Determination method for relieving high-temperature stress of bougainvillea glabra seedlings by utilizing salicylic acid

Abstract

The invention belongs to the technical field of high-temperature stress determination, particularly relates to a determination method for relieving high-temperature stress of bougainvillea spectabilis seedlings by utilizing salicylic acid, and aims to solve the problems that the existing salicylic acid can improve the resistance of plants under high-temperature stress, but the specific application of the salicylic acid to the bougainvillea spectabilis seedlings is less. In order to solve the problem that the prior art cannot accurately evaluate the protection effect of salicylic acid on bougainvillea glabra seedlings under high temperature stress, the invention provides the following scheme: the method comprises the following steps: S1, selecting the bougainvillea glabra seedlings, and carrying out spraying cultivation; s2, the treated seedlings are subjected to high-temperature treatment, and water is supplemented regularly; s3, sampling the seedlings subjected to high-temperature treatment, and treating a sample; s4, adding the sample into ethanol, uniformly shaking and storing; s5, determining the total amount of chlorophyll in the sample; the method can accurately evaluate the protection effect of salicylic acid on bougainvillea spectabilis seedlings under high temperature stress, and it is obtained that sprayed exogenous SA can relieve the influence of high temperature stress on seedling growth to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of high - temperature stress determination, and in particular to a method for determining the alleviation of high - temperature stress of Bougainvillea glabra seedlings by using salicylic acid. Background Technique

[0002] Bougainvillea glabra is a vine - shaped shrub of the genus Bougainvillea in the family Nyctaginaceae, mainly distributed in tropical and subtropical regions, and is now widely planted in warm regions of southern China. There are many varieties of Bougainvillea glabra. Its flower buds are brightly colored, with a soft and light texture and beautiful shapes. After blooming, it can create a spectacular landscape effect. The morphological and color diversification endows Bougainvillea glabra with various ornamental characteristics. It is one of the plants with high aesthetic value in garden landscaping and is widely used in urban road greening, garden greening and courtyard greening. With the continuous improvement of the living standards of the people in our country, people's spiritual needs are also increasing day by day. As an important part of people's spiritual needs, the garden landscape greening market will still continue to expand in the future. As one of the main garden greening plants in South China, Bougainvillea glabra has great market prospects. High temperature, as an important abiotic stress factor, seriously affects the growth and development of Bougainvillea glabra seedlings and reduces their survival rate.

[0003] In the prior art, salicylic acid can improve the resistance of plants under high - temperature stress, but there are few inventions specifically applied to Bougainvillea glabra seedlings, and it is impossible to accurately evaluate the protective effect of salicylic acid on Bougainvillea glabra seedlings under high - temperature stress. For this reason, we propose a method for determining the alleviation of high - temperature stress of Bougainvillea glabra seedlings by using salicylic acid to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem in the prior art that although salicylic acid can improve the resistance of plants under high - temperature stress, there are few inventions specifically applied to Bougainvillea glabra seedlings, and it is impossible to accurately evaluate the protective effect of salicylic acid on Bougainvillea glabra seedlings under high - temperature stress, and to propose a method for determining the alleviation of high - temperature stress of Bougainvillea glabra seedlings by using salicylic acid.

[0005] A method for determining the alleviation of high - temperature stress of Bougainvillea glabra seedlings provided by the present application adopts the following technical scheme:

[0006] A method for determining the alleviation of high - temperature stress of Bougainvillea glabra seedlings includes the following steps:

[0007] S1: Select Bougainvillea glabra seedlings and conduct spraying cultivation;

[0008] S2: Subject the treated seedlings to high - temperature treatment and replenish water regularly;

[0009] S3: Sample the seedlings after high-temperature treatment and process the samples.

[0010] S4: Add the samples to ethanol, shake well, and store.

[0011] S5: Measure the total chlorophyll content in the samples.

[0012] S6: Process the measured data and perform analysis.

[0013] Further, in S1, select Bougainvillea glabra seedlings with consistent growth and spray SA on the leaf surface from 8:00 to 9:00 every day.

[0014] Further, in S1, the spraying amount is appropriate when the liquid is about to drip on the leaves, and spray continuously for 2 days.

[0015] Further, in S2, 48 hours after the spraying ends, put the treated seedlings into an artificial constant temperature incubator for high-temperature treatment. The temperature of the artificial constant temperature incubator is 39°C during the day for 14 hours and 28°C at night for 10 hours, and replenish 250 ml of water every 72 hours.

[0016] Further, in S3, sample the leaves of the seedlings after high-temperature treatment through a sampling mechanism, fix them with liquid nitrogen, and then store them in a -80°C refrigerator.

[0017] Further, in S4, cut off the main veins of the treated leaves and cut them into pieces, and add 10 ml of 95% anhydrous ethanol.

[0018] Further, in S4, shake the samples added with anhydrous ethanol through a shaking device and store them in the dark for 48 hours.

[0019] Further, in S5, measure the total chlorophyll content through a spectrophotometer.

[0020] Further, in S5, the calculation formula for the chloroplast pigment concentration is: C a = 13.95×A 665 - 6.88×A 649 , C b = 24.96×A 649 - 7.32×A 665 , the chloroplast pigment content (mg / g) = (C a + C b )×V T ×n / FW×1000, where V T is the extraction liquid volume, n is the dilution factor, and FW is the fresh weight of the sample (g).

[0021] Further, in S6, the measured data is calculated and graphed using Microsoft Excel, and the single-factor results analysis and correlation analysis of the sample physiological and biochemical indexes are performed using the statistical analysis software SPSS26.

[0022] In summary, the present application includes at least one of the following beneficial technical effects:

[0023] This solution explores the alleviating effect of exogenous substances on the growth of Bougainvillea glabra seedlings by spraying different concentrations of SA on the leaves, and screens the SA concentration with the best alleviating effect, so as to provide a certain theoretical basis for improving the heat tolerance of Bougainvillea glabra seedlings subsequently.

[0024] The present invention can accurately evaluate the protective effect of salicylic acid on Bougainvillea glabra seedlings under high-temperature stress, and it is concluded that spraying exogenous SA can alleviate the impact of high-temperature stress on seedling growth to a certain extent. Description of the Drawings

[0025] Figure 1 It is a flowchart of a method for measuring the alleviation of high-temperature stress of Bougainvillea glabra seedlings using salicylic acid proposed by the present invention;

[0026] Figure 2 It is a schematic diagram of the effect of different concentrations of SA on the chlorophyll content of the leaves of Bougainvillea glabra seedlings in a method for measuring the alleviation of high-temperature stress of Bougainvillea glabra seedlings using salicylic acid proposed by the present invention;

[0027] Figure 3 It is a schematic diagram of the effect of different concentrations of SA on the MDA content of the leaves of Bougainvillea glabra seedlings in a method for measuring the alleviation of high-temperature stress of Bougainvillea glabra seedlings using salicylic acid proposed by the present invention;

[0028] Figure 4 It is a schematic diagram of the effect of different concentrations of SA on the Pro content of the leaves of Bougainvillea glabra seedlings in a method for measuring the alleviation of high-temperature stress of Bougainvillea glabra seedlings using salicylic acid proposed by the present invention;

[0029] Figure 5 It is a schematic diagram of the effect of different concentrations of SA on the POD activity of the leaves of Bougainvillea glabra seedlings in a method for measuring the alleviation of high-temperature stress of Bougainvillea glabra seedlings using salicylic acid proposed by the present invention;

[0030] Figure 6 It is a schematic diagram of the effect of different concentrations of SA on the SOD activity of the leaves of Bougainvillea glabra seedlings in a method for measuring the alleviation of high-temperature stress of Bougainvillea glabra seedlings using salicylic acid proposed by the present invention. Detailed Embodiments

[0031] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0032] Embodiment

[0033] Refer to Figure 1 , a method for measuring the alleviation of high - temperature stress in bougainvillea seedlings by salicylic acid, comprising the following steps:

[0034] S1: Select bougainvillea seedlings and carry out spraying cultivation;

[0035] S2: Subject the treated seedlings to high - temperature treatment and replenish water regularly;

[0036] S3: Take samples of the seedlings after high - temperature treatment and process the samples;

[0037] S4: Add the samples to ethanol, shake well and store;

[0038] S5: Measure the total chlorophyll content in the samples;

[0039] S6: Process the measured data and conduct analysis.

[0040] In this embodiment, in S1, select bougainvillea seedlings with consistent growth, spray SA on the leaf surface from 8:00 to 9:00 every day, and the spraying amount is appropriate when the liquid on the leaves is about to drip. Spray continuously for 2 days.

[0041] In this embodiment, in S2, 48 hours after the spraying ends, put the treated seedlings into an artificial constant - temperature incubator for high - temperature treatment. The daytime temperature in the artificial constant - temperature incubator is 39 °C for 14 hours, the nighttime temperature is 28 °C for 10 hours, and 250 ml of water is replenished every 72 hours.

[0042] In this embodiment, in S3, take samples of the leaves of the seedlings after high - temperature treatment through a sampling mechanism, fix them with liquid nitrogen, and then store them in a - 80 °C refrigerator.

[0043] In this embodiment, in S4, cut off the main veins of the treated leaves and cut them into pieces, add 10 ml of 95% anhydrous ethanol, shake the samples added with anhydrous ethanol through a shaking device, and store them in the dark for 48 hours.

[0044] In this embodiment, in S5, measure the total chlorophyll content through a spectrophotometer. The calculation formula for the chloroplast pigment concentration is: C a = 13.95×A 665 - 6.88×A 649 C b = 24.96×A 649 - 7.32×A665 , Chloroplast pigment content (mg / g) = (C a +C b ) × V T × n / FW × 1000, where V T is the volume of the extraction solution, n is the dilution factor, and FW is the fresh weight of the sample (g).

[0045] In this example, in S6, the measured data was calculated and graphed using Microsoft Excel, and the single-factor results analysis and correlation analysis of the sample physiological and biochemical indexes were performed using the statistical analysis software SPSS26.

[0046] Experimental Example

[0047] I. Experimental Materials

[0048] The experiment used cuttings of Bougainvillea glabra 'Tong'an Hong', purchased online from Yibin Bougainvillea Base. The substrate used was prepared from peat soil:loess:sand (2:1:1). One cutting was planted in each pot and transplanted in the garden base of Zhanjiang University of Science and Technology for 7 days of acclimation. During this period, normal cultivation and management were carried out. The exogenous substance SA used in the experiment was purchased from Guangdong Kecheng Laboratory Equipment Co., Ltd. The biological test kits for measuring SOD, POD, MDA, and Pro were all purchased from Nanjing Jiancheng Bioengineering Institute;

[0049] II. Experimental Methods

[0050] Select Bougainvillea glabra seedlings with consistent growth. Spray different concentrations of SA (1.0 mmol·L -1 , 2.0 mmol·L -1 , 3.0 mmol·L -1 ) on the leaf surface from 8:00 to 9:00 every day, using tap water as the control (CK). The spraying amount should be such that the liquid just drips from the leaves. Three plants were treated with each concentration and sprayed continuously for 2 days to ensure that the seedlings were fully absorbed. 48 hours after the spraying ended, the treated seedlings were placed in an artificial constant temperature incubator for high-temperature treatment (39°C for 14 hours during the day / 28°C for 10 hours at night). Three replicates were set for each treatment, and 250 ml of water was added every 72 hours. Samples were taken at 0, 36 hours, 72 hours, and 108 hours of stress. Leaves were randomly cut, fixed in liquid nitrogen, and then stored in a -80°C refrigerator for measuring various physiological indexes (chlorophyll was measured immediately after sampling);

[0051] At two time points of 0 and 108 hours, three plants were randomly selected from each concentration treatment, the substrate in the pot was removed, the plants were taken out, the roots were washed clean with distilled water, the plant height and root length were measured with a ruler, and photos were taken for recording;

[0052] III. Measurement Methods

[0053] Four indicators, namely superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), and proline (Pro), were measured using kits produced by Nanjing Jiancheng Bioengineering Co., Ltd.;

[0054] The chlorophyll content was determined by spectrophotometry. Leaves of plants treated with different concentrations were selected, the main veins were cut off and the leaves were shredded. Then 10 ml of 95% anhydrous ethanol was added, shaken well, and stored in the dark for 48 h. The total chlorophyll content was measured using a spectrophotometer. The calculation formula for the chloroplast pigment concentration is: C a = 13.95 × A 665 - 6.88 × A 649 , C b = 24.96 × A 649 - 7.32 × A 665 , the chloroplast pigment content (mg / g) = (C a + C b ) × V T × n / FW × 1000, where V T is the volume of the extraction solution, n is the dilution factor, and FW is the fresh weight of the sample (g);

[0055] IV. Data Processing

[0056] The experimental data and required pictures were calculated and plotted using Microsoft Excel, and the single-factor result analysis and correlation analysis of each physiological and biochemical index of the samples were performed using the statistical analysis software SPSS 26;

[0057] V. Results and Analysis

[0058] 1. Effects of SA on the growth of Bougainvillea spectabilis Willd. seedlings under high-temperature stress

[0059] Under adversity, the growth of plants will be inhibited, and the plant height and root length will also be affected. As shown in Table 1, with the prolongation of high-temperature stress time, the growth of Bougainvillea spectabilis Willd. seedlings slowed down. At 108 h of high-temperature stress, the average heights of the control group and the 1.0 mmol·L -1 , 2.0 mmol·L -1 , 3.0 mmol·L -1 treatment groups increased by 2.74, 2.8, 3.47, and 0.9 cm respectively compared with 0 h. At 108 h of high-temperature stress, the average main root lengths of the control group and the 1.0 mmol·L -1 , 2.0 mmol·L -1 , 3.0 mmol·L -1 treatment groups decreased by 15.87%, 14.84%, 15.87%, and 23.81% respectively compared with 0 h. It can be analyzed that the 2.0 mmol·L -1The highest average height of the treatment is 1.0 mmol·L -1 The lowest average reduction value of root length of the treatment;

[0060] Table 1 Effects of different concentrations of SA on plant height and root length of Bougainvillea spectabilis Willd. seedlings

[0061]

[0062] 2. Effects of SA on chlorophyll content in leaves of Bougainvillea spectabilis Willd. seedlings under high-temperature stress

[0063] As Figure 2 can be seen, with the prolongation of stress time, the chlorophyll content of all treatments showed a trend of first increasing and then decreasing. When the stress time reached 36 h, the chlorophyll content of 1.0 mmol·L -1 and 2.0 mmol·L -1 treatments reached the highest values of 0.806 and 0.734 mg·g -1 respectively. The chlorophyll content of 1.0 mmol·L -1 treatment was higher than that of CK and other treatments in each time period. The chlorophyll content of other treatments began to decline after 72 h, while the chlorophyll content of 1.0 mmol·L -1 treatment began to decline after 36 h. However, the decline rate of 1.0 mmol·L -1 treatment was smaller than that of CK and other treatments, and it was higher than CK and other treatments at 108 h of high temperature. It is considered that the 1.0 mmol·L -1 treatment had the best effect, could maintain a relatively high chlorophyll content, and was higher than CK in each time period;

[0064] 3. Effects of SA on MDA content in leaves of Bougainvillea spectabilis Willd. seedlings under high-temperature stress

[0065] As Figure 3 can be seen, after high-temperature stress, the MDA content in leaves of Bougainvillea spectabilis Willd. seedlings increased significantly. With the prolongation of time, the MDA content of all treatments increased accordingly and reached the highest value at 72 h, and then began to decline. The MDA content of 1.0 mmol·L -1 treatment was significantly lower than that of CK and other treatments. In the two time periods of 72 and 108 h, the MDA content of 3.0 mmol·L -1 treatment was significantly higher than that of CK and other treatments;

[0066] 4. Effects of SA on Pro content in leaves of Bougainvillea spectabilis Willd. seedlings under high-temperature stress

[0067] As Figure 4 can be seen, the 1.0 mmol·L -1With the prolongation of treatment time, the Pro content increased, and the increase amplitude was higher than that of CK and other treatments, but significantly lower than 2.0 mmol·L -1 , and it was higher than CK and other treatments at 72 h and 108 h, and reached the highest value of 36.92 μg·g at 108 h -1 , 3.0 mmol·L -1 With the prolongation of stress time, the Pro content in the 3.0 mmol·L

[0068] 5. Effects of SA on the POD activity in the leaves of Bougainvillea spectabilis Willd. seedlings under high temperature stress

[0069] POD is another antioxidant metalloenzyme commonly present in biological cells, which can catalyze the decomposition of H2O2 to scavenge free radicals. As can be seen from Figure 5 , the 1.0 mmol·L -1 treatment was higher than other treatments at each time period. The 2.0 mmol·L -1 and 3.0 mmol·L -1 treatments were slightly lower than CK at 72 h and 108 h. With the prolongation of stress time, all treatments showed a pattern of first increasing and then decreasing, and reached the highest value at 36 h. Between 36 h and 108 h, the 1.0 mmol·L -1 treatment had the lowest decline amplitude, and the 3.0 mmol·L -1 treatment had a more obvious decline amplitude. Through the above analysis, it can be seen that the POD activity of Bougainvillea spectabilis Willd. seedlings under high temperature stress is related to the SA spraying concentration, and the 1.0 mmol·L -1 treatment had the highest POD activity;

[0070] 6. Effects of SA on the SOD activity in the leaves of Bougainvillea spectabilis Willd. seedlings under high temperature stress

[0071] As can be seen from Figure 6 , with the prolongation of stress time, all treatments showed a trend of first increasing and then decreasing. The 1.0 mmol·L -1 , 2.0 mmol·L -1 and 3.0 mmol·L -1 treatments were lower than CK at 36 h. CK and the 3.0 mmol·L -1 treatment reached the highest value at 36 h, and then began to decline, and were all lower than the 1.0 mmol·L -1 treatment. Among them, the 3.0 mmol·L -1 treatment had the most obvious decline at 72 h and was significantly lower than other treatments;

[0072] VI. Discussion and conclusions

[0073] 1. Effects of SA on the growth of Bougainvillea seedlings under high-temperature stress

[0074] With the prolongation of stress time, the average plant height increment of the 1.0 mmol·L -1 and 2.0 mmol·L -1 treatments was greater than that of the CK. For the 3.0 mmol·L -1 treatment, it is considered that spraying an appropriate concentration of SA can alleviate the impact of high temperature on Bougainvillea. This is similar to the conclusion of Zhao Xin's invention on the effect of silicon addition on the growth of Medicago sativa under high-temperature stress. However, the negative growth of root length is different from the results of his invention, which is considered to be caused by human factors;

[0075] 2. Effects of SA on the chlorophyll content in the leaves of Bougainvillea seedlings under high-temperature stress

[0076] High temperature can inhibit the synthesis of new chlorophyll in plants, thereby inhibiting the photosynthesis and respiration of plants, causing plant wilting and even death. Dong Lei et al.'s invention found that the growth rate of Medicago hispida under high-temperature stress was severely inhibited. Spraying 2.5 mmol·L -1 SA had the most significant growth-promoting effect on Medicago hispida under high-temperature stress. Ghasemi M et al. found that high-temperature stress reduced the physiological characteristics and chlorophyll content of Matricaria chamomilla. Spraying an appropriate concentration of SA could improve the heat tolerance of Matricaria chamomilla. In this invention, with the prolongation of high-temperature stress time, all treatments showed a phenomenon of first increasing and then decreasing. The chlorophyll content of the 1.0 mmol·L -1 treatment was higher than that of the CK, and the contents of the other treatments were lower than that of the CK, which was similar to the invention results of Dong Lei et al. on Medicago hispida, indicating that spraying a high concentration of SA may inhibit the growth of plants, while spraying an appropriate concentration of SA is beneficial to improving its heat tolerance. The 1.0 mmol·L -1 treatment had the best effect;

[0077] 3. Effects of SA on the MDA content in the leaves of Bougainvillea seedlings under high-temperature stress

[0078] This invention shows that the MDA content of the 1.0 mmol·L -1 and 2.0 mmol·L -1 treatments was always lower than that of the CK, and the content of the 1.0 mmol·L -1 treatment was the lowest. The 3.0 mmol·L -1 treatment was significantly higher than that of the CK and the other treatments. After spraying an appropriate concentration of SA, the accumulation of MDA was significantly reduced, while the 3.0 mmol·L -1 treatment increased instead. The 1.0 mmol·L -1 and 2.0 mmol·L -1The results of the treatment were consistent with those of Liu Ruoxi et al. for the invention of pakchoi, while the treatment with 3.0 mmol·L -1 was inconsistent with theirs, indicating that spraying SA at too high a concentration might inhibit plant growth, while spraying an appropriate concentration of SA could enhance the heat tolerance of Bougainvillea glabra seedlings, and the SA at 1.0 mmol·L -1 significantly reduced the damage to its cell plasma membrane and had the best effect;

[0079] 4. Effects of SA on the Pro content in the leaves of Bougainvillea glabra seedlings under high-temperature stress

[0080] As one of the osmotic adjustment substances, Pro can protect lipid membranes and key enzymes, maintain the osmotic adjustment ability. Pro is highly water-soluble and its content will also increase significantly under high-temperature stress, thereby enhancing the water retention of plants. In this experiment, with the prolongation of time, the Pro content of all concentrations increased and reached the highest value at 108 h. The contents of the three treatments were all higher than that of CK. Among them, the treatment with 1.0 mmol·L -1 was significantly higher than that of CK, indicating that spraying SA could promote the synthesis and accumulation of Pro in Bougainvillea glabra seedlings under high-temperature stress, thereby increasing its osmotic pressure and enhancing heat tolerance. This was similar to the results of the invention of Trollius chinensis seedlings by Liu Jinyu et al.;

[0081] 5. Effects of SA on the activities of POD and SOD in the leaves of Bougainvillea glabra seedlings under high-temperature stress

[0082] Under high-temperature stress, a large amount of reactive oxygen species will accumulate in plant cells, resulting in serious damage to the cell membrane lipid system. Salicylic acid can act as an antioxidant to scavenge reactive oxygen species and resist the oxidative damage of metal toxicity by activating the plant antioxidant system and increasing enzyme activity, thereby reducing the impact of oxidation on plants. In the early stage of stress, the activity of antioxidant enzymes increased, enhancing their ability to scavenge reactive oxygen species and maintaining dynamic balance. The POD activity of all treatments was higher than that of CK, and the change in SOD activity was not obvious. In the middle and late stages of stress, the POD activity decreased to varying degrees. Among them, the treatment with 1.0 mmol·L -1 was always higher than that of CK, and the other two treatments were lower than CK; the SOD activity decreased after reaching the highest value, which was similar to the results of the invention of Davidia involucrata seedlings by Xu Lei et al. However, the POD and SOD activities of the treatment with 3.0 mmol·L -1 were lower than that of CK in the middle and late stages of stress. This result was inconsistent with the results of the invention of Davidia involucrata seedlings by Xu Lei et al. It was analyzed that the high concentration of SA might have an inhibitory effect on Bougainvillea glabra seedlings;

[0083] Under SA treatment, the activities of two antioxidant enzymes in Bougainvillea seedlings under high temperature stress showed a trend of first increasing and then decreasing with the prolongation of time, indicating that an appropriate concentration of SA can improve the antioxidant enzyme activity of Bougainvillea seedlings, maintain their high activity, and thus be more conducive to cell stability. Comprehensive analysis showed that the treatments of 1.0 mmol·L -1 , 2.0 mmol·L -1 performed better, and the treatment concentration of 3.0 mmol·L -1 might be too high, resulting in an inhibitory effect;

[0084] Finally, high temperature stress had an inhibitory effect on the growth of Bougainvillea seedlings. Spraying exogenous SA could alleviate the impact of high temperature stress on seedling growth to a certain extent. Under high temperature stress, an appropriate concentration of SA affected various physiological indexes of Bougainvillea seedlings, improved the heat tolerance of seedlings. Among them, the treatment effect of 1.0 mmol·L -1 was the best, and too high a concentration of SA (3.0 mmol·L -1 ) had an inhibitory effect on seedling growth.

[0085] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for measuring the effect of salicylic acid on the high temperature stress of bougainvillea seedlings, characterized in that: The following steps are involved: S1: Select bougainvillea seedlings and spray them for cultivation; S2: subjecting the treated seedlings to high temperature and replenishing water regularly; S3: sampling seedlings treated with high temperature and processing the samples; S4: Add ethanol to the sample, shake well and store; S5: Determine the total amount of chlorophyll in the sample; S6: Process and analyze the measured data.

2. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 1, characterized in that: In S1, bougainvillea seedlings with uniform growth were selected, and SA was sprayed on the leaves at 8:00-9:00 every day.

3. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 2, characterized in that: In S1, the spraying amount is preferably such that the liquid is about to drip on the leaves, and the spraying is continued for 2 days.

4. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 3, characterized in that: In S2, 48 hours after the spraying, the treated seedlings are placed in an artificial constant temperature box for high temperature treatment. The temperature of the artificial constant temperature box is 39°C during the day for 14 hours and 28°C at night for 10 hours. 250 ml of water is added every 72 hours.

5. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 4, characterized in that: In S3, the seedling leaves after high temperature treatment are sampled by a sampling mechanism, fixed by liquid nitrogen, and then stored in a -80°C refrigerator.

6. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 5, characterized in that: In the above S4, the main veins of the treated leaves are cut off and the leaves are chopped into pieces, and 10 ml of 95% anhydrous ethanol is added.

7. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 6, characterized in that: In S4, the sample to which anhydrous ethanol is added is shaken by a shaking device and stored in the dark for 48 hours.

8. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 7, characterized in that: In S5, the total amount of chlorophyll is measured by a spectrophotometer.

9. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 8, characterized in that: In S5, the chloroplast pigment concentration is calculated as: a =13.95×A 665 -6.88×A 649 , C b =24.96×A 649 -7.32×A 665 , chloroplast pigment content (mg / g) = (C a +C b )×V T ×n / FW×1000, where V T is the volume of the extract, n is the dilution multiple, and FW is the fresh weight of the sample.

10. The method for determining the effect of salicylic acid on the high temperature stress of bougainvillea seedlings according to claim 9, characterized in that: In S6, the measured data were calculated and plotted using Microsoft Excel, and single factor result analysis and correlation analysis were performed on the physiological and biochemical indicators of the samples using statistical analysis software SPSS26.

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