor activity (PIA) and the ratio of PIA to soluble plant proteins (SPP), whereas plant nutrients were measured as the level of soluble plant sugars (SPS) and SPP. Flowering ramets generally had a higher content of defence compared to vegetative ramets, which is consistent with the optimal defence theory predicting that defence compounds are allocated to the ramet stage of the highest fitness value. Compared to vegetative ramets, the flowering ramets had a lower content of SPP and a higher content of SPS. The lemmings showed preference differences between the ramet development stages, and to a large extent the ramet content of defence compounds and nutrient compounds covaried with these preferences in the predicted way. This study shows that defence allocation between ramet development stages of the clonal sedge Carex conforms to predictions of the optimal defence theory. [source] Northern Environment Predisposes Birches to Ozone DamagePLANT BIOLOGY, Issue 2 2007E. Oksanen Abstract: Ozone sensitivity of silver birch (Betula pendula Roth) has been thoroughly investigated since early 1990,s in Finland. In our long-term open-field experiments the annual percentage reduction in basal diameter and stem volume increment were the best non-destructive growth indicators for ozone impact when plotted against AOTX. Remarkable differences in defence strategies, stomatal conductance, and defence compounds (phenolics), clearly indicate that external exposure indices are ineffective for accurate risk assessment for birch. For flux-based approaches, site-specific values for gmax and gdark are necessary, and determinants for detoxification capacity, ageing of leaves, and cumulative ozone impact would be needed for further model development. Increasing CO2 seems to counteract negative ozone responses in birch, whereas exposure to springtime frost may seriously exacerbate ozone damage in northern conditions. Therefore, we need to proceed towards incorporating the most important climate change factors in any attempts for ozone risk assessment. [source] Silicon: its manifold roles in plantsANNALS OF APPLIED BIOLOGY, Issue 2 2009E. Epstein Abstract The title of this essay declares that silicon does have roles in plants and all participants in this conference know that that is so. This knowledge, however, is not shared by the general community of plant biologists, who largely ignore the element. This baffling contrast is based on two sets of experience. First, higher plants can grow to maturity in nutrient solutions formulated without silicon. That has led to the conventional wisdom that silicon is not an essential element, or nutrient, and thus can be disregarded. Second, the world's plants do not grow in the benign environment of solution culture in plant biological research establishments. They grow in the field, under conditions that are often anything but benign. It is there, in the real world with its manifold stressful features, that the silicon status of plants can make a huge difference in their performance. The stresses that silicon alleviates range all the way from biotic, including diseases and pests, to abiotic such as gravity and metal toxicities. Silicon performs its functions in two ways: by the polymerization of silicic acid leading to the formation of solid amorphous, hydrated silica, and by being instrumental in the formation of organic defence compounds through alteration of gene expression. The silicon nutrition of plants is not only scientifically intriguing but also important in a world where more food will have to be wrung from a finite area of land, for that will put crops under stress. [source] | ||||||||||||||||||||||