Search Results (131)

Anthropogenic infrastructure, such as inland wind turbines commonly found in agricultural fields, has substantially increased subterranean vibratory noise in the past decades. Plants, being rooted in soil, are continuously exposed to these vibrations, yet we have little understanding of how vibrational noise affects plant development and, consequently, plant–insect interactions. Here, we examine the impact of windmill-like vibrational noise on the growth of Pisum sativum and its full-factorial interaction with the generalist herbivore Spodoptera exigua. Plants were exposed to either high or low vibrational noise from seed germination to the seed production stage. We recorded germination, flowering, fruiting time, and daily shoot length. Additionally, we measured herbivory intensity by Spodoptera exigua caterpillars placed on a subset of plants. Plants exposed to high vibrational noise grew significantly faster and taller than those in the low-noise treatment. Additionally, we found a marginally significant trend for earlier flowering in plants exposed to high noise. We did not find a significant effect of vibrational noise on herbivory. Our results suggest that underground vibrational noise can influence plant growth rates, which may potentially have ecological and agricultural implications. Faster growth may alter interspecific competition and shift trade-offs between growth and defense. Understanding these effects is important in assessing the broader ecological consequences of renewable energy infrastructure. Full article

Arundo donax L. has been introduced in markets worldwide due to its economic value. However, it is listed in the world’s 100 worst alien invasive species because it easily escapes from cultivation, and forms dense monospecific stands in riparian areas, agricultural areas, and grassland areas along roadsides, including in protected areas. This species grows rapidly and produces large amounts of biomass due to its high photosynthetic ability. It spreads asexually through ramets, in addition to stem and rhizome fragments. Wildfires, flooding, and human activity promote its distribution and domination. It can adapt to various habitats and tolerate various adverse environmental conditions, such as cold temperatures, drought, flooding, and high salinity. A. donax exhibits defense mechanisms against biotic stressors, including herbivores and pathogens. It produces indole alkaloids, such as bufotenidine and gramine, as well as other alkaloids that are toxic to herbivorous mammals, insects, parasitic nematodes, and pathogenic fungi and oomycetes. A. donax accumulates high concentrations of phytoliths, which also protect against pathogen infection and herbivory. Only a few herbivores and pathogens have been reported to significantly damage A. donax growth and populations. Additionally, A. donax exhibits allelopathic activity against competing plant species, though the allelochemicals involved have yet to be identified. These characteristics may contribute to its infestation, survival, and population expansion in new habitats as an invasive plant species. Dense monospecific stands of A. donax alter ecosystem structures and functions. These stands impact abiotic processes in ecosystems by reducing water availability, and increasing the risk of erosion, flooding, and intense fires. The stands also negatively affect biotic processes by reducing plant diversity and richness, as well as the fitness of habitats for invertebrates and vertebrates. Eradicating A. donax from a habitat requires an ongoing, long-term integrated management approach based on an understanding of its invasive mechanisms. Human activity has also contributed to the spread of A. donax populations. There is an urgent need to address its invasive traits. This is the first review focusing on the invasive mechanisms of this plant in terms of adaptation to abiotic and biotic stressors, particularly physiological adaptation. Full article

This review provides an in-depth examination of the intricate interactions between plant metabolites and the digestive and antioxidative enzymes in insects, highlighting their essential roles in shaping insect herbivory and adaptation strategies. Plants have evolved a diverse arsenal of secondary metabolites to defend against herbivorous insects, which, in response, have developed sophisticated adaptations to overcome these defenses and efficiently exploit plant resources. We outline the importance of digestive enzymes, such as proteases and amylases, which allow insects to break down complex plant compounds and access vital nutrients. Additionally, the review focuses on antioxidative enzymes in the insect midgut, including superoxide dismutase and catalase, which play a crucial role in mitigating oxidative stress generated during digestion and other metabolic processes. Synthesizing findings from various studies, this review also considers how environmental factors, such as heavy metal exposure and temperature changes, influence these enzymes’ activity levels. It highlights the dual function of antioxidative enzymes in detoxifying harmful plant-derived compounds while preserving cellular stability. The implications of these biochemical interactions for pest management are discussed, with an emphasis on the potential for developing biopesticides that target specific enzymatic pathways to disrupt insect feeding and growth. By elucidating the biochemical mechanisms that underlie plant-insect interactions, this review enhances our understanding of co-evolutionary dynamics and offers insights into sustainable agricultural practices that could leverage these interactions for effective pest control. Finally, the review proposes future research directions aimed at identifying novel plant metabolites with enzyme-modulating properties and exploring the ecological impacts of enzyme-targeted pest management approaches. Full article

A two-year field study was conducted using canola to check the efficacy of different soil amendment treatments (SAT), i.e., with elemental sulfur (ES), bio-sulfur (BS), and compost (Cp) mixtures against insecticide-treated (Carbosulfan) and untreated controls regarding aphid populations. The results of the experiment revealed that ES treatments significantly reduced aphid abundance, followed by Cp and ES+Cp. However, BS improved aphid herbivory. The number of siliques, seeds, thousand-seed weight, and yield were improved with a trend of ES+Cp > Cp > BS+Cp. Similarly, physiological mechanisms revealed the regulation of nutrient and phenolic contents in canola with ES improving sulfur, BS nitrogen, Cp, and ES+Cp calcium, and BS+Cp enhancing phosphorus, potassium, iron, and zinc. Furthermore, RP-HPCL indicated that ferulic acid was highest in insecticide-treated plot. Similarly, Cp improved quercetin and gallic acid; ES+Cp caffeic, chlorogenic, m-coumaric, and sinapic acid; and BS+Cp enhances syringic, vanillic, ferulic, p-coumaric, and cinnamic acid. The analysis regarding health risk assessment revealed among different SAT, ES+Cp significantly reduced the Hazardous Quotient (HQ) of Cu and Zn. However, further research is still needed to explore SAT’s potential to remediate other heavy metal stresses with possible implications for pest management in different field crops. Full article

Plants are challenged regularly with multiple types of biotic stress factors, such as pathogens or insect herbivores, in their environment. To detect and defend against pathogens, plants have evolved an innate immune system in which intracellular receptors in the so-called effector-triggered immunity play a vital role. In Arabidopsis thaliana the Toll/interleukin-1 receptors (TIRs) domain is related to intracellular immunity receptors, for example in TIR-NBS-LRR (TNL) proteins. Among the TIR domain carrying proteins, very little is known about the function of the TIR-X proteins. Here, we focus on the recently described TIR-X (TIRP; At5g44900) to analyze its role in phytohormone-mediated plant defense through gene expression and phytohormone quantification. Therefore, we employed two fungal pathogens, the necrotrophic Alternaria brassicicola and the hemibiotrophic Verticillium dahliae, to infect A. thaliana WT (Col-0), TIRP knock-out, and TIRP overexpressing lines for comparative analyses. Furthermore, we included the insect herbivore Spodoptera littoralis and a treatment with S. littoralis egg extract on the plants to analyze any role of TIRP during these attacks. We found that both A. brassicicola and V. dahliae infections increased TIRP gene expression systemically. The salicylic acid content was higher in the TIRP overexpressing line, corresponding to a better S. littoralis larval growth performance in feeding assays. However, since we never observed clear infection-related differences in jasmonate or salicylic acid levels between the wild type and the two transgenic Arabidopsis lines, our results rule out the possibility that TIRP acts via the regulation of phytohormone synthesis and accumulation. Full article

Plants are naturally subjected to various types of biotic stresses, including pathogenic microorganisms and herbivory by insects, which trigger different signaling pathways and related defense mechanisms. Inoculation with microorganisms, such as plant growth-promoting rhizobacteria (PGPR), can be seen as a form of stress because it triggers a systemic resistance response in plants similar to that caused by insect herbivory. However, these interactions have typically been studied independently, which has limited the understanding of their combined effects. This study examines the effects of Bacillus amyloliquefaciens GB03 inoculation and Spodoptera frugiperda herbivory on the total phenolic contents of Ocimum basilicum. We also analyze the levels of endogenous phytohormones and the activity of phenylalanine ammonia-lyase (PAL), a crucial enzyme involved in the biosynthesis of phenolic defense-related metabolites. The results indicate that the total phenolic content significantly increased only in plants that were both inoculated by GB03 and damaged by larvae. Additionally, PAL activity showed an increase in plants that were damaged by larvae and in those subjected to the combined treatment of larval damage and inoculation with GB03. Regarding phytohormones, in plants damaged by insects, the levels of salicylic acid (SA) increased, regardless of whether they were inoculated or not, while the levels of jasmonic acid–isoleucine (JA-ile) rose in all treatments compared to the control. This study highlights the intricate relationships among beneficial microbes, herbivores, and plant defense mechanisms, emphasizing their potential impact on improving plant resilience and the production of secondary metabolites. Furthermore, understanding the independent effects of PGPR inoculation, beyond its interaction with herbivory, could provide valuable insights into its role as a sustainable alternative for enhancing plant defense responses and promoting crop productivity. Full article

Herbivores can negatively impact plant reproduction by altering floral traits, pollination, and fruit production. To counteract this, plants developed defense mechanisms, such as the biotic defense resulting from associations with ants. The aim of this study was to investigate whether leaf herbivory at different intensities influences reproductive success and extrafloral nectar secretion patterns in a savanna plant, Banisteriopsis malifolia (Malpighiaceae). Plants were subjected to simulated leaf herbivory and divided into three groups: Control (damage < 5%), T15 (15% leaf area removed), and T50 (50% leaf area removed). Assessments continued until fruiting. The findings indicate an increase in extrafloral nectar sugar concentration after simulated herbivory. Increasing foliar damage significantly delayed the time to bloom, decreased the number of inflorescences per plant, and reduced the size of buds and flowers. Foliar damage significantly decreased fruit size. Furthermore, ant foraging was influenced by herbivory, with a predominance of aggressive ants on plants with high levels of damage. Our study shows that varying levels of leaf damage affect extrafloral nectar secretion, ant foraging behavior, and plant reproductive structures. These findings highlight how insect herbivores and the level of damage they cause influence plant fitness and consequently community structure. Full article

Silicon (Si) is a widely recognized element in plant defense, often enhancing resistance to herbivory by strengthening cell walls and deterring feeding by external herbivores. However, its impact on internal, endophytic herbivores, such as gall-inducing insects, remains underexplored. This study investigates the role of silicon in Bauhinia brevipes, focusing on its effects on herbivory by insects. We hypothesize that while silicon strengthens plant tissues and reduces feeding by external herbivores, it may have a limited effect on internal feeders, such as gall-inducing insects. Our results indicate that silicon accumulation in leaves significantly reduces herbivory by chewing insects but has no direct effect on the occurrence of gall-inducing insects. Silicon content in galled tissues was lower compared to healthy leaves, suggesting that gall-inducing insects may manipulate silicon distribution to mitigate its defensive effects. Our results indicate that hypersensitivity reactions were positively influenced by silicon, highlighting the role of this element in enhancing localized defense mechanisms. Our findings reveal silicon’s tissue-specific roles in plant defense, emphasizing the need for more research on its nuanced interactions with endophytic herbivores and implications for ecological applications. This research contributes to the literature on silicon’s multifaceted role in plant–herbivore interactions and its potential applications in sustainable pest management. Full article

The Argentine stem weevil (ASW), a major pest in ryegrass pastures, causes significant agricultural losses. Ryegrass can establish a symbiotic association with Epichloë endophytic fungi, which supply chemical defenses, including peramine. This symbiosis helps protect ryegrass by providing peramine, which acts as a primary defense. In addition, ryegrass can activate induced defense mechanisms, with peramine remaining the central agent in response to herbivorous insect attacks. Therefore, this study assessed the feeding of the ASW on ryegrass carrying endophytic fungus and peramine levels in aerial organs and its effects on pest performance. Argentine stem weevil adults and larvae were placed on ryegrass leaves and stems to assess feeding. Two treatments were used: endophyte-free plants and endophyte-colonized plants. After ASW feeding damage, insect consumption was measured by the leaf area consumed. To evaluate peramine production and its increase in response to ASW attack, peramine levels in leaves were analyzed using liquid chromatography. Damaged E+ ryegrass plants showed significant increases in peramine, with adult and larval herbivory raising levels by 291% and 216% in stems and by 135% and 85% in leaves, respectively, compared to controls. Endophyte-free (E−) plants experienced more ASW damage, as insects preferred feeding on them, showing reduced activity as peramine levels rose in endophyte-infected (E+) plants. An oviposition assay confirmed insect preference for endophyte-free (E−) plants. Additionally, larvae reared on endophyte-infected (E+) plants had lower survival rates, correlating negatively with peramine levels. These results emphasize peramine’s role in strengthening ryegrass defenses against ASW, impacting both feeding and larval development. Full article

Plants express many types of defenses in response to herbivory damage. These defenses can be displayed as a sequence or they can overlap, increasing efficiency in protection. However, leaf defense shifts during leaf development, including extrafloral nectaries (EFNs), are neglected in natural tropical systems. To address this gap, our study evaluates the shifts in defense strategies of Eriotheca gracilipes, focusing on extrafloral nectaries and leaf toughness across leaf development stages. We also simulate herbivory by cutting the leaves to address the role of visiting ants against herbivores. We observed that E. gracilipes exhibits a defense turnover, shifting from indirect defenses (e.g., EFNs) in young leaves to physical defenses in adult leaves. Simulated herbivory led to heightened ant visitation, which correlated with decreased herbivory rates, indicating that ant recruitment acts as an effective deterrent. We observed a peak of EFN activity in young leaves, increased foliar toughness in adult leaves, and reduced herbivory on ant-patrolled young leaves. Additionally, E. gracilipes demonstrated tolerance to up to 10% foliar loss with no significant impact on leaf asymmetry, although 50% foliar loss increased asymmetry in newly flushed leaves. These results highlight E. gracilipes’ adaptive flexibility by attracting protective ants when vulnerable and enhancing structural defenses as leaves develops, E. gracilipes minimizes herbivory impact. This study provides valuable insight into the adaptive roles of EFNs and tolerance in E. gracilipes, contributing to a broader understanding of plant defense strategies. Full article

The ongoing interplay among plants, insects, and bacteria underscores the intricate balance of defense mechanisms in ecosystems. Regurgitant bacteria directly/indirectly impact plant immune responses, but the underlying mechanism is unclear. Here, we focus on the interaction between regurgitant bacteria, diamondback moth (DBM), and plant. Six culturable bacteria were isolated from DBM gut regurgitant, including three Enterobacter strains (RB1-3), Micrococcus sp. (RB4), Staphylococcus haemolyticus (RB5), and Bacillus cereus (RB6). These RB strains suppressed genes related to jasmonic acid and glucosinolate signaling pathways but had little effect on salicylic acid signaling pathway genes in Arabidopsis thaliana wounds. RB1 and RB5 inhibited DBM development on A. thaliana but not on an artificial diet. RB1 and RB5 significantly suppressed GOX genes and proteins in DBMs. However, the Pxgox2 insect mutant strain inoculated with RB1 or RB5 did not significantly affect DBM feeding on A. thaliana compared to the wild type. Six RB have been functionally identified, with RB1 and RB5 negatively regulating GOX-mediated host adaptability. The deliberate addition of RB1 and RB5 can negatively affect DBM herbivory and fitness. Our study provides a molecular basis for the further application of RB for insect pest management by modulating insect–plant interactions. Full article

The invasion of non-native plant species presents a significant ecological challenge worldwide, impacting native ecosystems and biodiversity. These invasive plant species significantly affect the native ecosystem. The threat of invasive plant species having harmful effects on the natural ecosystem is a serious concern. Invasive plant species produce secondary metabolites, which not only help in growth and development but are also essential for the spread of these plant species. This review highlights the important functions of secondary metabolites in plant invasion, particularly their effect on allelopathy, defense system, interaction with micro soil biota, and competitive advantages. Secondary metabolites produced by invasive plant species play an important role by affecting allelopathic interactions and herbivory. They sometimes change the soil chemistry to make a viable condition for their proliferation. The secondary metabolites of invasive plant species inhibit the growth of native plant species by changing the resources available to them. Therefore, it is necessary to understand this complicated interaction between secondary metabolites and plant invasion. This review mainly summarizes all the known secondary metabolites of non-native plant species, emphasizing their significance for integrated weed management and research. Full article

Trichomes play a key role in both heavy metal tolerance and herbivory defense, and both stressors have been shown to induce increased trichome density. However, the combined effect of these stressors on trichome density in general, and specifically on metal-hyperaccumulating plants, has yet to be examined. The aim of this study was to test the effect of cadmium availability and herbivory on leaf trichome density and herbivore deterrence in the metal hyperaccumulator Helianthus annuus. To test this, H. Annuus plants were grown in control pots or pots inoculated with 10 mg/kg cadmium and were subjected to either no herbivory or simulated herbivory using mechanical damage and foliar jasmonic acid application. Herbivore deterrence was tested in a feeding assay using Spodoptera littoralis caterpillars. Interestingly, while the trichome density of H. annuus increased by 79% or 53.5% under high cadmium availability or simulated herbivory, respectively, it decreased by 26% when the stressors were combined. Furthermore, regardless of cadmium availability, simulated herbivory induced a 40% increase in deterrence of S. littoralis. These findings suggest that the combination of metal availability and herbivory might present excessive stress to hyperaccumulators. Moreover, they suggest that the risk of metal bioaccumulation in phytoremediation can be reduced by simulated herbivory. Full article

Fall armyworm (FAW, Spodoptera frugiperda) has now spread to more than 26 Chinese provinces. The government is working with farmers and researchers to find ways to prevent and control this pest. The use of biochar is one of the economic and environmentally friendly strategies to increase plant growth and improve pest resistance. We tested four v/v combinations of bamboo charcoal with coconut bran [BC1 (10:1), BC2(30:1), BC3(50:1)] against a control (CK) in maize. We found that plant height, stem thickness, fresh weight and chlorophyll content were significantly higher in BC2, in addition to the lowest FAW survival %. We then compared the metabolome and transcriptome profiles of BC2 and CK maize plants under FAW herbivory. Our results show that the levels of flavonoids, amino acids and derivatives, nucleotides and derivatives and most phenolic acids decreased, while terpenoids, organic acids, lipids and defense-related hormones increased in BC-grown maize leaves. Transcriptome sequencing revealed consistent expression profiles of genes enriched in these pathways. We also observed the increased expression of genes related to abscisic acid, jasmonic acid, auxin and MAPK signaling. Based on these observations, we discussed the possible pathways involved in maize against FAW herbivory. We conclude that bamboo charcoal induces anti-herbivory responses in maize leaves. Full article

In wounded Arabidopsis thaliana leaves, four 13S-lipoxygenases (AtLOX2, AtLOX3, AtLOX4, AtLOX6) act in a hierarchical manner to contribute to the jasmonate burst. This leads to defense responses with LOX2 playing an important role in plant resistance against caterpillar herb-ivory. In this study, we sought to characterize the impact of AtLOX2 on wound-induced phytohormonal and transcriptional responses to foliar mechanical damage using wildtype (WT) and lox2 mutant plants. Compared with WT, the lox2 mutant had higher constitutive levels of the phytohormone salicylic acid (SA) and enhanced expression of SA-responsive genes. This suggests that AtLOX2 may be involved in the biosynthesis of jasmonates that are involved in the antagonism of SA biosynthesis. As expected, the jasmonate burst in response to wounding was dampened in lox2 plants. Generally, 1 h after wounding, genes linked to jasmonate biosynthesis, jasmonate signaling attenuation and abscisic acid-responsive genes, which are primarily involved in wound sealing and healing, were differentially regulated between WT and lox2 mutants. Twelve h after wounding, WT plants showed stronger expression of genes associated with plant protection against insect herbivory. This study highlights the dynamic nature of jasmonate-responsive gene expression and the contribution of AtLOX2 to this pathway and plant resistance against insects. Full article