Plant Nutritional Quality Research Articles

Climatic changes and the fate of mountain herbivores

Mountains are strongly seasonal habitats, which require special adaptations in wildlife species living on them. Population dynamics of mountain ungulates are largely determined by the availability of rich food resources to sustain lactation and weaning during summer. Increases of temperature affect plant phenology and nutritional quality. Cold-adapted plants occurring at lower elevations will shift to higher ones, if available. We predicted what could happen to populations of mountain ungulates based on how climate change could alter the distribution pattern and quality of high-elevation vegetation, using the “clover community-Apennine chamois Rupicapra pyrenaica ornata” system. From 1970 to 2014, increasing spring temperatures (2 °C) in our study area led to an earlier (25 days) onset of green-up in Alpine grasslands between 1700 and 2000 m, but not higher up. For 1970–2070, we have projected trends of juvenile winter survival of chamois, by simulating trajectories of spring temperatures and occurrence of clover, through models depicting four different scenarios. All scenarios have suggested a decline of Apennine chamois in its historical core range, during the next 50 years, from about 28% to near-extinction at about 95%. The negative consequences of climate changes presently occurring at lower elevations will shift to higher ones in the future. Their effects will vary with the species-specific ecological and behavioural flexibility of mountain ungulates, as well as with availability of climate refugia. However, global shifts in distributional ranges and local decreases or extinctions should be expected, calling for farsighted measures of adaptive management of mountain-dwelling herbivores.

Exploring context dependency in eco-evolutionary patterns with the stick insect Timema cristinae.

Rapid evolution can influence the ecology of populations, communities, and ecosystems, but the importance of evolution for ecological dynamics remains unclear, largely because the contexts in which evolution is powerful are poorly resolved. Here, we carry out a large observational study to test hypotheses about context dependency of eco‐evolutionary patterns previously identified on the stick insect Timema cristinae. Experiments and observations conducted in 2011 and 2012 documented predator‐mediated negative effects of camouflage maladaptation (i.e., evolutionary dynamics) on: (a) T. cristinae abundance and, (b) species richness and abundance of other arthropods. Here we show that camouflage maladaptation does not correlate with T. cristinae abundance and, instead, is associated with increased abundance and species richness of cohabitating arthropods. We furthermore find that plants with high levels of Timema maladaptation tend to have higher foliar nitrogen, that is, higher nutritional value, and more positive mass‐abundance slopes in the coexisting arthropod communities. We propose explanations for the observed contrasting results, such as negative density‐ and frequency‐dependent selection, feedbacks between herbivore abundance and plant nutritional quality, and common effects of predation pressure on selection and prey abundance. Our results demonstrate the utility of observational studies to assess the context dependency of eco‐evolutionary dynamics patterns and provide testable hypotheses for future work.

Shades of green: untying the knots of green photoperception.

The development of economical LED technology has enabled the application of different light qualities and quantities to control plant growth. Although we have a comprehensive understanding of plants' perception of red and blue light, the lack of a dedicated green light sensor has frustrated our utilization of intermediate wavelengths, with many contradictory reports in the literature. We discuss the contribution of red and blue photoreceptors to green light perception and highlight how green light can be used to improve crop quality. Importantly, our meta-analysis demonstrates that green light perception should instead be considered as a combination of distinct 'green' and 'yellow' light-induced responses. This distinction will enable clearer interpretation of plants' behaviour in response to green light as we seek to optimize plant growth and nutritional quality in horticultural contexts.

The phytotoxic air-pollutant O3 enhances the emission of herbivore-induced volatile organic compounds (VOCs) and affects the susceptibility of black mustard plants to pest attack

Stress-induced changes to plant biochemistry and physiology can influence plant nutritional quality and subsequent interactions with herbivorous pests. However, the effects of stress combinations are unpredictable and differ to the effects of individual stressors. Here we studied the effects of exposure to the phytotoxic air-pollutant ozone (O3), feeding by larvae of the large cabbage white butterfly (Pieris brassicae), and a combination of the two stresses, on the emission of volatile organic compounds (VOCs) by black mustard plants (Brassica nigra) under field and laboratory conditions. Field-grown B. nigra plants were also measured for carbon-nitrogen (C–N) content, net photosynthetic activity (Pn), stomatal conductance (gs) and biomass. The effects of O3 on interactions between plants and a herbivorous pest were addressed by monitoring the abundance of wild diamondback moth larvae (Plutella xylostella) and feeding-damage to B. nigra plants in an O3-free air concentration enrichment (O3-FACE) field site. Herbivore-feeding induced the emission of VOCs that were not emitted by undamaged plants, both under field and laboratory conditions. The combination of O3 and herbivore-feeding stresses resulted in enhanced emission rates of several VOCs from field-grown plants. Short-term O3 exposure (of 10 days) and P. brassicae-feeding did not affect C–N content, but chronic O3 exposure (of 34 and 47 days) and P. brassicae-feeding exacerbated suppression of Pn. Ozone exposure also caused visible injury and decreased the plant biomass. Field-grown B. nigra under elevated O3 were infested with fewer P. xylostella larvae and received significantly less feeding damage. Our results suggest that plants growing in a moderately polluted environment may be of reduced quality and less attractive to foraging herbivores.

Growth and Essential Carotenoid Micronutrients in Lemna gibba as a Function of Growth Light Intensity.

Duckweed is a promising food crop with multiple benefits for space applications. Fresh duckweed could deliver synergistically acting essential antioxidant nutrients to a crew – but only if growth conditions provide the plant with the right cues to trigger antioxidant formation. We grew Lemna gibba under continuous growth light ranging from low to very high intensities (photosynthetic photon flux densities = PPFDs) in order to investigate the effect on plant growth, photosynthesis, and level of carotenoid antioxidants that are essential human micronutrients. Lemna gibba achieved remarkably high growth rates under modest growth PPFD by virtue of superior light absorption resulting from minimal self-shading and high chlorophyll levels. Conversely, L. gibba’s growth rate remained high even under very high growth PPFDs. This notable ability of L. gibba to avoid inactivation of photosynthesis and diminished growth under very high growth PPFDs resulted from a combination of downregulation of chlorophyll synthesis and increased biochemical photoprotection that limited a build-up of excessive excitation energy. This biochemical photoprotection included accumulation of zeaxanthin (an essential human micronutrient) and high levels of zeaxanthin-catalyzed thermal energy dissipation of excess excitation. Compared to the light levels needed to saturate L. gibba photosynthesis and growth, higher light levels were thus required for strong induction of the essential antioxidant zeaxanthin. These results indicate a need for design of light protocols that achieve simultaneous optimization of plant yield, nutritional quality, and light-use efficiency to circumvent the fact that the light requirement to saturate plant growth is lower than that for production of high zeaxanthin levels. How this trade-off between light-use efficiency of growth and nutritional quality might be minimized or circumvented to co-optimize all desired features is discussed.

Plant resistance does not compromise parasitoid-based biocontrol of a strawberry pest

Plant nutritional quality can influence interactions between herbivores and their parasitoids. While most previous work has focused on a limited set of secondary plant metabolites, the tri-trophic effects of overall phenotypic resistance have been understudied. Furthermore, the joint effects of secondary and primary metabolites on parasitoids are almost unexplored. In this study, we compared the performance and survival of the parasitoid species Asecodes parviclava Thompson on wild woodland strawberry (Fragaria vesca L.) genotypes showing variation in resistance against the parasitoid’s host, the strawberry leaf beetle (Galerucella tenella L.). Additionally, we related the metabolic profiles of these plant genotypes to the tritrophic outcomes in order to identify primary and secondary metabolites involved in regulating plant potential to facilitate parasitism. We found that parasitoid performance was strongly affected by plant genotype, but those differences in plant resistance to the herbivore were not reflected in parasitoid survival. These findings could be explained in particular by a significant link between parasitoid survival and foliar carbohydrate levels, which appeared to be the most important compounds for parasitism success. The fact that plant quality strongly affects parasitism should be further explored and utilized in plant breeding programs for a synergistic application in sustainable pest management.

Olive fruit volatiles route intraspecific interactions and chemotaxis in Bactrocera oleae (Rossi) (Diptera: Tephritidae) females

Plant nutritional quality and chemical characteristics may affect the fitness of phytophagous insects. Here, the olfactory preferences of Bactrocera oleae (Rossi) females toward olives with different maturation and infestation status were evaluated in three cultivars: Ottobratica, Roggianella and Sinopolese. Volatile profiles from olives were identified by SPME/GC-MS. Choice tests were performed to determine the responses of B. oleae adult females toward fruits and pure chemicals linked to infestation degree. Cultivar was the main source of variability explaining the differences recorded in volatile emissions. Moreover, three VOCs [β-myrcene, limonene and (E)-β-ocimene] were associated to infestation status across all olive varieties. In choice-tests, B. oleae females always preferred the olfactory cues from low-infested over high-infested fruits. Therefore, choice-tests using synthetic VOCs, emitted in greater amount by high-infested fruit, were arranged in order to identify putative B. oleae kairomones. While females were indifferent to β-myrcene, the highest dosages of limonene and (E)-β-ocimene were unfavoured by the tested flies, which preferentially moved toward the empty arm of the Y-tube. Furthermore, females preferred the lowest concentration of β-ocimene compared to the highest one. These results supported our hypothesis that fruit VOCs may serve as kairomones for female flies.

Plant nutrient supply alters the magnitude of indirect interactions between insect herbivores: From foliar chemistry to community dynamics

Abstract Density‐ and trait‐mediated indirect interactions (DMIIs and TMIIs respectively) are important drivers of community dynamics but how plant nutrients (bottom‐up effects) affect the magnitude of such indirect interactions has been scarcely addressed. To assess the impact of bottom‐up forces on indirect interactions, we carried out laboratory and greenhouse experiments manipulating plant nutrient supplies in a four‐species diamond food web consisting of a plant (tomato), two phytophagous insects (a leafminer and an aphid) and a predator (a mirid bug) attacking both herbivores. Multiple negative indirect effects of the leafminer occurred towards the aphid. The presence of its eggs negatively affected aphid population growth through increased predator abundance (DMIIs), and larval herbivory slowed down aphid development and negatively modulated aphid behaviours, for example they spent less time feeding (TMIIs), likely owing to enhanced plant chemical defences and/or decreased plant nutritional quality. Moreover, the low plant nutrient supply further magnified TMIIs. Synthesis. Abiotic factors modulated predator‐ and plant‐mediated indirect interactions among herbivorous community members. Our study highlights the importance of using a holistic approach, from foliar chemistry to community dynamics, for disentangling interspecific interactions in a simple food web.

Rewilding with large herbivores: Positive direct and delayed effects of carrion on plant and arthropod communities.

Carrion of large animals is an extremely nutrient rich, ephemeral resource that is essential for many species, but is scarce in the anthropogenic Western-European landscape due to legislative restrictions. Rewilding, a novel conservation strategy that aims at restoring natural processes with minimal human intervention, is increasing in popularity and could lead to increased carrion availability in the landscape. It is therefore important to understand the effects of carrion on biodiversity. We investigated the direct and delayed (five months) effects of red deer (Cervus elaphus) carcasses on plants and arthropods in the Oostvaardersplassen, the Netherlands, one of the oldest rewilding sites in Europe. Specifically, we tested whether carrion has a positive direct effect on the abundances and diversity of various arthropod functional groups, as well as a delayed effect on the vegetation and arthropods through the increased nutrient availability. During the active decomposition stage in spring, we, not surprisingly, observed higher abundances of carrion associated species (scavengers and their specialized predators) at the carrion sites than at control sites without carrion, but no higher abundances of predators or detritivores. In late summer, after near-complete decomposition, plant biomass was five times higher, and nutritional plant quality (C:N ratio) was higher at the carrion sites than at the control sites. Arthropod abundance and diversity were also manifold higher, owing to higher numbers of herbivorous and predatory species. Regression analysis showed that abundances of herbivores and detritivores were positively related to plant biomass, and predator abundances were positively related to abundances of herbivores and detritivores, suggesting bottom-up effects propagating through the food chain. Our results show that even in a naturally nutrient-rich ecosystem like the Oostvaardersplassen, carrion can have strong positive effects on local plant biomass and nutritional quality and arthropod abundances, lasting the whole growing season. We found evidence that these effects were first directly caused by the presence of carrion, and later by the enhanced nutrient availability in the soil. This highlights the importance of the indirect pathways by which carrion can structure arthropod communities.

Nitrogen fertilizer promotes the rice pest Nilaparvata lugens via impaired natural enemy, Anagrus flaveolus, performance

The application of nitrogen (N) fertilizers to agricultural crops is a common practice globally and a crucial component in the current levels of productivity. Excessive N use, however, is costly and damaging to ecosystems. It is recognized that overuse of N fertilizer can promote pest herbivores by enhancing host plant nutritional quality, but less is known of the effects of N on natural enemies of pests via improved quality and availability of prey, and how these may cascade to indirect effects on pests. Here, we explored the effects of N fertilizer on a key egg parasitiod of Nilaparvata lugens (Stal) (Hemiptera: Delphacidae) (brown planthopper, BPH). Application of N to rice plants significantly prolonged the development time of Anagrus flaveolus (Hymenoptera: Mymaridae), increased wing size and decreased fecundity of adult females. Importantly, N application to rice plants significantly decreased the per capita parasitism of BPH eggs by A. flaveolus. Utilizing planthopper prey on N-treated rice plants led to reduced searching efficiency of A. flaveolus. Ultimately, the strength of biological control exerted by A. flaveolus was negatively affected by nitrogen application under field conditions. Parasitoids were able to discriminate between BPH infested rice plants with different levels of nitrogen using visual plant cues. We conclude that N fertilizer use can have profound effects on natural enemy efficiency which potentially increase the dependence on insecticides, another potentially hazardous input.

Identification of functional single nucleotide polymorphism of Populus trichocarpa PtrEPSP-TF and determination of its transcriptional effect.

In plants, the phenylpropanoid pathway is responsible for the synthesis of a diverse array of secondary metabolites that include lignin monomers, flavonoids, and coumarins, many of which are essential for plant structure, biomass recalcitrance, stress defense, and nutritional quality. Our previous studies have demonstrated that Populus trichocarpa PtrEPSP‐TF, an isoform of 5‐enolpyruvylshikimate 3‐phosphate (EPSP) synthase, has transcriptional activity and regulates phenylpropanoid biosynthesis in Populus. In this study, we report the identification of single nucleotide polymorphism (SNP) of PtrEPSP‐TF that defines its functionality. Populus natural variants carrying this SNP were shown to have reduced lignin content. Here, we demonstrated that the SNP‐induced substitution of 142nd amino acid (PtrEPSP‐TFD142E) dramatically impairs the DNA‐binding and transcriptional activity of PtrEPSP‐TF. When introduced to a monocot species rice (Oryza sativa) in which an EPSP synthase isoform with the DNA‐binding helix‐turn‐helix (HTH) motif is absent, the PtrEPSP‐TF, but not PtrEPSP‐TFD142E, activated genes in the phenylpropanoid pathway. More importantly, heterologous expression of PtrEPSP‐TF uncovered five new transcriptional regulators of phenylpropanoid biosynthesis in rice. Collectively, this study identifies the key amino acid required for PtrEPSP‐TF functionality and provides a strategy to uncover new transcriptional regulators in phenylpropanoid biosynthesis.

Potential of pistachio shell biochar and dicalcium phosphate combination to reduce Pb speciation in spinach, improved soil enzymatic activities, plant nutritional quality, and antioxidant defense system.

Lead-contaminated soils are becoming an ecological risk to the environment because of producing low-quality food which is directly causing critical health issues in humans and animals. We hypothesized that incorporation of dicalcium phosphate (DCP), eggshell powder (ESP) and biochar (BH) at diverse rates into a Pb-affected soil can proficiently immobilize Pb and decline its bioavailability to spinach (Spinacia oleracea L.). A soil was artificially spiked with Pb concentration (at 600mgkg-1) and further amended with DCP, ESP, and BH (as sole treatments at 2% and in concoctions at 1% each) for immobilization of Pb in the soil. The interlinked effects of applied treatments on Pb concentrations in shoots and roots, biomass, antioxidants, biochemistry, and nutrition of spinach were also investigated. Results depicted that the highest reduction in DTPA-extractable Pb and the concentrations of Pb in shoots and roots was achieved in DCP1%+BH1% treatment that was up to 58%, 66%, and 53%, respectively over control. Likewise, the DCP1%+BH1% treatment also showed the maximum shoot and root dry weight (DW), chlorophyll-a (Chl-a) and chlorophyll-b (Chl-b) contents and relative water content (RWC) in spinach up to 92%, 121%, 60%, 65%, and 30%, respectively, compared to control. Likewise, DCP1%+BH1% treatment noticeably improved antioxidant enzymes, biochemistry, and nutrition in the leaves. Moreover, the DCP1%+BH1% treatment depicted mostly enhanced activities of dehydrogenase, catalase, acid phosphatase, alkaline phosphatase, phosphomonoesterase, urease, protease and B-glucosidase in the post-harvested soil up to 118%, 345%, 55%, 92%, 288%, 107%, 53% and 252%, respectively over control.

Potential application of titanium dioxide nanoparticles to improve the nutritional quality of coriander (Coriandrum sativum L.)

TiO2 nanoparticles (nTiO2) have been widely used in many disciplines. However, whether they can be used to improve crops growth and nutritional quality is unknown. In this study, coriander (Coriandrum sativum L.) was treated with 0, 50, 100, 200, and 400 mg/L nTiO2 to evaluate their possible benefit to plant growth and nutritional quality under hydroponic conditions. Our observations showed that 50 mg/L nTiO2 only slightly but insignificantly increased the root and shoot fresh biomass by 13.2 % and 4.1 %, respectively, relative to the control. nTiO2 at this level promoted shoot K, Ca, Mg, Fe, Mn, Zn, and B accumulation, while spatial distribution of K, Ca, Fe, Mn, Cu and Zn in coriander leaves was not affected. No nTiO2 internalization or translocation to shoots occurred. 400 mg/L nTiO2 significantly reduced root fresh biomass by 15.8 % and water content by 6.7 %. Moreover, this high dose induced root cell membrane wrinkling, attributable to their aggregation and adsorption on root surfaces. At 100–400 mg/L, antioxidant defense systems (SOD, CAT and APX) in plant were triggered to alleviate oxidative stress. At an appropriate dose (50 mg/L), nTiO2 can improve nutrient quality of edible tissues without exerting toxicity to plant or posing health risk to consumers.

Potassium Fertilization for Fresh Market Potato Production in Tropical Soils

Potassium (K) is the most taken up and removed nutrient by potato (Solanum tuberosum L.), and has a great influence on tuber yield and quality. This study was performed to evaluate the effects of three rates (100, 200, and 400 kg K2O ha−1) and two timings of application of K (single application at planting furrow and split application of 50% at planting furrow plus 50% at hilling), as potassium chloride, as well as a control (without K application) on the plant nutrition and tuber yield and quality of potato ‘Agata’ grown in tropical clay soils. The split application of K fertilizer had little influence on plant nutrition and tuber yield and quality. The influence of K fertilization on increasing K and reducing Ca and Mg concentrations in the leaf was more significant in soil with low exchangeable K. In this soil, the maximum tuber yield (33.6 Mg ha−1; 107% higher than the control) was obtained with an estimated rate of 325 kg K2O ha−1, while in the soils with medium and high exchangeable K, the tuber yield was increased between 22 and 34% and only up to a rate of 200 kg K2O ha−1. The critical leaf K concentration to reach 95% of the maximum yield was 29.3 g K kg−1, but there was an extreme increase in the tuber yield even with K rates that provided leaf K concentrations above this limit. Potassium fertilization increased the firmness and reduced soluble solids and protein in tubers.Core Ideas K is the nutrient that is most taken up and removed by the potato crop. In clay soils, the splitting of K fertilization has little influence on potato tuber yield and quality. K fertilization increases tuber yield more, and up to higher rates in soil with low K concentration. K fertilization increases the tuber firmness, but reduces the soluble solids and protein concentration.

Microwave pretreatment of tomato seeds and fruit to enhance plant photosynthesis, nutritive quality and shelf life of fruit

The present study was undertaken to explore the effect of non-thermal microwave pretreatment of tomato seeds and fruit to enhance plant photosynthesis; nutritive value and shelf-life of fruit. The tomato fruit of two varieties i.e. NS-585 and NS-2535 were collected from the plants grown from control and single microwave dosed (9.3 GHz) seeds. The fruit collected from single dosed condition were again irradiated and further analyzed for various parameters. Cardinal points were calculated to assess the photosynthetic activity at the fruiting stage in plants of both the cultivars and were found to increase in plants raised from irradiated seeds in comparison to the control plants. The exposure of tomato fruit with double dosed microwave radiation showed high lycopene content, total protein content, phenolic and flavonoid content in unripe, ripe and overripe stages of both varieties. The activity of cell-wall degrading enzymes such as polygalacturonase, pectinmethylesterase and β-galactosidase decreased in doubled dosed microwave irradiated fruit of both varieties as compared with the other. The gene expression analysis of ACC synthase and ACC oxidase showed reduction in the enzyme activity in double dosed microwave irradiated tomato fruit. We conclude that post-harvest microwave exposure can be applied to increase the shelf-life of tomato fruit.

Spectral characterization of wheat functional trait responses to Hessian fly: Mechanisms for trait-based resistance.

Insect herbivores can manipulate host plants to inhibit defenses. Insects that induce plant galls are excellent examples of these interactions. The Hessian fly (HF, Mayetiola destructor) is a destructive pest of wheat (Triticum spp.) that occurs in nearly all wheat producing globally. Under compatible interactions (i.e., successful HF establishment), HF larvae alter host tissue physiology and morphology for their benefit, manifesting as the development of plant nutritive tissue that feeds the larva and ceases plant cell division and elongation. Under incompatible interactions (i.e., unsuccessful HF establishment), plants respond to larval feeding by killing the larva, permitting normal plant development. We used reflectance spectroscopy to characterize whole-plant functional trait responses during both compatible and incompatible interactions and related these findings with morphological and gene expression observations from earlier studies. Spectral models successfully characterized wheat foliar traits, with mean goodness of fit statistics of 0.84, 0.85, 0.94, and 0.69 and percent root mean square errors of 22, 10, 6, and 20%, respectively, for nitrogen and carbon concentrations, leaf mass per area, and total phenolic content. We found that larvae capable of generating compatible interactions successfully manipulated host plant chemical and morphological composition to create a more hospitable environment. Incompatible interactions resulted in lower host plant nutritional quality, thicker leaves, and higher phenolic levels. Spectral measurements successfully characterized wheat responses to compatible and incompatible interactions, providing an excellent example of the utility of Spectral phenotyping in quantifying responses of specific plant functional traits associated with insect resistance.

Altered leaf elemental composition with climate change is linked to reductions in photosynthesis, growth and survival in a semi‐arid shrubland

Abstract Climate change will increase heat and drought stress in many dryland areas, which could reduce soil nutrient availability for plants and aggravate nutrient limitation of primary productivity. Any negative impacts of climate change on foliar nutrient contents would be expected to negatively affect the photosynthetic capacity, water use efficiency and overall fitness of dryland vegetation. We conducted a 4‐year manipulative experiment using open top chambers and rainout shelters to assess the impacts of warming (~2°C, W), rainfall reduction (~30%, RR) and their combination (W + RR) on the nutrient status and ecophysiological performance of six native shrub species of contrasting phylogeny in a semi‐arid ecosystem. Leaf nutrient status and gas exchange were assessed yearly, whereas biomass production and survival were measured at the end of the study. Warming (W and W + RR) advanced shoot growth phenology and reduced foliar macro‐ (N, P, K) and micronutrient (Cu, Fe, Zn) concentrations (by 8%–18% and 14%–56% respectively), net photosynthetic rate (32%), above‐ground biomass production (28%–39%) and survival (23%–46%). Decreased photosynthesis and growth in W and W + RR plants were primarily linked to enhanced nutritional constraints on carbon fixation. Poor leaf nutrient status in W and W + RR plants partly decoupled carbon assimilation from water flux and led to drastic reductions in water use efficiency (WUEi; ~41%) across species. The RR treatment moderately decreased foliar macro‐ and micronutrients (6%–17%, except for Zn) and biomass production (22%). The interactive impacts of warming and rainfall reduction (W + RR treatment) on plant performance were generally smaller than expected from additive single‐factor effects. Synthesis. Large decreases in plant nutrient pool size and productivity combined with increased mortality during hotter droughts will reduce vegetation cover and nutrient retention capacity, thereby disrupting biogeochemical processes and accelerating dryland degradation with impending climate change. Increased macro‐ and micronutrient co‐limitation of photosynthesis with forecasted climate change conditions may offset any gains in WUEi and productivity derived from anthropogenic CO2 elevation, thereby increasing dryland vegetation vulnerability to drought stress in a warmer and drier climate. The generalized reduction in leaf nutrient contents with warming compromises plant nutritional quality for herbivores, with potential cascading negative effects across trophic levels.

Interspecific plant competition mediates the metabolic and ecological signature of a plant–herbivore interaction under warming and elevated CO2

Abstract Biotic interactions shape community evolution, but we lack mechanistic insights on how metabolic and ecological processes under climate change are altered by biotic interactions. We used a two‐trophic model community consisting of the aphid Dysaphis plantaginea feeding on the forb Plantago lanceolata, and a grass competitor Lolium perenne that does not experience herbivory by the aphid. Monocultures and mixtures were exposed to the herbivory treatment and to three relevant simulated environmental changes as prevalent under current climate change (increased temperature, CO2, and increased temperature and CO2) Elevated CO2 reduced the nitrogen content of P. lanceolata, while simultaneous increases of CO2 and temperature modified the plant metabolic component and the magnitude of these responses in different directions. Elevated CO2 enhanced defence systems in P. lanceolata, but these effects were not altered by warming. Interspecific plant competition did, however, neutralize these responses. There were no indirect effects of climate change on aphid population growth despite changes in plant defence, nutritional quality and biomass induced by our environmental change scenarios. We thus demonstrate interactions between abiotic and biotic processes on plant metabolite profiles, but more importantly, that climate change effects on a selection of the metabolic pathways are altered by herbivory and competition. Our experiment under semi‐natural conditions thus demonstrates the non‐additive and often neutralizing effects of biotic interactions on plant metabolism and species performance under climate‐associated environmental change. A free Plain Language Summary can be found within the Supporting Information of this article.

Vineyard Soil Microbiome Composition Related to Rotundone Concentration in Australian Cool Climate 'Peppery' Shiraz Grapes.

Soil microbial communities have an integral association with plants and play an important role in shaping plant nutrition, health, crop productivity and product quality. The influence of bacteria and fungi on wine fermentation is well known. However, little is known about the role of soil microbes, other than microbial pathogens, on grape composition or their role in vintage or site (terroir) impacts on grape composition. In this study, we used an amplicon sequencing approach to investigate the potential relationships between soil microbes and inherent spatial variation in grape metabolite composition – specifically, the concentration of the ‘impact aroma compound’ rotundone in Shiraz grapes (Vitis vinifera L.) grown in a 6.1 ha vineyard in the Grampians region of Victoria, Australia. Previous work had demonstrated temporal stability in patterns of within-vineyard spatial variation in rotundone concentration, enabling identification of defined ‘zones’ of inherently ‘low’ or ‘high’ concentration of this grape metabolite. 16S rRNA and ITS region-amplicon sequencing analysis of microbial communities in the surface soils collected from these zones indicated marked differences between zones in the genetic diversity and composition of the soil bacterial and fungal microbiome. Soils in the High rotundone zone exhibited higher diversity of bacteria, but lower diversity of fungi, compared to the soils in the Low rotundone zone. In addition, the network analysis of the microbial community in the High rotundone zone soils appeared well structured, especially with respect to the bacterial community, compared to that in the Low rotundone zone soils. The key differences in the microbial community structure between the rotundone zones are obvious for taxa/groups of both bacteria and fungi, particularly for bacteria belonging to Acidobacteria-GP4 and GP7, Rhizobiales, Gaiellaceae, Alphaproteobacteria and the Nectriaceae and Tremellaceae families of fungi. Although mulching in some parts of the vineyard caused changes in bacterial and fungal composition and overall microbial catabolic diversity and activity, its effects did not mask the rotundone zone-based variation. This finding of a systematic rotundone zone-based variation in soil microbiomes suggests an opportunity to bring together understanding of microbial ecology, plant biochemistry, and viticultural management for improved management of grape metabolism, composition and wine flavor.

Plant fertilization helps plants to compensate for aphid damage, positively affects predator efficiency and improves canola yield

Fertilizers utilization does not only play an important role in increasing the crop yield, but also they may influence the plant nutritional quality, thereby it affects the ecological interactions between herbivores and their natural enemies. In a field study, the effect of nitrogen fertilization (0, 75, 150 and 225 kg N ha−1) on population of mustard aphid, Lipaphis erysimi Kalt. (Hemiptera: Aphididae) and predatory gall midge, Aphidoletes aphidimyza (Diptera: Cecidomyiidae), in canola (Brassica napus L.), as well as their interactive impact on the plant yield was investigated. The population of aphid and predator were positively affected by nitrogen fertilization; the maximum abundances of which were observed in plants with 150 and 225 kg N ha−1 applied. However, predator to prey ratio was lower in the highest N level in comparison with the moderate level. The maximum suppression of the aphid by the predator was also observed in the moderate N level. The interactive effect of nitrogen fertilizing and the predator presence positively influenced the canola grain yield. The lowest yield losses due to aphid infestation were observed in plants fertilized with 150 kg N ha−1 in the presence of the predator. In this fertilization level, the plants could compensate the aphid damage more than the other treatment levels; hence, they produced significantly more grain yield. These findings indicate that adequate plant nutrition can help plants compensate for aphid damage and also positively affect the predator efficiency, leading to an improvement in the canola yield.