Chemical control method for relieving high temperature stress in peanut flowering needle stage

Abstract

A chemical control method for relieving high temperature stress in a peanut flowering needle stage comprises the following steps: when peanuts are subjected to high temperature stress with the highest temperature exceeding 35 DEG C for continuous 5 days in the flowering needle stage, spraying 24-epibrassinolide with proper concentration; the concentration of the sprayed 24-epibrassinolide is 0.2 umol / L, and the dosage of the sprayed 24-epibrassinolide is 100 ml / m < 2 >; the 24-epibrassinolide is sprayed at 8: 00 a.m. every day before the temperature reaches 35 DEG C; and when the 24-epibrassinolide is prepared, 0.1% of ethanol and 0.002% of Tween 80 need to be added. The method can reduce excessive accumulation of active oxygen in peanut bodies, protect the structural integrity of chloroplast membranes and maintain a high net photosynthetic rate under high-temperature stress, so that dry matter accumulation is increased, the pod yield is increased, and the method has remarkable scientificity and practicability and is of great significance in maintaining the yield of peanuts under high-temperature stress.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural production, in particular to a chemical control method for alleviating high temperature stress during the flowering and needle stage of peanuts. Background Art

[0002] As the climate warms, average surface temperatures are projected to rise by 0.4 to 1°C over the next 20 years, compared to 1995 to 2014, and by 2.4 to 4.8°C by the end of the century. Frequent climate-related extreme events will have more severe negative impacts on agricultural production and increase the number of people at risk of hunger, particularly in Asia and Africa.

[0003] Peanut is one of the world's most important cash crops, cultivated primarily in over 100 countries and regions, including China, India, the United States, Nigeria, Sudan, and Senegal, covering a total cultivated area of ​​37.2 million hectares. Peanut kernels are rich in vegetable oils, proteins, and carbohydrates, as well as beneficial minerals (such as calcium, iron, magnesium, and selenium), vitamins (including folate, thiamine, riboflavin, and tocopherols), and bioactive compounds. However, due to frequent and prolonged extreme heat events, peanut production is projected to decline by 16% to 20% by mid-century, posing a serious threat to global food security. Peanuts are most sensitive to heat stress during their reproductive stages, with an optimum temperature of 20–25°C. During the flowering stage, temperatures above 35°C severely inhibit peanut growth, development, and yield, and temperatures exceeding 40°C can even lead to a complete loss of yield. Previous studies have primarily considered floral organs to be the primary site of high-temperature yield suppression in peanuts, as heat damages virtually the entire process from flowering to seed set, including anther dehiscence, pollen number, viability, germination, pollen tube elongation, and fertilization, ultimately leading to a reduction in spicules and pods. However, due to the varying growth characteristics among cultivated peanut varieties, reduced seed set cannot fully explain the limitations of high-temperature stress on peanut productivity. This is primarily due to two factors. First, spicules and pods are redundant in most cultivated varieties. Peanut has a long flowering period (over 30 days), during which spicules continuously penetrate the soil to form young fruit. Although the number of spicules during the R1-R3 stages determines the potential number of pods, excess young pods may still develop. Reliable evidence suggests that extending the peanut growth cycle (reproductive stage) increases pod plumpness, pod number, and yield. Therefore, the reduction in spicules during heat stress may be compensated during normal temperature growth. Second, peanut flowers are located in a relatively cool environment under the canopy, and pollination is completed before flowering (5:00-7:00), which effectively avoids high temperature stress.

[0004] In most crops, photosynthesis plays a decisive role in crop yield and is the physiological process most sensitive to high temperature stress. High temperature stress significantly inhibits crop photosynthetic performance and reduces biomass accumulation, making it a major factor in suppressing crop productivity. Several studies have examined the importance of photosynthesis for peanut yield and the effects of high temperature stress on leaf area, photosynthetic performance, and pod development. However, based on the assumption that peanut photosynthesis is highly tolerant to high temperature stress (35°C), research in this area has received relatively little attention.

[0005] In fact, the sustained rise in temperatures in recent years has exceeded the heat tolerance threshold of peanut leaves across most of its distribution range. Cultural practices, such as exogenous plant growth regulators, can improve crop stress tolerance more quickly than time-consuming breeding methods, enabling them to cope with rapidly changing climates. Brassinosteroids have been shown to be beneficial in improving stress tolerance and photosynthetic performance in many plants, such as wheat and corn.

[0006] In this invention, a field trial was conducted using two different heat-tolerant peanut varieties. The objectives of the trial were: (1) Determine the effects of high temperature stress on the photosynthetic performance and yield of peanut; (2) To verify that the photosynthetic performance can be improved by using exogenous 24-epibrassinolide (EBR) to maintain the yield of peanut under high temperature stress. Summary of the Invention

[0007] In order to solve the above problems in the prior art, the present invention provides a chemical control method for alleviating high temperature stress during the flowering and needle stage of peanuts.

[0008] The technical solution adopted by the present invention to solve its technical problem is: A chemical control method for alleviating high temperature stress during the flowering and needle stage of peanuts, when the peanuts are subjected to high temperature stress with the maximum temperature exceeding 35°C for 5 consecutive days during the flowering and needle stage, spraying 24-epibrassinolide at an appropriate concentration; the spraying concentration of 24-epibrassinolide is 0.2 μmol / L, and the dosage is 100 ml / m 2 ; The time for spraying 24-epibrassinolide is 8:00 am every day, before the temperature reaches 35°C; 0.1% ethanol and 0.002% Tween 80 need to be added when preparing 24-epibrassinolide.

[0009] Compared with the prior art, the present invention has the following advantages: The method of the present invention has significant scientificity and practicality, and is of great significance for ensuring the yield of peanuts under high temperature stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of the temperature difference between high temperature stress and normal environment and the dry matter accumulation of each treatment; Figure 2 Schematic diagram of photosynthetic characteristics of peanuts under different treatments; Figure 3 Schematic diagram of chloroplast ultrastructure in peanut leaves with different treatments; Figure 4 Schematic diagram of antioxidant enzyme activity, reactive oxygen species and malondialdehyde content in peanut leaves under different treatments. DETAILED DESCRIPTION

[0011] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Example 1

[0012] A chemical control method for alleviating high temperature stress during the flowering and needle stage of peanuts, when the peanuts are subjected to high temperature stress with the maximum temperature exceeding 35°C for 5 consecutive days during the flowering and needle stage, spraying 24-epibrassinolide at an appropriate concentration; the spraying concentration of 24-epibrassinolide is 0.2 μmol / L, and the dosage is 100 ml / m 2 ; The time for spraying 24-epibrassinolide is 8:00 am every day, before the temperature reaches 35°C; 0.1% ethanol and 0.002% Tween 80 need to be added when preparing 24-epibrassinolide.

[0013] The ways in which 24-epibrassinolide alleviates high temperature and heat stress in peanuts during the flowering and needle stage include: (1) reducing the excessive accumulation of reactive oxygen species in peanuts, (2) protecting the integrity of chloroplast membrane structure, (3) maintaining a high net photosynthetic rate under high temperature stress, (4) increasing dry matter accumulation, and (5) improving peanut pod yield under high temperature environment. Example 2

[0014] The test method of Example 1 includes the following test design: Experimental location: The experiment was conducted at the Agricultural Experiment Station and the State Key Laboratory of Crop Biology of Shandong Agricultural University at 36°16'N, 117°16'E.

[0015] Experimental sandy loam: The soil type of the experimental field is sandy loam, with topsoil containing 1.5% organic matter and 1.28g / kg total nitrogen. -1 , alkaline nitrogen 80.54mgkg -1 , fast-acting phosphorus 43.15mg / kg -1 , fast-acting potassium 85.69mg / kg -1 .

[0016] Experimental materials: heat-resistant peanut variety Qinghua No. 7 and heat-sensitive peanut variety Shanhua 101.

[0017] Experimental period: sowing in mid-May, harvesting in mid-September, planting density 160,000 hectares -2(row spacing 30 cm, hole spacing 20 cm), the amount of watering for peanut seedlings is 40 mm, and the soil moisture during high temperature treatment can meet the normal growth of peanuts.

[0018] Experimental Design: A split-plot design was used, with the primary plot being temperature treatment and the secondary plots being peanut variety and hormone regulation. A total of 8 treatments were set up. Treatment group 1: Spray Qinghua No. 7 with clean water at room temperature (group name is Q).

[0019] Treatment group 2: Qinghua No. 7 was sprayed with exogenous 24-epibrassinolide (EBR) at room temperature (group name: QE).

[0020] Treatment group 3: Qinghua No. 7 was sprayed with clean water under high temperature (group name is QH).

[0021] Treatment group 4: Qinghua No. 7 was sprayed with exogenous 24-epibrassinolide (EBR) under high temperature (group name: QHE).

[0022] Treatment group 5: Shanhua 101 was sprayed with clean water at room temperature (group name is S).

[0023] Treatment group 6: Shanhua 101 was sprayed with exogenous 24-epibrassinolide (EBR) at room temperature (group name: SE).

[0024] Treatment group 7: Shanhua 101 was sprayed with clean water under high temperature (group name SH).

[0025] Treatment group 8: Shanhua 101 was sprayed with exogenous 24-epibrassinolide (EBR) under high temperature (group name: SHE).

[0026] Each treatment was replicated three times, with a plot area of ​​5.4 m 2 (3m×1.8m), with 180 plants in each plot. After entering the flowering period, the peanuts were subjected to heat stress treatment for 10 consecutive days in sunny and windless weather.

[0027] The experimental greenhouse was designed to be 3 meters wide, 20 meters long, and 1.5 meters high. The film on both sides could be rolled up. The film was lowered around 10:00 AM to increase the temperature, and lowered around 5:00 PM to cool it down. A 15-cm gap was left at the bottom of the film on both sides to ensure ventilation, and micro-sprayers were installed inside the film. An environmental monitor was placed above the peanut canopy to monitor changes in temperature, humidity, CO2 concentration, light intensity, and photosynthetically active radiation in real time.

[0028] Experimental operation method: High temperature treatment refers to the maximum temperature exceeding 35℃ for 5 consecutive days. During the high temperature treatment period, exogenous 24-epibrassinolide (EBR) and clean water were sprayed at 8:00 am every day. The concentration of exogenous 24-epibrassinolide (EBR) sprayed was 0.2umol / L, and the dosage was 100ml / m 2All solutions contained 0.1% ethanol and 0.002% Tween 80. The addition of Tween 80 can reduce the surface tension of the droplets and increase the adsorption between the EBR solution and the leaves.

[0029] The photosynthetic parameters of functional leaves were measured using a portable photosynthetic instrument (LI-6400XT) made in the United States. During the high temperature treatment period, the top three leaves of the main stem of peanuts were selected from 9:00 to 11:30 to measure Photo, Cond, Ci, and Trmmol.

[0030] The antioxidant enzyme activity, peroxidase activity, catalase activity and malondialdehyde content of the leaves were determined by cutting off the top three leaves of the main stem during the high temperature treatment, quickly removing the main veins, wrapping them with tin foil and freezing them with liquid nitrogen.

[0031] Determination of leaf antioxidant enzyme activity (SOD activity): refer to the method of Giannopolitis (1977) or Wang Aiguo (1983).

[0032] Determination of peroxidase activity (POD activity): guaiacol method (East China Normal University, 1980) method.

[0033] Determination of catalase activity (CAT activity): refer to the method of Luo Guanghua (1989).

[0034] Determination of malondialdehyde (MDA) content: according to the method of Lin Zhifang (1984).

[0035] The dynamic growth of plants was measured in the following way: every 10 days after the high temperature treatment, plants with the same growth were taken to examine the leaf area, main stem length, number of side branches, etc. of each plant, and the dry matter weight was measured after drying.

[0036] Mesophyll cell ultrastructure was determined by selecting mesophyll cells and spicules from the third leaf of the main stem during the high-temperature treatment. Tissue blocks were cut into 2 mm pieces using a double-edged razor blade (handling should be gentle, avoiding pulling, bruising, and squeezing). The pieces were immediately placed in a penicillin-containing fixative. After 24 hours, the fixative was replaced and stored. Cell ultrastructure was observed under a transmission microscope after sectioning.

[0037] The application of the chemical control test method is as follows: during the high temperature period of peanuts, exogenous 24-epibrassinolide (EBR) was sprayed at 8:00 am every day. The concentration of exogenous 24-epibrassinolide (EBR) was 0.2umol / L and the dosage was 100ml / m 2, and add 0.1% ethanol and 0.002% Tween 80. This method can reduce excessive accumulation of reactive oxygen species in peanuts, protect the integrity of chloroplast membranes, and maintain a high net photosynthetic rate under high temperature stress, thereby increasing dry matter accumulation, the number of effective pods per plant, and fruit weight, ultimately increasing pod yield. This method is more effective for heat-sensitive peanut varieties.

[0038] Analysis of the results of Example 2: (1) High temperature stress inhibits plant growth and reduces pod yield: During the treatment period (9:00-17:00), the temperature difference between the high temperature stress plot and the control plot fluctuated in the range of 1.7-5.4℃, with an average temperature difference of 4.2℃ ( Figure 1 a). After 10 days of high temperature stress, the dry matter accumulation of Qinghua No. 7 and Shanhua 101 decreased significantly by 33.89% and 21.48% respectively compared with the control ( Figure 1 b, c). In contrast, application of exogenous 2,4-epibrassinolide (EBR) significantly promoted plant growth under high temperature stress. Compared with the QH and SH treatments, the leaf dry weight (LDW) of the QHE and SHE treatments increased by 11.74% and 32.40%, respectively. Compared with the control, the pod yield of Qinghua 7 and Shanhua 101 decreased significantly by 24.64% and 32.82%, respectively. EBR treatment promoted grain filling, with the number of effective pods per plant increasing by 8.76% and 27.20% in the QHE and SHE treatments, respectively, compared with the QH and SH treatments (Table 1).

[0039] Table 1 Peanut pod yield under different treatments

[0040] (2) 24-Epibrassinolide can increase the photosynthetic rate of peanut leaves under high temperature stress: High temperature stress significantly reduced the Pn values ​​of the two varieties, with Shanhua 101 decreasing more than Qinghua 7 ( Figure 1 a, b). Compared with the control, stomatal conductance of Qinghua 7 increased significantly under high temperature stress, while Shanhua 101 showed the opposite trend. Stomatal conductance of both varieties increased significantly under high temperature stress. In addition, transpiration rate of both varieties increased under high temperature stress, with the increase in Qinghua 7 being greater than that of Shanhua 101. Compared with the QH and SH treatments, the application of EBR significantly increased the Pn value of peanuts in the QHE and SHE treatments by 8.02% and 16.05%, respectively.

[0041] (3) 24-Epibrassinolide can protect the integrity of chloroplasts under high temperature stress: To further elucidate the reasons why high temperature stress restricts peanut photosynthesis, the ultrastructure of chloroplasts of two varieties was observed. It was found that high temperature stress caused the shape of chloroplasts to be distorted, and the boundaries and thylakoid structures to be blurred ( Figure 4 This phenomenon indicates that high temperature stress significantly damaged the chloroplast membrane and led to the disintegration of the grana lamellae, while exogenous 24-epibrassinolide (EBR) treatment could effectively protect the chloroplast structure under high temperature stress. Compared with the QH and SH treatments, the chloroplast membrane structure and grana lamellae structure of the QHE and SHE treatments were relatively intact.

[0042] (4) 24-Epibrassinolide can improve the antioxidant capacity of peanut leaves under high temperature stress: Under high temperature stress, the activities of antioxidant enzymes changed significantly ( Figure 4 ah), with the same trend across the two growing seasons. Compared with the normal temperature treatment, the QH and SH treatments increased SOD activity, while POD, CAT, and APX activities decreased significantly. EBR treatment enhanced antioxidant enzyme activities under high temperature stress. Compared with the QH treatment, the SOD, POD, CAT, and APX activities in the QHE treatment increased by 7.68%, and compared with the SH treatment, the SOD, POD, CAT, and APX activities in the SHE treatment increased by 9.39%, 25.94%, 32.19%, and 118.49%, respectively, over the two growing seasons. Under high temperature stress, O₂-, H₂O₂, and MDA contents increased by 42.76%, 183.14%, and 35.47%, respectively, compared with the control. H₂O₂ and MDA contents increased by 183.14% and 35.47%, respectively. In contrast to the normal temperature treatment, the application of exogenous 2,4-epibrassinolide (EBR) significantly reduced their contents. This suggests that EBR application effectively alleviates membrane lipid peroxidation. In addition, it was found that the application of EBR at room temperature also significantly increased the content of H2O2, while the content of MDA did not change significantly ( Figure 4 in).

[0043] The above detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention but is merely representative of selected embodiments of the present invention.

Claims

1. A chemical control method for alleviating high temperature stress during the flowering and needle stage of peanuts, characterized by: When peanuts are subjected to high temperature stress with the maximum temperature exceeding 35°C for 5 consecutive days during the flowering period, spray 24-epibrassinolide at an appropriate concentration; the concentration of 24-epibrassinolide sprayed is 0.2 μmol / L, and the dosage is 100 ml / m 2 ; The time for spraying 24-epibrassinolide is 8:00 am every day, before the temperature reaches 35°C; 0.1% ethanol and 0.002% Tween 80 need to be added when preparing 24-epibrassinolide.

2. The chemical control method for alleviating high temperature stress during the flowering and needle stage of peanut according to claim 1, characterized in that The ways in which 24-epibrassinolide alleviates high temperature and heat stress in peanuts during the flowering and needle stage include: (1) reducing the excessive accumulation of reactive oxygen species in peanuts, (2) protecting the integrity of chloroplast membrane structure, (3) maintaining a high net photosynthetic rate under high temperature stress, (4) increasing dry matter accumulation, and (5) improving peanut pod yield under high temperature environment.

3. The chemical control method for alleviating high temperature stress during the flowering and needle stage of peanut according to claim 1, characterized in that Chemical control test methods include the following test designs: Test materials: heat-resistant peanut variety Qinghua No. 7 and heat-sensitive peanut variety Shanhua 101; Experimental period: sowing in mid-May, harvesting in mid-September, planting density 160,000 hectares -2 , the amount of irrigation for peanut seedlings is 40mm, and the soil moisture during high temperature treatment can meet the normal growth of peanuts; Experimental Design: A split-plot design was used, with the primary plot being temperature treatment and the secondary plots being peanut variety and hormone regulation. A total of 8 treatments were set up. Treatment group 1: spray Qinghua No. 7 with clean water at room temperature; Treatment group 2: Qinghua No. 7 was sprayed with exogenous 24-epibrassinolide at room temperature; Treatment group 3: Qinghua No. 7 sprayed with clean water at high temperature; Treatment group 4: Qinghua No. 7 was sprayed with exogenous 24-epibrassinolide under high temperature; Treatment group 5: spraying Shanhua 101 with clean water at room temperature; Treatment group 6: Shanhua 101 sprayed with exogenous 24-epibrassinolide at room temperature; Treatment group 7: Shanhua 101 was sprayed with water under high temperature; Treatment group 8: Shanhua 101 sprayed with exogenous 24-epibrassinolide under high temperature; After entering the flowering stage, peanuts were subjected to heat stress treatment for 10 consecutive days in clear and windless weather; The experimental greenhouse was designed to be 3 meters wide, 20 meters long, and 1.5 meters high. The film on both sides could be rolled up. The film was lowered around 10:00 a.m. to increase the temperature, and lowered around 5:00 p.m. to cool it down. A 15-cm gap was left at the bottom of the film on both sides, and micro-sprayers were placed inside the film. An environmental monitor was placed above the peanut canopy to monitor changes in temperature, humidity, CO2 concentration, light intensity, and photosynthetically active radiation in real time. Experimental operation method: High temperature treatment refers to the maximum temperature exceeding 35℃ for 5 consecutive days. During the high temperature treatment period, exogenous 24-epibrassinolide and clean water were sprayed at 8:00 am every day. The concentration of exogenous 24-epibrassinolide was 0.2umol / L and the dosage was 100ml / m 2 All solutions contain 0.1% ethanol and 0.002% Tween 80, which helps to evenly disperse the pesticide particles in the solution and avoid uneven spraying due to agglomeration; at the same time, it can also enhance the affinity of 24-epibrassinolide to the surface of peanut leaves, making it better absorbed and utilized by plants.

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