An overlooked function of trichomes in defense against parasitic plants

Abstract

Trichomes have rarely been considered as components of pre-attachment resistance mechanisms against parasitic plants, and their potential role in host defense has scarcely been addressed in reviews of trichome function. In this study, we investigated the interaction between tomato plants (Solanum lycopersicum ‘Minibel’) and the parasitic plant Cuscuta campestris. Analyses focused on trichome distribution and the structural modifications they undergo at various stages of infestation and host resistance. Parasite–host contact may occur through the direct attachment of Cuscuta seedlings following germination (primary parasitism), or via lateral branches originating from previously infested hosts (secondary parasitism). Primary parasitism on tomato stems was inefficient, seemingly due primarily to the long type I and II trichomes hindering parasite attachment to the host surface. Only ~20% of Cuscuta seedlings successfully overcame this physical barrier and developed haustoria. These long trichomes also appeared to contribute to resistance during secondary parasitism, as they seemingly impede penetration of the haustoria by bending under the pressure exerted by the dodder stem. As infestation progressed, marked changes were also observed in type VI glandular trichomes. In the vicinity of the parasite, the glandular heads of trichomes often turned brown, exhibited significant autofluorescence and sometimes ruptured, which is consistent with the release of secondary metabolites. During the formation of an epidermal and subepidermal defensive barrier, the heads of additional type VI trichomes darkened, lost turgor and acquired a flattened four-lobed appearance. Together, our findings highlight the importance of trichomes in the defense of tomato plants against dodder and expand our understanding of pre-attachment resistance mechanisms.

Introduction

Trichomes and their functions

Trichomes are commonly defined as unicellular or multicellular appended structures that typically originate as hair-like extensions of aerial epidermal cells in plants (Johnson, 1975). They can be classified according to their morphology and function as unicellular or multicellular, branched or unbranched, and glandular or non-glandular (Wang et al., 2021; Khan et al., 2026).

Trichomes contribute to thermoregulation and limit water loss through transpiration, while also providing protection against ultraviolet radiation (Xiao et al., 2016; Zhang et al., 2020; Wang et al., 2021). In addition to their role in abiotic stress tolerance, trichomes are also key players in defense against biotic stress. They can restrict movements, hindering herbivore feeding and oviposition, reduce the survival of insects and other pests by secreting toxic compounds, act as early sensors that alert the plant to the presence of potential attackers, in addition to post ingestive effects (Schuurink and Tissier, 2020; Shah et al., 2023; Blaschek, 2024; Ahmad et al., 2025).

Although the involvement of trichomes in defense against arthropods has been extensively documented, their potential role in resistance to parasitic plants has been largely overlooked. Reviews addressing trichome function typically fail to consider their contribution to resistance against parasitic plants (Zhang et al., 2020; Wang et al., 2021; Li et al., 2023; Tabary et al., 2024). Conversely, studies on plant resistance mechanisms to parasitic plants rarely mention trichomes as a contributing factor (Fishman and Shirasu, 2021; Albanova et al., 2023).

Primary and secondary parasitism

Some plant species are capable of mounting defense strategies against parasitic plant infestation, as reported for several tomato varieties in response to various Cuscuta spp. (dodders) in this way (Kaiser et al., 2015). These responses are generally classified as pre- or post-attachment (Fishman and Shirasu, 2021; Jhu and Sinha, 2022; Albanova et al., 2023; Shi et al., 2026). Pre-attachment resistance encompasses constitutive or early-induced mechanisms that prevent parasitic plants from attaching to their hosts. These mechanisms include strategies that reduce parasitic seed germination, render hosts unrecognizable to parasitic plants or impede haustorium development. In contrast, post-attachment resistance develops following physical contact, making it difficult for haustoria to intrude. It includes processes related to cell wall modifications and other immune-like reactions that restrict the parasite’s ability to invade and acquire resources (Shi et al., 2026).

In this context, the presence of a dense layer of trichomes may represent a previously overlooked form of pre-attachment resistance against dodder, potentially acting as a physical –and presumably chemical– barrier to parasite establishment.

Trichomes in tomato stems

Within the genus Solanum, there is substantial interspecific variation in both glandular and non-glandular trichome density (Bar and Shtein, 2019; Chang et al., 2021; Watts and Kariyat, 2022). In Solanum lycopersicum, seven distinct trichome types have been identified, with their distribution varying depending on the plant organ and developmental stage (Chang et al., 2021; Shah et al., 2023; Sun et al., 2024). See Supplementary Figure 1 for a depiction of the trichome distribution in the stem of the ‘Minibel’ tomato. Trichomes of types I, II, III, and IV are classified as long ones, whereas types V, VI, and VII are shorter. Types II, III, and V are non-glandular, while types I, IV, VI, and VII are glandular (Luckwill, 1943).

Glandular trichomes are specialized structures capable of synthesizing and storing a wide array of secondary metabolites that can negatively affect herbivores and pathogens. These include non-volatile compounds such as acylsugars and proteinase inhibitors, as well as semi-volatile or low-volatility metabolites such as phenylpropanoids, terpenoids, methyl ketones, flavonoids, and other phenolic compounds (Watts and Kariyat, 2022; Tabary et al., 2024).

Once synthesized, these compounds are secreted either onto the surface of the trichome or into specialized extracellular storage cavities. In type VI glandular trichomes, metabolites accumulate in an intercellular storage cavity formed by the glandular head cells and are rapidly released upon mechanical disruption (Bergau et al., 2015; Schuurink and Tissier, 2020; Popowski et al., 2025).

Hypothesis and objectives

Contact between dodders and other parasitic plants and their hosts can occur through two main pathways. In primary parasitism, the parasite establishes contact directly after germination of the seed, attaching itself to a nearby host. Secondary parasitism, in contrast, occurs when the parasite spreads from an already infected host via lateral stems that reach and colonize additional plants (Yokoyama et al., 2023; Bawin and Krause, 2024).

Preliminary unpublished observations of tomato plants (S. lycopersicum ‘Minibel’) suggested that their long stem trichomes (types I and II) may be involved in their resistance to both primary and secondary parasitism by Cuscuta campestris. These observations led us to hypothesize that trichomes contribute to resistance against Cuscuta and may function as a form of pre-attachment defense mechanism. This study aimed to test this hypothesis by analyzing the distribution of different trichome types and the changes they undergo during the progression of infestation and resistance in their interaction with C. campestris plants.

Method

Plant material and growth conditions

Tomato (Solanum lycopersicum) ‘Minibel’ and Cuscuta campestris were used as a model host–parasite system based on previous studies (Frey et al., 2026). Commercial tomato seeds (‘Minibel’; Mascarell Semillas S.L., Valencia, Spain) and mung bean (Vigna radiata; Legumbres La Asturiana, León, Spain) were germinated in 50-well plastic trays (100 mL per well) filled with pre-hydrated, fertilized universal substrate (Compo Sana^®, Barcelona, Spain).

Plants were then grown in a controlled growth chamber at 23 ± 1 °C under a 16 h light/and 8 h dark photoperiod (≈41 µmol m⁻² s⁻¹) and 50–60% relative humidity (Frey et al., 2023). The trays were watered twice weekly until reaching approximately 90% field capacity, and fertilized with a universal liquid fertilizer (COMPO NPK 7-5-6).

Cuscuta campestris seeds, originally collected from Medicago sativa fields in León (Spain) and stored under cold conditions, were germinated on P60 Petri dishes lined with moistened filter paper in the dark at 23 ± 1 °C.

Infestation assays

Three to four weeks after sowing, germinated dodder seedlings were used to infest five-week-old host plants (~20 cm tall), representing primary parasitism. The seedlings, which measured approximately 1.0–1.5 cm in length, were placed directly on the substrate in contact with host stems and allowed to grow freely. Three independent biological experiments were performed. Because the number of plants varied among experiments depending on their availability, each replicate included 10, 12, and 25 tomato plants and 6, 10, and 16 mung bean plants.

To facilitate secondary parasitism, tomato plants were placed next to mung bean plants that had been previously parasitized by dodder. This enabled the lateral dodder stems to reach and infest the tomato plants. Depending on the experiment, the setup consisted either of one row of parasitized mung bean plants flanked by two rows of tomato plants, or of one row of parasitized mung bean plants positioned next to a single row of tomato plants. Three independent biological experiments were also performed for this experimental system, each including 5, 9, and 24 tomato plants. Experiments were conducted under laboratory conditions; therefore, minor environmental variation among replicates cannot be excluded.

Definition of parasitism and resistance stages in the dodder-tomato interaction

Parasitism was categorized into four successive stages: (i) Pre-adhesive stage (F0), in which dodder stems coil around the host without visible haustoria; (ii) Adhesive stage (F1), where a disk-shaped structure, called an appressorium, forms on the dodder stem; (iii) Intrusive stage (F2) which is characterized by the presence of haustoria; and (iv) Proliferative stage (F3), where vascular connections are established and lateral branches emerge. Following parasite attachment, resistance responses in tomato were occasionally observed and classified into two stages: (i) Early resistance (R1), showing slight brown discoloration of the host epidermis at the contact site; and (ii) Late resistance (R2), where dodder tissues lost turgor and turned dark brown, accompanied by pronounced darkening of the surrounding tomato epidermis (Frey et al., 2026).

Imaging and stereomicroscopy

Macroscopic images were acquired using a Samsung A34 smartphone. High-resolution images were obtained with a Nikon SMZ25 stereomicroscope equipped with a Nikon DS-Ri2 camera. Fluorescence observations were performed using 460 nm excitation and a 520 nm emission filter. Image acquisition and processing were carried out using NIS-Elements AR software (v. 5.42.06). Type VI trichomes were quantified from stereomicroscopic images obtained during the different dodder-tomato interaction stages. Only trichomes located within the host stem region adjacent to the dodder stem, extending approximately one dodder-stem width on either side of the contact zone, were scored. A total of 2774 trichomes from at least 50 stereomicroscopic fields were scored.

Statistical analyses and modelization

Different statistical frameworks were applied depending on the nature of the variables. To evaluate the qualitative phase progression over time across experimental systems: primary parasitism in tomato (PP.Slyc), secondary parasitism in tomato (SP.Slyc) and primary parasitism in mung bean (PP.Vrad), cumulative link mixed models (CLMM) were fitted using the ordinal package in R, modeling the biological phase as an ordered factor (F0 < F1< F2 < F3 < R1 < R2). For the CLMM, experimental system, evaluation day, and their interaction were specified as fixed effects, while a unique plant identifier was treated as a random effect to account for the longitudinal design. Concurrently, to determine the relationship between trichome VI status and infestation stages, categorical trichome status profiles were analyzed using a multinomial generalized linear mixed model (GLMM). The biological phase was included as the fixed-effect predictor. Post-hoc pairwise comparisons within specific evaluation days (for the CLMM) and across biological phases (for the multinomial GLMM) were performed using the emmeans package, applying Tukey’s HSD adjustment for multiple comparisons (α = 0.05).

Results

Long trichomes hinder primary parasitism

During the pre-adhesive phase (F0), the presence of long trichomes (types I and II) (Supplementary Figure 1) on the stems of the ‘Minibel’ tomato plants largely prevented the attachment of Cuscuta campestris seedlings (Figures 1A–D). Only a subset of seedlings successfully overcame this barrier, becoming attached to the host (F1; Figure 1E). They subsequently developed haustoria (F2; Figure 1F), and eventually reached the proliferative stage (F3; Figure 1G).

Figure 1

Thirteen days after infestation, approximately 55% of dodder seedlings failed to attach to tomato plants, whereas nearly 75% successfully established on mung bean plants, a well-known susceptible host lacking long trichomes (Figures 1H, I). Temporal comparison of infestation stages further confirmed that dodder attachment and progression occurred more rapidly and efficiently in mung bean than in tomato, where resistance responses were frequently observed (Figures 1H, I). This effect is particularly relevant because dodder seedlings generally die once seed reserves are exhausted, approximately 15 days after germination (Nagao et al., 2025). Figure 1A, B illustrate dodder seedlings unable to establish on tomato stem, showing desiccation of their basal region.

CLMM revealed a significant interaction between host system and evaluation day, indicating distinct temporal trajectories in phase transitions (Supplementary Table 1). During the early stages (days 2–7), PP.Slyc showed a significantly higher probability of remaining in earlier phases than SP.Slyc and, at day 7, also than PP.Vrad. By day 9, all systems converged, with no significant differences in overall phase distribution. At day 13, although PP.Slyc and PP.Vrad did not differ in global phase scores, their biological outcomes diverged: PP.Vrad accumulated plants at the severe parasitism stage (F3), whereas PP.Slyc progressed to the terminal resistance stage (R2). SP.Slyc exhibited the greatest progression into R2, maintaining a significantly more advanced phase profile than both PP.Slyc and PP.Vrad.

Trichomes also restrict secondary parasitism

When dodder stems that had been previously established on mung bean plants were allowed to come into contact with tomato plants (secondary parasitism), the overall infestation rate on tomato plants increased to approximately 90% at thirteen days (Figure 2A). Nevertheless, trichomes continued to hinder parasite establishment.

Figure 2

Throughout the interaction stages, long trichomes (types I and II) bent under the mechanical pressure exerted by dodder stems, thereby limiting appressorial access to the epidermal surface and hindering haustorial penetration (Figures 2B–E). Successful attachment events (adhesive stage, F1) were typically associated with stem regions apparently displaying lower densities of long trichomes (Figure 3A).

Figure 3

Type VI trichomes undergo structural changes during the interaction

As the interaction progressed, a substantial proportion of type VI trichomes exhibited noticeable structural alterations (Figures 3B–E). These modifications were more readily detected under fluorescence illumination (Figures 3F–J).

At early interaction stages (F1), most of the type VI trichomes appeared structurally intact and displayed weak autofluorescence under blue-light excitation (Figures 3A, F). During the intrusive phase (F2), a part of the trichomes located within contact zones appeared decapitated, and several released sticky secretions exhibiting intense autofluorescence under blue-light excitation (Figures 3B, G). In parallel, another subset of trichomes became brownish and showed increased autofluorescence (Figures 3B, G). This pattern persisted during the proliferative phase (F3) (Figures 3C, H).

The structural modifications of the trichomes progressively expanded during resistance stages, both during early resistance (R1; Figures 3D, I) and late resistance (R2; Figures 3E, J). At advanced stages (R1–R2), the autofluorescence associated with brownish trichomes gradually disappeared. The resulting trichomes had a flattened, blackened appearance and were therefore more abundant. In parallel, formation of the subepidermal defensive barrier (“shield”), associated with the initial resistance phase (Frey et al., 2026), was accompanied by progressively stronger autofluorescent signals. At later stages, desiccated and dead dodder stems also displayed intense autofluorescence (Figures 3D, I, E, J).

Based on these observations, type VI trichomes were classified into five structural states: intact; brownish and turgid; blackened and flat; decapitated; and decapitated with secretions (Figure 4). Quantification of these trichomes states throughout the interaction revealed that, during the adhesive stage, approximately 80% of type VI trichomes remained intact, whereas around 5% appeared brownish and turgid, and over 10% were decapitated (Figure 4A). As the interaction progressed to the early stage of resistance (R1), the proportion of intact type VI trichomes decreased progressively, whereas blackened and flat trichomes and decapitated trichomes with secretions became slightly more abundant. In contrast, the proportions of brownish and turgid trichomes and decapitated trichomes lacking visible secretions remained comparatively stable. Finally, during the late resistance stage (R2), blackened and flat trichomes accounted for around 75% of those observed, while intact trichomes accounted for less than 25%.

Figure 4

Multinomial GLMM analysis showed that type VI trichome status was strongly associated with infection phase progression (Supplementary Table 2). As infection advanced, the probability of observing intact type VI trichomes decreased significantly, while structural alterations accumulated. The occurrence of blackened and flat trichomes increased markedly toward the terminal resistance phase, with all early phases showing highly significant negative estimates relative to R2.

Detailed observations further revealed additional structural modifications in type VI trichomes during the interaction (Figure 4, S2). Intact trichomes consisted of a basal cell, a stalk cell, a neck cell, and a four-celled glandular head, and displayed weak autofluorescence (Figures 4B, C). The outer cell wall of the glandular and neck cell walls were particularly conspicuous, (Supplementary Figures 2A, B). Neck cell walls showed intense cresyl violet staining (Supplementary Figures 2A, B), consistent with lignified cell walls, and displayed strong cellulose labelling (Supplementary Figure 2C), whereas the outer cell walls of the glandular cells were enriched in methyl-esterified pectins, as revealed by LM20 immunolabelling (Supplementary Figure 2C).

In the presence of coiling dodder stems, some trichomes showed detachment of the glandular head (Figures 4D, E), and in some cases, the detached glandular head remained attached to the stalk cell through the neck cell (Supplementary Figure 2D). In certain trichomes, part of the stored secondary metabolites accumulated alongside the stalk cell (Figures 4F, G, S2E). These sticky secretions displayed intense autofluorescence signals (Figure 4G).

Other trichomes progressively turned brown (Figures 4H, I), subsequently lost turgor and eventually became blackened, acquiring the characteristic four-lobed morphology resembling a clover and no longer exhibiting autofluorescence (Figures 4J, K). The browning of trichome heads and the release of sticky secondary metabolites were consistently associated with strong autofluorescence signals (Figures 4G, I, K), which frequently extended to adjacent long trichomes and pavement epidermal cells (Figure 4K).

Discussion

Species of the genus Cuscuta are capable of parasitizing a wide range of host plants. Nevertheless, some hosts exhibit partial or complete resistance responses. In tomato plants, resistance to different Cuscuta species has been described in several cultivars, including Heinz against C. reflexa (Kaiser et al., 2015), Halley 3155 against C. pentagona (Runyon et al., 2010), and M82 and Minibel against C. campestris (Jhu et al., 2022; Bawin et al., 2024; Frey et al., 2026).

These resistance responses are generally associated with hypersensitive-like reactions, local lignification, and inhibition of haustorial penetration (Jhu et al., 2022; Bawin et al., 2024; Frey et al., 2026). However, resistance to parasitic plants is likely determined by the combined action of multiple defense components, including constitutive barriers and inducible responses (Kaiser et al., 2015). In this context, passive mechanical barriers may also contribute significantly to pre-attachment and early pre-haustorial resistance. It is noteworthy that dodder attachment and subsequent progression occurred more rapidly in mung bean, a susceptible host lacking long stem trichomes, than in tomato. While these two host species differ in many traits besides trichome density —including stem anatomy, surface chemistry, tissue organization, and overall host compatibility— the dense layer of long tomato trichomes seems to contribute to the reduced efficiency of parasite establishment. The generalized linear mixed model further supports this interpretation by revealing significant differences in the temporal progression of the interaction among primary parasitism in tomato, secondary parasitism in tomato, and primary parasitism in mung bean.

Taken together, our observations suggest that long type I and II trichomes are likely to act as an initial constitutive barrier that limits parasite attachment. This may help explain why direct seedling attachment by C. campestris is less efficient than secondary parasitism in tomato ‘Minibel’ (Frey et al., 2026). In the present study, our observations suggest that the reduced efficiency of primary parasitism is at least partially associated with the difficulty dodder seedlings have in reaching and adhering to the tomato epidermis due to the dense trichome layer. Similarly, a pioneering study conducted with tomato cv. Halley 3155 showed that long trichomes reduced the efficiency of C. pentagona attachment in older plants, whereas younger plants with lower trichome density remained susceptible (Runyon et al., 2010).

Our observations further point to the idea that long trichomes also interfere with secondary parasitism. Although established dodder stems are mechanically stronger than seedlings and can more effectively constrict tomato stems, dense trichome layers still seem to hinder appressorial contact and haustorial penetration. Successful penetration was frequently associated with regions apparently displaying a lower density of long trichomes, although this relationship was not quantified. Likewise, dodder attachment appeared to be less frequent on mature basal stem regions, which typically bear a denser trichome cover, than on younger stem portions, although this trend was not quantified.

Because there is substantial variation in trichome density and morphology among tomato cultivars (Kaur et al., 2023), differences in trichome architecture may contribute to the variability in resistance observed among tomato genotypes (Jhu et al., 2022).

In addition, new experiments intending mechanical removal of trichomes followed by infestation assays, as well as a comparison with low-trichome tomato genotypes would provide direct experimental evidence for the contribution of long trichomes to resistance.

In addition to the role of long trichomes as constitutive barriers, quantitative analyses further showed that the structural states of type VI trichomes were strongly associated with the progression of the interaction, suggesting their involvement in induced defense responses against dodder.

Recent studies have shown that type VI trichomes participate in rapid defense responses against herbivorous arthropods (Popowski et al., 2025). These studies demonstrate that, in addition to physically hindering arthropod locomotion and releasing sticky secondary metabolites stored in their glandular heads, mechanical stimulation of long trichomes can also trigger Ca²⁺ signaling waves that propagate toward glandular trichomes and surrounding tissues, promoting defense-related responses including jasmonate signaling and terpene biosynthesis (Blaschek, 2024; Sun et al., 2024; Popowski et al., 2025).

Our observations suggest that a similar mechanism might be at work during dodder infestation. In the contact zones between dodder and tomato stems, long trichomes were mechanically bent, while nearby type VI trichomes frequently became brownish and displayed intense autofluorescence. Because autofluorescence alone does not identify the chemical nature of the fluorescent compounds, the following interpretations should be regarded as working hypotheses based on the spatial distribution of the signal together with previous studies on tomato glandular trichomes. This autofluorescent signal appeared to be localized within the glandular contents rather than in the cell walls, suggesting that it is associated primarily with compounds stored within the glandular cavity rather than with structural polymers such as lignin or suberin deposited in the cell wall. The coincidence between intracellular autofluorescence and the appearance of intensely fluorescent sticky secretions following trichome rupture is consistent with this interpretation. Although the chemical identity of these autofluorescent compounds remains unknown, accumulation and/or oxidation of phenolic secondary metabolites in the glandular head appear to be plausible candidates (Bergau et al., 2015).

These changes may reflect alterations in the accumulation, oxidation, or release of compounds stored within the glandular cavity, including defensive metabolites. Additionally, other type VI trichomes showed glandular head detachment associated with the release of sticky autofluorescent secretions. These responses resemble those previously described following arthropod-mediated mechanical stimulation of tomato trichomes (Blaschek, 2024; Sun et al., 2024; Popowski et al., 2025). Therefore, parasitic plants may also be included among the biotic agents against which trichomes contribute to plant defense, as previously suggested (Runyon et al., 2010).

Type VI trichomes could function as wound-sensitive structures due to the ease with which their glandular heads detach. In arthropods, rupture of these trichomes releases toxic and sticky glandular fluids that impair their movement. In our study, rupture of type VI trichomes appeared associated with the formation of a defensive shield in the epidermal and subepidermal layers of tomato stems (Frey et al., 2026), suggesting that trichome disruption may facilitate the release of glandular contents into the interaction zone, which may include defensive secondary metabolites. Rupture of type VI trichomes in Solanaceae has been reported to occur at the junction between the glandular cells and the neck cell, consistent with previous studies on trichome development (Bergau et al., 2015), and in agreement with our observations. The distinctive structural properties of this region might play an important role in facilitating trichome rupture.

Previous studies have reported lignification of the neck cell walls (Hao et al., 2026), which is also consistent with the intense cresyl violet staining observed in our study. In addition, our Calcofluor White staining revealed strong cellulose labelling in the neck cell walls. Together with the distinctive outer cell wall composition of the glandular cells, these structural features might contribute to the mechanical fragility of the trichome head and facilitate the release of glandular contents.

Interestingly, strong autofluorescence signals were frequently associated with sticky extracellular deposits on the stems of detached glandular heads. In some cases, the autofluorescence appeared to extend towards the neighboring bases of long trichomes and epidermal cells. Although the precise nature of this autofluorescence remains unknown, these observations are consistent with localized activation of defense-associated signaling pathways, though they do not provide direct evidence of such activation.

At later resistance stages, many type VI trichomes acquired a characteristic flattened tetralobed morphology and progressively lost autofluorescence. This morphology is consistent with collapse of the glandular head, accompanied by oxidation and darkening of its contents. These changes may result from alterations in cellular turgor associated with the formation of the subepidermal defensive barrier (“shield”) previously described in resistant tomato–Cuscuta interactions (Jhu et al., 2022; Frey et al., 2026). Resistance to parasitic plants also involves reinforcement of host tissues through deposition of lignin, suberin, callose, and other cell wall-associated compounds that inhibit haustorial penetration (Jhu et al., 2022; Albanova et al., 2023; Frey et al., 2026). Our observations therefore suggest that trichome-mediated responses may act coordinately with these structural defenses.

However, whether these trichome modifications actively contribute to resistance or instead represent secondary consequences of tissue reorganization associated with the defensive shield remains unresolved and deserves further investigation. Future experiments combining pharmacological inhibition of defense-related signaling pathways with genetic approaches targeting trichome development or function would help clarify this issue.

Overall, our findings are consistent with a model in which long tomato trichomes function not only as constitutive physical barriers but also as potential mechanosensory structures that detect dodder contact. Mechanical stimulation generated during parasite attachment may trigger signaling pathways involving type VI glandular trichomes and localized defense responses. Although further functional studies are required to validate this model, our results identify trichomes as a previously overlooked component of tomato resistance against parasitic plants.

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