Plant Defense Traits Research Articles

Indirect effect of earthworms on wheat-aphid interactions

Studies on interactions between plants and belowground organisms, or between plants and aboveground organisms, are numerous and highlight their importance in understanding ecosystem functioning. However, these two compartments are rarely studied together, despite the direct link formed by the plant itself. Soil organisms can influence interactions between plants and herbivores by changes in plant growth and chemistry. Under controlled conditions the influence of earthworms and aphids on wheat was investigated. The effect of earthworms on aphid reproduction was also investigated, to demonstrate the indirect plant-trait-mediated effects. We showed a significant effect of both above and belowground organisms on wheat. Interestingly, nitrogen content was higher in the presence of aphids (1.63 ± 0.07 %,) or earthworms alone (1.58 ± 0.04 %) and even higher in presence of both (2.07 ± 0.07 %). Moreover, we showed a strong effect of earthworms on aphid reproduction rates which are almost twice as high as in the absence of earthworms where we observed a reproduction rate of 32 individuals per day compared with 57 in the presence of earthworms. The presence of aphids led to a 16 % reduction in above-ground biomass compared with the control (1.83 ± 0.08 g vs 2.19 ± 0.09 g for the control), while the presence of earthworms led to an 46 % increase (3.20 ± 0.12 g vs 2.19 ± 0.09 g), and the presence of both organisms had no significant effect on the above-ground biomass of wheat compared with the control (2.39 ± 0.08 g vs 2.19 ± 0.09 g). These results could have implications for pest management, as they indicate that the presence of earthworms compensate the negative effect of aphids on plant biomass, probably by acting on nutrient uptake and plant defensive traits. By addressing the effects of earthworms on both the pest performances and plant traits, we highlight the need for further research on the indirect effects of below-ground compartments on pest performance. This study builds towards a better understanding of the interaction between soil, plant and pests and highlights the importance to study the pest management with a holistic view of agroecosystems.

The effect of drought‐induced leaf traits on Ficus leaf palatability is species specific

AbstractDrought has a significant impact on plant–insect interactions by altering plant survival, growth, leaf quality, and defense traits. Tropical plants are particularly vulnerable to water depression because of shallow root depth. In the context of climate change, drought events are expected to increase in frequency and intensity; however, their impact on tropical ecosystems remains poorly known. Insect herbivores represent the largest feeding guild of arthropods, and they devour four to five times more plant material than vertebrates do. Understanding how drought affects plant traits and leaf palatability in a keystone and ecologically diverse plant genus, such as Ficus (Moraceae), is crucial for predicting how climate change might alter tropical plant–insect interactions. We examined the impact of drought intensity and duration on the leaf nutritional quality, defensive traits, and herbivory damage by caterpillars in three tropical and one Mediterranean Ficus species in a greenhouse. We also conducted food choice trials with generalist caterpillars to evaluate the impact of drought on herbivores. Drought intensity and duration had no direct effect on leaf palatability across the Ficus species. However, drought indirectly affected leaf palatability via drought‐induced leaf traits in a species‐specific manner. Drought intensity and duration decreased leaf water content, resulting in decreased leaf palatability in F. benjamina and F. lyrata. Leaf defensive traits such as flavonoid concentration were affected by drought intensity and decreased leaf palatability in F. carica. Drought influenced the leaf traits of F. elastica, but none of them affected leaf palatability. Overall, this study establishes the link between drought and insect feeding on plants via leaf traits. The species‐specific responses to drought highlight the significance of climate‐related plant life histories in relation to climate change, underscoring the need for further investigations.

Evidence for Reductions in Physical and Chemical Plant Defense Traits in Island Flora.

Reduced defense against large herbivores has been suggested to be part of the "island syndrome" in plants. However, empirical evidence for this pattern is mixed. In this paper, we present two studies that compare putative physical and chemical defense traits from plants on the California Channel Islands and nearby mainland based on sampling of both field and common garden plants. In the first study, we focus on five pairs of woody shrubs from three island and three mainland locations and find evidence for increased leaf area, decreased marginal leaf spines, and decreased concentrations of cyanogenic glycosides in island plants. We observed similar increases in leaf area and decreases in defense traits when comparing island and mainland genotypes grown together in botanic gardens, suggesting that trait differences are not solely driven by abiotic differences between island and mainland sites. In the second study, we conducted a common garden experiment with a perennial herb-Stachys bullata (Lamiaceae)-collected from two island and four mainland locations. Compared to their mainland relatives, island genotypes show highly reduced glandular trichomes and a nearly 100-fold reduction in mono- and sesquiterpene compounds from leaf surfaces. Island genotypes also had significantly higher specific leaf area, somewhat lower rates of gas exchange, and greater aboveground biomass than mainland genotypes across two years of study, potentially reflecting a broader shift in growth habit. Together, our results provide evidence for reduced expression of putative defense traits in island plants, though these results may reflect adaptation to both biotic (i.e., the historical absence of large herbivores) and climatic conditions on islands.

Natural selection by pollinators on floral attractive and defensive traits did not translate into selection via fruits in common milkweed

Considering both pollinator and herbivore pressures on plant reproductive and defensive traits is key to understanding patterns of selection for plants. However, phenotypic selection studies connecting floral traits and plant defenses with pollinator activity and herbivore damage remain rare. We used the common milkweed, Asclepias syriaca (Apocynaceae), to study phenotypic selection on attractive and defensive traits, and nectar rewards. We measured herbivore (leaf damage) and pollinator activity (pollinia movement) and quantified selection via female (pollinia insertions and fruit number) and male fitness (pollinia removals). We found selection to increase plant and inflorescence size and to decrease floral size (i.e. petal width) via female fitness. We also detected selection to increase floral but not leaf latex. The lack of selection on leaf latex was congruent with the low herbivory observed, however we also did not observe florivory in the population that would explain the advantage of more floral latex. Interestingly, we found selection on attractive traits differed via pollinia insertions and fruits initiated, suggesting that something other than pollinators was driving selection via fruit production. In contrast to female fitness, we did not find selection on any trait through male fitness, suggesting no sexual conflicting selection, at least through these proxies. Our findings reinforce the importance of the direct assessment of pollinator pressures in phenotypic selection studies before assuming pollinators as drivers of floral evolution by natural selection. Further work in southern populations closer to the centre of the species range, where herbivory and plant defense investment are higher, may help elucidate selection on attractive and defensive traits.

The double life of trichomes: understanding their dual role in herbivory and herbicide resistance.

Understanding the evolutionary forces that maintain phenotypic variation in ecologically relevant traits has long been one of the central goals of evolutionary ecology. While the maintenance of variation in plant defense is most often hypothesized to be due to trait trade-offs or spatiotemporal variation in herbivore abundance, the role that heterogeneous selective agents may play on the maintenance of variation in plant defense is less examined. Trichomes are hair-like appendages on plant surfaces that can defend against multiple damaging agents such as pathogens, herbivores, and UV radiation. It is currently unknown however if conflicting selection from such heterogeneous agents of damage may act to maintain the variation observed in trichome traits. Here, we assess whether trichomes serve as an herbicide resistance trait and how it coincides with the conventionally studied defensive strategy of herbivory resistance. In a series of experiments, we exposed the annual invasive velvetleaf (Abutilon theophrasti) to glyphosate (active ingredient in "Roundup") to investigate whether trichome traits (type and density) are linked to herbicide resistance and to test whether herbicide influences selection on plant trichomes. We found that an increased proportion of branched trichomes positively impacted herbicide resistance and chewing herbivory resistance. We also found evidence that glyphosate imposes positive selection on branched trichomes in velvetleaf. Overall, our results indicate that branched trichomes can contribute to both herbicide and herbivory resistance, serving a concordant rather than conflicting role to reduce plant injury. Our findings further suggest that novel anthropogenic agents of selection can alter the composition of plant defense traits, potentially impacting trait-mediated interactions among external stressors.

Adaptation of an arthropod predator to a challenging environment is associated with a loss of a genome-wide plastic transcriptional response.

Structural and chemical plant defence traits may reduce the efficacy of biological control agents in integrated pest management. Breeding programmes have shown arthropod predators' potential to acclimate to challenging host plants. However, whether and how these predators adapt to novel plant environments remain unclear. Using the predatory mite Phytoseiulus persimilis - herbivorous mite Tetranychus urticae system in an experimental evolution setup, we studied the adaptation mechanisms to tomato and cucumber, plants that possess a distinct repertoire of defensive traits. Experimental evolution experiments on whole plants revealed that allowing P. persimilis to adapt to tomatoes led to an ~100% larger population size. Independent feeding assays showed that tomato- and cucumber-adapted prey reduced predator fecundity. The deleterious effect of ingesting low-quality prey persisted after adaptation of the predator to both cucumber and tomato. We demonstrated that jasmonic acid (JA)-dependent defences reduce prey quality by evaluating predator performance on prey fed on JA defence-deficient tomato plants. Transcriptomic profiling of the replicated P. persimilis lines showed that long-term propagation on tomato and cucumber plants produces distinctive gene-expression levels. Predator adaptation to tomatoes results in the loss of a large transcriptional response, in which predicted cuticle-building rather than detoxification pathways are affected. We showed that the adaptation of predatory arthropods to a novel, challenging plant does not necessarily occur via the prey, but rather through the physical environment of the plant. We provided first insights into the underlying molecular mechanisms. © 2023 Society of Chemical Industry.

Trade-offs among leaf toughness, constitutive chemical defense, and growth rates in oaks are influenced by the level of leaf mass per area

Key messageAmong the variety of leaf defensive strategies to counteract herbivory attacks, the oak species analyzed in this study maximize investment in no more than one, with high-LMA oaks developing very tough leaves and low-LMA oaks favoring between high concentrations of condensed tannins or high growth rates.ContextPlants develop a variety of defense strategies to counteract herbivory attacks, from physical and chemical defenses to tolerance strategies. Tradeoffs between strategies have been widely assessed from a resource allocation perspective, but there is a need to consider eventual interactions among them.AimWe evaluate the among-species tradeoff between three main constitutive plant defense traits, while considering the leaf mass per area ratio (LMA) as a proxy of leaf construction investment on area basis.MethodsLeaf toughness measured as work of fracture, condensed tannins, and relative growth rate (RGR) were analyzed in a set of 19 Quercus L. species with contrasting LMA.ResultsMost species had low values either in two or in the three traits analyzed. Moreover, the highest values of work of fracture appeared in the species with high LMA; the highest values of condensed tannins were found in the species with the lowest LMA; and high values of RGR were measured in species with intermediate or lower values of LMA.ConclusionOaks showed a trade-off among leaf defensive strategies influenced by LMA. Oaks with high LMA developed very tough leaves while oaks with low LMA presented lower values of toughness but favored between one of the two other strategies.

Preference and performance in an herbivorous coccinellid beetle: a comparative study of host plant defensive traits, insect preference, and survival

Preference and performance in an herbivorous coccinellid beetle: a comparative study of host plant defensive traits, insect preference, and survival

Plant defences as functional traits: A comparison across savannas differing in herbivore specialization

Abstract Top‐down and bottom‐up forces in tropical savannas have shaped the evolution of traits that enable plants to thrive in environments where soils are poor, dry seasons are long, fire is frequent, woody plants and grasses compete and herbivores range from cryptic caterpillars to elephants that topple entire trees. African savannas and the South American cerrado have similar climates and fire regimes, but differ in the presence of large mammal herbivores, which are mostly extinct in the cerrado. These biomes offer an instructive comparison to understand how plant defence traits evolved in response to differential herbivore pressure. Within Africa, mammalian herbivore pressure also differs across savannas, being lower in the miombo relative to more open, mixed savannas. The dominance of specialist insect herbivores in the cerrado, relative to the more generalist mammalian herbivores in Africa, suggests that defence traits will differ between savannas in accordance with herbivore identity and pressure. Wood is densest in mixed African savannas, as expected because large mammals often damage trees. Specific leaf area, related to palatability, is higher in mixed African savannas and the cerrado relative to the miombo, while leaf N is surprisingly higher in miombo species. Ant mutualists are important defences in mixed African savannas and the cerrado. Defensive chemistry has received less attention in the trait literature. Foliar phenolics, the most commonly studied chemical defences in savannas, vary in their efficacy. New analyses isolating specific compounds are informative as is the evaluation of phytochemical diversity as a defence. There are indications that phytochemical defences are more diverse in the cerrado, which may be related to greater specialization of cerrado herbivores. Synthesis. The dominance of specialist insect herbivores in the cerrado, relative to generalist mammalian herbivores in Africa, selected for different plant defence traits, contributing to the separation of species along the leaf economics spectrum and demonstrating the importance of plant defences as plant functional traits. African savanna species seem to follow a more acquisitive strategy, followed by miombo species. Cerrado species appear to follow a more conservative strategy with greater investments in tough leaves and chemical defences.

Ecosystem stability is determined by plant defence functional traits and population stability under mowing in a semi‐arid temperate steppe

Abstract As a common grassland management practice in many high‐latitude regions worldwide, mowing has great impacts on grassland functioning and stability. Species richness, species asynchrony and species stability have been suggested as central in responses to environmental change. Mowing can evoke plant defence system due to physical damages to plants. However, no studies have comprehensively evaluated the role of plant defence functional traits, species richness, species asynchrony and stability in ecosystem functioning under mowing regimes across timescales. In this study, we set up short‐term (4 years) and long‐term (16 years) mowing experiments with three stubble heights (control, 10 cm, 2 cm) in a temperate steppe of Inner Mongolia. We investigated the effects of mowing‐induced changes in distribution metrics associated with plant defence traits, that is mean, variance, skewness and kurtosis of trait distribution, on ecosystem stability of grassland communities using structural equation modelling. We found that grassland ecosystem stability was enhanced by increasing mowing duration and decreasing stubble height. Mowing‐induced increase in abundance and diversity of plant defence traits contributed to greater ecosystem stability by enhancing species asynchrony and population stability. Moreover, we found that mowing enhanced the abundance and diversity of plant defence traits of dominant species and contributed to population stability and species asynchrony, thus enhancing temporal stability of grassland ecosystems. These results demonstrate the important roles of plant defence traits in maintaining stability of grasslands under mowing, and highlight that, in addition to species richness, asynchrony and population stability, plant functional defence trait acts in stabilizing ecosystem functions under human‐induced environmental changes. Read the free Plain Language Summary for this article on the Journal blog.

Integrating defense and leaf economic spectrum traits in a tropical savanna plant.

Allocation to plant defense traits likely depends on resource supply, herbivory, and other plant functional traits such as the leaf economic spectrum (LES) traits. Yet, attempts to integrate defense and resource acquisitive traits remain elusive. We assessed intraspecific covariation between different defense and LES traits in a widely distributed tropical savanna herb, Solanum incanum, a unique model species for studying allocations to physical, chemical, and structural defenses to mammalian herbivory. We found that in a multivariate trait space, the structural defenses - lignin and cellulose - were positively related to the resource conservative traits - low SLA and low leaf N. Phenolic content, a chemical defense, was positively associated with resource acquisitive traits - high SLA and high leaf N - while also being associated with an independent third component axis. Both principal components 1 and 3 were not associated with resource supply and herbivory intensity. In contrast, spine density - a physical defense - was orthogonal to the LES axis and positively associated with soil P and herbivory intensity. These results suggest a hypothesized "pyramid" of trade-offs in allocation to defense along the LES and herbivory intensity axes. Therefore, future attempts to integrate defense traits with the broader plant functional trait framework, such as the LES, needs a multifaceted approach that accounts for unique influences of resource acquisitive traits and herbivory risk.

Landscape variation in defense traits along gradients of multiple resources in a tropical savanna plant

Many plant species are widely distributed and consequently are exposed to multiple abiotic factors and diverse herbivores, each of which may distinctly affect the magnitude of different defense traits. Alternative theories for optimal allocation to plant defense traits predict both positive and negative associations between magnitude of defense and resource availability. These predictions may apply even within species. This suggests potential for a single species' patterns of association of defense traits and resources to vary with both the type of defense and identity of resource, but relatively few studies have explored intraspecific variation in multiple defense traits along several resource gradients simultaneously. In order to address this gap, especially in an ecosytem dominated by large mammalian herbivores, we assessed relationships between multiple resources (rainfall, soil N, and soil P) and plant defense traits (prickle density, phenolics, and lignin content) using a widely distributed tropical savanna herb, Solanum incanum, growing in naturally occuring resource gradients within the Serengeti National Park. We found substantial intraspecific variation in all three defense traits across sites (n = 43). Variation in prickle density was positively associated with rainfall and soil P, but not soil N. In contrast to prickle density, phenolics and lignin were uncorrelated with all three resource gradients. This independent association of soil P with a carbon‐based defense, prickle density, suggests potential for resources that are not components of defenses to influence allocation to defense traits. Such influence may reflect association between resource and herbivore abundance and/or preference. These varied patterns in resource–defense associations further emphasize the tremendous variation in anti‐herbivore traits which may be influenced by different plant resources and highlight the need to consider multiple resource gradients in understanding evolution of plant traits.

Host filtering, not competitive exclusion, may be the main driver of arbuscular mycorrhizal fungal community assembly under high phosphorus

Abstract A major goal in ecology is understanding the factors which determine the diversity and distribution of organisms. The outcome of the symbiotic relationship between plants and arbuscular mycorrhizal (AM) fungi is strongly influenced by soil phosphorus (P) availability. Despite this knowledge, there is still much to uncover about how soil P status can shape the taxonomic and phylogenetic assembly of root‐colonising AM fungi. Additionally, there is a paucity of understanding about the implications of these changes for the outcome of the AM symbiosis in terms of plant growth, nutrient status and defence traits. We conducted a factorial pot experiment where sorghum (Sorghum bicolor) was grown under three different P treatments (low, medium and high), in the presence or absence of a natural AM fungal community. By analysing the diversity and community structure of the fungal community colonising roots, we aimed to determine if and how soil P influences the relatedness of these communities and whether competitive exclusion or environmental filtering play a more significant role in their assembly. Additionally, we evaluated the concomitant outcomes for plant growth, nutrient acquisition and defensive chemistry (phenolics). Increasing P availability reduced AM fungal richness and increased community evenness. Root‐colonising AM fungal communities under the high P treatment had significantly reduced phylogenetic diversity and comparatively lower mean pairwise distances among all treatments. This indicated that AM fungal communities became more closely related (phylogenetically clustered) with increasing soil P. The mycorrhizal growth and mycorrhizal P responses of plants were positive under low and medium P, but this was lost under high P, however, plant phenolics were increased. Our results suggest that under high P conditions, environmental filtering plays an important role in AM fungal community assembly as host plants alter their selectivity of fungal functional groups prioritising those associated with enhancing plant stress resistance and defences, rather than nutrient acquisition. Here we demonstrated how soil P status can shape taxonomic and phylogenetic assembly of AM fungi and the associated functional outcomes for the host. Read the free Plain Language Summary for this article on the Journal blog.

Variation in Leaf Functional and Plant Defense Traits of Introduced Eucalyptus Species across Environmental Gradients in Their New Range in Southern China

Due to the rapid development of China’s economy, the demand for wood is steadily increasing. Eucalyptus species have been introduced in large quantities because of their fast growth, strong adaptability, and wide utility. To understand the phenological changes in introduced Eucalyptus in its new range, we carried out a field investigation to examine leaf functional and chemical defense traits of three introduced species (E. saligna, E. grandis and E. robusta) over latitudinal and altitudinal gradients in southern China. We sampled multiple stands of each species, and measured the leaf physical characteristics (e.g., leaf width, leaf thickness, and specific leaf area [SLA]), leaf nitrogen (N) and phosphorus (P) content, and phenolic compounds. We found that many functional traits (e.g., leaf size and thickness) decreased at lower latitudes, especially in E. grandis, possibly to reduce heat and water loss under higher temperatures. In E. grandis, we found that leaf P was lower at higher latitudes and altitude, and phenolics increased with elevation, while in E. robusta, both leaf N and P decreased with altitude. These findings suggested that both species were more conservative in resource allocation, with E. grandis possessing enhanced chemical defenses in response to the conditions experienced at higher elevations. In addition, we found the tree populations at the northern range limit of E. robusta had lower SLA, suggesting a more conservative growth strategy, In contrast, small populations in the northern part of the ranges of E. grandis had higher SLA, indicating range expansion at the edge of the species’ geographic distribution. Overall, it is particularly important to consider intraspecific trait differences across wide geographic areas when studying the spread of invasive species in the new range.

Experimental warming increases the vulnerability of high‐elevation plant populations to a specialist herbivore

Abstract Ongoing climate change may impact alpine plant populations via both direct effects of increased temperature and climate‐driven changes in interactions between plants and other organisms, such as insect herbivores. Rates of herbivory in high‐elevation environments are predicted to increase with warmer temperatures, which may also lead to changes in morphological and physiological traits that influence plant resistance. Yet, we currently know little about how temperature‐mediated changes in traits will impact alpine plant vulnerability to herbivores, as well as the extent to which populations from high‐elevation environments might need to rapidly adapt to increasing herbivore pressure with rising temperatures. We assessed the effect of experimental warming on the relative vulnerability of populations of the alpine plant Arabis alpina from different elevations to a specialist herbivore. Herbivore performance was measured on plants from nine populations grown in climate chambers at two temperatures, representing low (warm) and high (cold) elevations. We also measured changes in putative drivers of performance: plant phenological, chemical and defence traits. Assuming populations would be adapted to local climates and levels of herbivory, we predicted that low‐elevation populations would be more resistant to herbivores under warmer temperatures than high‐elevation populations. We found reduced performance of a specialist herbivore on A. alpina grown under warm rather than cold conditions, though this effect varied with elevation. Larvae grew faster on high‐elevation populations than low‐elevation populations when grown under warm temperatures, whereas similar growth rates were observed for plants grown under colder temperatures, consistent with plant adaptation to the lower existing herbivore pressure in cold, high‐elevation environments. Regression analyses suggested that polar metabolite variation explained more variance in larval performance than changes in defensive glucosinolates or morphological traits. Our results suggest that although physiological responses to warming may increase the resistance of cold‐adapted plants to herbivory, populations from different elevations may differ in their interactions with herbivores under climate warming. Without genetic adaptation, existing physiological responses of high‐elevation populations to warmer temperatures may leave these populations vulnerable to the increases in herbivore pressure predicted under climate change. Read the free Plain Language Summary for this article on the Journal blog.

Plant defence traits among discrete vegetation assemblages in a mesic savanna landscape in Kenya

Abstract A trade-off between structural and chemical defences against herbivory in woody plants is alleged to depend on edaphic factors in African savannas. We studied anti-herbivory traits, in an edaphic mosaic of fertile and infertile soils within a savanna landscape in East Africa, towards elucidating herbivory defence traits expressions in woody plants of African savannas. We used data of 81 plants for 8 species from 8 sites — four sites from fertile soils (42 plants) and another four sites from infertile soils (39 plants). We did not find a general divide between structural and chemical strategies in our data. Instead, we found a range of defence traits combinations. Our results highlight that in woody plants of African savannas, chemical and structural defences can augment each other, and not necessarily trade-off. The diversity of herbivores, ranging from insects to mesobrowsers, may have driven the evolution of multiple defence strategies within the African savannas.

Field Experiments on Common Milkweed Support Hypothesized Synergies Between Plant Defense Traits

Field Experiments on Common Milkweed Support Hypothesized Synergies Between Plant Defense Traits

Plant defense synergies and antagonisms affect performance of specialist herbivores of common milkweed.

As a general rule, plants defend against herbivores with multiple traits. The defense synergy hypothesis posits that some traits are more effective when co-expressed with others compared to their independent efficacy. However, this hypothesis has rarely been tested outside of phytochemical mixtures, and seldom under field conditions. We tested for synergies between multiple defense traits of common milkweed (Asclepias syriaca) by assaying the performance of two specialist chewing herbivores on plants in natural populations. We employed regression and a novel application of random forests to identify synergies and antagonisms between defense traits. We found the first direct empirical evidence for two previously hypothesized defense synergies in milkweed (latex by secondary metabolites, latex by trichomes) and identified numerous other potential synergies and antagonisms. Our strongest evidence for a defense synergy was between leaf mass per area and low nitrogen content; given that these "leaf economic" traits typically covary in milkweed, a defense synergy could reinforce their co-expression. We report that each of the plant defense traits showed context-dependent effects on herbivores, and increased trait expression could well be beneficial to herbivores for some ranges of observed expression. The novel methods and findings presented here complement more mechanistic approaches to the study of plant defense diversity and provide some of the best evidence to date that multiple classes of plant defense synergize in their impact on insects. Plant defense synergies against highly specialized herbivores, as shown here, are consistent with ongoing reciprocal evolution between these antagonists.

Seed priming with Calcium oxide nanoparticles improves germination, biomass, antioxidant defence and yield traits of canola plants under drought stress

• Seed priming with calcium oxide nanoparticles have remediating effects of drought in canola plants. • Seed priming with calcium oxide nanoparticles improves germination parameters of canola plants exposed to drought stress. • Seed priming with calcium oxide nanoparticles improves the growth and antioxidant defence of canola plants under drought. • •Seed priming with calcium oxide nanoparticles improves performance of canola in terms of yield attributes. Recent advances in calcium signalling have proved that calcium plays a key role in mitigating abiotic stresses and strengthening the internal defence of plants. In the present research, calcium was imparted through seed nano-priming with calcium oxide nanoparticles (CaONPs) at concentrations of 25, 50, 75, and 100 ppm compared to control (0 ppm) under PEG-induced drought in the canola plants. During the germination experiment, seedlings were given drought conditions simulated by PEG-6000 treatment maintaining water potential at -0.15 MPa and pH of 5.5 supplemented with Hoagland solution at room temperature. As a control, no PEG-6000 was given. After the germination experiment, a pot experiment was conducted under artificial climate chambers. Seed nano-priming with 75 ppm CaONPs improved germination percentage and seedling fresh weight by 30% and 34% respectively under drought stress. Seed nano-priming with 75 ppm CaONPs increased the number of leaves by 16%, total chlorophyll contents by 28.9%, improved the number of pods per branch, number of seeds per pod, 100 seed weights, and yield by 29.99%, 73.076%, 35.13%, and 35.18% respectively under drought stress. Furthermore, the levels of antioxidant enzymes were improved and levels of stress indicators declined significantly. Present research recommends the use of CaONPs as pre-sowing treatments to the seed to improve the performance of canola plants.

Climate and the biotic community structure plant resistance across biogeographic groups of yellow monkeyflower.

Characterizing correlates of phytochemical resistance trait variation across a landscape can provide insight into the ecological factors that have shaped the evolution of resistance arsenals. Using field-collected data and a greenhouse common garden experiment, we assessed the relative influences of abiotic and biotic drivers of genetic-based defense trait variation across 41 yellow monkeyflower populations from western and eastern North America and the United Kingdom. Populations experience different climates, herbivore communities, and neighboring vegetative communities, and have distinct phytochemical resistance arsenals. Similarities in climate as well as herbivore and vegetative communities decline with increasing physical distance separating populations, and phytochemical resistance arsenal composition shows a similarly decreasing trend. Of the abiotic and biotic factors examined, temperature and the neighboring vegetation community had the strongest relative effects on resistance arsenal differentiation, whereas herbivore community composition and precipitation have relatively small effects. Rather than simply controlling for geographic proximity, we jointly assessed the relative strengths of both geographic and ecological variables on phytochemical arsenal compositional dissimilarity. Overall, our results illustrate how abiotic conditions and biotic interactions shape plant defense traits in natural populations.