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• Attack from natural enemies on plants may be reduced in metal contaminated sites. • Plants may elevate defenses to simultaneously deal with enemies and metal stress. • Herbivory was lower in a copper mine than adjacent site in four of seven plant species. • Mine site plants had more physical and chemical defenses than adjacent site plants. • Hyperaccumulator species showed relatively few increased defenses in the mine. Heavy metal pollution in soil can impact the relationships between plants and their natural enemies. Enemy attack from herbivores and pathogens is predicted to be lower in metal-contaminated areas such as mine sites. However, whether this is the case is remains to be tested. It is also unknown how defense traits differ in polluted sites compared to adjacent sites. To address this gap in knowledge, we compared the standing leaf damage in populations of two invasive and five native plant species at the abandoned Jiuhua copper mine and an adjacent site. We also compared physical and chemical defense traits of the populations. Herbivory on four plant species was significantly lower in a copper mine than in an adjacent site. Overall, plants growing in the mine were more physically and chemically defended than plants growing adjacent to the mine. Copper hyperaccumulator species (Cynodon dactylon and Kummerowia stipulacea) increased defense levels in the mine for only one of the traits. In contrast, defenses were higher in the mine site for most traits relative to their respective adjacent populations in the non-hyperaccumulator species. Our results suggest that the damage herbivores inflict on plants may be strongly influenced by how plants respond to stressors in mine site environments, such as metal pollution. Metal hyperaccumulation and increased non-elemental defenses may be alternate responses used by plants to simultaneously deal with metal pollution and natural enemies in contaminated sites. [ABSTRACT FROM AUTHOR]

Objective: By using effective factors in the design of safe structures, it is possible to create a suitable level of protection for Nahaja fighter planes in the environment of future battles; in such a way that they are hidden and safe from detection and damage sensors and advanced weapons of the enemy. Therefore, in this research, the factors affecting the design of the safe structures of Nahaja fighter planes have been identified and explained with the approach of physical defense.Method: The type of applied-developmental research is a descriptive-case study method with a mixed approach. The statistical population of the study included all experts and experts of the military apparatus who are familiar with the topics of passive defense. Using purposive sampling method, 30 people were selected as the sample. Data collection tools included interviews, questionnaires, and standard documents whose validity was confirmed by content validity and their reliability by Cronbach's alpha.Findings: Based on the data analysis, the most influential components of the independent variable are location; Related to territorial planning with an average of 4/533 and a variance of 0/315, and the lowest impact related to technical and engineering factors with an average of 4/1 and a variance of 0.83, the highest impact of independent variable components of architectural principles and techniques related to interior architecture design with an average of 47 4.4 and variance 0.38 and the lowest effect related to multi-purpose use with an average of 3.13 and variance 1.18, the highest effect of the component in the field of using electrical facilities with an average of 4.43 and variance 0.57 and the lowest effect related to using the fire alarm system with a mean of 4.33 and a variance of 0.56.Conclusion: Failure to observe the factors affecting the design of safe structures of Nahaja fighter jets with the physical defense approach, in addition to the vulnerability of these places during the threat, leads to irreparable damage.

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. [ABSTRACT FROM AUTHOR]

Egg batches of Spodoptera moths are protected by scales deposited by females around and/or over eggs as a physical defense. These scales may affect the parasitism of some parasitoids, rendering biocontrol of Spodoptera eggs ineffective. In this study, we investigated the daily oviposition pattern of moths and the dynamics of egg mass scales of three Spodoptera species and examined the fitnesses of three potential egg parasitoid species to different egg mass scale thicknesses. The observations revealed that the three Spodoptera species share similar scale dynamics. From initial oviposition, S. exigua egg batches maintained a relatively high level of scale thickness (> 134.7 μm) for 2 days and S. frugiperda and S. litura for 3 days (> 105.9 μm, > 161.2 μm, respectively). During this period, the scales effectively hindered parasitism by Trichogramma species (parasitized 0.4%–14.9% eggs). Thereafter, the thickness of the scales decreased daily. The scales of the three Spodoptera species were all relatively thin (< 20.0 μm) after oviposition for 8 days, and subsequently, Trichogramma parasitized eggs more actively (parasitized up to 33.4%–36.5% eggs). Relatively, Trichogramma dendrolimi on S. frugiperda eggs, and Trichogramma chilonis on S. exigua eggs had higher parasitism. Meanwhile, Telenomus remus maintained a very stable and better performance than Trichogramma on Spodoptera species eggs with different scale thicknesses (parasitized 100% egg masses and 46.2%–60.0% eggs), which demonstrated its excellent potential as a Spodoptera species biocontrol agent. The findings elucidate the effect of egg mass scale thickness on effective parasitism by these egg parasitoid species and provide baseline information for the mixed use of Te. remus and Trichogramma against Spodoptera species. [ABSTRACT FROM AUTHOR]

Introduction: 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. Methods: 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. Results: 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. Discussion: 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. [ABSTRACT FROM AUTHOR]

Soil bacteria that associate with plant roots promote host vigor. Legume plants form mutualisms with rhizobial bacteria, and legumes grown with rhizobia have more nutrients and defenses than those grown without rhizobia. However, few studies have tested how stressors such as herbivores affect soil rhizobia, and the mechanisms mediating these interactions. Here we tested reciprocal interactions between a chewing herbivore, Sitona lineatus (pea leaf weevil), and Pisum sativum (pea) plants grown with or without rhizobia (Rhizobium leguminosarum biovar. viciae), and the plant-defense and nutritional mechanisms mediating these interactions. We hypothesized that plants grown with rhizobia would have less feeding from S. lineatus due to greater expression of phytohormones or physical defenses. We also predicted that herbivory might impede the mutualism between P. sativum and rhizobia. Our experiments showed that leaf defoliation by S. lineatus was indeed lowest on plants with rhizobia. Plants grown with rhizobia had increased gene transcript expression associated with hormone-related defense (jasmonic acid, ethylene, abscisic acid) as well as physical and antioxidant-related defense, which may explain reduced feeding by S. lineatus. Conversely, S. lineatus feeding reduced the number of root nodules and nodule fresh weight, suggesting a disruption of the symbiosis between plants and rhizobia. Our study shows that aboveground herbivores can engage in mutually antagonistic interactions with soil microbes that are mediated through multiple plant-mediated pathways.

IntroductionAllocation 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.MethodsWe 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.ResultsWe 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.DiscussionThese 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.

Nahaja, as an equipment-oriented force, needs centers of gravity and Resistant and safe infrastructure in order to be at the highest level of combat readiness to respond to any threat.The main purpose of the research is to develop physical defense strategies in Nahaja and answer the raised research questions using a mixed method and case study. The total statistical population is 65 people, of whom twenty people were known as experts of the community. Data collection was by field method using interview with experts, questionnaire and library method, and the reliability of the questionnaire, Cronbach's alpha, was 0.889. To do so, expertise approach was run to extract the environmental factors namely strengths, weaknesses, threats and opportunities. Drawing upon the David method, following that, the environmental internal and external factors were separated, and the effective variables and cyrrent status were determined Accordingly, based on the determined IFE and EFE, the current status compared to the desired one was defined, and by forming a SWOT matrix, physical defense strategies in Nahaja were developed. Ultimately, using the QSPM matrix and consideirng the priorities, "upgarding the physical quality through the development of local capacities using intelligent and integrative technical knowledge management with the aim of reducing the physical vulnerability of Nahaja" with a value of 7.90 was rated first.

Many grasses (Poaceae) defend their basal meristems with silicified trichomes, prickles, and spines. These leaf features are often unidirectional, pointing from the leaf base to the tip. They have been hypothesized to direct small herbivores away from vulnerable meristems, making grasses tolerant of the loss of leaf tissue. The aim of this study was to determine whether leaves of rice (Oryza sativa L.) and broomsedge (Andropogon virginicus L.) with silicified non‐glandular trichomes and prickles experience more chewing damage to leaf tips than to leaf bases, and whether the unidirectional leaf features were responsible for this pattern. Rice and A. virginicus leaves received 4× and 3× more chewing damage, respectively, to tips than middle sections, and 3× and 8× more damage to middle sections compared to basal sections. Removing trichomes and prickles from half of each leaf did not increase the overall frequency of damage to those leaves. However, removing silicified structures caused herbivores to increase the frequency of damage to leaf sections without trichomes and prickles, including basal leaf sections. Leaves of A. virginicus were experimentally folded in half such that the middle section was above the tip and basal sections; folded leaves received more damage to tips and bases than to middle sections. This indicates that herbivores do not choose to feed on the tallest leaf tissue but are likely influenced by the orientation of the silicified leaf features. Previous studies have shown variation in silicified structures on the leaves of many crop species. As these structures are involved in directing herbivores away from basal meristems, they should be considered as targets for crop breeding. [ABSTRACT FROM AUTHOR]

• Aboveground herbivores often engage in indirect interactions with soil microbes. • Soil rhizobia and chewing herbivores engaged in mutually-antagonistic interactions. • Rhizobia protected plants by inducing defenses and increasing nutritional quality. • Manipulation of soil microbes could aid in sustainable pest management. Soil bacteria that associate with plant roots promote host vigor. Legume plants form mutualisms with rhizobial bacteria, and legumes grown with rhizobia have more nutrients and defenses than those grown without rhizobia. However, few studies have tested how stressors such as herbivores affect soil rhizobia, and the mechanisms mediating these interactions. Here we tested reciprocal interactions between a chewing herbivore, Sitona lineatus (pea leaf weevil), and Pisum sativum (pea) plants grown with or without rhizobia (Rhizobium leguminosarum biovar. viciae) , and the plant-defense and nutritional mechanisms mediating these interactions. We hypothesized that plants grown with rhizobia would have less feeding from S. lineatus due to greater expression of phytohormones or physical defenses. We also predicted that herbivory might impede the mutualism between P. sativum and rhizobia. Our experiments showed that leaf defoliation by S. lineatus was indeed lowest on plants with rhizobia. Plants grown with rhizobia had increased gene transcript expression associated with hormone-related defense (jasmonic acid, ethylene, abscisic acid) as well as physical and antioxidant-related defense, which may explain reduced feeding by S. lineatus. Conversely, S. lineatus feeding reduced the number of root nodules and nodule fresh weight, suggesting a disruption of the symbiosis between plants and rhizobia. Our study shows that aboveground herbivores can engage in mutually antagonistic interactions with soil microbes that are mediated through multiple plant-mediated pathways. [ABSTRACT FROM AUTHOR]

The fall armyworm (FAW) Spodoptera frugiperda (Smith) is a major agricultural pest in Americas, Africa and Asia. Egg masses are covered with scale layers and the various scale layer thicknesses of these masses can affect parasitoids efficiency. The present study aimed to determine dynamics of the scale thickness on egg masses and its effect on Trichogramma parasitoid performance. The scale thickness ranged from 0μm to 400 μm and can be graded in three levels. Level I was the naked egg masses without or covered with a thin scale, and the thickness was below 80 μm. Level II was medium covered, with scales where 20%–80% eggs could be seen; the thickness was between 80 μm to 180 μm. Level III was fully-covered with scales and the thickness was above 180 μm (up to 400 μm). The egg mass scale thickness decreased with increasing age of egg laying FAW females; the proportion at level I increased during female aging, while proportion of levels II and III decreased during oviposition period. During FAW female lifetime, the level I showed the highest proportion (51.9%) while the level III showed the lowest (9.9%). The parasitism rate of FAW eggs by Trichogramma dendrolimi varied according to scale thickness, with higher parasitism on eggs and egg masses at level I (31.6%, 78.3%, respectively) and lowest parasitism on level III (eggs: 1.9%; egg masses: 23.1%). We documented factors modulating parasitism effectiveness on FAW and we suggested that timely parasitoid releases targeting egg masses at Level I scale thickness could enable maximizing biocontrol service provided by Trichogramma on FAW. [ABSTRACT FROM AUTHOR]

Nitrogen(N) is considered the most important factor to help the growth and development of plants. This is the building block for plant protoplasm and the chlorophyll molecule component for the photosynthesis process as well. Although it is apparent that the availability of N affects disease, the underlying mechanisms remain unknown. Many data indicate that the greater use of N fertilizers affected crop disease incidence. In comparison, cases are also recorded in which a decrease in N fertilization increases the severity of the disease, suggesting a complex relationship between them. N plays a significant role in regulating signaling networks that are active in reacting to a broad variety of biotic and abiotic stresses. In terms of physical, biochemical, and molecular mechanisms, the relationship between N and plant defense is considered. N has negative effects on physical defenses and the development of anti-microbial phytoalexins, but positive effects on defense-related enzymes and proteins that influence both local defense and systemic resistance. These all factors are implicated in plant defense signaling pathways but their role in plant defense is less well studied. This review aims to explain current knowledge of pathways connecting plant N status with the plant disease severity and plant defense. While this analysis highlights the crucial role of N nutrition in plant defense, further research is desperately required to provide a thorough overview of how interacting networks affect competing virulence and defense mechanisms. [Fundam Appl Agric 2020; 5(3.000): 303-314]

Several experimental studies on aquatic plants have reported the prevalence of chemical defense mechanism against herbivory, as opposed to structural, life-forms or other traits. Here, our laboratory feeding experiments and integrative analysis explored the relationship among palatability (fresh or reconstituted plants used as artificial diet) and various chemical/nutritional traits (i.e., contents of dry mass, ash, nitrogen, protein, and phenols) of diverse aquatic plants and their susceptibility to consumption by the generalist gastropod Biomphalaria glabrata. Biomphalaria glabrata consumed all of the assayed aquatic plants in a hierarchical yet generalized way, with the consumption of fresh plants, their reconstituted forms and defensive properties of lipophilic extracts not being significantly correlated with plant physical or chemical traits to determine the feeding preference of the gastropod. Our results do not reveal a prevalence for a specific plant attribute contributing to herbivory. Instead, they indicate that the susceptibility of aquatic plants to generalist consumers is probably related to a combination of their chemical and physical properties, resulting in moderate grazing rates by generalist consumers. [ABSTRACT FROM AUTHOR]

Several experimental studies on aquatic plants have reported the prevalence of chemical defense mechanism against herbivory, as opposed to structural, life-forms or other traits. Here, our laboratory feeding experiments and integrative analysis explored the relationship among palatability (fresh or reconstituted plants used as artificial diet) and various chemical/nutritional traits (i.e., contents of dry mass, ash, nitrogen, protein, and phenols) of diverse aquatic plants and their susceptibility to consumption by the generalist gastropod Biomphalaria glabrata. Biomphalaria glabrata consumed all of the assayed aquatic plants in a hierarchical yet generalized way, with the consumption of fresh plants, their reconstituted forms and defensive properties of lipophilic extracts not being significantly correlated with plant physical or chemical traits to determine the feeding preference of the gastropod. Our results do not reveal a prevalence for a specific plant attribute contributing to herbivory. Instead, they indicate that the susceptibility of aquatic plants to generalist consumers is probably related to a combination of their chemical and physical properties, resulting in moderate grazing rates by generalist consumers.

Plants deploy an arsenal of chemical and physical defenses against arthropod herbivores, but it may be most cost efficient to produce these only when attacked. Herbivory activates complex signaling pathways involving several phytohormones, including jasmonic acid (JA), which regulate production of defensive compounds. The Poaceae also have the capacity to take up large amounts of silicon (Si), which accumulates in plant tissues. Si accumulation has antiherbivore properties, but it is poorly understood how Si defenses relate to defense hormone signaling. Here we show that Si enrichment causes the model grass Brachypodium distachyon to show lower levels of JA induction when attacked by chewing herbivores. Triggering this hormone even at lower concentrations, however, prompts Si uptake and physical defenses (e.g., leaf hairs), which negatively impact chewing herbivores. Removal of leaf hairs restored performance. Crucially, activation of such Si‐based defense is herbivore‐specific and occurred only in response to chewing and not fluid‐feeding (aphid) herbivores. This aligned with our meta‐analysis of 88 studies that showed Si defenses were more effective against chewing herbivores than fluid feeders. Our results suggest integration between herbivore defenses in a model Si‐accumulating plant, which potentially allows it to avoid unnecessary activation of other costly defenses. [ABSTRACT FROM AUTHOR]

Recent research shows that earthworms can alter defense traits of plants against herbivores and pathogens by affecting soil biochemistry. Yet, the effects of invasive earthworms on defense traits of native plants from previously earthworm‐free ecosystems as well as the consequences for multitrophic interactions are virtually unknown.Here we use a combination of an observational study and a complementary experimental study to investigate the effects of invasive earthworms on leaf defense traits, herbivore damage and pathogen infection in two poplar tree species (Populus balsamifera and Populus tremuloides) native to North American boreal forests.Our observational study showed that earthworm invasion was associated with enhanced leaf herbivory (by leaf‐chewing insects) in saplings of both tree species. However, we only detected significant shifts in the concentration of chemical defense compounds in response to earthworm invasion for P. balsamifera. Specifically, leaf phenolic concentrations, including salicinoids and catechin, were lower in P. balsamifera from earthworm‐invaded sites.Our experimental study confirmed an earthworm‐induced reduction in leaf defense levels in P. balsamifera for one of the defense compounds, tremulacin. The experimental study additionally showed that invasive earthworms reduced leaf dry matter content, potentially increasing leaf palatability, and enhanced susceptibility of trees to infection by a fungal pathogen, but not to aphid infestation, in the same tree species.Synthesis. Our results show that invasive earthworms can decrease the concentrations of some chemical defense compounds in P. balsamifera, which could make them susceptible to leaf‐chewing insects. Such potential impacts of invasive earthworms are likely to have implications for tree survival and competition, native tree biodiversity and ecosystem functioning. [ABSTRACT FROM AUTHOR]

Plant defense theory explores how plants invest in defenses against natural enemies but has focused primarily on the traits expressed by juvenile and mature plants. Here we describe the diverse ways in which seeds are chemically and physically defended. We suggest that through associations with other traits, seeds are likely to exhibit defense syndromes that reflect constraints or trade-offs imposed by selection to attract dispersers, enable effective dispersal, ensure appropriate timing of seed germination, and enhance seedling performance. We draw attention to seed and reproductive traits that are analogous to defense traits in mature plants and describe how the effectiveness of defenses is likely to differ at pre- and postdispersal stages. We also highlight recent insights into the mutualistic and antagonistic interactions between seeds and microbial communities, including fungi and endohyphal bacteria, that can influence seed survival in the soil and subsequent seedling vigor. [ABSTRACT FROM AUTHOR]

Vascular plants exhibit defense syndromes, a variety of interdependent defensive traits against herbivores, which may considerably differ between plant groups. Although ferns are an abundant component of tropical forest understories, studies of fern–herbivore interactions are scarce, and none has focused on the underlying defense syndromes. To examine the potential defense syndromes of 34 species of tropical ferns of Brazilian forests, we measured ten leaf traits and examined their correlation with parallelly assessed leaf damages. The first three components of categorical PCA were related (1) with SLA, water content, nitrogen, and phosphorus (33.2% of variance); (2) with tannins and saponins, but negatively with trichome density (22.5%); and (3) with phenol concentrations (16.1%). We identified three groups of fern species with similar leaf damages but different defense syndromes: (I) 14 species were of high nutritional quality (= high SLA, N and water content), but a variable trichome density; (II) 4 species were of low nutritional quality, but had high phenol concentrations, and often a high trichome density; and (III) 16 species were of intermediate nutritional quality and had a low trichome density or were glabrous. Most species (groups I and III) including tree ferns used chemical defenses to protect their highly valuable, nutritious leaves. Group II, exemplified by bracken fern, combined however a low nutritional quality with a powerful chemical defense, including high phenol concentrations, and many trichomes. Because leaf damages did not differ significantly among groups, we conclude that each defense syndrome provides species with a similar resistance against their herbivores. [ABSTRACT FROM AUTHOR]

SUMMARY Thallus mechanical strength, as well as production of secondary metabolites as defensive compounds, of tropical macroalgae is often essential for protection from herbivory. In tropical macroalgae, thallus mechanical strength is negatively correlated with productivity — a trade‐off between productivity and thallus toughness. The tropical fucoids, Turbinaria ornata which has defensive morphological traits against herbivory and Sargassum ilicifolium which is expanding its distribution in Japanese waters, were examined to determine thallus traits related to mechanical strength and productivity and their pair‐wise relationships were also examined. These traits that are directly or indirectly related to the trade‐off between productivity and thallus toughness were compared to data for various other temperate macroalgae by regression analyses. We found two strong positive correlations between thallus mechanical strength and thallus mass or thallus thickness, confirming that higher levels of mechanical strength for tropical fucoids is associated with higher biomass or thallus thickness. Also, negative correlations between thallus toughness and productivity were found indicating structural and physiological trade‐offs. However, the tropical fucoids exhibited relatively high productivity regardless of their higher level of thallus toughness. These traits of the tropical fucoids slightly deviate from the typical conservative strategy with higher thallus toughness and lower productivity as a trade‐off between productivity and thallus toughness. [ABSTRACT FROM AUTHOR]

ABSTRACT Plant-herbivore interactions have directed the evolution of defense mechanisms in plants, which can vary intraspecifically according to environmental quality. This study evaluated variation in the production of antiherbivory defenses in plant species distributed along an environmental gradient of restinga. The study was performed in Parque Estadual Acaraí, state of Santa Catarina, Brazil. Three species of four plant formations with different abiotic conditions were selected for study. Specific leaf area; water, nitrogen and carbon content; and presence of phenols, tannins, lignin and alkaloids, were evaluated in leaves of ten plants per species per plant formation. The results indicated that Symphyopappus casarettoi possesses Low Nutritional Quality Syndrome, characterized by low specific leaf area, presence of secondary metabolites and low nitrogen content. Dodonaea viscosa and Varronia curassavica possess Nutrition and Defense Syndrome, characterized by a balance between nutritional quality (high nitrogen content and lower C:N ratio) and protection (greater thickness of leaves and higher density of trichomes). The results did not confirm the Resource Availability Hypothesis. The absence of a pattern in antiherbivory response due to the environmental gradient may indicate that the investment in defense by plants is not unidirectional and that certain morpho-anatomical attributes are typically related to conservation of resources.

Silicon plays an important role in providing tolerance to various abiotic stresses and augmenting plant resistance against diseases. However, there is a paucity of reports about the effect of silicon on bacterial and viral pathogens of plants. In general, the effect of silicon on plant resistance against bacterial diseases is considered to be due to either physical defense or increased biochemical defense. In this study, the interaction between silicon foliar or soil-treatments and reduced bacterial and viral severity was reviewed. The current review explains the agricultural importance of silicon in plants, refers to the control of bacterial pathogens in different crop plants by silicon application, and underlines the different mechanisms of silicon-enhanced resistance. A section about the effect of silicon in decreasing viral disease intensity was highlighted. By combining the data presented in this study, a better comprehension of the complex interaction between silicon foliar- or soil-applications and bacterial and viral plant diseases could be achieved.

The classical “low latitude-high defense” hypothesis is seldom supported by empirical evidence. In this context, we tested latitudinal patterns in the leaf defense traits of deciduous broadleaved (DB) and evergreen broadleaved (EGB) tree species, which are expected to affect herbivore diversity. We examined the co-occurrence of leaf defense traits (tannin and phenol content, leaf mechanical strength, leaf dry matter content, leaf mass per area, and leaf thickness) in 741 broadleaved tree species and their correlations with species geographical range in East Asian island flora. We discovered contrasting latitudinal defense strategy gradients in DB and EGB tree species. DB species employed chemical defenses (increasing tannin and phenol content) at higher latitudes and physical defenses (softer and thinner leaves) at lower latitudes, whereas EGB tree species exhibited opposite latitudinal defense patterns. The “low latitude high defense” hypothesis included a paradoxical aspect in chemical and physical defense traits across broadleaved tree species. To reconcile paradoxical defense strategies along the latitudinal gradient, we conclude that interactive correlations among leaf traits are controlled by leaf longevity, which differs between DB and EGB tree species. [ABSTRACT FROM AUTHOR]

Silicon (Si) is the second most abundant element in the lithosphere. Soils commonly contain as much as 30% Si, the majority of which is found in minerals and rocks. In plants, the element Si is recognized as a “beneficial quasi-essential” mineral nutrient. It is taken up by the plant roots and trans-located to aerial parts through transpiration streams. Naturally, its accumulation in aerial parts augments its polymerization in the intercellular spaces and beneath the cuticles creates a barrier against pathogen attack. Moreover, soluble Si in the cytosol triggers various metabolic pathways that result in the production of jasmonic acid and herbivore induced plant organic compounds. Combination of these Si-mediated physical and biochemical processes enhances plant defenses against biotic stresses (insects, fungus and bacteria). In addition, soluble Si in the plant system attracts natural predators and parasitoids during pest attack and consequently increases biological control. Although, a large set of data shows that Si provides natural defense against pest attack, application of Si as a pest control agent has not gained much attention from the scientists, policy makers and farming communities. Here, current knowledge regarding Si-mediated plant defense to pest attack is reviewed. Si-application tends to reduce pest infestations and may provide a sustainable environment friendly integrated strategy as an alternative to extensive pesticide use. [ABSTRACT FROM AUTHOR]

Some animals have evolved the use of environmental materials as “portable armour” against natural enemies. Portable bags that bagworm larvae (Lepidoptera: Psychidae) construct using their own silk and plant parts are generally believed to play an important role as a physical barrier against natural enemies. However, no experimental studies have tested the importance of bags as portable armour against predators. To clarify the defensive function, I studied the bagworm Eumeta minuscula and a potential predator Calosoma maximoviczi (Coleoptera: Carabidae). Under laboratory conditions, all bagworm larvae were attacked by carabid adults, but successfully defended themselves against the predators’ mandibles using their own bags. The portable bags, which are composed mainly of host plant twigs, may function as a physical barrier against predator mandibles. To test this hypothesis, I removed the twig bags and replaced some with herb leaf bags; all bag-removed larvae were easily caught and predated by carabids, while all bag-replaced larvae could successfully defend themselves against carabid attacks. Therefore, various types of portable bags can protect bagworm larvae from carabid attacks. This is the first study to test the defensive function of bagworm portable bags against invertebrate predators.

Aims We test the hypothesis that invasive plant species at their range edges experience lower herbivory and allocate less to defense at the edge of an expanding range edge than from more central parts of their distribution, during secondary invasion in a new range. Invasive plants are often able to spread rapidly through new areas. The success of invasive species in new ranges is frequently attributed to enemy release in these new areas and associated evolutionary changes minimizing allocation to defense in favor of growth and reproduction. Enemy release could also explain rapid advances of invasive species upon arriving in new habitats. If invasive species accumulate enemies over time in a new location, then these species may experience a release from their enemies at expanding range fronts. Enemy release at these range fronts may accelerate range expansion. Methods We used populations of four woody invasive species within the invaded range, and four native control species. We quantified leaf herbivory and leaf physical defense traits at both range central and range edge locations, over two 1-month sampling periods, sampled 7 months apart. Important Findings Herbivory at the range edge did not differ to the range center but patterns were not consistent across species. There was a trend for lower herbivory at the range edge for Lantana camara, which was reflected in lower leaf toughness. Overall, leaf toughness was greater at the range edge location across invasive and control species. Physical defenses were different among range locations in a few species, though most species show the same trend, suggesting higher herbivory pressures at the range edge location or differences may be due to climatic factors. Leaves of L. camara were significantly less tough at range edges, suggesting that some species can potentially escape their enemies at range edges. However, our results overall do not support the hypothesis that plants at the edge of their ranges experience reduced impact from their enemies. [ABSTRACT FROM AUTHOR]

Nanosilicon applications have been shown to increase plant defenses against both abiotic and biotic stresses. Silicon quantum nanodots (Si NDs), a form of nanosilicon, possess excellent biological and physiochemical properties ( e.g. , minimal size, high water solubility, stability, and biocompatibility), potentially making them more efficient in regulating plant responses to stress than other forms of silicon. However, to date, we still lack mechanistic evidence for how soil-applied Si NDs alter the regulation of plant physical and chemical defenses against insect herbivores. To address this gap, we compared the effect of fluorescent amine-functionalized Si NDs (5 nm) and the conventional fertilizer sodium silicate on maize ( Zea mays L.) physical and chemical defenses against the oriental armyworm ( Mythimna separata , Walker) caterpillars. We found that 50 mg/kg Si NDs and sodium silicate additions inhibited the growth of caterpillars the most (35.7% and 22.8%, respectively) as compared to other application doses (0, 10, and 150 mg/kg). Both Si NDs and silicate addition activated biosynthesis genes responsible for chemical (benzoxazinoids) and physical (lignin) defense production. Moreover, Si NDs upregulated the gene expression of antioxidant enzymes (SOD, CAT, and POD) and promoted the antioxidant metabolism (flavonoids) in maize leaves under M. separata attack. Finally, we show that, under field conditions, Si ND addition increased maize cob weight (28.7%), cob grain weight (40.8%), and 100-grain weight (26.5%) as compared to the control, and more so than the conventional silicon fertilizer. Altogether, our findings highlight the potential for Si NDs to be used as an effective and ecofriendly crop protection strategy in agroecosystems.

Trichomes are an important physical resistance mechanism of plants, as they reduce insect herbivore movement, feeding, and digestion. However, we know little about how trichomes influence herbivore distributions and populations. We conducted laboratory and field experiments to evaluate the preferences of Platyprepia virginalis ( Boisduval) ( Lepidoptera: Arctiidae) caterpillars to natural and manipulated densities of trichomes on their primary food, Lupinus arboreus Sims ( Fabaceae). We then conducted field surveys to determine whether variation in trichome density among lupine bushes affected caterpillar spatial distribution on the landscape. Platyprepia virginalis caterpillars preferred lupine leaves with fewer trichomes in choice and no-choice experiments. In the field, caterpillar feeding damage was found more often on leaves with fewer trichomes. These preferences scaled up to the level of bushes in the landscape such that more caterpillars were found on bushes with lower trichome densities than on bushes with higher trichome densities. This is one of few studies to show the potential for trichome density to influence herbivore population size and distribution in a natural system at a landscape level. The results are consistent with trichomes functioning as a resistance mechanism with consequences for herbivore choice, performance, and distribution. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compared investment in defense systems of two related species of grapevine moth. [•] E. ambiguella larvae invest more into morphological defenses. [•] L. botrana larvae invested more into behavioral defenses. [•] E. ambiguella strongly responded to immune challenge contrary to L. botrana. [•] L. botrana larvae were more parasitized by various parasitoid species. [Copyright &y& Elsevier]

Plants defend their leaves using multiple defense traits that change functions with leaf age. We examined the effects of leaf age on the development of multiple defense traits in two related Mallotus ( Euphorbiaceae) species: young plants of the fast-growing Mallotus japonicus ( Spreng.) Müll. Arg. and the slow-growing Mallotus philippensis ( Lam.) Müll. Arg. Sequential leaves of the two species were measured for their leaf area, leaf mass/area, densities of trichomes and pellucid dots, extrafloral nectar volume, and the numbers of extrafloral nectaries and pearl bodies. Mallotus japonicus shifted its defense tactics from direct defense using trichomes and pellucid dots in young leaves to biotic defense using extrafloral nectar and pearl bodies in middle-aged leaves. In contrast, M. philippensis used direct, chemical defense throughout all leaf ages, together with the shift from indirect, biotic defense using extrafloral nectar in young leaves to direct, physical defense using leaf toughness in middle-aged leaves. These results strongly suggest that, in relation to life history, plants can alter optimal combinations of multiple defense traits with leaf age. [ABSTRACT FROM AUTHOR]

Plants often lose natural enemies (herbivores and pathogens) while invading new geographic regions, as predicted by the Enemy Release Hypothesis. However, a similar reduction in attack might occur at a more local scale within an invader's range as plants in marginal areas escape enemies that fail to find them or cannot maintain local populations. In this study, we test the hypothesis that isolated populations near the northern edge of an invader's range escape the enemies present in more southern populations, using the non-native monocarpic biennial, common burdock ( Arctium minus), as a model species. In southern Ontario, this plant is attacked by a wide range of insect herbivores, including generalist leaf chewers as well as leaf-mining flies ( Liriomyza arctii, Calycomyza flavinotum) and an abundant lepidopteran seed predator ( Metzneria lappella). Surveys over an 815 km transect from temperate southern to boreal northern Ontario indicate that damage by all of these enemies declines sharply with latitude, while plants in more northern areas are slightly larger and more fecund. Critically, seed parasitism drops from more than 85 % in the south to less than 25 % in the north. These results indicate that populations of Arctium near this species' northern limit escape many of their usual natural enemies, potentially counteracting less favourable environmental conditions. Such escape from enemies near invaders' range margins may accelerate further spread, including expected migration in response to climate change. [ABSTRACT FROM AUTHOR]

Plants use different defense strategies throughout their ontogenetic development. In this study, three questions were proposed: (1) Is there a greater abundance of ants on young leaves, which possess active extrafloral nectaries, than on mature leaves? (2) Do ants exert an indirect defense that is effective against the attack of herbivorous insects? (3) Do mature leaves have a greater concentration of physical and chemical defense than young leaves? These questions were addressed through an ant-exclusion experiment in which two branches of Copaifera langsdorffii ( n = 25) were marked and monitored throughout the entire foliar expansion and development period. A reduction in the abundance of ants throughout foliar development was observed. The ants exerted an effective defense against herbivores on C. langsdorffii: the branches where ants were excluded had a greater number of herbivores. The mature leaves possessed a greater index of leaf sclerophylly than young leaves, but the leaves did not differ in the concentration of tannins. The foliar ontogeny of C. langsdorffii promoted an inversion in the defense strategy against herbivores, and despite showing an opportunistic relationship, the interaction between ants and extrafloral nectaries appears to play an important role in structuring the interactions between herbivorous insects and their host plants. [ABSTRACT FROM AUTHOR]

Some plant species develop multiple defense traits. To test the hypothesis that plants with both direct and indirect defense traits mainly develop the direct and indirect defense traits under the low and high soil moisture conditions, respectively, the development of multiple defense traits on the young plants of Mallotus japonicus (Thunb.) Muell. Arg., and the number of ants on the plants were experimentally examined under different soil moisture conditions. Under the low soil moisture condition, the plant growth declined, and the trichomes and pellucid dots developed well. The pearl bodies developed on the plants under the high soil moisture condition. The volume of extrafloral nectar secreted and the number of ants on the plants significantly increased under the high soil moisture condition. These results clearly show that the young plants of M. japonicus firmly develop sound direct defense traits under the low soil moisture condition, and they develop indirect defense traits that are less reliable but have relatively low costs under the high soil moisture condition. [ABSTRACT FROM AUTHOR]

Plant invasions create novel plant-insect interactions. The EICA (evolution of increased competitive ability) hypothesis proposes that invasive plants will reallocate resources from defense to growth and/or reproduction because they have escaped from their co-evolved insect natural enemies. Testing multiple herbivory by monophagous and oligophagous herbivores and simultaneous measurement of various plant traits will provide new insights into the evolutionary change of invasive plants. In this context, we conducted a common garden experiment to compare plant growth and reproduction, chemical and physical defense, and plant responses to herbivory by different types of herbivores between invasive North American populations and native East Asian populations of mile-a-minute weed, Persicaria perfoliata. We found that invasive mile-a-minute exhibited lower biomass, flowered earlier and had greater reproductive output than plants from the native range. Compared with native populations, plants from invasive populations had lower tannin content, but exhibited higher prickle density on nodes and leaves. Thus our results partially support the EICA hypothesis. When exposed to the monophagous insect, Rhinoncomimus latipes and the oligophagous insects, Gallerucida grisescens and Smaragdina nigrifrons, more damage by herbivory was found on invasive plants than on natives. R. latipes, G. grisescens and S. nigrifrons had strong, moderate and weak impacts on the growth and reproduction of mile-a-minute, respectively. The results indicate that mile-a-minute may have evolved a higher reproductive capacity in the introduced range, and this along with a lack of oligophagous and monophagous herbivores in the new range may have contributed to its invasiveness in North America. [ABSTRACT FROM AUTHOR]

Abstract: Tryptophan-derived secondary metabolites, including serotonin and its hydroxycinnamic acid amides, markedly accumulate in rice leaves in response to pathogen attack. These compounds have been implicated in the physical defense system against pathogen invasion by being deposited in cell walls. Serotonin is biosynthesized from tryptophan via tryptamine, and tryptophan decarboxylase (TDC) catalyzes the first committed reaction. In this study, (S)-α-(fluoromethyl)tryptophan (S-αFMT) was utilized to investigate the effects of the inhibition of TDC on the defense responses of rice leaves. S-αFMT, enantiospecifically synthesized from l-tryptophan, effectively inhibited TDC activity extracted from rice leaves infected by Bipolaris oryzae. The inhibition rate increased dependently on the incubation time, indicating that S-αFMT served as a suicide substrate. Treatment of rice seedlings with S-αFMT suppressed accumulation of serotonin, tryptamine, and hydroxycinnamic acid amides of serotonin in a dose-dependent manner in B. oryzae-inoculated leaves. The lesions formed on seedlings treated with S-αFMT lacked deposition of brown materials, and those leaves were severely damaged in comparison with leaves without S-αFMT treatment. Administrating tryptamine to S-αFMT-treated leaves restored accumulation of tryptophan-derived secondary metabolites as well as deposition of brown material. In addition, tryptamine administration reduced damage caused by fungal infection. Accordingly, the accumulation of tryptophan-derived secondary metabolites was suggested to be part of the effective defense mechanism of rice. [Copyright &y& Elsevier]

Many insect herbivores can only use hosts during a specific phenological stage, i.e., a phenological window. Previous studies have primarily examined the effects of these windows on insect herbivores, but relatively little is known about the mechanisms controlling the phenological windows. In most gall insect systems, phenological windows have been attributed to the short duration of physiologically active plant tissues that induce gall formation (reactive plant tissue). In the fruit gall midge, Asphondylia aucubae Yukawa and Ohsaki, and the host plant (i.e., Aucuba japonica) system, the disappearance of reactive plant tissue closes the phenological window, but its presence does not define the opening of the window. The hard endocarp of the fruit covers most potential oviposition sites just before the midge emergence season, but decreases in proportional cover during the emergence season. We experimentally manipulated the timing of oviposition relative to fruit development. Midges that emerged earliest and attacked fruits during their earliest developmental stages were unable to oviposit because of intact, hard endocarps, whereas their counterparts that emerged later could oviposit more readily through cracks in the endocarp. We noted possible oviposition avoidance behavior and the necessity of more frequent (repeated) ovipositor insertions to intensively stimulate the decreased reactive tissues during the latter half of the emergence season. Overall, our results indicated that the fragmentation of the defensive, hard endocarp of the host plant defines the opening of the phenological window in this plant- herbivore system. [ABSTRACT FROM AUTHOR]

Abstract: Marine sponges often harbor an abundance of associated organisms. We characterized mesofauna associated with the common tropical sponge Amphimedon viridis, and then tested whether physical (spicules) or chemical (lipophilic or hydrophilic extracts) properties of this sponge provide a prospective refuge for mesofauna from fish predation. Sponge analyses revealed a moderately diverse and numerically rich community of sponge-associated mesofauna comprised primarily of mesocrustaceans (82% of total fauna). Eighty-nine percent of these were amphipods, but smaller numbers of tanaids, decapods, and isopods also occurred. Quantitative sampling of outer surfaces and interstices of fifteen A. viridis yielded a total mean±1 SD density of sponge–associated mesofauna of 53±9.3 individuals per 100 cm3 wet sponge tissue. Among the numerically dominant amphipods, 65% occurred on outer sponge surfaces where they are most vulnerable to fish predators. We evaluated whether A. viridis provides a prospective refuge from predation by assessing the palatability of this sponge to the sympatric generalist pinfish Lagodon rhomboides. When presented small (2 mm) bite-size pieces of whole sponge tissue, similar in size to what fish might incidentally ingest should they attempt to consume sponge-mesofaunal associates, pinfish displayed strong feeding deterrence. Alginate food pellets containing tissue-level concentrations of sponge spicules caused a weak but significant deterrent response. In contrast, alginate pellets containing tissue-level concentrations of either lipophilic or hydrophilic extracts of A. viridis were highly deterrent to pinfish. Thus, chemical, and to a considerably lesser degree, physical defenses (spicules) may contribute to this sponge serving as a protective refuge for associated mesofauana. [Copyright &y& Elsevier]

The upregulation of the tryptophan (Trp) pathway in rice leaves infected by Bipolaris oryzae was indicated by: (i) enhanced enzyme activity of anthranilate synthase (AS), which regulates metabolic flux in the Trp pathway; (ii) elevated levels of the AS ( OASA2, OASB1, and OASB2) transcripts; and (iii) increases in the contents of anthranilate, indole, and Trp. The measurement of the contents of Trp-derived metabolites by high-performance liquid chromatography coupled with tandem mass spectrometry revealed that serotonin and its hydroxycinnamic acid amides were accumulated in infected leaves. Serotonin accumulation was preceded by a transient increase in the tryptamine content and by marked activation of Trp decarboxylase, indicating that enhanced Trp production is linked to the formation of serotonin from Trp via tryptamine. Feeding of radiolabeled serotonin to inoculated leaves demonstrated that serotonin is incorporated into the cell walls of lesion tissue. The leaves of a propagating-type lesion mimic mutant ( sl, Sekiguchi lesion) lacked both serotonin production and deposition of unextractable brown material at the infection sites, and showed increased susceptibility to B.  oryzae infection. Treating the mutant with serotonin restored deposition of brown material at the lesion site. In addition, the serotonin treatment suppressed the growth of fungal hyphae in the leaf tissues of the sl mutant. These findings indicated that the activation of the Trp pathway is involved in the establishment of effective physical defenses by producing serotonin in rice leaves. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the effect on host plants of defending against herbivores is important in grazing ecology and grassland management. In this study, the morphological and reproductive responses of Caragana microphylla Lam. to grazing sheep were investigated using a 15-year grazing experiment with six stocking rates in the Inner Mongolia steppe of China. Plant height, rachis length, leaflet size, and number of pods decreased significantly, whereas spine density and length increased significantly with increased stocking rate. Significant negative correlations were observed between production of vegetative and reproductive organs and defensive organs, indicating that it is costly for C. microphylla to defend against herbivores and that morphological miniaturization and a tradeoff between production and defense were main responses of C. microphylla to herbivores. [Copyright &y& Elsevier]

To date, theoretical or laboratory simulations of aposematic evolution in prey animals have focused narrowly on internally stored chemical defense as the source of unprofitability and ignore aposematic advertisement of physical defenses such as spines (and defensive hairs, claws, etc.). This has occurred even though aposematism in spiny animals has been recognized since the 19th century. In this paper we present the first detailed theoretical consideration of aposematism in spiny animals, focusing on questions of initial evolution, costs of display, and coevolution of displays with defenses. Using an individual-based evolutionary model, we found that spines (or similar physical defenses) can easily evolve without aposematism, but when spines do evolve, aposematic displays can also easily evolve if they help to make the prey animal distinctive and if they draw attention to the physical threat. When aposematic displays evolve, they cause reduced investment in costly spines, so that, in addition to signaling unprofitability, aposematic display may enhance the cost-effectiveness of antipredator defenses (one exception to this conclusion is if the display is itself as costly as the defense). For animals with stinging spines, combining physical and chemical defense, the evolution of aposematic display may lead to reduced investment in the toxin compared to the spine. This occurs because spines act as both secondary (repellent) defenses and as primary defenses (their own visible, honest advertisement), whereas internally stored toxins only (generally) act as repellent secondary defenses. We argue that conspicuous aposematism in spines functions as an attention-getting mechanism, whereas conspicuous aposematic display in purely toxic animals may be explained by signal reliability arguments. Finally, one (more) route by which aposematism may initially evolve is by spiny rather than purely chemically defended species, spreading to species with other forms of secondary defense as the signal becomes common. [ABSTRACT FROM AUTHOR]

Southeastern fox squirrels were observed feeding preferentially on seeds of certain clones of loblolly pine in a central Georgia seed orchard in the early 1990s and, similarly, on slash pine seed in an orchard in central Florida in the late 1990s. In each orchard, the degree of feeding preference and avoidance among selected clones was documented and quantified. We tested three hypotheses to explain this phenomenon: (1) seeds of preferred clones have greater nutritional quality or energy content; (2) cone armature differed between preferred and avoided clones; or (3) preferred clones have lower quantities of deterrent compounds present in cone tissue. Hypothesis 1 was tested using cones collected from three preferred and two avoided clones within a loblolly pine seed orchard. We found no consistent differences in total number of seeds per cone, viable seeds per cone, seed weight per cone, average weight per seed, energy content per seed, and energy content per cone between preferred and avoided cones. Hypotheses 2 and 3 were tested using cones collected from four preferred and four avoided clones within a slash pine seed orchard. We found a strong positive association between spine length and cone avoidance. Avoided cones had significantly higher concentrations of myrcene, α-phellandrene, β-phellandrene, β-caryophyllene, and α-humulene but lower concentrations of α-pinene. These physical and chemical cone defenses may increase handling time or reduce seed palatability and therefore act as significant deterrents to seed predation by fox squirrels when preferred feeding options are readily available, such as in a seed orchard. [Copyright &y& Elsevier]

Several experimental studies on aquatic plants have reported the prevalence of chemical defense mechanism against herbivory, as opposed to structural, life-forms or other traits. Here, our laboratory feeding experiments and integrative analysis explored the relationship among palatability (fresh or reconstituted plants used as artificial diet) and various chemical/nutritional traits ( i.e., contents of dry mass, ash, nitrogen, protein, and phenols) of diverse aquatic plants and their susceptibility to consumption by the generalist gastropod Biomphalaria glabrata . Biomphalaria glabrata consumed all of the assayed aquatic plants in a hierarchical yet generalized way, with the consumption of fresh plants, their reconstituted forms and defensive properties of lipophilic extracts not being significantly correlated with plant physical or chemical traits to determine the feeding preference of the gastropod. Our results do not reveal a prevalence for a specific plant attribute contributing to herbivory. Instead, they indicate that the susceptibility of aquatic plants to generalist consumers is probably related to a combination of their chemical and physical properties, resulting in moderate grazing rates by generalist consumers., Competing Interests: The authors declare there are no competing interests., (©2021 Pereira et al.)

We examined the defensive function of spines of Damnacanthus indicus against deer herbivory by experimentally removing spines in the field where deer density is high. Individuals of D. indicus whose spines had been removed had a higher probability of being browsed by deer than control individuals. In addition, plant height was significantly lower for individuals that were browsed than those that were not. These results support the notion that spines of D. indicus have a function to deter deer browsing. This study is the first to demonstrate experimentally the defensive function of spines against large mammals in temperate areas. [ABSTRACT FROM AUTHOR]