English

• Fungicides play an indispensable role in modern agriculture, serving as the primary means of protecting crops from pests and plant pathogens, thereby increasing yield [1–3]. However, traditional fungicides are prone to evaporation and photolysis, significantly reducing effectiveness against organisms. According to estimates by the Food and Agriculture Organization, using fungicides can recover 30%–40% of the total global crop output [4], however, fungicide residues can subsequently harm both plants and aquatic life [5,6]. Reducing fungicide losses, ensuring efficient fungicide delivery, and enabling on-demand release are crucial for improving the efficiency of fungicide usage and minimizing environmental pollution.

  Sclerotinia sclerotiorum (S. sclerotiorum) is one of the most destructive plant pathogens that infects romaine lettuce and can lead to substantial production losses. Upon colonization of the romaine lettuce surface, S. sclerotiorum produces extracellular enzymes that foster an acidic microenvironment [7–9], which damages the plant cell walls and contributes to a marked reduction in romaine lettuce yield. Dimethachlon (Dim) is a common fungicide that is remarkably effective at inhibiting S. sclerotiorum. However, their effectiveness, utilization, and persistence are significant because they decompose in the presence of acid-base and sunlight [10]. Therefore, there is an urgent need to design a delivery system that extends the duration of fungicide use, enhances the utilization rate, ensures biosafety, and remains environmentally friendly.

  Hollow mesoporous silica nanoparticles (HMSNs) have been widely utilized as a delivery system for both medicines and fungicides owing to their advantageous properties, such as large surface area, tunable size, high stability, and biocompatibility [11–16]. Wang et al. developed an oxidation-resistant ferrous foliar fertilizer delivery system that utilizes hollow silicon as a carrier for ferrous foliar. This not only enhances the adhesion efficiency of the foliar but also boosts its antioxidant capacity, effectively addressing iron deficiency in crops, and thus significantly elevating crop yield [17]. Similarly, Ding et al. a mesoporous silica nano-carrier pesticide delivery system loaded with acetamiprid was constructed, which improved the control effect of aphids and reduced pesticide residues [18]. Leveraging HMSNs for pesticide delivery can bolster formulation stability, curtail soil leaching, and prolong effectiveness while minimizing environmental toxicity [19–24].

  In this study, we encapsulated Dim in HMSNs using a one-pot method, followed by a CaCO₃ film coating on the surface of the HMSNs through the reaction of Na₂CO₃ and CaCl₂, creating a Dim delivery system called D/H@CaCO₃ (Fig. 1a). The CaCO₃ film exhibited pH-responsive release properties and acted as a regulator of Dim release. When romaine lettuce leaves were contaminated with S. sclerotiorum and treated with D/H@CaCO₃, the CaCO₃ film acted as a "gatekeeper", facilitating the controlled degradation of D/H@CaCO₃ in the acidic microenvironment of S. sclerotiorum-infested romaine lettuce and ensuring the pH-responsive release of Dim from the HMSNs. This effectively enhances the antifungal effect, thus curtailing the growth of S. sclerotiorum. Simultaneously, the decomposed CaCO₃ produces CO₂, which aids plant photosynthesis and benefits plant growth. Furthermore, D/H@CaCO₃ is environmentally safe and does not hamper the growth of romaine lettuce because the main component of D/H@CaCO₃ is HMSNs.

  Figure 1

  

  Figure 1.  (a) Schematic illustration for preparing D/H@CaCO₃ and the mechanism of enhanced S. sclerotiorum inhibition and plant photosynthesis. The preparation procedure of D/H@CaCO₃. D/H@CaCO₃ responds to the acidic microenvironment of S. sclerotiorum to release Dim and CO₂. This enhances the inhibitory effect of Dim on S. sclerotiorum, and the CO₂ generated by CaCO₃ further promotes photosynthesis in romaine lettuces. (b) SEM and (c) TEM of D/H@CaCO₃. Scale bar: 100 nm. (d) Hydrodynamic diameters of HMSNs and D/H@CaCO₃. (e) Zeta potentials of Dim, HMSNs, and D/H@CaCO₃. (f) EDS mapping of D/H@CaCO₃. Scale bar: 100 nm. (g) XPS image of D/H@CaCO₃. (h) FTIR spectra of Dim, HMSNs, D/H and D/H@CaCO₃. (i) TGA curves of H@CaCO₃ and D/H@CaCO₃. (j) Zeta potential and hydrodynamic diameters changes of D/H@CaCO₃ at 0 ℃ for 7 days. (k) Release behavior of D/H@CaCO₃ at pH 5, 6, and 7 (35 ℃) and (l) temperatures at 25, 35, 45 ℃ (pH 5). Data are presented as means ± SEM (n = 3).

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  Dim was loaded into the HMSNs, followed by the coating of a film of CaCO₃ onto the surface via the reaction of Na₂CO₃ and CaCl₂. This resulted in the formation of pH-responsive fungicide nanoparticles (D/H@CaCO₃) for delivery to romaine lettuce. The morphology of D/H@CaCO₃ was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), D/H@CaCO₃ was spherical with a rough surface (Fig. 1b) and a visible coating CaCO₃ layer on its surface (Fig. 1c). We also investigated the particle size and potential of D/H@CaCO₃. The size of D/H@CaCO₃ was approximately 255 nm, about 40 nm larger than HMSNs (Fig. 1d). The zeta potential of Dim, HMSNs, and D/H@CaCO₃ was −8.72, −14.20, and −23.69 mV, respectively (Fig. 1e). The energy dispersive spectrometer (EDS) mapping analysis revealed that D/H@CaCO₃ primarily contained Cl, N, Si, Ca, C, and O. Ca and C were mainly attributed to CaCO₃, whereas Si originated from SiO₂, Cl and N originated from Dim (Fig. 1f). The X-ray photoelectron (XPS) analysis of D/H@CaCO₃ (Fig. 1g) showed a pronounced Si 2p peak at 103.22 eV, corresponding to the primary element of the HMSNs (Fig. S1a in Supporting information). Distinct Cl 2p and C 1s peaks were observed at 198.74 and 285.38 eV, respectively, indicating the presence of Dim as the main component in D/H@CaCO₃ (Figs. S1b and c in Supporting information). Additionally, a well-defined Ca 2p peak at 345.94 eV confirms the presence of coated CaCO₃ (Fig. S1d in Supporting information), validating the structural composition of D/H@CaCO₃. The functional groups in D/H@CaCO₃ were characterized through Fourier transform infrared spectroscopy (FTIR) (Fig. 1h), showing characteristic peaks associated with Si-O-Si bonds at 1094.89 cm⁻¹ in the HMSNs group. As for the Dim group, distinctive absorption peaks corresponded to C—Cl bond at 616.102 cm⁻¹, along with peaks at 1632.282 cm⁻¹ for C=O. The absorption peak at 3411.178 cm⁻¹ was attributed to the stretching vibration of the =C—H bond. The D/H@CaCO₃ spectra exhibited peaks originating from both Dim and HMSNs. The Dim loading efficiency of D/H@CaCO₃ was determined by thermogravimetric analysis (TGA) (Fig. 1i). The HMSNs exhibited a final mass loss rate of 3.31%, attributed to water evaporation and decomposition of organic functional groups. In comparison, D/H@CaCO₃ showed a higher final mass loss rate of 36.41%, which indicated the loss of both organic matter and Dim, and the Dim loading rate was calculated to be 33.1%.

  The stability of D/H@CaCO₃ was assessed by monitoring the variations in zeta potential and particle size at 0 ℃ and 54 ℃ [25]. At 0 ℃, the potential remained stable at approximately −21 mV for 7 days, and the particle size distributed around 241 nm (Fig. 1j). Similarly, at 54 ℃, the potential was stable at around −24 mV for 14 days, and the particle size distribution was around 238 nm (Fig. S2 in Supporting information). These results demonstrate the optimal stability of D/H@CaCO₃.

  To effectively control the release of fungicides into the acidic microenvironment of S. sclerotiorum, a pH-responsive system that releases Dim under acidic conditions is crucial. The designed CaCO₃ coating on the D/H surface degraded under acidic conditions. We tested the pH-responsive release efficacy of D/H@CaCO₃ at pH 5, 6, and 7 and temperatures of 25, 35, and 45 ℃. As depicted in Fig. 1k, the cumulative release rates at 35 ℃ over a 48 h period were 76.48%, 50.76%, and 22.08% at pH 5, 6, and 7, respectively. This indicates that, in a weakly acidic microenvironment, D/H@CaCO₃ can respond to degradation, enabling the responsive release of Dim. Furthermore, we studied release rates at pH 5 and 25, 35, and 45 ℃, which were 65.68%, 72.60%, and 80.38% at 48 h, respectively, suggesting that higher temperatures facilitate Dim release (Fig. 1l). Additionally, we utilized zero-, first-, and higher-order release kinetic models to analyze the release kinetics of D/H@CaCO₃ (Figs. S3 and S4 in Supporting information).

  We have previously demonstrated that D/H@CaCO₃ is degraded in the acidic microenvironment of S. sclerotiorum. Moreover, degraded CaCO₃ can generate CO₂ under acidic conditions. We used a bromothymol blue solution to test the generation of CO₂ using D/H@CaCO₃ under acidic conditions. By adding an oxalic acid solution to D/H@CaCO₃, we simulated the microenvironment of S. sclerotiorum, the degradation of D/H@CaCO₃ caused the CO₂ release, progressively changing the color of bromothymol blue from blue to green and ultimately to yellow. As shown in Fig. 2a, when the D/H@CaCO₃ concentration ranged from 0 to 1 mg/mL, the indicator changed from blue to yellow. This color shift suggests that as the concentration of D/H@CaCO₃ increased, the CO₂ production increased. We further investigated whether the CO₂ produced by D/H@CaCO₃ in the acidic microenvironment of S. sclerotiorum could enhance photosynthetic pigments in plants (Fig. 2b). In Fig. 2c different concentrations of D/H@CaCO₃ were used to treat romaine lettuce in the acidic microenvironment. When the D/H@CaCO₃ concentrations were 0, 100, 200, 400, 800, and 1600 mg/L, the chlorophyll a content was 0.69, 0.82, 0.91, 0.96, 1.03, and 1.09 mg/g, respectively. The chlorophyll b content also increased with increasing D/H@CaCO₃ concentration (Fig. 2d). When the D/H@CaCO₃ concentration reached 200 mg/L, its carotenoid content surged to 0.059 mg/g, as evident in Fig. 2e. This shows that the CO₂ released from D/H@CaCO₃ in the S. sclerotiorum microenvironment promotes photosynthesis, benefiting plant growth. When the D/H@CaCO₃ concentration exceeded 400 mg/L, it could generate excess CO₂ for photosynthesis over the long term. This elevated CO₂ treatment could lead to more membrane damage due to reactive oxygen species, thus resulting in the loss of photosynthetic pigments and lowering of the carotenoid accumulation [26,27].

  Figure 2

  

  Figure 2.  (a) Color changes in bromothymol blue indicator after treatment with CO₂ generated by different concentrations D/H@CaCO₃. (b) Schematic illustration of D/H@CaCO₃ promoting plant photosynthesis. CaCO₃ coated on D/H@CaCO₃ degrading and generating CO₂ in the acidic microenvironment of S. sclerotiorum, which could be beneficial for plant photosynthesis and plant growth. (c) Chlorophyll a, (d) chlorophyll b, and (e) carotenoids levels in the leaves treated with different concentrations of D/H@CaCO₃. Data are presented as means ± SEM (n = 3).

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  To evaluate the antifungal activity of D/H@CaCO₃ against S. sclerotiorum, the fungus was exposed to various concentrations of D/H@CaCO₃. As depicted in Fig. 3a, after a 7-day exposure to D/H@CaCO₃, the fungal colony size decreased with increasing D/H@CaCO₃ concentration, indicating enhanced suppression of S. sclerotiorum. A quantitative analysis of the inhibition rate in Fig. 3a was shown in Fig. 3b. At Dim concentrations of 0.25, 0.50, 1.00, 1.50, and 2.00 mg/L, D/H@CaCO₃ displayed inhibition rates of 24.55%, 31.82%, 38.18%, 50.00%, and 68.18% respectively. In contrast, Dim alone resulted in inhibition rates of 12.04%, 25.93%, 29.63%, 30.56%, and 57.41% (Fig. 3b). Figs. 3c and d reveal that on the second day, the Dim-treated group exhibited a smaller average diameter of the inhibition zone than the D/H@CaCO₃ group at an effective Dim concentration of 1.5 mg/L. On the third day, the Dim group displayed a S. sclerotiorum growth rate of 0.08 cm/d, whereas that of the D/H@CaCO₃ group was 0.08 cm/d. By the seventh day, these rates were 0.27 cm/d for the Dim group and 0.20 cm/d for D/H@CaCO₃ group (Fig. 3e). For a more detailed evaluation, we further utilized an effective Dim concentration of 0.25, 0.50, 1.00 and 2.00 mg/L to gage the S. sclerotiorum growth rate with D/H@CaCO₃ group at intervals of 1, 2, 3, 4, 5, 6 and 7 days (Figs. S5a–d in Supporting information). These findings suggest that D/H@CaCO₃ maintains its antifungal activity longer than Dim alone. This enhancement can be attributed to D/H@CaCO₃ facilitating the controlled release of Dim, with CaCO₃ serving as a protective "gatekeeper", triggering the release of Dim in acidic microenvironments and enhancing its inhibition against fungi. Upon administering D/H@CaCO₃ to S. sclerotiorum, retardation of hyphal growth was observed. The hyphae showed progressive fragmentation over 0, 4, 8, 12, 24, and 48 h (Fig. 3f). However, pronounced hyphal death was observed at the 12 h mark. In addition, we examined the effects of D/H@CaCO₃ on the fungicidal activity on romaine lettuce. Romaine lettuce leaves were inoculated with S. sclerotiorum and treated with different concentrations of D/H@CaCO₃ and Dim. Seven days later, a distinct reduction in the fungicidal plaque size was observed as the solution concentration increased, and the leaves appeared healthy (Fig. 3g). According to our quantitative analysis, at Dim concentrations of 100, 200, 400, and 800 mg/L, the control efficiencies of D/H@CaCO₃ reached 32.42%, 66.88%, 78.43%, and 90.44%, respectively, while the efficiencies of the Dim group in the precaution and control groups were 17.97%, 48.65%, 64.31%, and 80.38%, respectively (Fig. 3h). Compared with Dim alone, D/H@CaCO₃ could protect Dim from decomposition in the presence of sunlight, which enhanced the utilization of fungicides. Furthermore, the CaCO₃ film could release Dim in the acidic microenvironment of S. sclerotiorum-infested romaine lettuce, which provided better antifungal effectiveness and persistence of Dim for the responsive release. Therefore, D/H@CaCO₃ showed more effective in inhibiting on S. sclerotiorum than that of Dim alone.

  Figure 3

  

  Figure 3.  (a) Photos of S. Sclerotiorum colony on the 7^th day after administration of Dim or D/H@CaCO₃. A red circle represents the fungal colony (scale bar: 2 cm). (b) The quantitative analysis of inhibition rate of Dim or D/H@CaCO₃ against S. sclerotiorum. (c, d) The colony diameter was measured at 0, 1, 2, 3, 4, 5, 6 and 7 days after treatment with Dim or D/H@CaCO₃ at an effective Dim concentration of 1.5 mg/L. (e) The growth rate of Dim and D/H@CaCO₃ against S. sclerotiorum at an effective Dim concentration of 1.5 mg/L. (f) Microscopic images of hyphae at 0, 4, 8, 12, 24 and 48 h after D/H@CaCO₃ treatment. Scale bar: 50 µm. (g) Photos of S. sclerotiorum-infested romaine leaves on the 7^th day after being treated with different concentrations of D/H@CaCO₃ or Dim. Scale bar: 1 cm. (h) Control efficacy of Dim and D/H@CaCO₃ in controlling Sclerotinia disease. Data in (b) and (h) are compared by one-way ANOVA. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001. Data are presented as means ± SEM (n = 4).

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  We assessed the safety of the D/H@CaCO₃. Figs. 4a and b show that plants treated with 20 mg/L D/H@CaCO₃ still exhibited a germination rate greater than 85%. When applying concentrations of D/H@CaCO₃ at 0, 5, 10, 15 and 20 mg/L to plants, the recorded plant heights were 6.27, 7.12, 7.65, 6.82, and 6.37 cm, respectively (Figs. 4c and d). This demonstrates that D/H@CaCO₃ did not adversely affect plant height. Moreover, after treatment with HMSNs or D/H@CaCO₃, there was no discernible difference in the germination rate or rapeseed biomass, further validating the negligible effect of D/H@CaCO₃ on seedling growth. The infiltration of Dim residues into soil and water poses a significant danger to soil organisms and aquatic ecosystems. Earthworms and zebrafish were evaluated to assess the environmental safety of D/H@CaCO₃. Figs. 4e and f show the mortality rates of earthworms and zebrafish exposed to D/H@CaCO₃. At concentrations of 12.5, 25, 50, 100, or 200 mg/L, the average mortality rates were 27.77%, 33.80%, 43.37%, 51.34%, or 56.89% for earthworms, and 19.84%, 22.22%, 41.27%, 63.69%, or 66.67% for zebrafish. The lethal concentration 50% (LC₅₀) values of the D/H@CaCO₃ group surpassed those of the Dim group for both organisms. For earthworms, it was 51.83 mg/L in the Dim group (95% confidence interval: 26.17 to 110.7) and 73.15 mg/L in the D/H@CaCO₃ group (95% confidence interval: 47.24 to 127.5). For zebrafish, it was 57.36 mg/L in the Dim group (95% confidence interval: 38.08 to 90.72) and 73.15 mg/L in the D/H@CaCO₃ group (95% confidence interval: 81.93 to 122.2). These results indicated that D/H@CaCO₃ offers improved biocompatibility and environmental safety.

  Figure 4

  

  Figure 4.  (a) Photographs (scale bar: 20 mm) and (b) germination rate of seeds after 5 days of treatment with HMSNs or D/H@CaCO₃ at different concentrations. (c) Photographs (scale bar: 5 cm) and (d) plant height after 12 days of treatment with HMSNs or D/H@CaCO₃ at different concentrations. The death rate of (e) earthworms and (f) zebrafish after 48 h of treatment with Dim or D/H@CaCO₃. (g) Confocal images of romaine roots, stems, and leaves after being treated with FITC-stained D/H@CaCO₃. Green fluorescence represents FITC-stained D/H@CaCO₃. Scale bar: 100 µm. Data are presented as means ± SEM (n = 3).

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  To examine the distribution of D/H@CaCO₃ within the plants, we treated romaine lettuce roots and leaves with FITC-tagged D/H@CaCO₃. After exposing the romaine lettuce roots to stained D/H@CaCO₃ for 12 h, fluorescence was discernible in both the roots and stems. This indicated that D/H@CaCO₃ entered the roots from the water and was subsequently transported to the stems. Upon applying D/H@CaCO₃ to romaine lettuce leaves, a distinct green fluorescence was visible within the leaf stomata, highlighting the entry of D/H@CaCO₃ through these stomata (Fig. 4g). Additionally, we co-incubated the mycelia of S. sclerotiorum with D/H@CaCO₃ for 12 h and observed fluorescent signals in the mycelia, suggesting that D/H@CaCO₃ was successfully taken up by S. sclerotiorum (Fig. S6 in Supporting information).

  In this study we formulated a delivery system, D/H@CaCO₃, by coating HMSNs with CaCO₃ to encapsulate Dim for treating S. sclerotiorum in romaine lettuce. The D/H@CaCO₃ had a uniform particle size. The CaCO₃ on the surface of D/H@CaCO₃ functioned as a protective barrier, ensuring the stability of Dim by mitigating leakage, volatilization, and photodegradation. Crucially, in the acidic microenvironment induced by S. sclerotiorum on romaine lettuce leaves, CaCO₃ is degraded, thereby facilitating the pH-responsive release of Dim to combat the pathogen effectively. This approach demonstrated heightened antifungal efficacy against S. sclerotiorum compared with Dim alone, offering extended protection against plant fungal infections. Furthermore, the CaCO₃ coating of D/H@CaCO₃ upon degradation releases CO₂, increasing the content of pigments such as chlorophyll a, chlorophyll b, and carotenoids for photosynthesis, which is conducive to plant growth. Notably, our findings showed that D/H@CaCO₃ could penetrate romaine lettuce roots, get transported to the stems, and enter leaves via stomata, underscoring its potential as a carrier for fungicide delivery to plants. Dim as a fungicide has been applied in the plant for inhibiting S. sclerotiorum under the good agricultural practice settings dose [28,29]. In addition to the enhanced delivery, SiO₂ has been exploited as Food and Drug Administration (FDA) approved excipient for carrying drugs in oral administration with good characteristics of biological safety and economy [30–33]. Our data from the comprehensive safety evaluations of D/H@CaCO₃ revealed that it was nontoxic to seeds, seedlings, earthworms, and zebrafish, emphasizing its potential as a biosafe and environmentally friendly solution for fungicide delivery. These results indicated that the high efficacy of D/H@CaCO₃ in inhibiting S. sclerotiorum. and turn promoting plant growth could be beneficial to the planting and marketing of lettuce as edible vegetables. This involved HMSNs@CaCO₃-based fungicide delivery system with antifungal activity and pH-responsive release could have applications in several protecting crops from pests and plant pathogens, such as HMSNs@CaCO₃-based anti-pests and anti-bacteria in modern agriculture.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  Acknowledgments

  The authors gratefully acknowledge the support of this research by National Key R&D Program of China (No. 2022YFE0139800), National Natural Science Foundation of China (Nos. 82272154, 32201101), the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (No. 2023-JKCS-12), Tianjin Science Fund for Distinguished Young Scholars (No. 22JCJQJC00120), the Fundamental Research Funds for the Central Universities (Nos. 2021-RC310–005, 3332023069), Science and Technology Program of Tianjin City (the Basic Research Cooperation Special Foundation of Beijing-Tianjin-Hebei Region, No. 22JCZXJC00060), the Key Project of Basic Research of Shenzhen (No. JCYJ20200109113603854), Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (Nos. 2021-I2M-1–058, 2022-I2M-2–003), the Central Government Guides Local Special Funds for Scientific and Technological Development (No. ZY20198002), and Guilin Scientific Research and Technology Development Plan (No. 20210227–3).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.109697.

  
  
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  Figure 1  (a) Schematic illustration for preparing D/H@CaCO₃ and the mechanism of enhanced S. sclerotiorum inhibition and plant photosynthesis. The preparation procedure of D/H@CaCO₃. D/H@CaCO₃ responds to the acidic microenvironment of S. sclerotiorum to release Dim and CO₂. This enhances the inhibitory effect of Dim on S. sclerotiorum, and the CO₂ generated by CaCO₃ further promotes photosynthesis in romaine lettuces. (b) SEM and (c) TEM of D/H@CaCO₃. Scale bar: 100 nm. (d) Hydrodynamic diameters of HMSNs and D/H@CaCO₃. (e) Zeta potentials of Dim, HMSNs, and D/H@CaCO₃. (f) EDS mapping of D/H@CaCO₃. Scale bar: 100 nm. (g) XPS image of D/H@CaCO₃. (h) FTIR spectra of Dim, HMSNs, D/H and D/H@CaCO₃. (i) TGA curves of H@CaCO₃ and D/H@CaCO₃. (j) Zeta potential and hydrodynamic diameters changes of D/H@CaCO₃ at 0 ℃ for 7 days. (k) Release behavior of D/H@CaCO₃ at pH 5, 6, and 7 (35 ℃) and (l) temperatures at 25, 35, 45 ℃ (pH 5). Data are presented as means ± SEM (n = 3).

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  Figure 2  (a) Color changes in bromothymol blue indicator after treatment with CO₂ generated by different concentrations D/H@CaCO₃. (b) Schematic illustration of D/H@CaCO₃ promoting plant photosynthesis. CaCO₃ coated on D/H@CaCO₃ degrading and generating CO₂ in the acidic microenvironment of S. sclerotiorum, which could be beneficial for plant photosynthesis and plant growth. (c) Chlorophyll a, (d) chlorophyll b, and (e) carotenoids levels in the leaves treated with different concentrations of D/H@CaCO₃. Data are presented as means ± SEM (n = 3).

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  Figure 3  (a) Photos of S. Sclerotiorum colony on the 7^th day after administration of Dim or D/H@CaCO₃. A red circle represents the fungal colony (scale bar: 2 cm). (b) The quantitative analysis of inhibition rate of Dim or D/H@CaCO₃ against S. sclerotiorum. (c, d) The colony diameter was measured at 0, 1, 2, 3, 4, 5, 6 and 7 days after treatment with Dim or D/H@CaCO₃ at an effective Dim concentration of 1.5 mg/L. (e) The growth rate of Dim and D/H@CaCO₃ against S. sclerotiorum at an effective Dim concentration of 1.5 mg/L. (f) Microscopic images of hyphae at 0, 4, 8, 12, 24 and 48 h after D/H@CaCO₃ treatment. Scale bar: 50 µm. (g) Photos of S. sclerotiorum-infested romaine leaves on the 7^th day after being treated with different concentrations of D/H@CaCO₃ or Dim. Scale bar: 1 cm. (h) Control efficacy of Dim and D/H@CaCO₃ in controlling Sclerotinia disease. Data in (b) and (h) are compared by one-way ANOVA. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001. Data are presented as means ± SEM (n = 4).

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  Figure 4  (a) Photographs (scale bar: 20 mm) and (b) germination rate of seeds after 5 days of treatment with HMSNs or D/H@CaCO₃ at different concentrations. (c) Photographs (scale bar: 5 cm) and (d) plant height after 12 days of treatment with HMSNs or D/H@CaCO₃ at different concentrations. The death rate of (e) earthworms and (f) zebrafish after 48 h of treatment with Dim or D/H@CaCO₃. (g) Confocal images of romaine roots, stems, and leaves after being treated with FITC-stained D/H@CaCO₃. Green fluorescence represents FITC-stained D/H@CaCO₃. Scale bar: 100 µm. Data are presented as means ± SEM (n = 3).

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