Hydroponic seedling raising method for mangrove plant kandelia candel

Abstract

The invention discloses a hydroponic seedling raising method for mangrove plant kandelia candel, and belongs to the technical field of mangrove plant breeding and seedling raising methods and hydroponic plants. The method comprises the four steps of seed pretreatment, seed field planting, seed germination and seedling water culture. By using the hydroponic seedling culture method, the culture environment conditions (illumination, nutrient elements of the hydroponic solution, temperature and salinity) can be manually regulated and controlled, the constraint of soil, climate, land fertility and sunlight can be got rid of, a new seedling culture thought is provided for artificial afforestation of kandelia candel, and the method has important social and scientific significance.

Description

Technical Field

[0001] The invention belongs to the technical field of mangrove plant breeding and seedling raising methods and hydroponic plants, and particularly relates to a hydroponic seedling raising method for a mangrove plant Kandelia candel. Background Art

[0002] Mangroves are woody plant communities that grow on intertidal mudflats in tropical and subtropical coasts. The mangrove ecosystems dominated by them play a huge role in maintaining the productivity and biodiversity of coastal wetlands. Candelia candel ) is a widely distributed species, mainly distributed in shallow seas, river alluvial belts and salt flats in Guangdong, Guangxi, Fujian, Taiwan and other places in my country. However, with the increase of latitude, the canopy height of the Kandelia ovata species tends to decrease. Although China is one of the countries with more mangrove species, it has not paid attention to the rational use of this resource for a long time, resulting in a decrease in the area of ​​mangroves in the country. In order to improve the growth and development ability of Kandelia ovata and the success rate of afforestation, the research on the cultivation of Kandelia ovata seedlings is very important.

[0003] At present, the cultivation of autumn candel mainly adopts the traditional outdoor soil seedling cultivation method. Due to the limited land resources, soil fertility, temperature, salinity, light and other conditions, there are problems such as low planting density, not conducive to manual management, high regional restrictions, not suitable for promotion and high cost.

[0004] Hydroponic cultivation is an emerging plant seedling and cultivation technology that has rapidly developed into a trend. It has been studied more on many herbaceous plants, but less on woody plants, especially the mangrove plant Kandelia candel. Compared with the traditional soil culture method, the hydroponic method for plant cultivation can accurately regulate the environmental and nutritional conditions for plant growth, making it easier to manage and realize agricultural automation and factory production. In addition, hydroponics greatly reduces water consumption, and the process does not require operations such as turning the soil and weeding, which greatly reduces the input of human resources; it can get rid of the traditional demand for soil, and can avoid problems such as soil pests and diseases and soil salinization; at the same time, soil resources are no longer a limiting condition for plant cultivation, and it can also be promoted in deserts, islands and reefs, etc., which can expand production space and improve space utilization. Summary of the invention

[0005] The invention aims to provide a method for hydroponic seedling cultivation of a mangrove plant Kandelia candel.

[0006] To solve the above problems, the present invention adopts the following technical solutions: A method for hydroponic seedling cultivation of a mangrove plant Kandelia candel, comprising the following specific steps: (1) Seed pretreatment: Soak the hypocotyl seeds of Kandelia candel in a carbendazim solution for 20 to 30 min, and then rinse them with clean water 2 to 3 times to obtain treated Kandelia candel hypocotyl seeds; (2) Seed planting: Pour clean water into the hydroponic container, insert the treated Kandelia candel hypocotyl seeds into the foam float and float on the water surface, with the bottom of the seeds 12-20 cm away from the bottom of the container; (3) Seed germination: Use LED plant lights as light sources, add compound fertilizer and trace element concentrate to the hydroponic container as hydroponic solution, set the hydroponic solution temperature and environmental humidity until the seeds germinate; (4) Seedling hydroponics: When the hypocotyl seeds of Kandelia candela grow 2 to 4 true leaves, use LED plant lights as the light source, add compound fertilizer, trace element concentrate and medium element concentrate into the hydroponic container as the hydroponic solution, set the hydroponic solution temperature and environmental humidity, and culture for 60 to 80 days before transplanting.

[0007] Furthermore, the carbendazim solution in step (1) is prepared by dissolving carbendazim powder containing 50% of the active ingredient in clean water at a concentration of 1 g / L, and the water temperature is 20-30°C.

[0008] Furthermore, the seed planting in step (2) is to insert one third of the Kandelia candel hypocotyl seeds into the foam floating board, and the spacing between the Kandelia candel hypocotyl seeds is 55-75 mm.

[0009] Furthermore, in step (3), the temperature of the hydroponic solution is 28-32°C, the salinity of the hydroponic solution is 0‰, and the pH is 7-8; the light intensity of the light source is 50-100 μmol·m -2 ·s -1 , the light duration is 10-12 h / d, the light quality is red: blue: green = 3:1:1; the environmental humidity is 80-90%; the compound fertilizer application amount is 1.6g per liter of hydroponic solution, and the trace element concentrate application amount is 1 mL per liter of hydroponic solution. The compound fertilizer and trace element concentrate are applied once every 20 days, and the evaporated water is replenished every day until the seeds germinate.

[0010] Furthermore, the hydroponic temperature in step (4) is 28-32°C, the salinity of the hydroponic solution is 10‰, and the pH is 7-8; the light intensity of the light source is 150-200 μmol·m -2 ·s -1 , the light duration is 10-12 h / d, the light quality is red: blue: green = 3:1:1; the environmental humidity is 80-90%; the application amount of the compound fertilizer is 0.4g per liter of hydroponic solution, the application amount of the trace element concentrate is 0.5-3mL per liter of hydroponic solution, and the application amount of the medium element concentrate is 0.5 mL per liter of hydroponic solution. The compound fertilizer and the medium and trace element concentrates are applied once every 20 days, and the evaporated water is replenished every day.

[0011] Furthermore, the trace element concentrate in step (3) and step (4) is 2.860 g / L H3BO3, 1.015 g / L MnSO4, 0.079 g / L CuSO4•5H2O, 0.220 g / L ZnSO4•7H2O, 0.090 g / L H2M O O4, 5.570 g / LFeSO4·7H2O and 7.450 g / L EDTA-Na2.

[0012] Furthermore, the concentrated solutions of the intermediate elements in step (3) and step (4) are 183.80 g / L CaCl2•2H2O and 154.05 g / L MgSO4•7H2O.

[0013] Furthermore, the effective ingredients of the compound fertilizer in step (3) and step (4) are 15% N, 15% P2O5 and 15% K2O.

[0014] The hydroponic seedling method of the mangrove plant Kandelia candel of the present invention has the following beneficial effects: The candel of the present invention adopts a hydroponic method, and specific cultivation environment conditions (light, hydroponic solution temperature and salinity) and nutritional conditions (compound fertilizer and application amount of medium and trace elements) can be set to achieve rapid germination of candel seeds and rapid and high-density cultivation of seedlings, which is expected to break free from the constraints of soil, temperature, soil fertility and sunshine. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 To verify the optimal conditions for hydroponic germination of Kandelia candel seeds.

[0016] Figure 2 Optimization of hydroponic solution temperature for Kandelia candel seedlings.

[0017] Figure 3 Optimizing the salinity of hydroponic solution for Kandelia candel seedlings.

[0018] Figure 4 To optimize the concentration of elements in the hydroponic solution for Kandelia candel seedlings.

[0019] Figure 5 Optimization of trace element concentration in hydroponic solution for Kandelia candel seedlings.

[0020] Figure 6 Optimize the application amount of compound fertilizer in hydroponic liquid for Kandelia candel seedlings.

[0021] Figure 7 To verify the optimal conditions for hydroponic growth of Kandelia candel seedlings. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with specific embodiments. It should be emphasized that the following description is only a partial embodiment of the present invention, rather than a complete embodiment. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The reagents required for the hydroponic solution in the following examples were purchased from Xilong Science Co., Ltd., and the compound fertilizer was purchased from Stanley Agricultural Group Co., Ltd.; A method for hydroponic seedling cultivation of a mangrove plant Kandelia candel, comprising the following steps: (1) Seed pretreatment: Select seeds with uniform size, no obvious pests and diseases, relatively thick and long, and dark green or dark brown hypocotyls, soak them in carbendazim for 20 min, and then rinse them twice with 26°C water. The carbendazim soaking disinfection is to dilute the active ingredient 50% carbendazim powder at 1 g / L deionized water, and the water temperature is 26°C.

[0024] (2) Seed planting: Pour clean water into the hydroponic container, insert the treated Kandelia candel hypocotyl seeds into the foam float and float on the water surface, with the bottom of the seeds 15 cm away from the bottom of the container. The specific steps are to insert one-third of the Kandelia candel hypocotyl seeds into the foam float, with the spacing between Kandelia candel hypocotyl seeds being 60 mm.

[0025] (3) Seed germination: Using LED plant lights as the light source, place the floating plate with seeds in a hydroponic container containing hydroponic solution. The temperature of the hydroponic solution is controlled at 28-32°C, the salinity is 0‰, and the pH is 7-8. The light intensity of the light source is 50-100 μmol·m -2 ·s -1 , the light duration is 10-12 h / d, the light quality is red: blue: green = 3:1:1; the environmental humidity is 80-90%; the application amount of compound fertilizer is 1.6g per liter of hydroponic solution, and the application amount of trace element concentrate is 1 mL per liter of hydroponic solution. Compound fertilizer and trace element concentrate are applied once every 20 days, and evaporated water is replenished every day until the seeds germinate.

[0026] (4) Seedling hydroponics: When the Kandelia candel seeds grow 2 to 4 true leaves, the hydroponic solution is replaced and the temperature of the hydroponic solution is controlled at 28 to 32°C, the salinity is 10‰, and the pH is 7 to 8. The light intensity is 150 to 200 μmol·m -2 ·s -1, the light duration is 10-12 h / d, the light quality is red: blue: green = 3:1:1; the environmental humidity is 80-90%; the application amount of compound fertilizer is 0.4g per liter of hydroponic solution, the application amount of trace element concentrate is 0.5-3 mL per liter of hydroponic solution, and the application amount of medium element concentrate is 0.5 mL per liter of hydroponic solution. Compound fertilizer and medium and trace element concentrates are applied once every 20 days, and evaporated water is replenished every day. After 70 days, it can reach the transplanting standard.

[0027] The trace element concentrate in step (3) and step (4) is 2.860 g / L H3BO3, 1.015 g / L MnSO4, 0.079 g / L CuSO4·5H2O, 0.220 g / L ZnSO4·7H2O, 0.090 g / L H2M O O4, 5.570 g / L FeSO4·7H2O, and 7.450 g / L EDTA-Na2.

[0028] The concentrated solutions of the intermediate elements in step (3) and step (4) are 183.80 g / L CaCl2•2H2O and 154.05 g / L MgSO4•7H2O.

[0029] The effective ingredients of the compound fertilizer in step (3) and step (4) are 15% N, 15% P2O5 and 15% K2O.

[0030] The following examples only list the parts that are different from the above steps, and the same contents are not listed again. At the same time, in order to obtain the best implementation method, the following several examples are set based on the above-mentioned mangrove plant seed pretreatment, seed planting, and seedling hydroponics.

[0031] Example 1 Verification of the optimal conditions for hydroponic germination of Kandelia candel seeds The temperature of the hydroponic solution for seed germination was set at 24, 28, 32, and 36 °C, the salinity was set at 0, 5, 10, 15, and 25‰ (a certain mass of sea salt was dissolved in deionized water to obtain the corresponding salinity), and the amount of compound fertilizer applied was set at 0, 0.4, 0.8, 1.6, and 2.4 g·L -1 , the trace element application amount was 0, 0.5, 1, 2, and 3 times (0, 0.5, 1, 2, and 3 mL of trace element concentrate was applied per liter of hydroponic solution). Other environmental conditions were: light duration was 12 h / d, light quality was red: blue: green = 3:1:1, and light intensity was 100 μmol·m -2 ·s -1, pH 7, and environmental humidity 85%. The optimal conditions for seed germination were screened out (i.e., the temperature of the hydroponic solution was 28-32°C, the salinity was 0‰, the amount of compound fertilizer applied was 1.6g per liter of hydroponic solution, and the amount of trace element concentrate applied was 1 mL per liter of hydroponic solution). Then, the optimal conditions of each single factor (i.e., the temperature of the hydroponic solution was set to 32°C, the salinity was 0‰, the amount of compound fertilizer applied was 1.6g per liter of hydroponic solution, and the amount of trace element concentrate applied was 1 mL per liter of hydroponic solution) were compared with the seed germination under the optimal conditions of each single factor, and a control group for seed germination in natural seawater and tap water was added.

[0032] Table 1 Experimental settings for verification of optimal conditions for hydroponic germination of Kandelia candel seeds The evaporated water was replenished every 7 days, and compound fertilizer and trace elements were applied once every 20 days to maintain the culture conditions within a stable range. The seed germination rate was recorded after 43 days.

[0033] Figure 1 This is a diagram to verify the optimal conditions for hydroponic germination of Kandelia candel seeds. Figure 1 It can be seen that the germination speed of Kandelia candel seeds was the fastest in the comprehensive optimal group, followed by the temperature optimal group. On the 43rd day, the germination rates of the comprehensive optimal group, the temperature optimal group, the compound fertilizer optimal group, the trace element optimal group, and the salinity optimal group were all 100%.

[0034] In summary, when the temperature of the hydroponic solution is 28-32℃, the salinity is 0‰, the application amount of compound fertilizer is 1.6 g per liter of hydroponic solution, and the application amount of trace element concentrate is 1 mL per liter of hydroponic solution, the germination rate of Kandelia candel seeds is high, which can effectively promote seed germination within a certain period of time.

[0035] Example 2 Optimization of the temperature of the hydroponic solution for Kandelia candel seedlings The hydroponic temperature of Kandelia candel seedlings was set at 24, 28, 32, and 36°C. Other culture conditions: salinity of 0‰, pH of 7, and compound fertilizer concentration of 0.4 g·L -1 The illumination time was 12 h / d, the light quality was red: blue: green = 3:1:1, and the light intensity was 200 μmol·m -2 ·s -1 , the ambient humidity is 85%.

[0036] The evaporated water was replenished every 7 days and compound fertilizer was applied once every 20 days to maintain the culture conditions within a stable range. Various indicators of seedling growth were measured after 60 days.

[0037] Figure 2 This paper is the effect of hydroponic solution temperature on the growth of mangrove plant Kandelia candel seedlings. Figure 2It can be seen that the apparent growth index of Kandelia candel seedlings is the best when the hydroponic solution temperature is 32℃. The growth of plant height, leaf number, leaf width and leaf length of Kandelia candel seedlings first increases and then decreases with the increase of temperature. The growth of plant height, leaf number, leaf length and leaf width all reach the maximum value at 32℃, which are 3.02±0.91cm / plant, 3.33±0.29 leaves / plant, 2.66±0.26 cm / plant and 1.49±0.19cm / plant, respectively. The apparent growth index of Kandelia candel seedlings is second best when the hydroponic solution temperature is 28℃. Therefore, the growth rate of Kandelia candel seedlings can be improved when the hydroponic solution temperature is 28~32℃.

[0038] Example 3 Optimization of salinity of hydroponic solution for Kandelia candel seedlings The salinity of the hydroponic solution for Kandelia candel seedlings was set to 0, 5, 10, 15, and 25‰ (a certain mass of sea salt was dissolved in deionized water to obtain the corresponding salinity). Other culture conditions: the hydroponic solution temperature was 28°C, the compound fertilizer concentration was 0.4 g·L -1 The illumination time was 12 h / d, the light quality was red: blue: green = 3:1:1, and the light intensity was 200 μmol·m -2 ·s -1 , relative humidity is 85%.

[0039] The evaporated water was replenished every 7 days and compound fertilizer was applied once every 20 days to maintain the culture conditions within a stable range. Various indicators of seedling growth were measured after 60 days.

[0040] Figure 3 This paper is the effect of different salinity in hydroponic solution on the growth of mangrove plant Kandelia candel seedlings. Figure 3 It can be seen that the apparent growth index of Kandelia candel seedlings is better when the salinity is 10‰. The growth of plant height, leaf width and leaf length of Kandelia candel seedlings first increases and then decreases with the increase of salinity, and the growth of leaf number shows a gradual downward trend. The growth of plant height, leaf length and leaf width all reach the maximum value at a salinity of 10‰, which are 2.71±1.38 cm / plant, 1.99±0.69 cm / plant and 1.22±0.35 cm / plant, respectively. Therefore, the growth rate of Kandelia candel seedlings can be improved when the salinity of the hydroponic solution is 10‰.

[0041] Example 4 Optimization of the amount of elements applied to the hydroponic solution for Kandelia candel seedlings The application amount of middle elements in the hydroponic solution of Kandelia candel seedlings was set to: 0, 0.5, 1, 2, 3 times (0, 0.5, 1, 2, 3 mL of middle element concentrate was applied per L of hydroponic solution). Other culture conditions: hydroponic solution temperature was 28°C, salinity was 0‰, and compound fertilizer concentration was 0.4 g·L -1 The illumination time was 12 h / d, the light quality was red: blue: green = 3:1:1, and the light intensity was 200 μmol·m -2 ·s-1 , the ambient humidity is 85%.

[0042] The evaporated water was replenished every 7 days, and compound fertilizer and medium element concentrate were applied once every 20 days to maintain the culture conditions within a stable range. After 60 days, various indicators of seedling growth were measured.

[0043] Figure 4 The effect of trace elements in hydroponic solution on the growth of mangrove Kandelia candel seedlings. Figure 4 It can be seen that when the amount of medium elements applied was 0.5 times, the plant height and leaf number of the Kandelia candel seedlings reached the maximum value, which were 2.06±0.44cm / plant and 2.33±0.29 leaves / plant, respectively. At this time, the leaf length and leaf width also increased greatly, which were 0.79±0.15cm / plant and 0.53±0.20 cm / plant, respectively. Therefore, when the amount of medium elements applied in the hydroponic solution was 0.5 times, the growth rate of Kandelia candel seedlings could be increased.

[0044] Example 5 Optimization of trace element application amount in hydroponic solution for Kandelia candel seedlings The application amount of trace element concentrate in the hydroponic solution of Kandelia candel seedlings was set as: 0, 0.5, 1, 2, 3 times (0, 0.5, 1, 2, 3 mL of trace element concentrate was applied per L of hydroponic solution). Other culture conditions: hydroponic solution temperature was 28°C, salinity was 0‰, and compound fertilizer concentration was 0.4 g·L -1 The illumination time was 12 h / d, the light quality was red: blue: green = 3:1:1, and the light intensity was 200 μmol·m -2 ·s -1 , the ambient humidity is 85%.

[0045] The evaporated water was replenished every 7 days, and compound fertilizer and trace element concentrate were applied once every 20 days to maintain the culture conditions within a stable range. After 70 days, various indicators of seedling growth were measured.

[0046] Figure 5 The effect of trace elements in hydroponic solution on the growth of mangrove Kandelia candel seedlings. Figure 5 It can be seen that when the amount of trace elements applied was 0.5~3 times, the growth of plant height, leaf number, leaf length and leaf width of Kandelia candel seedlings were significantly improved compared with the blank group. Among them, when the amount of trace elements applied was 1 times, the plant height growth of Kandelia candel seedlings reached the maximum value, which was 2.34±0.47 cm / plant, while the leaf length, leaf width and leaf number growth reached the maximum value when the amount of medium elements applied was 3 times, which were 1.58±0.51 cm / plant, 0.98±0.13 cm / plant, and 3.17±0.76 leaves / plant, respectively. Therefore, when the amount of trace elements applied in the hydroponic solution was 0.5~3 times, the growth rate of Kandelia candel seedlings could be improved.

[0047] Example 6 Optimization of the amount of compound fertilizer applied to Kandelia candel seedlings in hydroponic culture The compound fertilizer concentrations for hydroponic cultivation of Kandelia candel seedlings were set as follows: 0.1, 0.2, 0.4, 0.8, and 1.6 g·L -1 The implementation standard of compound fertilizer is GB / T15063-2020, and the effective ingredients are: 15% N, 15% P2O5, and 15% K2O. Other culture conditions: The temperature of the hydroponic solution is 28°C, the salinity is 0‰, the light duration is 12 h / d, the light quality is red: blue: green = 3:1:1, and the light intensity is 200 μmol·m -2 ·s -1 , the ambient humidity is 85%.

[0048] The evaporated water was replenished every 7 days and compound fertilizer was applied once every 20 days to maintain the culture conditions within a stable range. Various indicators of seedling growth were measured after 60 days.

[0049] Figure 6 This paper is the effect of different compound fertilizer concentrations in hydroponic solution on the growth of mangrove plant Kandelia candel seedlings. Figure 6 It can be seen that the Kandelia candel seedlings have a strong -1 The apparent growth index was the best when the fertilizer application rate was 0.4 g·L. The growth of plant height, leaf number, leaf width and leaf length of Kandelia candela seedlings first increased and then decreased with the increase of fertilizer application rate. -1 The maximum values ​​were 0.82±0.30 cm / plant, 2.33±0.58 pieces / plant, 0.68±0.20 cm / plant, and 0.77±0.23 cm / plant. -1 It can increase the growth rate of Kandelia candel seedlings.

[0050] Example 7 Verification of the optimal conditions for hydroponic growth of Kandelia candel seedlings According to the optimal conditions of each single factor for hydroponic culture of Kandelia candel seedlings (i.e., the temperature of the hydroponic solution is 28-32°C, the salinity is 10‰, the application amount of compound fertilizer is 0.4g per liter of hydroponic solution, the application amount of trace element concentrate is 0.5-3mL per liter of hydroponic solution, and the application amount of medium element concentrate is 0.5mL per liter of hydroponic solution). Then, the optimal conditions of each single factor (i.e., the hydroponic solution temperature is set to 32°C, the salinity is 10‰, the application amount of compound fertilizer is 0.4g per liter of hydroponic solution, the application amount of trace element concentrate is 1mL per liter of hydroponic solution, and the application amount of medium element concentrate is 0.5mL per liter of hydroponic solution) are compared with the growth of seedlings under the optimal conditions of each single factor. Other environmental conditions are: light duration is 12 h / d, light quality is red: blue: green = 3:1:1, and light intensity is 200 μmol·m -2 ·s-1 , pH is 7, and ambient humidity is 85%.

[0051] Table 2 Experimental settings for verification of optimal conditions for hydroponic growth of Kandelia candel seedlings The evaporated water was replenished every 7 days, and compound fertilizer and medium and trace elements were applied once every 20 days to maintain the culture conditions within a stable range. The seed germination rate was recorded after 60 days.

[0052] On the 60th day, the plant height, leaf length, leaf width and leaf growth of Kandelia candela seedlings in the optimal comprehensive group reached the maximum values, which were 3.47±0.82 cm / plant, 2.84±0.61 leaves / plant, 1.54±0.16 cm / plant and 3.33±0.38 cm / plant, respectively.

[0053] In summary, from the screening of the environmental conditions (light, hydroponic solution temperature and salinity) and nutritional conditions (application amount of compound fertilizer, medium elements and trace elements) (Examples 1 to 7) of the hydroponic solution for seed germination and seedling cultivation, it can be seen that the germination rate index is good when the hydroponic solution temperature is 28 to 32°C, the salinity is 0‰, the application amount of compound fertilizer is 1.6g per liter of hydroponic solution, and the application amount of trace element concentrate is 1 mL per liter of hydroponic solution, which is conducive to seed germination. The seedlings grow under the conditions of hydroponic solution temperature of 28 to 32°C, salinity of 10‰, compound fertilizer application of 0.4g per liter of hydroponic solution, trace element concentrate application of 0.5 to 3 mL per liter of hydroponic solution, and medium element concentrate application of 0.5 mL per liter of hydroponic solution. The growth indicators are good, which is conducive to seedling growth.

[0054] The above describes the specific content of the present invention through embodiments. For those skilled in the art, it is easy to make several changes and modifications to the content of the present invention based on known principles, so the above embodiments do not represent the entire patent protection scope of the present invention. Therefore, in accordance with the concept limited by the claims, modifications based on the present invention also belong to the protection scope of the claims.

Claims

1. A method for hydroponic seedling cultivation of a mangrove plant Kandelia candel, characterized in that: The specific steps are as follows: (1) Seed pretreatment: Soak the hypocotyl seeds of Kandelia candel in a carbendazim solution for 20 to 30 min, and then rinse them with clean water 2 to 3 times to obtain treated Kandelia candel hypocotyl seeds; (2) Seed planting: Pour clean water into the hydroponic container, insert the treated Kandelia candel hypocotyl seeds into the foam float and float on the water surface, with the bottom of the seeds 12-20 cm away from the bottom of the container; (3) Seed germination: Use LED plant lights as light sources, add compound fertilizer and trace element concentrate to the hydroponic container as hydroponic solution, set the hydroponic solution temperature and environmental humidity until the seeds germinate; (4) Seedling hydroponics: When the hypocotyl seeds of Kandelia candela grow 2 to 4 true leaves, use LED plant lights as the light source, add compound fertilizer, trace element concentrate and medium element concentrate into the hydroponic container as the hydroponic solution, set the hydroponic solution temperature and environmental humidity, and culture for 60 to 80 days before transplanting.

2. The hydroponic seedling method of the mangrove plant Kandelia candel according to claim 1, characterized in that: The carbendazim solution in step (1) is prepared by dissolving carbendazim powder containing 50% of the active ingredient in clean water at a concentration of 1 g / L, with the water temperature being 20-30°C.

3. The hydroponic seedling method of a mangrove plant Kandelia candel according to claim 1, characterized in that: The seed planting in step (2) is to insert one third of the Kandelia candel hypocotyl seeds into the foam floating board, and the spacing between the Kandelia candel hypocotyl seeds is 55-75 mm.

4. The hydroponic seedling method of the mangrove plant Kandelia candel according to claim 1, characterized in that: In step (3), the temperature of the hydroponic solution is 28-32°C, the salinity of the hydroponic solution is 0‰, and the pH is 7-8; the light intensity of the light source is 50-100 μmol·m -2 ·s -1 The lighting duration is 10-12 h / d, and the light quality is red: blue: green = 3:1:1; the environmental humidity is 80-90%; the application amount of the compound fertilizer is 1.6 g per liter of hydroponic solution, and the application amount of the trace element concentrate is 1 mL per liter of hydroponic solution. The compound fertilizer and trace element concentrate are applied once every 20 days, and the evaporated water is replenished every day until the seeds germinate.

5. The hydroponic seedling method of the mangrove plant Kandelia candel according to claim 1, characterized in that: The temperature of the hydroponic solution in step (4) is 28-32°C, the salinity of the hydroponic solution is 10‰, and the pH is 7-8; the light intensity of the light source is 150-200 μmol·m -2 ·s -1 The lighting duration is 10-12 h / d, and the light quality is red: blue: green = 3:1:1; the environmental humidity is 80-90%; the application amount of the compound fertilizer is 0.4 g per liter of hydroponic solution, the application amount of the trace element concentrate is 0.5-3 mL per liter of hydroponic solution, and the application amount of the medium element concentrate is 0.5 mL per liter of hydroponic solution; the compound fertilizer and the medium and trace element concentrates are applied once every 20 days, and the evaporated water is replenished every day.

6. The hydroponic seedling method of the mangrove plant Kandelia candel according to claim 1, characterized in that: The trace element concentrate in step (3) and step (4) is 2.860 g / L H3BO3, 1.015 g / L MnSO4, 0.079 g / L CuSO4·5H2O, 0.220 g / L ZnSO4·7H2O, 0.090 g / L H2M O O4, 5.570 g / L FeSO4·7H2O and 7.450 g / LEDTA-Na2.

7. The hydroponic seedling method of the mangrove plant Kandelia candel according to claim 5, characterized in that: The intermediate element concentrate contains 183.80 g / L CaCl2•2H2O and 154.05 g / L MgSO4•7H2O.

8. The hydroponic seedling method of the mangrove plant Kandelia candel according to claim 1, characterized in that: The effective ingredients of the compound fertilizer in step (3) and step (4) are 15% N, 15% P2O5 and 15% K2O.

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