Method for promoting main root bending and lateral root formation of seed-sown Diospyros kaki and application thereof

Abstract

This invention discloses a method and application for promoting root bending and lateral root formation in seed-sown persimmon (Diospyros kaki). This invention belongs to the technical field of persimmon seedling cultivation and bonsai material cultivation. The method includes low-temperature stratification treatment of persimmon seeds; disinfection and imbibition treatment of the stratified seeds followed by sowing in a gibberellin-containing GA3 medium; periodic artificial adjustment of the radicle growth direction when the radicle reaches 1 cm in length to induce taproot bending; removal of 1 cm of root tip when the taproot reaches 4 cm in length to promote lateral root and fibrous root germination; and subsequent hardening-off and transplanting. This invention, by regulating early geotropism of the radicle and taproot apical dominance, enables the taproot of persimmon seed-sown seedlings to form a natural bending shape and significantly promotes lateral root germination, resulting in good ornamental value, growth vitality, and promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of persimmon cultivation technology, specifically relating to a method and application for promoting root bending and lateral root formation in seed-sown persimmon. Background Technology

[0002] Diospyros rhombifolia Hemsl., a deciduous shrub belonging to the genus Diospyros in the family Ebenaceae, is highly valued in bonsai cultivation and ornamental horticulture due to its ornamental fruit, vigorous branches, tolerance to pruning, and suitability for shaping. For Diospyros rhombifolia bonsai, root morphology not only affects the plant's ability to absorb water and nutrients but also directly relates to its ornamental effect and the foundation for later shaping; in particular, a naturally curved, evenly distributed root system with well-developed lateral and fibrous roots is more conducive to forming high-quality bonsai material. Early Diospyros rhombifolia bonsai primarily relied on wild-collected specimens. However, with increasing requirements for wild resource protection, the acquisition of wild Diospyros rhombifolia has become limited, thus seed propagation has become one of the important sources of Diospyros rhombifolia bonsai material. However, in the traditional seed-seeding process of Persimmon, the taproot of seedlings typically grows vertically downwards, resulting in a relatively simple root system with a limited number of lateral and fibrous roots. This leads to insufficient nutrient absorption, weak root system for soil stabilization, and slow growth, making it difficult to meet the requirements of bonsai materials for naturally curved roots, a rich root base, and sufficient root quantity. Later attempts to remedy this by artificially binding the roots, pulling, or mechanically bending them can easily cause root bark damage, taproot breakage, decreased survival rate, and unnatural shapes. Furthermore, Persimmon seeds have a certain dormancy characteristic; without proper treatment, germination takes a long time and results in poor uniformity of germination, which is detrimental to large-scale seedling cultivation and standardized production. This invention is based on the principles of early geotropism response of plant roots and regulation of taproot apical dominance. During the seed germination and radicle development stages, low-temperature stratification is used to improve germination uniformity. Under aseptic culture conditions, the spatial orientation of the radicle is periodically changed during its sensitive growth period to induce the taproot to form a natural curve. After the taproot grows to a certain length, root cutting is performed to weaken the taproot apical dominance and promote the formation of lateral roots and fibrous roots, thereby obtaining persimmon seed-sown material that has both aesthetic value and growth vitality. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method for promoting the bending of the root system and the formation of lateral roots in seed-sown persimmon, in order to solve the problems of existing seed-sown persimmon seedlings having mostly straight taproots, few lateral roots, and insufficient root ornamental value, as well as the fact that traditional manual tying methods easily damage the root system and affect subsequent growth.

[0004] Technical solution: The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to the present invention includes the following steps:

[0005] (1) Seed pretreatment: After washing the seeds of Persimmon, they were mixed with wet sand and subjected to low-temperature stratification to obtain stratified seeds;

[0006] (2) Seed disinfection and swelling: The stratified seeds obtained in step (1) are rinsed, surface disinfected, and soaked in sterile water until fully swollen;

[0007] (3) Aseptic sowing and germination induction: The imbibition seeds obtained in step (2) are inoculated into the germination medium and cultured until the radicles elongate to a certain length;

[0008] (4) Root bending induction: After the radicle from step (3) has been cultured to a certain length, its growth direction is artificially adjusted to induce the main root to bend;

[0009] (5) Lateral root induction: After the main root in step (4) is bent and induced to a certain length, the root tip is cut off and transferred to hormone-free basic culture medium to continue to cultivate into seedlings;

[0010] (6) Hardening off seedlings: Harden off seedlings after the seedlings cultivated in step (5) have grown true leaves and have reached a certain number of lateral roots;

[0011] (7) Transplanting and maintenance: Transplant the seedlings cultivated in step (6) into the cultivation substrate for slow seedling cultivation to obtain persimmon seedlings with curved taproots and abundant lateral roots.

[0012] Preferably, in step (1), the volume ratio of the persimmon seeds to the wet sand is 1:(2-4); the moisture content of the wet sand is 60%-70%; the low-temperature stratification treatment temperature is 2-6℃, the stratification time is 21-35 days, and the sand is turned over once every 6-8 days during the stratification period.

[0013] More preferably, in step (1), the volume ratio of the persimmon seeds to the wet sand is 1:3; the moisture content of the wet sand is 65%; the low-temperature stratification treatment temperature is 4°C; and the stratification time is 28 days.

[0014] Preferably, the surface disinfection in step (2) includes soaking in 70-80% alcohol for 2-3 minutes, rinsing with sterile water 3-5 times, then disinfecting with 4-6% sodium hypochlorite solution by shaking for 15-20 minutes, and rinsing with sterile water 5-7 times; the soaking time in sterile water is 20-24 hours.

[0015] More preferably, the surface disinfection in step (2) includes soaking in 75% alcohol for 3 minutes, rinsing with sterile water 3 times, then disinfecting with 5% sodium hypochlorite solution by shaking for 20 minutes, and rinsing with sterile water 6 times; the soaking time in sterile water is 24 hours.

[0016] Preferably, the germination medium in step (3) is WPM medium with 0.5-2.0 mg / L gibberellin (GA3), 5-7 g / L agar, and pH 5.8-6.2; the radicle length is 1-2 cm.

[0017] More preferably, the germination medium in step (3) is a WPM medium with 2 mg / L gibberellin (GA3), 6 g / L agar, and pH 6.

[0018] Preferably, the culture conditions in steps (3) and (5) are: temperature 23-25℃, light intensity 2000-2500 lux, and light duration 12-14 h / d.

[0019] More preferably, the culture conditions in steps (3) and (5) are: temperature 24°C, light intensity 2200 lux, and light duration 14 h / d.

[0020] Preferably, the manual adjustment in step (4) is carried out in a clean bench: using sterile tweezers, the radicle is adjusted to grow at an upward tilt or laterally to periodically interfere with the geotropic response of the radicle, once every 1–3 days, for a total of 2–3 adjustments.

[0021] More preferably, the manual adjustment in step (4) is carried out in a clean bench: using sterile tweezers, the radicle is adjusted to grow at an upward tilt or laterally, so as to periodically interfere with the geotropic response of the radicle, once every 2 days, for a total of 2 adjustments.

[0022] Preferably, the hormone-free basic culture medium in step (5) is WPM basic culture medium without plant growth regulators; the induction length of the main root bending is 3-4 cm; the length of the root tip removed is 0.5-1 cm; and the culture time is 14-28 days.

[0023] More preferably, the root bending induction length in step (5) is 4 cm; the root tip removal length is 1 cm; and the culture time is 28 days.

[0024] Preferably, the number of true leaves in step (6) is 2-4, and the number of lateral roots is not less than 4; the hardening-off process includes: hardening off the seedlings in the culture bottle under natural light conditions for 3-7 days with the bottle closed, then hardening off the seedlings for 2-3 days with the bottle cap partially opened, and then hardening off the seedlings for 2-3 days with the bottle cap fully opened.

[0025] More preferably, the number of true leaves in step (6) is 4, and the number of lateral roots is 4; the hardening-off includes: hardening off the seedlings in the culture bottle for 7 days under natural light conditions, then hardening off the seedlings for 3 days with the bottle cap partially opened, and then hardening off the seedlings for 3 days with the bottle cap fully opened.

[0026] Preferably, the cultivation substrate in step (7) is a mixture of garden soil, akadama soil and river sand, with a volume ratio of (2-4):(1-2):(1-2); the cultivation involves placing the seedlings in an environment with a shading rate of 50-70% for 7-10 days to allow them to recover, and promoting transplant survival by spraying to keep them moist.

[0027] More preferably, the cultivation substrate in step (7) is a mixture of garden soil, akadama soil and river sand in a volume ratio of 3:1:1; the cultivation involves placing the seedlings in an environment with a 60% shading rate for 10 days to allow them to recover, and promoting transplant survival by spraying to keep them moist.

[0028] Preferably, the method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to the present invention includes the following steps:

[0029] (1) Seed pretreatment: Select persimmon seeds, wash them and mix them with wet sand at a ratio of 1:3. Then, perform stratification treatment under low temperature conditions to break dormancy and improve germination uniformity.

[0030] (2) Seed disinfection and swelling: After stratification, the seeds are rinsed and surface disinfected, and then soaked in sterile water to allow the seeds to fully swell.

[0031] (3) Aseptic sowing and germination induction: The imbibed seeds are inoculated on the surface of the germination medium, which is WPM medium with added gibberellin GA3, and cultured until the seeds germinate and the radicle length reaches 1-2 cm;

[0032] (4) Root bending induction: When the length of the radicle reaches 1-2 cm, the growth direction of the radicle is artificially adjusted to make the radicle deviate from the original direction of the ground. The adjustment is made once every 2 days, and a total of 2-3 adjustments are made to induce the main root to form a bending shape.

[0033] (5) Lateral root induction: When the length of the main root after bending induction reaches 3-4 cm, cut off 0.5-1 cm of the root tip, and then transfer the seedling to WPM basic medium without plant growth regulators for 14-28 days to promote the formation of lateral roots and fibrous roots.

[0034] (6) Hardening off seedlings: After the seedlings have grown 2-4 true leaves and have more than 4 lateral roots, first harden off the seedlings by closing the bottle, and then harden off the seedlings by opening the bottle.

[0035] (7) Transplanting and maintenance: After hardening, the seedlings are transplanted into a breathable cultivation substrate for slow growth and maintenance, so as to obtain persimmon seedlings with curved taproots and abundant lateral roots.

[0036] The method for promoting root bending and lateral root formation in seed-sown persimmon described in this invention is applied in the cultivation of persimmon seedlings and commercial materials for persimmon bonsai.

[0037] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0038] (1) This invention can significantly improve the curvature of the taproot of persimmon seedlings by periodically adjusting the growth direction of the radicle during the germination period of the persimmon seeds and interfering with the geotropic response of the radicle. It does not require artificial shaping in the later stage, avoids the mechanical damage to the root system caused by traditional coiling, and the obtained root system morphology is more in line with the aesthetic requirements of bonsai that "although made by man, it is as if created by nature".

[0039] (2) This invention can significantly promote the formation of lateral roots by removing the root tip to suppress the apical dominance of the main root;

[0040] (3) The present invention adopts a technical route that combines low temperature stratification, gibberellin induction, aseptic germination, bending induction, root cutting to promote root growth and hardening and transplanting, which can improve the uniformity of seed germination, enhance the consistency of seedling growth, and facilitate standardized operation.

[0041] (4) The method of the present invention has a clear operation process and good repeatability, and achieves the technical goals of high germination, strong root system, excellent morphology and high survival rate of persimmon seedlings; it is suitable for promotion and application in persimmon seedling cultivation and persimmon bonsai commercial material cultivation. Attached Figure Description

[0042] Figure 1 This is a schematic diagram illustrating the adjustment of the radicle growth direction of *Persimmon radicle* in Embodiment 1 of the present invention;

[0043] Figure 2 These are seedlings of Diospyros kaki with varying taproot curvatures cultivated using the method described in Example 1 of this invention.

[0044] Figure 3 This is a root morphology diagram showing the induced formation of lateral roots after root cutting treatment using the method of Embodiment 1 of the present invention;

[0045] Figure 4 This is a diagram showing the root morphology of seedlings without root pruning in Comparative Example 1.

[0046] Figure 5 The root morphology diagram of the seedling in Comparative Example 2 without adjustment of the radicle growth direction;

[0047] Figure 6 To compare the results of seeds not being stratified in Example 3, the seed emergence status was observed 78 days after sowing;

[0048] Figure 7 This is a diagram showing the root morphology of seedlings sown in pots and grown in soil, as shown in Comparative Example 4. Detailed Implementation

[0049] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0050] Example 1: A method to promote root bending and lateral root formation in seed-sown Diospyros kaki.

[0051] (1) Seed pretreatment: Select mature, plump, undamaged and moldy persimmon seeds, wash them and mix them with wet sand (which can be squeezed into a ball and not fall apart when released) at a volume ratio of 1:3. Place them at 4℃ for low temperature stratification for 28 days, turning them over once every 7 days.

[0052] (2) Seed disinfection and swelling: After stratification, the seeds were rinsed with running water for 10 minutes to remove the sand attached to the surface, and then transferred to a clean bench. They were first soaked in 75% alcohol for 3 minutes, rinsed with sterile water 3 times, then disinfected with 5% sodium hypochlorite solution for 20 minutes by shaking, rinsed with sterile water 6 times, and finally soaked in sterile water for 24 hours.

[0053] (3) Aseptic sowing and germination induction: Germination medium: WPM + GA3 2.0 mg / L (agar 6 g / L, pH 6.0), dispensed, sterilized, and cooled for later use; seeds that have absorbed moisture were sown into the prepared medium (3-4 seeds per bottle). The culture conditions were: temperature 24℃, light intensity 2200 Lx, light duration 14 h / d. After about 12 days of culture, the seeds began to sprout.

[0054] (4) Root bending induction: When the seeds germinate and the radicle reaches 1 cm in length, the radicle direction is adjusted: Open the culture bottle in the clean bench and gently lift the radicle with sterile forceps to change its downward growth to an upward tilting growth (e.g. Figure 1 (As shown). Adjustments are made every two days, for a total of two adjustments, so that the growth direction of the radicle deviates from the original ground-facing direction each time, thereby inducing the taproot to form a natural curved shape during subsequent growth. Figure 2 The image shows seed-sown persimmon seedlings with varying induced taproot bending morphologies in this embodiment.

[0055] (5) Lateral root induction: When the radicle elongates to about 4 cm, about 1 cm is cut off from the root tip with a sterile blade in a clean bench. Then, it is inoculated into WPM basic medium without plant growth regulators and cultured for 28 days under the same temperature and light conditions as in step (3) to promote lateral root formation (e.g., ...). Figure 3 (As shown).

[0056] (6) Hardening off seedlings: After the seedlings have grown more than two true leaves, first move the culture bottle to natural light for hardening off seedlings for 7 days, then half open the bottle cap for hardening off seedlings for 3 days, and then fully open the bottle cap for hardening off seedlings for another 3 days, so that the seedlings can adapt to the external environment.

[0057] (7) Potting and maintenance: Remove the seedlings, wash the root culture medium, and transplant them into a sterilized mixed substrate (garden soil: Akadama soil: river sand = 3:1:1); after watering thoroughly, place them under a shade net (60% shading rate) and spray twice a day to keep the leaves moist. After 10 days of recovery, remove the shade net and transfer to normal maintenance to obtain persimmon seedlings with curved taproots and abundant lateral roots.

[0058] Comparative Example 1

[0059] The method of promoting root bending and lateral root formation in seed-sown Diospyros kaki is the same as that in Example 1, except that the root tip is not removed in step (5) lateral root induction.

[0060] The results are as follows Figure 4 As shown, the taproot of the seedling is naturally curved, but no lateral roots are formed.

[0061] Comparative Example 2

[0062] Comparative Example 2 uses the same method as Example 1 for promoting root bending and lateral root formation in seed-sown Diospyros kaki, except that step (4) of root bending induction is omitted, and lateral root induction, hardening-off, potting, and maintenance are performed directly. See also Figure 5 Using this method, the seedlings have a large number of lateral roots, but the root system exhibits a typical straight-growing shape.

[0063] Comparative Example 3

[0064] Comparative Example 3 is consistent with Example 1 in promoting root bending and lateral root formation in seed-sown Diospyros kaki. The difference is that in step (1), no stratification was performed, and subsequent steps were carried out directly.

[0065] Compared with Example 1, the germination of seeds in this comparative example was significantly delayed, with some seeds only showing signs of sprouting 78 days after sowing. Figure 6 The germination uniformity decreases, which is not conducive to the subsequent uniform bending induction and root cutting to promote root growth, resulting in a lower overall seedling efficiency.

[0066] Comparative Example 4

[0067] The difference between Comparative Example 4 and Example 1 is that the seeds of Persimmon after low-temperature stratification treatment in step (1) were directly sown in flowerpots containing sterilized mixed substrate (garden soil: Akadama soil: river sand = 3:1:1) and placed in a greenhouse for routine maintenance without undergoing any tissue culture stage. After the seedlings emerged and grew for 1 month, the root system was carefully dug up for observation.

[0068] The results are as follows Figure 7 As shown, the root system has only one thin taproot that extends straight downwards, with almost no lateral roots or fibrous roots, resulting in a simple morphology.

[0069] The seed germination rate, average number of lateral roots, taproot curvature, and transplant survival rate of *Persimmon* seedlings obtained from Examples 1 and Comparative Examples 1-4 were statistically analyzed. The results are shown in Table 1.

[0070] Table 1. Comparison of growth-related indicators of *Persimmon* seedlings in Example 1 and Comparative Examples 1-4

[0071]

[0072] Note: In this invention, "main root curvature" refers to the percentage of seedlings with obviously non-straight curved main roots out of the total number of seedlings surveyed; the criteria for judging curvature are: the main root has at least one visible curvature, and the angle between the main root axis and the straight direction is ≥30°.

[0073] Each experimental group was set up with 3 replicates, with 40 seeds per replicate, and the results were averaged.

[0074] Based on the data analysis in Table 1, Example 1 showed a germination rate of 96.00%, an average number of lateral roots of 4.6, a taproot bending rate of 100%, and a transplant survival rate as high as 95.33%, demonstrating excellent performance across all indicators. In contrast, Comparative Example 1 did not involve root tip removal during lateral root induction. While its germination rate (94.00%) and taproot bending rate (100%) were similar to Example 1, the average number of lateral roots decreased to 0, and the transplant survival rate dropped significantly to 67.33%. This indicates that root tip removal during lateral root induction is a necessary step to promote lateral root formation and improve transplant survival rate. Although omitting this step does not affect germination or taproot bending, the lack of lateral roots leads to weak root water absorption and poor transplant adaptability.

[0075] Comparative Example 2 did not undergo root bending induction. Its germination rate (94.00%), average number of lateral roots (4.7), and transplant survival rate (94.67%) were basically the same as those of Example 1. However, the main root bending rate dropped sharply to 4%, indicating that the root bending step had little effect on seed germination, lateral root development, and transplant survival, but it was a key measure to induce the main root to bend and form.

[0076] Comparative Example 3, which did not undergo stratification treatment, showed significantly delayed seed germination, with some seeds only showing signs of sprouting 78 days after sowing. Figure 6 The germination uniformity decreased, and the germination rate was only 48.67% after 90 days of sowing. At this time, the culture medium water had already cracked in some areas. Because the germination uniformity of this comparison ratio was poor, the subsequent main root bending induction and root cutting were not carried out. This indicates that step (1) is the basic core link of this invention. Its absence will seriously inhibit seed germination and lead to a decrease in germination uniformity, which is not conducive to the subsequent unified implementation of main root bending induction and root cutting.

[0077] Comparative Example 4 did not undergo any tissue culture stage. The seeds treated with low temperature stratification were directly sown in flower pots for soil cultivation. During the cultivation process, no taproot bending induction or root tip removal was performed. In this comparative example, the germination rate dropped to 84.00%, the average number of lateral roots was only 0.1, the taproot bending rate was 0, and the transplant survival rate dropped to 71.33%. This shows that adding gibberellin GA3 to the culture medium in this invention can further improve the seed germination rate. Steps (4) and (5) are the basic core links of this invention. Without them, taproot bending cannot be induced, lateral roots cannot be formed, and the transplant survival rate will be further reduced.

[0078] In summary, the method for promoting root bending and lateral root formation in seed-sown Diospyros kaki described in this invention features complementary and synergistic effects in each step. Stratification and the addition of gibberellin GA3 lay the foundation for germination. Root bending induction significantly increases the taproot bending rate of seed-sown Diospyros kaki seedlings, eliminating the need for subsequent artificial shaping and avoiding the mechanical damage to the roots caused by traditional coiling. Root tip removal during lateral root induction constructs a functional lateral root system. The resulting root morphology better meets the aesthetic requirements of bonsai, which are "made by man, yet appear as if created by nature." Seedling hardening enhances seedling resistance and improves transplant survival rate. Each step is indispensable, collectively achieving the technical goals of high germination, strong root system, superior morphology, and high survival rate in seed-sown Diospyros kaki seedlings.

[0079] This invention employs a technical approach that combines low-temperature stratification, gibberellin induction, aseptic germination, bending induction, root cutting to promote root growth, and hardening and transplanting. This approach can improve the uniformity of seed germination, enhance the consistency of seedling growth, and facilitate standardized operation. Furthermore, the method of this invention has a clear operation process and good repeatability, making it suitable for widespread application in the cultivation of Persimmon seedlings and commercial materials for Persimmon bonsai.

Claims

1. A method for promoting root bending and lateral root formation in seed-sown Diospyros kaki, characterized in that, Includes the following steps: (1) Seed pretreatment: After washing the seeds of Persimmon, they were mixed with wet sand and subjected to low-temperature stratification to obtain stratified seeds; (2) Seed disinfection and swelling: The stratified seeds obtained in step (1) are rinsed, surface disinfected, and soaked in sterile water until fully swollen; (3) Aseptic sowing and germination induction: The imbibition seeds obtained in step (2) are inoculated into the germination medium and cultured until the radicles elongate to a certain length; (4) Root bending induction: After the radicle from step (3) has been cultured to a certain length, its growth direction is artificially adjusted to induce the main root to bend; (5) Lateral root induction: After the main root in step (4) is bent and induced to a certain length, the root tip is cut off and transferred to hormone-free basic culture medium to continue to cultivate into seedlings; (6) Hardening off seedlings: Harden off seedlings after the seedlings cultivated in step (5) have grown true leaves and have reached a certain number of lateral roots; (7) Transplanting and maintenance: Transplant the seedlings cultivated in step (6) into the cultivation substrate for slow seedling cultivation to obtain persimmon seedlings with curved taproots and abundant lateral roots.

2. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, In step (1), the volume ratio of the persimmon seeds to the wet sand is 1:(2-4); the moisture content of the wet sand is 60%-70%; the low-temperature stratification treatment temperature is 2-6℃, the stratification time is 21-35 days, and the sand is turned over once every 6-8 days during the stratification period.

3. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The surface disinfection in step (2) includes soaking in 70-80% alcohol for 2-3 minutes, rinsing with sterile water 3-5 times, then disinfecting with 4-6% sodium hypochlorite solution by shaking for 15-20 minutes, and rinsing with sterile water 5-7 times; the soaking time in sterile water is 20-24 hours.

4. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The germination medium in step (3) is WPM medium with 0.5-2.0 mg / L gibberellin (GA3), 5-7 g / L agar, and pH 5.8-6.2; the radicle length is 1-2 cm.

5. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The cultivation conditions in steps (3) and (5) are: temperature 23-25℃, light intensity 2000-2500 lux, and light duration 12-14h / d.

6. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The manual adjustment described in step (4) is carried out in a clean bench. Sterile forceps are used to adjust the radicle to grow at an upward tilt or laterally in order to periodically interfere with the geotropic response of the radicle. The adjustment is made once every 1–3 days, for a total of 2–3 times.

7. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The hormone-free basic culture medium mentioned in step (5) is WPM basic culture medium without plant growth regulators; the induction length of the main root bending is 3-4 cm; the root tip is cut off by 0.5-1 cm; and the culture time is 14-28 days.

8. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The number of true leaves mentioned in step (6) is 2-4, and the number of lateral roots is no less than 4; the hardening-off process includes: hardening off the seedlings in the culture bottle under natural light conditions for 3-7 days with the bottle closed, then hardening off the seedlings for 2-3 days with the bottle cap partially opened, and then hardening off the seedlings for 2-3 days with the bottle cap fully opened.

9. The method for promoting root bending and lateral root formation in seed-sown Diospyros kaki according to claim 1, characterized in that, The cultivation substrate mentioned in step (7) is a mixture of garden soil, akadama soil and river sand, with a volume ratio of (2-4):(1-2):(1-2); the cultivation involves placing the seedlings in an environment with a shading rate of 50-70% for 7-10 days to allow them to recover, and promoting transplant survival by spraying to keep them moist.

10. The method for promoting root bending and lateral root formation of seed-sown Diospyros kaki as described in claim 1 is applied to the cultivation of Diospyros kaki seedlings and commercial materials for Diospyros kaki bonsai.

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