A polyvinyl alcohol-based plant wound repair film using yellow silk algae pulp and a preparation method and application thereof

Abstract

The application discloses a polyvinyl alcohol-based plant wound repair film using yellow silk algae slurry and a preparation method and application thereof, and belongs to the technical field of plant wound protection and repair materials. The polyvinyl alcohol-based plant wound repair film is prepared by combining the biological activity of the yellow silk algae slurry and the physical barrier function of the polyvinyl alcohol hydrogel, forming a network structure through hydrogen bond and ester bond crosslinking, and has the following effects: ① excellent flexibility and adhesion, and can be closely attached to an irregular plant wound surface; ② good air permeability and moisture balance, and can prevent the wound from dehydrating; ③ the sustained-release effect of the yellow silk algae slurry can continuously activate the callus differentiation of the plant wound site and accelerate the wound closure; and ④ the film body can be gradually degraded in a natural environment, and does not need to be removed secondarily, thereby saving labor and effort.

Description

Technical Field

[0001] This invention belongs to the technical field of plant wound protection and repair materials, and in particular relates to a polyvinyl alcohol-based plant wound repair membrane using yellow algae pulp, its preparation method and application. Background Technology

[0002] After grafting, pruning, or mechanical damage, plants develop wounds on their branches or stems. If these wounds are not treated promptly, they can easily lead to water loss and invasion of pathogenic microorganisms, resulting in stunted plant growth or even death. Currently, commercially available plant wound repair films mainly use agricultural plastic films, household plastic wrap, or special polyethylene (PE) self-adhesive grafting films. However, these traditional repair films generally suffer from poor air permeability, poor compatibility with plant tissues, and difficulty in degradation. Long-term use may inhibit callus formation and even cause secondary diseases. Furthermore, they only provide physical isolation and do not possess any biological activity that promotes callus formation, thus failing to actively accelerate wound healing.

[0003] Existing plant wound protection films generally suffer from a single functional limitation, specifically manifested in: a lack of physiological healing-promoting activity, an imbalance between breathability and moisture retention, and non-degradability. They only provide physical sealing and lack the ability to actively promote callus formation and disease resistance. For example, the paper "Preparation and Performance Study of Reversible and Tough Polyvinyl Alcohol-Based Hydrogels" discloses a process for preparing hydrogels by crosslinking vanillic acid with PVA. Using natural vanillic acid as a crosslinking agent, it mixes with PVA in one step to prepare a tough and reversible hydrogel. The hydrogel obtained achieves a maximum stress of 1.31 MPa and an elongation at break of 600%. However, its technical defects include relying solely on vanillic acid to provide limited antioxidant effects, lacking physiologically active factors that actively promote plant callus formation, failing to promote healing, and lacking the bio-inducing function to stimulate the plant's immune system and enhance disease resistance. Patent CN118085124A provides a method for preparing β-1,3-glucan and its application in bio-induced plant disease prevention and resistance. Specifically, it involves an enzymatic hydrolysis-impurity removal process for preparing β-1,3-glucan derived from yeast cell walls, and a method for using it as a bio-inducer to stimulate the plant immune system and enhance disease resistance. However, its technical defect is that β-1,3-glucan only plays the role of stimulating immunity as a bio-inducer and lacks film-forming and physical sealing capabilities. It cannot form a continuous protective film on the surface of plant wounds and cannot effectively isolate external pathogens and water loss. Therefore, there is an urgent need in the field to develop a plant wound repair material that combines physical protection, breathability and moisture retention, biodegradability and active healing functions. Summary of the Invention

[0004] To address the problems of existing plant wound repair membranes, such as limited functionality, poor breathability, and unsatisfactory healing effects, this invention provides a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry, its preparation method, and its application. This polyvinyl alcohol-based plant wound repair membrane possesses both good biodegradability and active healing-promoting function, and can significantly improve the healing speed and survival rate of plant wounds.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry, comprising the following raw materials by weight: 0.5-5 parts *Phyllostachys edulis* slurry, 10 parts polyvinyl alcohol, 0.5 parts vanillic acid, 10-30 parts glycerin, and 53.5-59 parts water.

[0006] This invention utilizes *Phyllostachys edulis* algal slurry, which not only contains β-glucan but also retains natural components such as cell wall cellulose, protein, and lipids. By adding PVA, vanillic acid, and glycerol, the algal slurry is immobilized in a PVA-vanillic acid crosslinked hydrogel matrix to create a wound repair membrane. This polyvinyl alcohol-based plant wound repair membrane not only possesses plant immune-inducing functions but also exhibits multiple synergistic effects, including physical barrier function, oxygen permeability and water retention, and local healing promotion. Its healing effect on grafting wounds is significantly superior to simply spraying or drenching with β-glucan solution. The algal cells in the *Phyllostachys edulis* algal slurry in the polyvinyl alcohol-based plant wound repair membrane provided by this invention are plant-based, resulting in better integration and direct application to plant wounds, while also possessing antibiotic effects.

[0007] This invention, by adding glycerol and yellow algae pulp, enables the prepared polyvinyl alcohol-based plant wound repair membrane to not only possess the mechanical reversibility of PVA-vanillic acid hydrogel, but also to promote plant callus formation, broad-spectrum antibacterial activity, and flexible adhesion.

[0008] Furthermore, the preparation method of the yellow filamentous algae slurry includes the following steps: mixing yellow filamentous algae mud with buffer solution in an equal volume ratio, and ultrasonically crushing under ice bath conditions to obtain the yellow filamentous algae slurry.

[0009] Based on the current state of the industry, this invention proposes a porous network structure utilizing whole algal slurry of *Hygrophytes globosum* combined with polyvinyl alcohol hydrogel. This structure endows the membrane with dual functions of water retention and biodegradation promotion, significantly reducing raw material costs. Furthermore, the algal slurry retains natural components such as cell wall cellulose, protein, and lipids, making it closer to the chemical environment of plant tissues and exhibiting better biocompatibility with plant wounds. Special metabolic products of algal cells, such as some proteins, possess antibacterial and anti-inflammatory effects, which are beneficial for the formation and development of plant callus tissue. Simultaneously, the fine fibers and cell wall fragments in the algal slurry can be embedded in the hydrogel network, acting as a "biological filler" to provide support and significantly improve the membrane's mechanical strength and structural stability.

[0010] Secondly, the present invention provides a method for preparing a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry, comprising the following steps: weighing raw materials according to mass parts, adding polyvinyl alcohol and vanillic acid to a mixed solvent of water and glycerin, and sequentially stirring and swelling and heating to obtain a polyvinyl alcohol mixed solution; defoaming the polyvinyl alcohol mixed solution and adding *Phyllostachys edulis* slurry, stirring until uniform, casting the resulting mixture into a mold, then covering it with a backing layer, and finally performing a freeze-thaw cycle treatment, and obtaining the polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry after demolding.

[0011] Furthermore, the stirring and swelling process involves stirring and swelling at room temperature for 30 minutes at a stirring speed of 700 rpm.

[0012] Furthermore, the heating treatment is as follows: heating to 90°C and holding at that temperature while stirring for 30 minutes, wherein the stirring rate is 700 rpm.

[0013] Furthermore, the defoaming process involves defoaming under vacuum for 4 minutes.

[0014] Furthermore, the freeze-thaw cycle is performed three times.

[0015] Furthermore, in the freeze-thaw cycle, freezing is performed at -20°C for 12 hours, and thawing is performed at room temperature for 4 hours.

[0016] Furthermore, the backing layer is a biodegradable nonwoven fabric.

[0017] This invention utilizes a combination of PVA (polyvinyl alcohol), vanillic acid, glycerol, and *Hylocereus undatus* algal paste, along with a solution blending-crosslinking-casting film-forming process, to create a polyvinyl alcohol-based plant wound repair film that possesses multiple effects, including active healing promotion and biodegradability. This addresses the problems of existing grafting binding films, which only provide physical isolation, lack antibacterial function, and suffer from imbalances in breathability and moisture retention, thus achieving rapid wound healing and high survival rates. The amount of *Hylocereus undatus* algal paste added is crucial, as it can be specifically recognized by plant cell membrane pattern recognition receptors, triggering the expression of genes related to callus formation. This allows the repair film to continuously provide healing-promoting signals during the critical 10-day period of graft union healing, thereby fundamentally improving the quality of wound healing. The β-glucan and extracellular protein macromolecules in the phycocyanin algae pulp have broad-spectrum antibacterial activity, which can continuously inhibit the growth of common wound pathogens such as gray mold and penicillium in the grafting interface microenvironment, forming a dual disease prevention mechanism. In addition, the phycocyanin algae pulp contains a large amount of cellulose, which can provide more suitable plant-based support components for wound adhesion repair and accelerate the healing speed.

[0018] Thirdly, the present invention provides an application of the polyvinyl alcohol-based plant wound repair film using yellow algae pulp in plant grafting, pruning or mechanical damage repair.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: This invention combines the bioactivity of *Phyllostachys edulis* slurry with the physical barrier function of polyvinyl alcohol hydrogel, forming a network structure through hydrogen and ester crosslinking, so that the prepared polyvinyl alcohol-based plant wound repair membrane has the following effects: ① excellent flexibility and conformability, which can be tightly attached to irregular plant wounds. ② Good air permeability and moisture balance prevent wound dehydration; ③ The slow-release effect of *Phyllostachys edulis* algal slurry can continuously activate callus differentiation at the plant wound site, accelerating wound closure; ④ The membrane can gradually degrade in the natural environment, eliminating the need for secondary removal and saving labor. Control experiments show that, compared with plant wound repair membranes without *Phyllostachys edulis* algal slurry and a blank control, the polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* algal slurry provided by this invention has a significant healing-promoting effect. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The curves showing the dynamic changes in wound healing length of Christmas cactus under different treatments as a function of treatment days; Figure 2 To process the wound healing length statistics of different samples on day 8 and the results of Tukey HSD multiple comparisons; Figure 3 This is a schematic diagram of the callus formation at the grafting site, taken on the 8th day after grafting. In the diagram, ac represents the grafting site treated with polyvinyl alcohol-based plant wound repair film prepared using *Phyllostachys edulis* slurry prepared in Examples 1, 2, and 3, respectively; d represents the grafting site of the blank control group; and e represents the grafting site treated with plant wound repair film prepared in Comparative Example 1. Figure 4 This is a schematic diagram of the cross-sectional structure of the polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry provided by the present invention. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] This invention provides a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry, comprising the following raw materials by weight: 0.5-5 parts of *Phyllostachys edulis* slurry (exemplary: 0.5 parts, 2.5 parts, 5 parts), 10 parts of polyvinyl alcohol, 0.5 parts of vanillic acid, 10-30 parts of glycerin (exemplary: 10 parts, 20 parts, 30 parts), and 53.5-59 parts of water (exemplary: 53.5 parts, 58.5 parts, 59 parts). Figure 4 This is a schematic diagram of the cross-sectional structure of the polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry provided by the present invention.

[0028] This invention also provides a method for preparing the polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry, comprising the following steps: S1. Weigh the raw materials according to their mass fractions; S2. Mix deionized water and glycerin to obtain a mixed solvent; S3. Add PVA to the mixed solvent and stir to disperse at room temperature; S4. Add vanillic acid and stir at room temperature for 30 minutes to allow it to swell. S5. Heat to 90℃ and stir at a constant temperature for 30 minutes to form a uniform and transparent PVA mixed solution; S6. Vacuum defoam the obtained PVA mixture solution for 4 minutes, add the yellow algae pulp, stir and disperse evenly, cast it into a mold, cover it with biodegradable non-woven fabric, freeze-thaw cycle 3 times (freeze at -20℃ for 12 hours, thaw at room temperature for 4 hours), demold, and obtain the polyvinyl alcohol-based plant wound repair film using yellow algae pulp.

[0029] This invention provides an application of the polyvinyl alcohol-based plant wound repair film using *Phyllostachys edulis* slurry in plant grafting, pruning, or mechanical damage repair.

[0030] The room temperature / normal temperature in this invention refers to 25±2℃.

[0031] Unless otherwise specified, "parts" in this embodiment of the invention refers to "parts by mass".

[0032] Unless otherwise specified, all materials used in this invention are commercially available products.

[0033] The preparation method of the yellow silk algae slurry in the embodiments of the present invention includes the following steps: mixing yellow silk algae mud with phosphate buffer (pH 7.0) in an equal volume ratio, and crushing it using an ultrasonic disruptor under ice bath conditions, wherein the frequency is 20kHz (standard probe), the power is 150W, the interval is 5s between every 3s of operation, the total ultrasonic time is 5min, and the temperature of the ice bath is controlled at <25℃ throughout the process.

[0034] Example 1: A method for preparing a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry. The raw materials used in this embodiment, by weight, include: 53.5 parts deionized water, 10 parts glycerol, 10 parts polyvinyl alcohol, 0.5 parts vanillic acid, and 0.5 parts yellow algae pulp.

[0035] The preparation method of the polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry in this embodiment is as follows: S1. Add deionized water and glycerin to a beaker, then add PVA (polyvinyl alcohol), stir at room temperature (700 rpm) until fully dispersed, add vanillic acid, continue stirring at room temperature (700 rpm) and swell for 30 min, heat the resulting mixture to 90℃, keep warm and stir (700 rpm) for 30 min to form a uniform and transparent PVA mixed solution. S2. Place the PVA mixture prepared in S1 into a vacuum defoamer for 4 minutes to defoam. Add the yellow algae pulp to the PVA mixture and stir (700 rpm) until it is evenly dispersed. Cast the evenly dispersed mixture into a mold and cover its surface with a layer of pre-cut biodegradable non-woven fabric as a backing layer. Freeze in a -20℃ freezer for 12 hours. After taking it out, thaw it at room temperature for 4 hours. Repeat this freeze-thaw cycle 3 times to obtain a polyvinyl alcohol-based plant wound repair film using yellow algae pulp.

[0036] Example 2: A method for preparing a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry. The raw materials used in this embodiment, by weight, include: 58.5 parts deionized water, 20 parts glycerol, 10 parts polyvinyl alcohol, 0.5 parts vanillic acid, and 2.5 parts yellow algae pulp.

[0037] The preparation method of the polyvinyl alcohol-based plant wound repair membrane using yellow silk algae pulp in this embodiment is the same as in Example 1.

[0038] Example 3: A method for preparing a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry. The raw materials used in this embodiment, by weight, include: 59 parts deionized water, 30 parts glycerol, 10 parts polyvinyl alcohol, 0.5 parts vanillic acid, and 5 parts yellow algae pulp.

[0039] The preparation method of the polyvinyl alcohol-based plant wound repair membrane using yellow silk algae pulp in this embodiment is the same as in Example 1.

[0040] Comparative Example 1 Same as Example 1, except that no yellow algae slurry was added.

[0041] The raw materials used in this comparative example, by mass parts, include: 53.5 parts deionized water, 10 parts glycerin, 10 parts polyvinyl alcohol, and 0.5 parts vanillic acid.

[0042] The preparation method of the plant wound repair membrane in this comparative example is as follows: S1. Add deionized water and glycerin to a beaker, then add PVA (polyvinyl alcohol), stir at room temperature (700 rpm) until fully dispersed, then add vanillic acid, continue stirring at room temperature (700 rpm) and swell for 30 min, heat the resulting mixture to 90℃, keep warm and stir for 30 min to form a uniform and transparent PVA mixed solution. S2. Place the PVA mixed solution prepared in S1 into a vacuum defoamer for 4 minutes to defoam. Cast the defoamed PVA mixed solution into a mold and cover its surface with a layer of pre-cut biodegradable nonwoven fabric as a backing layer. Freeze in a -20℃ freezer for 12 hours. After taking it out, thaw at room temperature for 4 hours. Repeat this freeze-thaw cycle 3 times to obtain a plant wound repair film.

[0043] Application examples The polyvinyl alcohol-based plant wound repair membranes using *Phyllostachys edulis* slurry prepared in Examples 1-3 and the plant wound repair membrane prepared in Comparative Example 1 were tested and verified in plant wound repair experiments.

[0044] Experimental Procedure: The experiment was conducted from March 2025 to May 2026. Each embodiment and comparative example was repeated five times, and a blank control group (no treatment was given to the wound, repeated five times) was set up, with randomized block design. Specific procedures were as follows: Healthy, uniformly growing two-year-old Christmas cactus plants were selected as rootstocks, and stem segments of the same variety were taken as scions. A longitudinal cut was made on the rootstock stem segment with a blade to create an artificial wound 10mm long and 5mm deep. The aforementioned plant wound repair membrane was cut into 2.00cm × 1.00cm pieces, centered on the graft union, and placed over the wound. Gently press to ensure a tight seal against the wound surface, completely enveloping the wound area and creating a closed environment. Routine water and fertilizer management was then applied to the plants.

[0045] Figure 1 The dynamic change curves of wound healing length of Christmas cactus under different treatments as a function of treatment days are shown. Figure 1 As can be seen, the wound healing length of the polyvinyl alcohol-based plant wound repair membrane (algae slurry hydrogel group) prepared in Examples 1-3 of this invention showed a significant and rapid upward trend over time. On the 8th day after treatment, the average wound healing length reached 10.0 mm, significantly higher than the 5.80 mm of Comparative Example 1 (blank hydrogel group) and the 5.59 mm of the blank control group at the same time. The example group showed a clear healing advantage as early as the 3rd day, and the 3rd-6th day was the period of rapid healing growth. In contrast, the average daily healing length of the blank control group was only 0.52-1.00 mm during the same period, and the average daily healing length of Comparative Example 1 was only 0.7-0.8 mm during the same period. There was no significant difference in the healing rate throughout the process, indicating that the hydrogel matrix itself did not have a significant promoting effect on the wound healing of Christmas cactus, and the healing effect came from the algae slurry added to the formula.

[0046] Figure 2To process the wound healing length statistics of different samples on day 8 and the Tukey HSD multiple comparison results, where different lowercase letters indicate significant differences between groups (P<0.05), the statistical results can be divided into two groups with significant differences: Group "a" includes the blank control group and Comparative Example 1. The average wound healing length in this group on day 8 was 5.59-5.80 mm, with no significant difference within the group, further verifying that pure PVA hydrogel has no significant healing-promoting effect. Group "b" includes all example groups (Examples 1, 2, and 3). The average wound healing length in this group reached 9.75-10.00 mm on day 8, an increase of 72%-79% compared to group "a," with no significant difference within the group. This indicates that the examples with different formulation gradients in this invention can stably and significantly promote wound healing in Christmas cactus. The above experimental results demonstrate that the polyvinyl alcohol-based plant wound repair film using yellow algae pulp provided by the present invention has a highly significant positive promoting effect on wound healing of Christmas cactus, and this effect is stable within the range of raw material dosage gradients in this experiment.

[0047] Figure 3 This is a schematic diagram of callus formation at the grafting interface, taken on the 8th day after grafting. In the diagram, ac represents the grafting interface treated with polyvinyl alcohol-based plant wound repair film prepared using *Phyllostachys edulis* slurry, as described in Examples 1, 2, and 3, respectively. As can be seen from the diagram, the callus tissue is significantly enlarged, enveloping the interface, and the tissue is fresh and healthy. d represents the grafting interface of the blank control group, and e represents the grafting interface treated with the plant wound repair film prepared in Comparative Example 1. From d and e, it can be seen that less callus tissue has formed, and slight shrinkage is visible at the interface.

[0048] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A polyvinyl alcohol-based plant wound repair membrane utilizing *Phyllostachys edulis* slurry, characterized in that, The ingredients, by weight, include the following: 0.5-5 parts of yellow algae pulp, 10 parts of polyvinyl alcohol, 0.5 parts of vanillic acid, 10-30 parts of glycerol, and 53.5-59 parts of water.

2. The polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry according to claim 1, characterized in that, The preparation method of the yellow filamentous algae slurry includes the following steps: mixing yellow filamentous algae mud with buffer solution in an equal volume ratio, and ultrasonically crushing under ice bath conditions to obtain the yellow filamentous algae slurry.

3. A method for preparing a polyvinyl alcohol-based plant wound repair membrane using *Phyllostachys edulis* slurry as described in claim 1 or 2, characterized in that, The process includes the following steps: weighing the raw materials according to the mass fractions, adding polyvinyl alcohol and vanillic acid to a mixed solvent of water and glycerin, stirring and swelling in sequence, and heating to obtain a polyvinyl alcohol mixed solution; after defoaming the polyvinyl alcohol mixed solution, adding yellow algae pulp, stirring until uniform, casting the resulting mixture into a mold, then covering it with a backing layer, and finally performing a freeze-thaw cycle treatment, and after demolding, obtaining the polyvinyl alcohol-based plant wound repair film using yellow algae pulp.

4. The preparation method according to claim 3, characterized in that, The stirring and swelling process involves stirring and swelling at room temperature for 30 minutes at a stirring speed of 700 rpm.

5. The preparation method according to claim 3, characterized in that, The heat treatment is as follows: heat to 90°C and keep warm while stirring for 30 minutes, with a stirring rate of 700 rpm.

6. The preparation method according to claim 3, characterized in that, The defoaming process involves defoaming under vacuum for 4 minutes.

7. The preparation method according to claim 3, characterized in that, The freeze-thaw cycle is performed three times.

8. The preparation method according to claim 7, characterized in that, In the freeze-thaw cycle, freezing is performed at -20°C for 12 hours, and thawing is performed at room temperature for 4 hours.

9. The preparation method according to claim 3, characterized in that, The backing layer is a biodegradable nonwoven fabric.

10. The application of a polyvinyl alcohol-based plant wound repair film using *Phyllostachys edulis* slurry as described in claim 1 or 2 in plant grafting, pruning, or mechanical damage repair.

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