Seedling raising and transplanting method for mangrove plant Aegiceras corniculatum based on external application of gibberellin

Abstract

The invention discloses a seedling raising and transplanting method for mangrove plant Aegiceras corniculatum based on external application of gibberellin, and belongs to the technical field of saline-alkali plant cultivation and mud flat ecological restoration. The method mainly comprises the four stages of seed disinfection and gibberellin soaking, germination cultivation, seedling cultivation, salinity domestication and mud flat transplanting. After being disinfected, the seeds are soaked in a gibberellin solution with the concentration being 300 mg / L, gibberellin with the same concentration is sprayed regularly during germination, and the germination rate and the germination speed are increased. In the seedling stage, humus soil and mud flat bottom mud mixed matrix is adopted for cultivation, and growth is promoted by spraying 100 mg / L gibberellin to leaf surfaces and injecting 25 mg / L gibberellin to rhizosphere. After seedlings are formed, the seedlings are subjected to step-by-step salinity domestication (5 per thousand to 30 per thousand), gibberellin spraying and rhizosphere injection are carried out at regular intervals, and the stress resistance of the seedlings is enhanced. The method can effectively shorten the seedling raising period of Aegiceras corniculatum, improve the seedling raising efficiency, enhance the adaptive capacity of seedlings to the tidal zone environment, and facilitate rapid recovery of a mangrove forest ecosystem.

Description

Technical Field

[0001] This invention belongs to the technical field of salt-alkali plant cultivation and tidal flat transplantation, specifically relating to a method for seedling cultivation and transplantation of the mangrove plant *Acer negundo* based on the external application of gibberellin. Background Technology

[0002] Mangrove plants, as an important component of the intertidal ecosystems of tropical and subtropical coasts, play an irreplaceable ecological role in maintaining coastal ecological balance, protecting seawalls from wind and waves, purifying seawater, and providing habitats for marine life. Among them, the tung tree (… Aegiceras corniculatum Mangrove spp. is one of the pioneer and community-building species in the mangrove ecosystem. It is mainly distributed in the intertidal zone along the coast of Guangdong, Guangxi, and Fujian provinces in my country. It is highly adaptable, widely distributed, and can quickly establish itself and form communities, creating conditions for the growth of other mangrove plants.

[0003] The natural reproduction of *Tung Blossom Tree* is limited by various environmental factors such as tides, salinity, and pests and diseases. In its natural environment, its seed germination rate is low, seedling growth is slow, and survival rate is unstable, which severely restricts the artificial restoration and large-scale planting of mangroves. Therefore, improving the cultivation speed of *Tung Blossom Tree* seedlings through efficient and controllable seedling cultivation techniques is of great significance for improving the survival rate and efficiency of artificial mangrove afforestation.

[0004] In the exploration of new seedling cultivation technologies, the application of plant hormones has shown great potential. Gibberellins, in particular, are a class of plant growth hormones widely present in plants that can regulate various growth and development processes. They can break seed dormancy, promote stem growth, enhance plant resistance to stress, and delay leaf senescence. Exogenous gibberellin application, as a direct and efficient supplement, can compensate for deficiencies in endogenous plant hormones. By artificially intervening in the hormone balance of seedlings, it can guide them towards the desired growth and development state. Therefore, systematically integrating exogenous gibberellin application into the mangrove seedling cultivation process to achieve hormone regulation throughout the entire process of seed germination, seedling cultivation, and tidal flat transplanting, thereby efficiently obtaining high-quality mangrove seedlings, has extremely important theoretical and practical significance for overcoming the seedling bottleneck in artificial mangrove restoration. Summary of the Invention

[0005] The purpose of this invention is to provide a method for raising and transplanting mangrove plants, such as the tung tree, based on the external application of gibberellin.

[0006] To solve the above problems, the present invention adopts the following technical solution: A method for raising and transplanting seedlings of the mangrove plant *Symplocos buergeriana* based on external application of gibberellin includes the following steps: (1) Soak the tung tree seeds in a carbendazim solution for 30 minutes to disinfect them, then rinse them with clean water 2-3 times and air dry them. (2) Soak the tung tree seeds treated in step (1) in gibberellin solution for 9 hours, and then take them out and air dry them. (3) Insert the radicle end of the tung tree seed treated in step (2) downward into a seedling tray containing substrate, with the insertion depth being about one-third of the seed length, for germination cultivation. During this period, spray the seed surface with gibberellin solution once every 5 days. (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and have the same growth status in step (3), plant them in seedling bags filled with substrate, and carry out seedling cultivation. During this period, spray the seedling leaves with gibberellin solution once every 5 days and inject gibberellin solution into the root zone once. (5) Select the tung tree seedlings cultivated in step (4) to a height of 25-35cm, and carry out gradual salinity acclimatization. During this period, spray the leaves of the tung tree seedlings with gibberellin solution once every 5 days and inject gibberellin solution into the root zone once. (6) Transplant the tung tree seedlings treated in step (5) to the high tide zone of the tidal flats for growth; Furthermore, in step (1), the concentration of the carbendazim aqueous solution is 1 g / L.

[0007] Furthermore, in step (2), the concentration of the gibberellin solution is 300 mg / L.

[0008] Furthermore, in step (3), the substrate is humus soil; the concentration of the gibberellin solution sprayed is 300 mg / L; and the amount sprayed is such that the seed coat is moistened and no droplets fall.

[0009] Furthermore, in step (4), the substrate is made by mixing coastal mudflats and humus in a volume ratio of 3:1; the concentration of the sprayed gibberellin solution is 100 mg / L, and the amount of spraying is such that the leaf surface is evenly moistened and no droplets fall; the concentration of the injected gibberellin solution is 25 mg / L, and the amount of injection is 2 mL / plant.

[0010] Furthermore, in step (5), the method of gradual salinity acclimatization is as follows: select tung tree seedlings cultivated to a height of 25-35cm in step (4), place them together with the seedling bags in a water tank, and use sea salt to prepare seawater for gradual salinity acclimatization. The immersion time for each salinity level is 5 days, and the salinities are 5‰, 10‰, 15‰, 20‰, 25‰, and 30‰ respectively. During immersion, the roots of the seedlings are submerged and the water level is controlled below the first leaf. The concentration of the gibberellin solution sprayed is 100mg / L, and the amount sprayed is enough to evenly wet the leaf surface without dripping. The concentration of the gibberellin solution injected is 25mg / L, and the amount injected is 2mL / plant.

[0011] The application of the above-mentioned seedling raising and transplanting method in mangrove ecological restoration.

[0012] The above-mentioned seedling raising and transplanting method is applied to afforestation and greening of coastal mudflats.

[0013] The above-mentioned seedling raising and transplanting method is applied in coastal ecological protection engineering.

[0014] The above-mentioned seedling raising and transplanting method is applied to improve the ability of mature tung tree seedlings to adapt to adverse conditions in tidal flats.

[0015] The beneficial effects of this invention are as follows: During the seed germination stage, soaking and spraying with exogenous gibberellin effectively improved the germination rate and speed of *Tungus tungus* seeds, shortening the germination time. In the seedling cultivation and salinity acclimatization stage, applying appropriate concentrations of gibberellin through a combination of rhizosphere injection and foliar spraying significantly promoted the growth of *Tungus tungus* seedlings and enhanced their adaptability to the saline-alkali environment of tidal flats, providing efficient and controllable seedling cultivation and transplanting technology support for mangrove ecological restoration. Attached Figure Description

[0016] Figure 1 The effect of different concentrations of GA3 solution on the germination rate of tung tree seeds.

[0017] Figure 2 The effects of foliar spraying of different concentrations of GA3 solution on the growth of tung tree seedlings.

[0018] Figure 3 The effects of injecting different concentrations of GA3 solution into the rhizosphere on the growth of tung tree seedlings.

[0019] Figure 4 The effect of the application method of GA3 solution on the growth of tung tree seedlings.

[0020] Figure 5 The effect of applying GA3 solution on the growth of mature tung tree seedlings transplanted to tidal flats. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments. It should be emphasized that the following description is only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] The total nutrient content of the compound fertilizer involved in the following examples is 45%, wherein N:P2O5:K2O=15:15:15.

[0023] Example 1: Optimization of Gibberellin (GA3) Solution Concentration for Tung Tree Seed Germination (1) Select well-developed and fully mature tung tree seeds, soak them in a 1g / L carbendazim aqueous solution for 30 minutes at a temperature of 30℃, rinse them with clean water 2-3 times, and place them in a ventilated place to air dry naturally for 24 hours.

[0024] (2) The experimental group was set with GA3 solution soaking concentration gradients of 100, 150, 200, 300 and 350 mg / L, while the control group was soaked in water at room temperature. The tung tree seeds treated in step (1) were placed in the above-mentioned GA3 solution of different concentrations and water, soaked for 9 hours, and then placed in a ventilated place to air dry naturally for 24 hours.

[0025] (3) Insert the treated tung tree seeds, with the radicle end facing down, into a seedling tray filled with substrate (humus soil). The insertion depth is approximately one-third of the seed length. Then, germinate and cultivate the seeds under LED light. During this period, spray the seeds of each experimental group with the corresponding GA3 solution according to the same concentration gradient as in step (2), while spraying the control group with water. The spraying frequency is once every 5 days, and the amount sprayed each time is enough to evenly moisten the seed coat without dripping. The LED light conditions are: light intensity of 300 μmol·m -2 ·s -1 The light quality was red light:blue light:green light = 3:1:1, and the light duration was 6 hours / day. Other conditions during the cultivation period were: ambient temperature at room temperature, relative humidity controlled at 60%, and regular watering to keep the substrate in the seedling tray moist but not waterlogged. Seed germination rate was recorded every 2 days.

[0026] Figure 1 The effect of different concentrations of GA3 solution on the germination rate of tung tree seeds. Figure 1 As shown, on day 70, the germination rate of *Paulownia tomentosa* seeds in the GA3 300 mg / L group reached 100% first, while the germination rate of the control group was only 66.67%. Compared with the control group, the germination rate of *Paulownia tomentosa* seeds in the GA3 300 mg / L group was significantly improved. On day 100, only the GA3 200 mg / L and GA3 300 mg / L groups achieved a 100% germination rate. Therefore, the optimal GA3 solution concentration for *Paulownia tomentosa* seed germination is 300 mg / L.

[0027] Example 2: Optimization of GA3 solution concentration for foliar spraying of tung tree seedlings (1) Select well-developed and fully mature tung tree seeds, soak them in a 1g / L carbendazim aqueous solution for 30 minutes at a temperature of 30℃, rinse them with clean water 2-3 times, and place them in a ventilated place to air dry naturally for 24 hours.

[0028] (2) Soak the tung tree seeds treated in step (1) in a GA3 solution with a concentration of 300 mg / L for 9 hours at room temperature, and then take them out and place them in a ventilated place to air dry naturally for 24 hours.

[0029] (3) Insert the treated *Pterocarya stenoptera* seeds, with the radicle end facing down, into a seedling tray filled with substrate (humus). The insertion depth should be approximately one-third of the seed length. Then, germinate the seeds under LED light conditions. During this period, spray the seed surface with a 300 mg / L GA3 solution every 5 days, ensuring the seed coat is evenly moistened without dripping. The LED light conditions are: light intensity of 300 μmol·m⁻². -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 6 hours / day. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, and watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged.

[0030] (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and are in a uniform growth state from step (3), and plant them in seedling bags filled with substrate (a mixture of coastal mudflat bottom mud and humus soil at a volume ratio of 3:1). Cultivate the seedlings under LED light conditions. During this period, spray the seedling leaves with different concentrations of GA3 solution (25mg / L, 50mg / L, 75mg / L, 100mg / L, 125mg / L) every 5 days. At the same time, spray the leaves with water as a control. The amount of spraying each time should be enough to evenly moisten the leaves without dripping. The LED light conditions are: light intensity of 200μmol·m -2 ·s -1 The light quality was red light:blue light:green light = 3:1:1, and the light duration was 12 hours / day. Other conditions during the cultivation period were: ambient temperature at room temperature, relative humidity controlled at 60%, and regular watering to keep the substrate in the seedling bags moist but not waterlogged. Seedlings harvested after 80 days of cultivation were considered mature seedlings, and their various growth indicators were measured.

[0031] Figure 2 The effects of foliar spraying with different concentrations of GA3 solution on the growth of tung tree seedlings. Figure 2As shown, the growth rates of plant height, leaf number, and plant height ratio of *Paulownia tomentosa* seedlings all showed a trend of first increasing and then decreasing with increasing GA3 solution concentration. Compared with the control group, the GA3 foliar spraying treatment group showed significantly improved plant height and leaf number growth. Specifically, the 100 mg / L GA3 solution resulted in the largest increases in plant height, leaf number, and plant height ratio, at 16.88 ± 0.99 cm / plant, 4.7 ± 0.26 leaves / plant, and 0.21 ± 0.01 cm / day, respectively. Therefore, the optimal GA3 solution concentration for foliar spraying of *Paulownia tomentosa* seedlings is 100 mg / L.

[0032] Example 3: Optimization of Gibberellin GA3 Solution Concentration for Rhizosphere Injection into Paulownia Seedlings (1) Select well-developed and fully mature tung tree seeds, soak them in a 1g / L carbendazim aqueous solution for 30 minutes at a temperature of 30℃, rinse them with clean water 2-3 times, and place them in a ventilated place to air dry naturally for 24 hours.

[0033] (2) Soak the tung tree seeds treated in step (1) in a GA3 solution with a concentration of 300 mg / L for 9 hours at room temperature, and then take them out and place them in a ventilated place to air dry naturally for 24 hours.

[0034] (3) Insert the treated *Pterocarya stenoptera* seeds, with the radicle end facing down, into a seedling tray filled with substrate (humus). The insertion depth should be approximately one-third of the seed length. Then, germinate the seeds under LED light conditions. During this period, spray the seed surface with a 300 mg / L GA3 solution every 5 days, ensuring the seed coat is evenly moistened without dripping. The LED light conditions are: light intensity of 300 μmol·m⁻². -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 6 hours / day. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, and watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged.

[0035] (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and are in a uniform growth state from step (3), and plant them in seedling bags filled with substrate (a mixture of coastal mudflat bottom mud and humus soil at a volume ratio of 3:1). Cultivate the seedlings under LED light conditions. During this period, inject the seedlings with different concentrations of GA3 solution (25 mg / L, 50 mg / L, 75 mg / L, 100 mg / L, 125 mg / L) every 5 days. Simultaneously, inject water into the rhizosphere as a control. The injection volume is 2 mL per seedling each time. The LED light conditions are: light intensity of 200 μmol·m⁻². -2·s -1 The light quality was red light:blue light:green light = 3:1:1, and the light duration was 12 hours / day. Other conditions during the cultivation period were: ambient temperature at room temperature, relative humidity controlled at 60%, and regular watering to keep the substrate in the seedling bags moist but not waterlogged. Seedlings harvested after 80 days of cultivation were considered mature seedlings, and their various growth indicators were measured.

[0036] Figure 3 The effects of injecting different concentrations of GA3 solution into the rhizosphere on the growth of *Paulownia tomentosa* seedlings. Figure 3 As shown, the increases in plant height, number of leaves, leaf length, and leaf width of *Paulownia tomentosa* seedlings all showed a trend of first increasing and then decreasing with increasing GA3 solution concentration. The overall growth of *Paulownia tomentosa* seedlings treated with rhizosphere injection of GA3 was better than that of the control group. Specifically, when injected with 25 mg / L GA3 solution into the rhizosphere, the increases in plant height, number of leaves, leaf length, and leaf width were the largest, at 8.19±0.78 cm / seedling, 8.13±0.67 leaves / seedling, 5.35±0.12 cm / seedling, and 2.60±0.11 cm / seedling, respectively. Therefore, the optimal GA3 solution concentration for rhizosphere injection of *Paulownia tomentosa* seedlings is 25 mg / L.

[0037] Example 4: Optimization of GA3 application method for tung tree seedlings (1) Select well-developed and fully mature tung tree seeds, soak them in a 1g / L carbendazim aqueous solution for 30 minutes at a temperature of 30℃, rinse them with clean water 2-3 times, and place them in a ventilated place to air dry naturally for 24 hours.

[0038] (2) Soak the tung tree seeds treated in step (1) in a GA3 solution with a concentration of 300 mg / L for 9 hours at room temperature, and then take them out and place them in a ventilated place to air dry naturally for 24 hours.

[0039] (3) Insert the treated *Pterocarya stenoptera* seeds, with the radicle end facing down, into a seedling tray filled with substrate (humus). The insertion depth should be approximately one-third of the seed length. Then, germinate the seeds under LED light conditions. During this period, spray the seed surface with a 300 mg / L GA3 solution every 5 days, ensuring the seed coat is evenly moistened without dripping. The LED light conditions are: light intensity of 300 μmol·m⁻². -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 6 hours / day. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, and watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged.

[0040] (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and are in a uniform growth state from step (3), and plant them in seedling bags containing substrate (a mixture of coastal mudflat bottom mud and humus soil at a volume ratio of 3:1). Cultivate the seedlings under LED light conditions, and set different treatments during the period, as follows: Experimental group 1 (foliar spraying group): spray the seedling leaves with a GA3 solution of 100mg / L every 5 days (each spraying amount is enough to evenly wet the leaves without dripping); Experimental group 2 (root injection) Group 1): Seedlings were injected with a 25 mg / L GA3 solution into the rhizosphere every 5 days (2 mL per seedling each time). Group 2 (Follicular Spray + Rhizosphere Injection): Seedlings were sprayed with a 100 mg / L GA3 solution on the leaves every 5 days (the amount sprayed should be enough to evenly wet the leaves without dripping), and simultaneously injected with a 25 mg / L GA3 solution into the rhizosphere (2 mL per seedling each time). Control group: No GA3 solution was applied. LED lighting conditions were: light intensity 200 μmol·m⁻². -2 ·s -1 The light quality was red light:blue light:green light = 3:1:1, and the light duration was 12 hours / day. Other conditions during the cultivation period were: ambient temperature at room temperature, relative humidity controlled at 60%, regular watering to keep the substrate in the seedling tray moist but not waterlogged, and application of compound fertilizer every 20 days (0.8g per kg of substrate). Seedlings harvested after 60 days of cultivation were considered mature seedlings, and their various growth indicators were measured.

[0041] Figure 4 The effect of GA3 application method on the growth of tung tree seedlings. Figure 4 It can be seen that the foliar spraying + root injection group showed better growth in plant height, number of leaves, and leaf length, which were 6.30±0.58 cm / plant, 16.50±0.85 leaves / plant, and 5.58±0.10 cm / plant, respectively. The combined application of the two GA3 methods was more beneficial to the growth of *Tung Tree* seedlings. Therefore, the optimal GA3 application method for *Tung Tree* seedlings is a combined foliar spraying of 100 mg / L GA3 solution and a root injection of 25 mg / L GA3 solution.

[0042] Example 5: Effects of Gibberellin GA3 Application on the Growth of Tung Tree Seedlings Transplanted from Tidal Flats (1) Select well-developed and fully mature tung tree seeds, soak them in a 1g / L carbendazim aqueous solution for 30 minutes at a temperature of 30℃, rinse them with clean water 2-3 times, and place them in a ventilated place to air dry naturally for 24 hours.

[0043] (2) Soak the tung tree seeds treated in step (1) in a GA3 solution with a concentration of 300 mg / L for 9 hours at room temperature, and then take them out and place them in a ventilated place to air dry naturally for 24 hours.

[0044] (3) Insert the treated *Pterocarya stenoptera* seeds, with the radicle end facing down, into a seedling tray filled with substrate (humus). The insertion depth should be approximately one-third of the seed length. Then, germinate the seeds under LED light conditions. During this period, spray the seed surface with a 300 mg / L GA3 solution every 5 days, ensuring the seed coat is evenly moistened without dripping. The LED light conditions are: light intensity of 300 μmol·m⁻². -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 6 hours / day. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, and watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged.

[0045] (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and are in a uniform growth state from step (3), and plant them in seedling bags filled with substrate (a mixture of coastal mudflat bottom mud and humus soil at a volume ratio of 3:1). Cultivate the seedlings under LED light conditions. During this period, spray the seedling leaves with a 100 mg / L GA3 solution every 5 days (each spray should be enough to evenly wet the leaves without dripping), and simultaneously inject the root zone with a 25 mg / L GA3 solution (each injection should be 2 mL per seedling). The LED light conditions are: light intensity of 200 μmol·m -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 12h / d. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged, and compound fertilizer is applied once every 20 days (the amount applied is 0.8g per kg of substrate).

[0046] (5) Select the tung tree seedlings cultivated in step (4) to a height of 25-35cm, and place them together with the seedling bags in an outdoor water tank. Under natural light, perform salinity acclimatization in the following order: submerge the roots of the seedlings in seawater with a salinity of 5‰ prepared with sea salt, with the water level below the first leaf, for 5 days; then submerge the roots of the seedlings in seawater with a salinity of 10‰ prepared with sea salt, with the water level below the first leaf, for 5 days; then submerge the roots of the seedlings in seawater with a salinity of 10‰ prepared with sea salt, with the water level below the first leaf, for 5 days; then submerge the roots of the seedlings in seawater prepared with sea salt... The seedlings were submerged in seawater with a salinity of 15‰, with the water level below the first leaf, for 5 days. Then, the roots were submerged in seawater with a salinity of 20‰ (prepared with sea salt), again with the water level below the first leaf, for 5 days. Next, the roots were submerged in seawater with a salinity of 25‰ (prepared with sea salt), again with the water level below the first leaf, for 5 days. Finally, the roots were submerged in seawater with a salinity of 30‰ (prepared with sea salt), again with the water level below the first leaf, for 5 days. During the salinity acclimatization period, the leaves of the mature tung tree seedlings were sprayed with a 100 mg / L GA3 solution every 5 days (the amount sprayed each time should be enough to evenly wet the leaves without dripping), and simultaneously, a 25 mg / L GA3 solution was injected into the root zone (2 mL per seedling each time).

[0047] (6) The tung tree seedlings treated in step (5) were planted in the high tide zone of the tidal flats with a seawater salinity of 25‰-30‰, and were managed in a conventional manner. Growth indicators were measured after 30 days.

[0048] Comparative example (without gibberellin GA3): (1) Select well-developed and fully mature tung tree seeds, soak them in a 1g / L carbendazim aqueous solution for 30 minutes at a temperature of 30℃, rinse them with clean water 2-3 times, and place them in a ventilated place to air dry naturally for 24 hours.

[0049] (2) Soak the tung tree seeds treated in step (1) in clean water for 9 hours at room temperature, and then take them out and place them in a ventilated place to air dry naturally for 24 hours.

[0050] (3) Insert the treated tung tree seeds, with the radicle end facing down, into a seedling tray filled with substrate (humus soil). The insertion depth should be approximately one-third of the seed length. Then, germinate and cultivate the seeds under LED light conditions. The LED light conditions are: light intensity of 300 μmol·m -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 6 hours / day. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, and watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged.

[0051] (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and are in a uniform growth state from step (3), and plant them in seedling bags containing a substrate (a mixture of coastal mudflat bottom mud and humus in a volume ratio of 3:1). Cultivate the seedlings under LED light conditions. The LED light conditions are: light intensity of 200 μmol·m⁻². -2 ·s -1 The light quality is red light: blue light: green light = 3:1:1, and the light duration is 12h / d. Other conditions during the cultivation period are: ambient temperature is room temperature, relative humidity is controlled at 60%, watering is done regularly to keep the substrate in the seedling tray moist but not waterlogged, and compound fertilizer is applied once every 20 days (the amount applied is 0.8g per kg of substrate).

[0052] (5) Select the tung tree seedlings cultivated in step (4) to a height of 25-35cm, and place them together with the seedling bags in an outdoor water tank. Under natural light, perform salinity acclimatization in the following order: submerge the roots of the seedlings in seawater with a salinity of 5‰ prepared with sea salt, with the water level below the first leaf, for 5 days; then submerge the roots of the seedlings in seawater with a salinity of 10‰ prepared with sea salt, with the water level below the first leaf, for 5 days; then submerge the roots of the seedlings in seawater with a salinity of 10‰ prepared with sea salt, with the water level below the first leaf, for 5 days; then submerge the roots of the seedlings in seawater prepared with sea salt... The seedlings were submerged in seawater with a salinity of 15‰, with the water level below the first leaf, for 5 days. Then, the roots of the seedlings were submerged in seawater with a salinity of 20‰ prepared with sea salt, with the water level below the first leaf, for 5 days. Next, the roots of the seedlings were submerged in seawater with a salinity of 25‰ prepared with sea salt, with the water level below the first leaf, for 5 days. Finally, the roots of the seedlings were submerged in seawater with a salinity of 30‰ prepared with sea salt, with the water level below the first leaf, for 5 days.

[0053] (6) Transplant the tung tree seedlings treated in step (5) to the high tide zone of the tidal flats with a seawater salinity of 25‰-30‰, manage them routinely, and measure their growth indicators after 30 days.

[0054] Figure 5 This figure compares the growth indicators of *Tung Blossom Trees* seedlings from Example 5 and the comparative example 30 days after transplanting. As shown in the figure, the *Tung Blossom Trees* seedlings from Example 5 exhibited superior growth rates in plant height, leaf number, and plant height-to-span ratio after transplanting to the tidal flat environment, at 7.2±0.72 cm / plant, 11.75±0.86 leaves / plant, and 0.24±0.02 cm / day, respectively. In contrast, the *Tung Blossom Trees* seedlings from the comparative example showed no significant increase in plant height or leaf number. After transplanting, the growth of the *Tung Blossom Trees* seedlings from the comparative example almost stagnated in the tidal flat environment, while the *Tung Blossom Trees* seedlings from Example 5 continued to grow significantly. This indicates that the gibberellin-treated tidal flat transplanting method can alleviate the stress of the tidal flat environment, allowing the *Tung Blossom Trees* seedlings to maintain normal growth under adverse conditions.

Claims

1. A method for raising and transplanting seedlings of the mangrove plant *Symplocos edulis* based on external application of gibberellin, characterized in that: Includes the following steps: (1) Soak the tung tree seeds in a carbendazim solution for 30 minutes to disinfect them, then rinse them with clean water 2-3 times and air dry them. (2) Soak the tung tree seeds treated in step (1) in gibberellin solution for 9 hours, and then take them out and air dry them. (3) Insert the radicle end of the tung tree seed treated in step (2) downward into a seedling tray containing substrate, with the insertion depth being about one-third of the seed length, for germination cultivation. During this period, spray the seed surface with gibberellin solution once every 5 days. (4) Select the tung tree seedlings that have germinated and grown to have 2-4 true leaves and have the same growth status in step (3), plant them in seedling bags filled with substrate, and carry out seedling cultivation. During this period, spray the seedling leaves with gibberellin solution once every 5 days and inject gibberellin solution into the root zone once. (5) Select the tung tree seedlings cultivated in step (4) to a height of 25-35cm, and carry out gradual salinity acclimatization. During this period, spray the leaves of the tung tree seedlings with gibberellin solution once every 5 days and inject gibberellin solution into the root zone once. (6) Transplant the tung tree seedlings treated in step (5) to the high tide zone of the tidal flats for growth.

2. The seedling raising and transplanting method according to claim 1, characterized in that: In step (1), the concentration of the carbendazim aqueous solution is 1 g / L.

3. The seedling raising and transplanting method according to claim 1, characterized in that: In step (2), the concentration of the gibberellin solution is 300 mg / L.

4. The seedling raising and transplanting method according to claim 1, characterized in that: In step (3), the substrate is humus soil; the concentration of the gibberellin solution sprayed is 300 mg / L; and the amount sprayed is such that the seed coat is moistened and no droplets fall.

5. The seedling raising and transplanting method according to claim 1, characterized in that: In step (4), the substrate is made by mixing coastal mud and humus in a volume ratio of 3:1; the concentration of the gibberellin solution sprayed is 100 mg / L, and the amount sprayed is such that the leaf surface is evenly moistened and no droplets fall; the concentration of the gibberellin solution injected is 25 mg / L, and the amount injected is 2 mL / plant.

6. The seedling raising and transplanting method according to claim 1, characterized in that: In step (5), the method of gradual salinity acclimatization is as follows: select tung tree seedlings cultivated to a height of 25-35cm in step (4), place them together with the seedling bags in a water tank, and use sea salt to prepare seawater for gradual salinity acclimatization. The immersion time for each salinity level is 5 days, and the salinities are 5‰, 10‰, 15‰, 20‰, 25‰ and 30‰ respectively. When immersing, the roots of the seedlings are submerged and the water level is controlled below the first leaf. The concentration of the gibberellin solution sprayed is 100mg / L, and the amount sprayed is enough to evenly wet the leaf surface without dripping. The concentration of the gibberellin solution injected is 25mg / L, and the amount injected is 2mL / plant.

7. The application of the seedling raising and transplanting method according to any one of claims 1 to 6 in mangrove ecological restoration.

8. The application of the seedling raising and transplanting method according to any one of claims 1 to 6 in afforestation and greening of coastal mudflats.

9. The application of the seedling raising and transplanting method according to any one of claims 1 to 6 in coastal ecological protection engineering.

10. The application of the seedling raising and transplanting method according to any one of claims 1 to 6 in improving the adaptability of mature tidal flat seedlings to adverse conditions.

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