Method for improving quality of mesembryanthemum crystallinum based on short-term UV-B illumination

Abstract

The invention relates to the technical field of greenhouse vegetable production, in particular to a method for improving the quality of mesembryanthemum crystallinum based on short-term UV-B illumination. According to the method, a conventional white light source serves as basic light, and low-dose UV-B synergistic irradiation is supplemented before crops are harvested. According to the preparation method, low-dosage UV-B is added for a short time, so that the content of nutrient substances such as soluble protein of the mesembryanthemum crystallinum is not inhibited, the content of phenols and flavonoids of the mesembryanthemum crystallinum is increased, and the antioxidant activity of the mesembryanthemum crystallinum is greatly improved. Compared with the prior art, the method is convenient to operate, easy to popularize, environmentally friendly, free of pollution and capable of being directly applied to production to improve the quality of mesembryanthemum crystallinum and has good economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of facility vegetable production, and particularly relates to a method for improving the quality of ice plant based on short-term UV-B illumination. BACKGROUND

[0002] Ice plant (Mesembryanthemum crystallinum L.) is a dwarf succulent plant of Mesembryanthemum L. in the family Aizoaceae. Ice plant contains rich minerals, carotene, amino acids, inositol, etc., and has the ability to rapidly accumulate secondary metabolites, and has the effects of preventing fatty liver and relieving diabetes. In addition, ice plant is also used for cosmetic development and treatment of eye infections due to its good moisturizing effect and ability to supplement natural vitamins. At present, ice plant as a new health vegetable has been widely commercialized and planted, and has important economic value.

[0003] Ultraviolet light is an important component of the solar spectrum. Due to the absorption of the ozone layer, the ultraviolet light reaching the earth's surface is mainly long-wave ultraviolet light (UV-A, 320-400 nm) and medium-wave ultraviolet light (UV-B, 280-320 nm). UV-B, although only accounts for 1.5% of the total solar radiation reaching the earth's surface, is an important light signal for plant morphological development and quality formation. Excessive UV-B is an environmental stress factor that can damage the photosynthetic function and protein and other macromolecular structures of plants. SUMMARY

[0004] The present application provides a method for improving the quality of ice plant based on short-term UV-B illumination, which can improve the content of total phenol and total flavonoid nutrients in ice plant and improve the DPPH (1,1-diphenyl-2-trinitrobenzene hydrazine) and FRAP (ferric ion reduction / antioxidant capacity method) antioxidant capacity by supplementing short-term UV-B illumination before harvesting. The method is convenient to operate, easy to popularize, and environmentally friendly and pollution-free.

[0005] A method for improving the quality of ice plant, comprising: applying UV-B illumination to ice plant every day for 1-7 days before harvesting the ice plant; the UV-B has a wavelength of 280-315 nm and a radiation intensity of 1.4 W m -2 The following medium-wave ultraviolet light.

[0006] Preferably, the UV-B has a wave peak of 311 nm.

[0007] Preferably, the UV-B has a radiation intensity of 0.7-1.4 W m -2 , and more preferably a radiation intensity of 0.7 W m -2 .

[0008] Preferably, the UV-B light is applied to the ice plant for 6-14 hours per day, more preferably 6-8 hours per day.

[0009] Preferably, the UV-B light is applied to the ice plant for 6-14 hours per day, more preferably 6-8 hours per day.

[0010] Preferably, the period of time during which the UV-B light is applied to the ice plant per day is 8:00-22:00.

[0011] Preferably, the UV-B light is applied to the ice plant per day is supplemented with white light source light. That is, the method of the present application is based on conventional white light source light, supplemented with low-dose UV-B light during the period before the crop is harvested.

[0012] Typically, the white light source light can be conventional white light source light, such as LED light, used in the production of facility vegetables.

[0013] Preferably, the white light source has a wavelength of 400-700 nm and an illumination intensity of ≤200 μmol m -2 s -1 , for example 150-200 μmol m -2 s -1 .

[0014] Preferably, the photoperiod (including UV-B light and white light source light) is 10-14 hours,

[0015] Preferably, the method for improving the quality of the ice plant comprises applying 6-8 hours of UV-B light per day to the ice plant for 5 days before the ice plant is harvested, while applying white light source light; the UV-B has a wavelength of 280-315 nm and a radiation intensity of 0.7 W m -2 .

[0016] Preferably, the above method is carried out under the conditions of facility vegetable production.

[0017] It has been found that under the above preferred conditions, the total phenolic and total flavonoid nutrient content of the ice plant is increased, and the DPPH and FRAP antioxidant capacities are also improved, thereby improving the quality of the ice plant.

[0018] It has been found through experiments that the application of appropriate doses of UV-B does not reduce the soluble protein content of the ice plant, but rather increases the total phenolic and total flavonoid content of the leaves, and significantly improves the antioxidant activity of the plant. It has been found that the application of 0.7 W m -2 of UV-B to the ice plant for 5 days before harvesting is optimal for improving the overall quality of the ice plant. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 1 is a graph showing the different UV-B treatment spectra in Example 1 of the present application.

[0020] Figure 2 The experimental setup for different UV-B intensity treatment in Example 1 of the present application.

[0021] Figure 3 The bar chart of the maximum photosynthetic efficiency (F v / F m ) of photosystem II of the leaves of the ice plant under different UV-B treatment in Example 1 of the present application.

[0022] Figure 4 The spectral diagram of the UV-B treatment in Example 2 of the present application.

[0023] Figure 5 The experimental setup diagram for different UV-B irradiation time periods in Example 2 of the present application.

[0024] Figure 6 The bar chart of the maximum photosynthetic efficiency (F v / F m ) of photosystem II of the leaves of the ice plant under different UV-B treatment time periods in Example 2 of the present application. DETAILED DESCRIPTION

[0025] The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0026] The wavelength of the UV-B below is 280-315 nm, and the peak is 311 nm.

[0027] Example 1: Influence of different UV-B intensities on the quality of the ice plant

[0028] Experimental material: water crystal ice plant (Mesembryanthemum crystallinum L.), Xinghai County Hezhiyuan Agricultural Development Co., Ltd.

[0029] Environmental conditions: temperature 25℃ / 18℃ (light period / dark period), relative humidity 65%~75%. The seeds of the ice plant were sown in a 72-hole tray, and cultured under white light (150 μmol m -2 s -1 ) until two leaves and one heart (4 weeks), with a photoperiod of 14h / 10h (light period / dark period), and then transplanted into a cultivation substrate of peat:vermiculite:perlite = 3:1:1 for culture until maturity (6 weeks), with irrigation of 1 / 2 times Hoagland nutrient solution during the period. There were independent air ducts on the upper, middle and lower three layers of the climate chamber. In order to avoid mutual influence between treatments, different treatments were separated by a light-reflecting board.

[0030] Experimental treatment: three treatments were set up in the experiment, and the spectral diagram is shown in Figure 1 , and the light intensity treatment during the light period is shown in Figure 2 .

[0031] Control group was no UV-B treatment (150 μmol m -2 s -1 white light), experimental group one (UV-B-0.7) was added 0.7 W m -2 UV-B (150 μmol m -2 s -1 white light + 0.7 W m -2 UV-B) on the basis of the control group, experimental group two (UV-B-1.4) was added 1.4 W m -2 UV-B (150 μmol m -2 s -1 white light + 1.4 W m -2 UV-B) on the basis of the control group. Photoperiod 14 hours, UV-B irradiation time of each day was 8:00-14:00 for a total of 6 hours.

[0032] UV-B light intensity experiment results

[0033] 1. Peroxide and antioxidant changes of ice leaf

[0034] As shown in Table 1, compared with the control group, after supplementing UV-B light, the content of hydrogen peroxide H2O2 was significantly increased under UV-B-1.4 treatment, while under UV-B-0.7 treatment, there was no significant difference. Membrane quality peroxide MDA was increased under UV-B-1.4 treatment compared with other treatments. At the same time, after supplementing UV-B treatment, the DPPH free radical scavenging rate and total antioxidant capacity FRAP in the antioxidant system were significantly increased compared with the control group. The above shows that UV-B treatment can improve the antioxidant activity of ice and improve its nutritional quality. At the same time, low-dose UV-B treatment does not cause obvious stress to plants, while under 1.4 W m -2 UV-B treatment, the plant has been stressed.

[0035] Table 1 Effect of different UV-B intensity on peroxide and antioxidant of ice leaf

[0036] Treatment Control UV-B-0.7 UV-B-1.4 Membrane quality peroxide MDA (nmol / g FW) 17.21±2.97 a 12.31±2.73 a 32.53±9.12 a Hydrogen peroxide H2O2 (pmol / g FW) 1.63±0.47 b 13.44 ± 0.96 ab 18.10±4.65 a DPPH radical scavenging rate (%) 14.55±2.60 b 32.13±1.57 a 33.39±1.88 a Total antioxidant capacity FRAP (mmol Fe 2+ / g FW) 3.62±0.69 b 8.18±0.77 a 8.21±0.84 a

[0037] 2. Changes of biochemical components of ice leaf

[0038] As shown in Table 2, after UV-B treatment, the total phenolic content of ice plant leaves increased significantly under UV-B-0.7 treatment, reaching 3.95 times that of the control group, and under UV-B-1.4 treatment, the total phenolic content was 3.11 times that of the control group. Compared with the control group, the total flavonoid content of ice plant leaves increased by 156.1% and 139.0% under UV-B-0.7 and UV-B-1.4 treatments, respectively. Furthermore, compared with UV-B-1.4 treatment, the total chlorophyll content of ice plant leaves increased significantly by 24.1% under UV-B-0.7 treatment. There were no significant differences in soluble protein and soluble sugar content among the three groups. These findings indicate that UV-B can increase the content of secondary metabolites in ice plant leaves without affecting protein synthesis.

[0039] Table 2 Effects of different UV-B intensities on the biochemical components of ice plant leaves

[0040] Treatment Control UV-B-0.7 UV-B-1.4 Total chlorophyll (mg / g FW) 0.139 ± 0.002 ab 0.149±0.007a 0.120±0.008b Chlorophyll a / b value 2.52±0.05a 2.55±0.13a 2.15±0.10a Carotenoid (mg / g FW) 0.042±0.001a 0.044±0.002a 0.042±0.003a Soluble protein (mg / g FW) 0.65±0.01a 0.65±0.02a 0.60±0.01a Soluble sugar (mg / g FW) 0.99±0.13a 0.99±0.00a 1.21±0.21a Total phenol (pg GAE / g FW) 0.19±0.01b 0.75±0.15a 0.59 ± 0.09 ab Total flavonoids (pg RUE / g FW) 0.41±0.02a 1.05±0.14a 0.98±0.18a

[0041] 3. Changes in the photosystem activity of ice plant leaves

[0042] like Figure 3 As shown, compared with the control group, F under UV-B-1.4 treatment v / F m There was a slight decrease, but no significant change was observed under UV-B-0.7 treatment, indicating that the ice plant at 1.4W m -2 Under UV-B treatment, its photosystem II was slightly stressed. This is consistent with the aforementioned increase in its hydrogen peroxide content.

[0043] In conclusion, both UV-B treatments increased the content of secondary metabolites and antioxidant capacity of ice plant. However, due to the increased peroxide content in ice plant leaves under UV-B-1.4 treatment and the mild stress on photosystem II, a light intensity of 0.7 W / m² was selected. -2 The UV-B intensity of Example 2 is used as the optimized UV-B light intensity.

[0044] Example 2: Effect of different UV-B light exposure times on the quality of ice plant

[0045] Experimental materials: Crystal ice plant (Mesembryanthemum crystallinum L.), Xinghai County Hezhiyuan Agricultural Development Co., Ltd.

[0046] Environmental conditions: Temperature 25℃ / 18℃ (light / dark period), relative humidity 65%-75%. Ice plant seeds were sown in 72-cell trays under white light (150 μmol / m²). -2 s -1LEDs until two-leaf stage (4 weeks), photoperiod 14h / 10h (light / dark), then transplanted into peat:vermiculite:perlite=3:1:1 medium until mature (6 weeks), irrigated with 1 / 2 Hoagland nutrient solution during the period. The climate room has three layers, each with independent air ducts. To avoid the influence between treatments, different treatments were separated by a light-reflecting board.

[0047] Experimental treatments: The experiment selected 0.7 W m -2 UV-B for treatment, and the spectrum is as shown in Figure 4 . The experiment sets five UV-B light time period treatments, as shown in Figure 5 , the control group is without UV-B treatment, experimental group one (UV-B-1Day) is to add 0.7 W m -2 UV-B to the control group starting one day before harvest; experimental group two (UV-B-3Day) is to add 0.7 W m -2 UV-B to the control group starting three days before harvest; experimental group three (UV-B-5Day) is to add 0.7 W m -2 UV-B to the control group starting five days before harvest; experimental group four (UV-B-7Day) is to add 0.7 W m -2 UV-B to the control group starting seven days before harvest. The photoperiod is 14 hours, and the UV-B irradiation time is 8:00-14:00 for a total of 6 hours per day.

[0048] Results of different UV-B light time experiments

[0049] 1. Changes in peroxide and antioxidant systems of ice lettuce

[0050] As shown in Table 3, compared with the control group, after increasing the UV-B treatment time, the membrane peroxide MDA content was the highest under UV-B-3Day treatment and the lowest under UV-B-5Day treatment. The hydrogen peroxide content was significantly different from the control group under UV-B treatment. In UV-B-1Day, UV-B-3Day, UV-B-5Day, and UV-B-7Day treatments, the total antioxidant capacity FRAP increased by 45.3%, 91.1%, 142.0%, and 12.1%, respectively; the DPPH free radical scavenging rate increased by 49.4%, 171.9%, 98.8%, and 59.4%, respectively.

[0051] Table 3 Effects of different UV-B time period treatments on peroxide and antioxidant properties of ice lettuce

[0052]

[0053] 2. Changes in biochemical components of ice lettuce leaves

[0054] As shown in Table 4, the total phenol and total flavonoid contents in leaves were highest under the UV-B-5 Day treatment, with increases of 167.9% and 176.3%, respectively. In the UV-B-3 Day and UV-B-5 Day treatments, the total chlorophyll content increased by 24.6% and 22.1% compared to the control group, respectively. However, there were no significant differences in protein, chlorophyll a / b ratio, and carotenoids among the five treatments.

[0055] Table 4. Effects of different UV-B time periods on the biochemical components of ice plant leaves.

[0056]

[0057] 3. Changes in the photosystem activity of ice plant leaves

[0058] like Figure 6 As shown, compared with the control group, the leaf F under UV-B-1 Day, UV-B-3 Day, UV-B-5 Day, and UV-B-7 Day treatments... v / F m There was no significant difference. This indicates that the photosystem II of the ice plant leaves was not affected by stress.

[0059] Experiments showed that total phenols and total flavonoids increased significantly under different UV-B irradiation durations, with the largest increase observed under five days of irradiation before harvest.

[0060] The above experiments concluded that different UV-B irradiation periods can improve the quality of ice plant. Specifically, irradiating ice plant with 0.7W m² of UV-B irradiation 5 days before harvest is most effective. -2 UV-B has the best effect on improving the overall quality of ice plant.

[0061] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for improving the quality of ice plant, characterized in that, include: Apply UV-B light to the ice plant daily for 1-7 days before harvesting; the UV-B light has a wavelength of 280-315nm and a radiation intensity of 1.4W / m². -2 The following is mid-wave ultraviolet light.

2. The method for improving the quality of ice plant according to claim 1, characterized in that, The peak wavelength of the UV-B is 311 nm.

3. The method for improving the quality of ice plant according to claim 1 or 2, characterized in that, The UV-B radiation intensity is 0.7-1.4 W / m². -2 The preferred radiation intensity is 0.7 W / m. -2 .

4. The method for improving the quality of ice plant according to any one of claims 1-3, characterized in that, Apply UV-B light to the ice plant daily for 5-7 days before harvesting, preferably 5 days before harvesting.

5. The method for improving the quality of ice plant according to any one of claims 1-4, characterized in that, The duration of UV-B light exposure for ice plant should be 6-14 hours per day, preferably 6-8 hours.

6. The method for improving the quality of ice plant according to any one of claims 1-5, characterized in that, While applying UV-B light to the ice plant daily, it was also exposed to white light. Preferably, the wavelength of the white light source is 400-700 nm, and the illuminance is ≤200 μmol m. -2 s -1 More effectively, the illuminance of the white light source is 150-200 μmol / m². -2 s -1 .

7. The method for improving the quality of ice plant according to any one of claims 1-6, characterized in that, The photoperiod is 10-14 hours.

8. The method for improving the quality of ice plant according to any one of claims 1-7, characterized in that, The method for improving the quality of ice plant includes: applying UV-B light to the ice plant for 6-8 hours daily for 5 days before harvesting, while simultaneously applying white light; the UV-B wavelength is 280-315nm, and the radiation intensity is 0.7W / m². -2 .

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