A hydroponic method for improving lettuce quality

Abstract

The present invention belongs to the technical field of crop cultivation, and discloses a hydroponic method for improving the quality of lettuce. The present invention provides a hydroponic method for improving the quality of lettuce, wherein during the hydroponic period of the lettuce seedlings, 2-9 mM glycine is added to the nutrient solution, and light is applied, and the light intensity is 200 μmol·m ‑2 ·s ‑1 , the photoperiod is 14 hours, and the light quality is red light: blue light = (1-3): 1. The present invention significantly increases the content of chlorophyll, anthocyanin and other phenolic compounds in lettuce, reduces the bitterness of lettuce, and improves the quality of lettuce by adding glycine to the lettuce hydroponic nutrient solution and coordinating the light conditions to control the light quality.

Description

Technical Field

[0001] The invention relates to the technical field of crop cultivation, and in particular to a hydroponic method for improving the quality of lettuce. Background Art

[0002] In the hydroponic technology of lettuce, although the existing nutrient solution formula can support the basic growth of lettuce, it is often not fully optimized to promote the accumulation of specific secondary metabolites. In addition, there are also deficiencies in the control of light conditions, the stability of temperature and pH value, the health of the root system, and targeted cultivation strategies. These problems together limit the improvement of the quality of hydroponic lettuce.

[0003] Specifically, the nutrient solution formulas in the prior art mostly adopt universal solutions, lacking specialized adjustments to increase specific nutrients and improve taste. Fluctuations in temperature and pH have an adverse effect on the growth and metabolism of lettuce, especially inhibiting the synthesis of secondary metabolites such as anthocyanins and phenols. Problems in the interaction between root health and the environment cannot be ignored. A poor rhizosphere environment limits the plant's absorption of nutrients. In addition, existing hydroponic technologies lack specialized cultivation strategies to increase specific nutrients and improve taste.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] In response to the above problems, the present invention aims to provide a hydroponic method for improving the quality of lettuce, by optimizing the nutrient solution formula, accurately controlling the lighting conditions, stabilizing the temperature and pH value, improving the interaction between root health and the environment, formulating a cultivation strategy optimized for specific nutrients, and reducing production costs, thereby significantly increasing the content of chlorophyll, anthocyanins and phenols in lettuce and optimizing its taste.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A hydroponic method for improving the quality of lettuce, wherein during the hydroponic period of lettuce seedlings, 2-9 mM glycine is added to the nutrient solution, and light is applied, and the light intensity is 200 μmol·m -2 ·s -1 The photoperiod is 14 hours, and the light quality is red light: blue light = (1-3):1.

[0007] Preferably, 2.25-9 mM glycine is added to the nutrient solution.

[0008] Preferably, 9 mM glycine is added to the nutrient solution.

[0009] Preferably, the light quality is red light: blue light = 1:1.

[0010] Preferably, the daytime temperature during hydroponics is 22-28°C and the nighttime temperature is 13-17°C.

[0011] Preferably, lettuce seeds are sown in a sponge for seedling raising, and the lettuce seedlings are obtained after 14 days.

[0012] Preferably, the composition of the nutrient solution is N / 9 mM, P / 1mM, K / 5 mM, Ca / 2 mM, Mg / 1 mM, S / 1mM, Fe / 80 μM, B / 14 μM, Mn / 5 μM, Cu / 0.7 μM, Mo / 4.9 μM, Zn / 3 μM; pH is about 5.8.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention adds glycine to the lettuce hydroponic nutrient solution, coordinates the lighting conditions, controls the light quality, and significantly increases the content of anthocyanins, total flavonoids, total phenols, etc. in the lettuce, reduces the bitterness of the lettuce, and improves the quality of the lettuce. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a graph showing the anthocyanin content in the lettuce in Example 1; Figure 2 a, c, and e are graphs showing the total flavonoid content, total phenol content, and total phenolic acid content of the lettuce in Example 1, and b, d, and f are graphs showing the total flavonoid content, total phenol content, and total phenolic acid content of the lettuce in Example 2; Figure 3 The content of lactucin in lettuce in Example 2 is shown; Figure 4 It is a graph of anthocyanin content of cauliflower in Example 1E4, Example 2E4, and Examples 3-6; Figure 5 It is a graph showing the contents of total flavonoids, total polyphenols, and total phenolic acids in lettuce in Example 1E4, Example 2E4, and Examples 3-6; Figure 6 This is a graph showing the content of the bitter substances Lactucopicrin and Lactucopicrin-15-oxalate in lettuce in Examples 1E4, 2E4, and 3-6. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments.It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention.In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.Unspecified conditions in the embodiments are carried out according to the conditions of normal conditions or manufacturer recommendations.Reagents used or instruments that do not specify manufacturers are conventional products that can be purchased and obtained commercially.

[0016] The embodiment of the present invention provides a hydroponic method for improving the quality of lettuce. During the hydroponic period of lettuce seedlings, 2-9 mM glycine is added to the nutrient solution, and light is applied at a light intensity of 200 μmol·m -2 ·s -1 The photoperiod is 14 hours, and the light quality is red light: blue light = (1-3):1.

[0017] When glycine is used in combination with appropriate light quality, the two can exert a stronger synergistic effect.

[0018] Glycine, as a kind of amino acid, participates in protein synthesis and is essential for plant growth and development. Glycine can increase the content of plant chlorophyll, promote the absorption and utilization of carbon dioxide by crops, and improve the rate and effect of photosynthesis. Light quality affects the absorption of light by chlorophyll a and chlorophyll b, thereby affecting the light reaction phase of photosynthesis. The addition of glycine in the embodiment of the present invention and the lighting conditions of specific light quality (red light: blue light = (1-3): 1) work together to significantly increase the content of chlorophyll and anthocyanin in lettuce. In addition, this synergistic effect may reduce the bitterness of lettuce and improve the taste of lettuce by reducing the synthesis of bitter substances in lettuce or increasing its degradation rate.

[0019] The embodiment of the present invention uses organic nitrogen fertilizer (glycine) instead of inorganic nitrogen (nitrate), thereby reducing the input of inorganic nitrogen, improving the quality of lettuce without affecting the yield of lettuce.

[0020] In some preferred embodiments, 2.25-9 mM glycine is added to the nutrient solution; in some more preferred embodiments, the molar concentration of glycine is 9 mM.

[0021] In some preferred embodiments, the light quality is red light: blue light = 1:1.

[0022] In some preferred embodiments, the daytime temperature during the hydroponic culture is 22-28°C and the nighttime temperature is 13-17°C.

[0023] The method for raising lettuce seedlings is a common technical means in the art, for example, sowing lettuce seeds in a sponge for raising seedlings, and obtaining the lettuce seedlings after 14 days.

[0024] In some preferred embodiments, the composition of the nutrient solution is N / 9 mM, P / 1mM, K / 5 mM, Ca / 2 mM, Mg / 1 mM, S / 1mM, Fe / 80 μM, B / 14 μM, Mn / 5 μM, Cu / 0.7 μM, Mo / 4.9 μM, Zn / 3 μM; pH is about 5.8.

[0025] In order to make the technical solution of the present invention clearer, the hydroponic method and effect of improving the quality of lettuce are described in detail through multiple specific embodiments below.

[0026] Example 1 Lettuce "Red Lollo Rossa" seeds were sown in sponges and placed in white mesh baskets, and then planted in the Chengdu Academy of Agriculture and Forestry Sciences. Subsequently, the 14-day-old seedlings were transferred to the hydroponic experimental device. After a three-day recovery period in water, the seedlings were hydroponically cultured in a nitrogen-containing nutrient solution for four weeks. During the hydroponic period, a modified Hoagland nutrient solution (N / 9 mM, P / 1mM, K / 5 mM, Ca / 2 mM, Mg / 1 mM, S / 1mM, Fe / 80 μM, B / 14 μM, Mn / 5 μM, Cu / 0.7 μM, Mo / 4.9 μM, Zn / 3 μM; pH around 5.8; EC 1.5-1.8 mS·cm -1 During the experiment, the environmental conditions were maintained at 25°C during the day and 15°C at night, and the light intensity was approximately 200 μmol·m -2 ·s -1 The photoperiod was 14 hours. The following experimental and control groups were set up for glycine dosage and light quality: Experimental group 1 (E1): glycine 2.25 mM, light quality red light: blue light = 1:1; Experimental group 2 (E2): glycine 4.6 mM, light quality red light: blue light = 1:1; Experimental group 3 (E3): glycine 6.75 mM, light quality red light: blue light = 1:1; Experimental group 4 (E4): glycine 9 mM, light quality red light: blue light = 1:1; Control group (C): glycine 6.75 mM, white light.

[0027] Example 2 Lettuce "Green Lollo Rossa" seeds were sown in sponges and placed in white mesh baskets, and then planted in the Chengdu Academy of Agriculture and Forestry Sciences. Subsequently, the 14-day-old seedlings were transferred to the hydroponic experimental device. After a three-day recovery period in water, the seedlings were hydroponically cultured in a nitrogen-containing nutrient solution for four weeks. During the hydroponic period, a modified Hoagland nutrient solution (N / 9 mM, P / 1mM, K / 5 mM, Ca / 2 mM, Mg / 1 mM, S / 1mM, Fe / 80 μM, B / 14 μM, Mn / 5μM, Cu / 0.7 μM, Mo / 4.9 μM, Zn / 3 μM; pH around 5.8; EC 1.5-1.8 mS·cm -1 The nutrient solution used nitrogen sources in different forms and concentrations, including 9 mM NaNO3 (control group, G0), 2.25 mM glycine and 6.75 mM NaNO3 (G2.25), 4.5 mM glycine and 4.5 mM NaNO3 (G4.5), 6.75 mM glycine and 2.25 mM NaNO3 (G6.75), and 9 mM glycine (G9). During the experiment, the environmental conditions were maintained at 27°C during the day and 16°C at night, and the light intensity was approximately 200 μmol·m -2 ·s -1 The photoperiod was 14 hours. The following experimental and control groups were set up for glycine dosage and light quality: Experimental group 1 (E1): glycine 2.25 mM, light quality red light: blue light = 1:1; Experimental group 2 (E2): glycine 4.6 mM, light quality red light: blue light = 1:1; Experimental group 3 (E3): glycine 6.75 mM, light quality red light: blue light = 1:1; Experimental group 4 (E4): glycine 9 mM, light quality red light: blue light = 1:1; Control group (C): glycine 6.75 mM, white light.

[0028] Test example 1. Harvest the lettuce in Example 1-2, and detect the anthocyanin content in the lettuce in Example 1-2. The detection method refers to the literature (Yang et al., 2023. Pre-harvest Nitrogen Limitation and Continuous Lighting Improve the Quality and Flavor of Lettuce (Lactuca sativa L.) under Hydroponic Conditions in Greenhouse). The detection results are as follows: Figure 1 shown.

[0029] from Figure 1 It can be seen that the anthocyanin content in the control groups in Examples 1 and 2 is the lowest, with the value of the control group in Example 1 being 0.4 and the value of the control group in Example 2 being 0.23. As the concentration of glycine increases, the anthocyanin content gradually increases, with the highest value of E4 in Example 1 being 0.87 and the highest value of E4 in Example 2 being 0.67, indicating that the use of glycine and the synergy of light quality can significantly increase the anthocyanin content in lettuce.

[0030] 2. The lettuce in Example 1-2 was harvested, and the total flavonoids content, total polyphenols content, and total phenolic acid content in the lettuce in Example 1-2 were detected. The detection method was based on the literature (Yang et al., 2023. Pre-harvest Nitrogen Limitation and Continuous Lighting Improve the Quality and Flavor of Lettuce (Lactuca sativa L.) under Hydroponic Conditions in Greenhouse). The detection results are as follows: Figure 2 shown.

[0031] from Figure 2 It can be seen that the use of glycine and light quality have a significant effect on the total flavonoids, total polyphenols and total phenolic acid content of both lettuces. As the concentration of glycine increases, the content of these bioactive components generally increases. This shows that the method of the present invention can increase the content of beneficial components in lettuce and may be beneficial to health.

[0032] 3. Harvest the lettuce in Example 2, and detect the content of the bitter substances Lactucopicrin and Lactucopicrin-15-oxalate in Example 2. The detection method refers to the literature (Yang et al., 2023. Pre-harvest Nitrogen Limitation and Continuous Lighting Improve the Quality and Flavor of Lettuce (Lactuca sativa L.) under Hydroponic Conditions in Greenhouse). The detection results are as follows Figure 3 As shown, Figure 3 The bitter substance content of the control group in Example 1 was the highest, the Lactucopicrin content of the treatment group 4 was close to 0, and Lactucopicrin-15-oxalate was not detected.

[0033] from Figure 3 It can be seen that the use of glycine and the synergy of light quality significantly reduced the content of bitter substances in lettuce and significantly improved the taste.

[0034] Example 3 Compared with Example 1E4, the only difference is that the light quality is red light: blue light = 2:1, and the other culture conditions are the same as Example 1E4.

[0035] The content of anthocyanins in the cauliflower in this embodiment is as follows Figure 4 As shown in Figure 2, the contents of total flavonoids, total polyphenols, and total phenolic acids are as follows: Figure 5 As shown ( Figure 5 The unit of total flavonoid content is mg QE 100 g -1 FW, total polyphenol content in mg GAE 100 g -1 FW, total phenolic acid content in mg CAE 100 g -1 FW,) the content of Lactucopicrin and Lactucopicrin-15-oxalate is as follows Figure 6 shown.

[0036] Example 4 Compared with Example 1E4, the only difference is that the light quality is red light: blue light = 3:1, and the other culture conditions are the same as Example 1E4.

[0037] The content of anthocyanins in the cauliflower in this embodiment is as follows Figure 4 As shown in Figure 2, the contents of total flavonoids, total polyphenols, and total phenolic acids are as follows: Figure 5As shown, the contents of Lactucopicrin and Lactucopicrin-15-oxalate are as follows Figure 6 shown.

[0038] Example 5 Compared with Example 2E4, the only difference is that the light quality is red light: blue light = 2:1, and the other culture conditions are the same as Example 2E4.

[0039] The content of anthocyanins in the cauliflower in this embodiment is as follows Figure 4 As shown in Figure 2, the contents of total flavonoids, total polyphenols, and total phenolic acids are as follows: Figure 5 As shown, the contents of Lactucopicrin and Lactucopicrin-15-oxalate are as follows Figure 6 shown.

[0040] Example 6 Compared with Example 2E4, the only difference is that the light quality is red light: blue light = 3:1, and the other culture conditions are the same as Example 2E4.

[0041] The content of anthocyanins in the cauliflower in this embodiment is as follows Figure 4 As shown in Figure 2, the contents of total flavonoids, total polyphenols, and total phenolic acids are as follows: Figure 5 As shown, the contents of Lactucopicrin and Lactucopicrin-15-oxalate are as follows Figure 6 shown.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydroponic method for improving the quality of lettuce, characterized in that: During the hydroponic culture period of lettuce seedlings, 2-9 mM glycine was added to the nutrient solution and the seedlings were exposed to light at an intensity of 200 μmol·m -2 ·s -1 The photoperiod is 14 hours, and the light quality is red light: blue light = (1-3):

1.

2. A hydroponic method for improving the quality of lettuce as claimed in claim 1, characterized in that: Add 2.25-9 mM glycine to the nutrient solution.

3. A hydroponic method for improving the quality of lettuce as claimed in claim 2, characterized in that: Add 9 mM glycine to the nutrient solution.

4. The hydroponic method for improving the quality of lettuce according to claim 1, characterized in that: Light quality: red light: blue light = 1:

1.

5. The hydroponic method for improving the quality of lettuce according to claim 1, characterized in that: During the hydroponic period, the daytime temperature is 22-28°C and the nighttime temperature is 13-17°C.

6. The hydroponic method for improving the quality of lettuce according to claim 1, characterized in that: Lettuce seeds are sown in a sponge for seedling raising, and the lettuce seedlings are obtained after 14 days.

7. The hydroponic method for improving the quality of lettuce according to claim 1, characterized in that: The composition of the nutrient solution is N / 9 mM, P / 1 mM, K / 5 mM, Ca / 2 mM, Mg / 1 mM, S / 1 mM, Fe / 80 μM, B / 14 μM, Mn / 5 μM, Cu / 0.7 μM, Mo / 4.9 μM, Zn / 3 μM; pH is around 5.8.

Images