Plant growth regulator for rice ear differentiation period under high temperature stress and use method of plant growth regulator

Abstract

The invention discloses a plant growth regulator used in a rice panicle differentiation stage under high temperature stress and a use method thereof, the plant growth regulator comprises jasmonic acid methyl ester, fertilizer is applied 7 days after rice transplanting (tillering stage) and the panicle differentiation stage respectively, and a shallow water layer is kept after transplanting; spraying the plant growth regulator used in the rice panicle differentiation stage under high temperature stress at the initial stage of rice panicle differentiation; other management is carried out according to conventional field high-yield cultivation management. According to the plant growth regulator, by exogenous spraying of MeJA, the rice yield can be increased by 60% or above, multiple physiological indexes can be improved at the same time, the stress resistance of rice is enhanced, the nutritional requirements of rice spike growth and development are met, damage of high temperature stress to rice is relieved, the rice spikelet differentiation number is increased, and therefore the grain number per spike is increased, and the yield is increased. The method is beneficial for regulating endogenous growth hormones such as cytokinin of rice, optimizing the growth and development process and relieving the influence of high-temperature stress on the morphogenesis of young ears.

Description

Technical Field

[0001] The invention relates to a plant growth regulator used in the rice panicle differentiation period under high temperature stress and a use method thereof, belonging to the technical field of agriculture. Background Art

[0002] With climate change, extreme high temperature events have increased frequently, exacerbating the negative impact of high temperature stress on rice yield. High temperature stress during the rice panicle differentiation period mainly leads to rice yield reduction by reducing the number of grains per panicle. Plant hormones play an important role in regulating the morphological construction of young panicles (differentiation and degeneration of branches and spikelets). Early studies focused on the effects of classical plant hormones such as auxin, cytokinin, gibberellin and abscisic acid on the number of grains per panicle under high temperature stress, but the physiological mechanism of the new plant hormone methyl jasmonate in alleviating the obstacle of high temperature stress to the number of grains per panicle is still unclear. It is of great significance to deeply understand the mechanism of high temperature stress on rice growth and development and take effective cultivation measures to alleviate its impact on yield. High temperature events may occur in all stages of rice, but it is most susceptible to high temperature stress during its reproductive stage. A large number of studies have shown that when the temperature exceeds the critical threshold of 35°C, the number of grains per panicle of rice decreases, the spikelets are sterile, the grain filling time is shortened, and the grain weight is reduced, which has an adverse effect on yield. Even during the flowering or grain filling stage, short-term high temperature stress (over 35°C) can lead to a decrease in rice yield. However, previous studies have mainly focused on high temperature stress during the flowering and post-flowering stages, while ignoring the potential impact of high temperature stress before heading, which has an impact on yield formation that is comparable to or even greater than the impact of high temperature on yield after heading. During the panicle differentiation stage, high temperature stress can lead to a decrease in the number of grains per panicle and the fruiting rate, which is attributed to a decrease in the number of differentiated spikelets, an increase in the number of degenerated spikelets, and abnormal development of floral organs; under similar temperature treatments, the decrease in the number of grains per panicle and the grain filling rate caused by high temperature stress during the booting stage is more significant than the decrease caused by high temperature after heading. Therefore, it is urgent to develop a plant growth regulator that can be used during the rice panicle differentiation period under high temperature stress to ensure the normal development of rice panicles during this period. Summary of the invention

[0003] Purpose of the invention: The first purpose of the present invention is to provide a plant growth regulator for use in the rice panicle differentiation period under high temperature stress. The second purpose of the present invention is to provide a method for using the plant growth regulator to promote rice growth.

[0004] Technical solution: The plant growth regulator for rice panicle differentiation period under high temperature stress described in the present invention comprises methyl jasmonate.

[0005] Furthermore, the plant growth regulator also includes ethanol, acetone, ether, chloroform and / or water.

[0006] Furthermore, the plant growth regulator is an ethanol aqueous solution of methyl jasmonate.

[0007] Furthermore, the concentration of methyl jasmonate in the plant growth regulator is 10-200 μmol L -1 , preferably 50-150 μmol L -1 , more preferably 100 μmol L -1 .

[0008] Furthermore, the rice is Yangdao 6 and / or Nanjing 9108.

[0009] Furthermore, the high temperature is above 35°C.

[0010] The method for using the plant growth regulator for promoting rice growth during the rice panicle differentiation period under high temperature stress of the present invention comprises the following steps:

[0011] (1) Fertilizers were applied during the tillering stage (7 days after transplanting) and panicle differentiation stage after rice transplanting, and a shallow water layer was maintained after transplanting;

[0012] (2) spraying the plant growth regulator for rice panicle differentiation under high temperature stress according to the present invention at the beginning of rice panicle differentiation;

[0013] (3) The rest of the management is carried out according to conventional field high-yield cultivation management.

[0014] Furthermore, in step (1), the fertilizer is urea, potassium dihydrogen phosphate, or superphosphate and potassium chloride.

[0015] Furthermore, in step (1), 0.2-0.4 g of fertilizer is applied to each hole during the tillering stage, and 0.1-0.2 g of fertilizer is applied to each hole during the ear differentiation stage.

[0016] Furthermore, in step (1), the shallow water layer is 2-3 cm.

[0017] Furthermore, in step (2), the initial stage of rice panicle differentiation is when the panicle primordium at the top of the stem tip is visible.

[0018] Furthermore, in step (2), the plant growth regulator is sprayed each time until beads are attached to the leaf surface without falling off, and the spraying is performed more than three times in total.

[0019] Furthermore, in step (2), the spraying is carried out continuously for more than three times, or once every one day, or once every two days, preferably once every one day, and the spraying time is preferably in the morning, especially 8:00-9:00 in the morning.

[0020] Furthermore, in step (3), conventional field high-yield cultivation management includes conventional irrigation. Except for the mid-term field irrigating (to control ineffective tillering), a shallow water layer is maintained throughout the entire growth period until water is cut off one week before harvest, during which pests and diseases are strictly controlled.

[0021] The exogenous spraying of methyl jasmonate solution of the present invention can reduce plant damage caused by high temperature, thereby reducing the demand for manpower input in field management and pest control. In addition, it is simple to prepare and easy to spray, which can reduce manpower consumption; compared with traditional strategies for coping with high temperature stress such as additional irrigation or fertilization, although spraying regulators will increase initial investment, by improving crop resistance and yield, the demand for resources such as water, fertilizer, and pesticides can be reduced in the long term; resource optimization utilization: methyl jasmonate can improve the water and nutrient utilization efficiency of plants, reduce resource waste caused by high temperature, and ultimately improve yield economic efficiency. By enhancing plant resistance, reducing dependence on water sources, and alleviating the pressure of irrigation on water resources, sustainable agricultural development is promoted; ecological balance: methyl jasmonate promotes plant disease resistance, reduces the use of pesticides, helps protect the ecological environment, and maintains biodiversity; responding to climate change: under climatic conditions with frequent high temperatures, the use of regulators can help crops adapt to changes and improve the resilience of agricultural systems. Methyl jasmonate can stimulate plant growth, promote root development, and increase the absorption of water and nutrients; improve photosynthetic capacity: improve chlorophyll content and photosynthetic efficiency, enhance the plant's adaptability to high temperatures, and ensure the energy required for growth; promote panicle development: when sprayed during the panicle differentiation period, it can effectively promote the development of young panicles, increase the number of spikelet differentiation and the number of grains per panicle, and increase rice yield; optimize physiological processes: improve the plant's antioxidant capacity, reduce the accumulation of reactive oxygen, and reduce cell damage.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) Improving economic benefits: The exogenous spraying of MeJA in the present invention can increase rice yield by more than 60%. Compared with the existing conventional water and nitrogen management measures to reduce high temperature damage, the positive effect of exogenous MeJA on yield is more obvious.

[0024] (2) Rapid response and quick effect: The exogenous spraying of methyl jasmonate solution of the present invention can be quickly absorbed and transported by rice leaves, and can simultaneously improve multiple physiological indicators such as carbon and nitrogen metabolic enzyme activities, improve material accumulation, transportation and distribution, and meet the nutritional needs of rice panicle growth and development.

[0025] (3) Improving stress resistance: The exogenous spraying of methyl jasmonate solution of the present invention can enhance the stress resistance of rice, promote the activity of antioxidant enzymes in plants, reduce the accumulation of active oxygen, thereby reducing the damage of high temperature to plants, alleviating high temperature stress and promoting the differentiation number of rice spikelets (22.3%), thereby increasing the number of grains per panicle and improving rice yield.

[0026] (4) Optimizing growth hormone balance: The exogenous spraying of the methyl jasmonate solution of the present invention helps to regulate growth hormones such as cytokinins in plants, optimize the growth and development process, and alleviate the impact of high temperature stress on the morphological construction of young panicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The temperature changes with the year and the setting diagram of the day and night temperature in Example 1;

[0028] Figure 2 This is the result diagram of the effect of methyl jasmonate on leaf area at different growth stages under high temperature stress during rice panicle differentiation period;

[0029] Figure 3 This is the result diagram of the effect of methyl jasmonate on plant height, panicle length and panicle neck length under high temperature stress during rice panicle differentiation period;

[0030] Figure 4 This is the effect of methyl jasmonate on the accumulation of aboveground dry matter at different periods under high temperature stress during rice panicle differentiation period;

[0031] Figure 5 This is a graph showing the effect of methyl jasmonate on the dry matter accumulation of various parts at different stages under high temperature stress during rice panicle differentiation period;

[0032] Figure 6 This is the effect of methyl jasmonate on nitrogen accumulation in the aboveground parts at different periods under high temperature stress during rice panicle differentiation period;

[0033] Figure 7 This is the effect of methyl jasmonate on nitrogen accumulation in different parts of rice during different periods under high temperature stress during rice panicle differentiation period;

[0034] Figure 8 This is the effect of methyl jasmonate on the content of malondialdehyde (MDA) in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0035] Fig. 9 This is the effect of methyl jasmonate on the activity of peroxidase (POD) in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0036] Fig.10 This is the effect of methyl jasmonate on catalase (CAT) activity in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0037] Fig.11 This is the effect of methyl jasmonate on the activity of superoxide dismutase (SOD) in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0038] Fig.12This is the effect of methyl jasmonate on nitrate reductase (NR) activity in leaves and panicles under high temperature stress during rice panicle differentiation period;

[0039] Fig.13 This is the effect of methyl jasmonate on the activity of NADH-glutamate synthase (NADH-GOGAT) in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0040] Fig.14 This is the effect of methyl jasmonate on glutamine synthase (GS) activity in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0041] Fig.15 This is the effect of methyl jasmonate on the activity of sucrose synthase (SS-I) in leaves and panicles under high temperature stress during rice panicle differentiation period;

[0042] Fig.16 This is the effect of methyl jasmonate on the activity of sucrose synthase (SS-II) in leaves and panicles under high temperature stress during rice panicle differentiation period;

[0043] Fig.17 This is the effect of methyl jasmonate on the activity of sucrose phosphate synthase (SPS) in leaves and panicles under high temperature stress during rice panicle differentiation period;

[0044] Fig.18 This is the effect of methyl jasmonate on the content of zeatin + zeatin riboside (Z + ZR) in leaves and young panicles under high temperature stress during rice panicle differentiation period;

[0045] Fig.19 This is the effect of methyl jasmonate on the contents of jasmonic acid (JA) and methyl jasmonate (MeJA) in leaves and panicles under high temperature stress during rice panicle differentiation period;

[0046] Fig. 20 This figure shows the effect of methyl jasmonate on the expression levels of genes related to jasmonic acid synthesis in young ears under high temperature stress during the ear differentiation period. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0048] All data from the following experiments were processed and statistically analyzed using Microsoft Excel 2016 and IBM SPSS Statistics 27 software, and the least significant difference method (LSD) was used with P = 0.05. 0.05 ) were used to test the significance of mean differences, and Origin 2021 and R (Corrplot, version 4.2.1) software were used to draw the graphs.

[0049] Example 1

[0050] 1. The experiment was conducted from May to October 2022-2023 at the Experimental Farm of the Key Laboratory of Crop Cultivation Physiology of Yangzhou University, Jiangsu Province (32°30'N, 119°25'E), using potted soil culture. The conventional indica rice variety Yangdao No. 6 (YD6) and the conventional japonica rice variety Nanjing 9108 (NJ9108) were selected. Both varieties were sown on May 15 and transplanted on June 8. Each pot (30cm high × 25cm top diameter) was filled with 14kg of sandy loam, 3 holes per pot, and double planting in each hole. The base fertilizer was 2.2g of urea, and 1.1g of urea and 0.5g of urea were applied as topdressing 7d after transplanting (tillering stage) and panicle differentiation stage, respectively. Conventional irrigation was used throughout the growth period. Except for the mid-term field shelving (to control ineffective tillering), a shallow water layer (2-3cm) was maintained in the pot until water was cut off one week before harvest. Strictly control pests and diseases.

[0051] The leaf age index or leaf age remainder method was used to observe the development of young panicles (see Ling Qihong, Cai Jianzhong, Su Zufang. Application value of leaf age remainder in identifying the process of rice panicle differentiation, Chinese Agricultural Science, 1980, (04): 1-11). Rice plants were grown under natural conditions to the initial stage of panicle differentiation (the panicle primordium at the top of the stem tip was visible), and then placed in an artificial climate chamber for high temperature treatment. After the meiotic period of pollen mother cells was over, the potted plants were moved to a natural environment until harvest. High temperature stress treatment was carried out in two independent artificial climate chambers. Rice plants were grown under the following controlled conditions: relative humidity 60%, light 13h (6:00am-19:00pm), dark 11h (19:00pm-6:00am). This experiment used normal temperature control (NT, day / night: 32℃ / 26℃) and high temperature stress (HT, day / night: 38℃ / 29℃) treatments. The temperature setting was based on historical weather data records. The results showed that the temperature in 2017 exceeded the average level from 1981 to 2010 and the actual daily temperature distribution in the growth room. Figure 1 shown.

[0052] At the beginning of panicle differentiation (the panicle primordium is visible at the top of the stem tip), methyl jasmonate (MeJA) treatment was carried out simultaneously with high temperature treatment (sprayed at 8:00-9:00 in the morning of the treatment day until beads were attached to the leaf surface without falling off, and sprayed again every other day, for a total of three times). The MeJA treatment concentration was 100 μmol L -1 The specific preparation method is to dissolve 44 μL of 95% methyl jasmonate solution in 100 mL (95%) ethanol solution, and then add ultrapure water to 2L. Each treatment is 36 pots. A total of 4 groups are set up, as follows:

[0053] (1) Normal temperature treatment setting: normal temperature + spraying ultrapure water (NT-CK); normal temperature + spraying methyl jasmonate solution (NT-MeJA); (2) High temperature treatment setting: high temperature + spraying ultrapure water (HT-CK); high temperature + spraying methyl jasmonate solution (HT-MeJA).

[0054] The number of days from sowing to maturity is the whole growth period of rice. In the tillering stage, main stems with consistent growth were selected for each treatment for hanging, and the panicle development process was observed by referring to the leaf age index or leaf age remainder method. The leaf age index was observed during the spikelet primordium differentiation period (PS) and the pollen mother cell meiosis period (ME), and the young panicles were peeled off and observed under a microscope, and the panicle differentiation stages were checked one by one. The number of days from the beginning to the end of panicle differentiation is the panicle development days.

[0055] 2. Three potted plants with the same growth were selected at PS, ME and heading stage (HD), and the leaf area of ​​each hole was measured using the Li-Cor 3050 leaf area meter produced by LI-COR Company of the United States. The plant height was measured at HD. Three potted rice plants with the same growth were selected at HD, and 10 spikelets were selected from each pot. The spike length and spike neck length were measured using a ruler. The results are as follows: Figure 2-3 shown. Figure 2 This is the result of the effect of methyl jasmonate on leaf area at different growth stages under high temperature stress during rice panicle differentiation period. Figure 2 It can be seen that compared with NT-CK, the leaf area of ​​YD6 and NJ9108 responded inconsistently to NT-MeJA. During the panicle differentiation period (PS and ME), the leaf area of ​​YD6 increased significantly, while that of NJ9108 decreased. During the HD period, the leaf area of ​​the two varieties had no significant response to NT-MeJA. High temperature stress significantly reduced the leaf area of ​​the two varieties. There were differences in the response of the two varieties to HT-MeJA during the PS period. YD6 actively responded to exogenous MeJA and increased the leaf area, while the leaf area of ​​NJ9108 further decreased. During the ME and HD periods, HT-MeJA could significantly increase the leaf area of ​​the two varieties.

[0056] Figure 3 This is the result of the effect of methyl jasmonate on plant height, panicle length and panicle neck length under high temperature stress during rice panicle differentiation period. Figure 3 It can be seen that compared with NT-CK, NT-MeJA had no significant effect on plant height, ear length and ear neck length, but significantly decreased under high temperature treatment. Under HT treatment, exogenous MeJA (HT-MeJA) had no significant effect on plant height of YD6 and NJ9108, but significantly increased ear length and ear neck, and the response amplitude of YD6 ear neck to exogenous MeJA was greater than that of NJ9108.

[0057] 3. Sampling was performed at the heading stage (HD, 50% of the rice spikelets in each pot were extracted from the flag leaf). Three pots of rice with consistent growth were selected for each treatment. According to the method of Wang et al. (see Wang W, Cai C, Lam SK, et al. Elevated CO2 cannot compensate for japonica grain yield losses under increasing air temperature because of the decrease in spikelet density [J]. European Journal of Agronomy, 2018, 99: 21–29 and Wang W, Xu X, Zhu C, et al. Elevated CO2-induced changes incytokinin and nitrogen metabolism are associated with different responses in the panicle architecture of two contrasting ricegenotypes [J]. Plant Growth Regulation, 2019, 89 (2): 119–129), 15 spikelets of uniform size were taken from each pot for observation. Under a stereomicroscope, the degenerated spikelets were light white in color and covered with white bract hairs, which could be easily distinguished from the green surviving spikelets. The number of surviving and degenerate spikelets was counted and their positions on the primary and secondary branches were recorded respectively. Spikelets that developed to normal size and remained green were considered surviving spikelets, while deformed spikelets were considered degenerate spikelets.

[0058] The number of branch peduncles / spikelets differentiated = the number of branch peduncles / spikelets existing + the number of branch peduncles / spikelets degenerated

[0059] Total spikelet differentiation number = primary spikelet differentiation number + secondary spikelet differentiation number

[0060] The existing rate of branches or spikelets / (degeneration rate) (%) = the existing number of branches or spikelets (the number of degenerated branches) / the number of differentiated branches or spikelets × 100%.

[0061] The results are shown in Tables 1-2. As shown in Table 1, the number of differentiated and existing primary and secondary branches showed significant and extremely significant differences among varieties, temperatures or methyl jasmonate, while the number of degenerated primary and secondary branches showed significant and extremely significant differences among varieties, temperatures, and varieties × temperatures. High temperature stress significantly reduced the number of differentiated primary and secondary branches of the two varieties, which was attributed to the significant decrease in the existing number (existing rate) of primary and secondary branches and the significant increase in their degenerated number (degeneration rate). Under high temperature treatment, exogenous MeJA had no significant effect on the number of differentiated primary branches, the existing number (existing rate) and the degenerated number (degeneration rate) of YD6 and NJ9108, but the secondary branches of the two varieties increased significantly under exogenous MeJA.

[0062] As shown in Table 2, the total spikelet differentiation number showed significant or extremely significant effects among varieties, temperature, methyl jasmonate, and temperature × variety / methyl jasmonate. Compared with NT-CK, the total spikelet differentiation number of YD6 and NJ9108 in HT-CK decreased by 41.3% and 54.5%, respectively, while that in HT-MeJA increased by 21.3% and 23.3%, respectively. The number of primary and secondary branch spikelets of YD6 and NJ9108 decreased significantly under HT-CK treatment. Compared with HT-CK treatment, the existing number of primary and secondary branch spikelets of YD6 increased significantly by 14.0% and 38.3% under HT-MeJA, respectively; the existing number of primary branch spikelets of NJ9108 increased significantly by 33.8%, while there was no significant difference in the existing number of secondary branch spikelets.

[0063]

[0064]

[0065] 4. At the rice maturity stage (MD), 3 pots of rice plants with the same growth were selected for each treatment, and the number of panicles per pot, the number of grains per panicle, the fruit setting rate and the thousand-grain weight were counted. The number of panicles and the number of grains per panicle were calculated manually. The rice was threshed by hand, and the full grains, half-full grains and empty grains were separated by water bleaching method and 80% ethanol solution respectively. The fruit setting rate was calculated as the ratio of full grains to the total number of grains. The yield was calculated by harvesting 5 pots for each treatment. According to the variance analysis, the yield and its components (except the number of panicles) showed extremely significant differences among varieties, temperature or methyl jasmonate (see Table 3).

[0066] Table 3 Effects of methyl jasmonate on rice yield and its components under high temperature stress during rice panicle differentiation period

[0067]

[0068] NT-CK: normal temperature treatment + spraying water solvent; NT-MeJA: normal temperature treatment + spraying methyl jasmonate; HT-CK: high temperature treatment + spraying water solvent; HT-MeJA: high temperature treatment + spraying methyl jasmonate; Values ​​are mean ± standard deviation (n = 3); Different lowercase letters in the same column indicate significant differences at the P = 0.05 level; ns: P>0.05; *: P≤0.05; **: P≤0.01.

[0069] As shown in Table 3, the effect of high temperature stress on the yield of NJ9108 was greater than that of YD6. Compared with the NT-CK treatment, HT-CK significantly reduced the yield of YD6 by 61.0%, while that of NJ9108 was significantly reduced by 94.5%. Compared with HT-CK, HT-MeJA significantly increased the yield of YD6 and NJ9108. The yield reduction caused by high temperature was attributed to the significant reduction in the number of grains per ear, the fruit setting rate and the thousand-grain weight. Under HT-CK, the number of grains per ear, the fruit setting rate and the thousand-grain weight of YD6 decreased by 34.0%, 37.5% and 5.8%, respectively, while that of NJ9108 decreased by 49.7%, 87.2% and 14.9%, respectively. Under high temperature stress, exogenous spraying of MeJA significantly increased the number of grains per ear (44.5%) and the fruit setting rate (27.1%) of YD6, and also significantly increased the number of grains per ear (25.4%) and the 1000-grain weight (13.0%) of NJ9108.

[0070] 5. Select 3 pots of rice plants with the same growth from PS, ME, HD and MD respectively, and pack them into kraft paper bags according to the roots, stems, leaves and panicles (except panicles of PS and ME), place them in a 105℃ oven for 30 minutes, then cool to 75℃ and dry to constant weight and weigh them. Crush the dried samples, pass them through a 100-mesh sieve, weigh 0.50g of the samples into a digestive tube, and add the catalyst (K2S04:CuSO 4 .5H2O mass ratio = 7:1) and 12mL pure H2SO4 were digested in a digestion furnace at 420℃ for 1.5h. After the digestion solution turned green and clear, it was cooled to room temperature and the nitrogen content of the sample was determined using a fully automatic Kjeldahl nitrogen analyzer. The results are as follows Figure 4-7 And as shown in Table 4.

[0071] Figure 4 This is the effect of methyl jasmonate on the accumulation of aboveground dry matter at different stages under high temperature stress during rice panicle differentiation period. Figure 4It can be seen that NT-MeJA can significantly increase the aboveground dry matter accumulation of YD6 before flowering (PS, ME, HD), but has no significant effect on NJ9108. High temperature stress during panicle differentiation significantly inhibits the aboveground dry matter accumulation. Compared with HT-CK, exogenous MeJA (HT-MeJA) can alleviate the high temperature damage and significantly increase the aboveground dry matter accumulation of YD 6 during ME, HD and MD periods; the aboveground dry matter accumulation of NJ9108 in the HD and MD periods was significantly increased by HT-MeJA treatment compared with HT-CK.

[0072] Figure 5 This is the effect of methyl jasmonate on the dry matter accumulation of different parts of rice during different periods under high temperature stress during rice panicle differentiation. Figure 5 It can be seen that HT-CK reduced the dry matter accumulation of the ear of the two varieties during the HD and MD periods. Exogenous spraying of MeJA can alleviate the negative effect of high temperature on the dry matter of the ear of YD6, while NJ9108 has no significant effect. During the ear differentiation period (PS and ME), compared with NT-CK, NT-MeJA significantly increased the dry matter accumulation of the vegetative organs (roots, stems and leaves) of YD6, and reduced the dry matter accumulation of the vegetative organs of NJ9108; under HT-CK conditions, the dry matter accumulation of each organ in each period before flowering of YD6 and NJ9108 was significantly reduced. Under high temperature treatment, exogenous MeJA can significantly increase the dry matter accumulation of leaves and stems of the two varieties as a whole. During the MD period, high temperature stress caused the retention of dry matter in the leaves of YD6, while that of NJ9108 was the retention of stem matter, reducing the accumulation and transport of dry matter to the ear; HT-MeJA can significantly increase the dry matter accumulation of stems and leaves of the two varieties and the dry matter accumulation of the ear of YD6.

[0073] The effects of methyl jasmonate on nitrogen content in different parts at different periods under high temperature stress during rice panicle differentiation are shown in Table 4. As can be seen from Table 4, under NT-CK conditions, exogenous spraying of MeJA had no significant effect on the nitrogen content in leaves, stems and roots of the two varieties at different periods, significantly reduced the nitrogen content in the panicles of YD6 at HD, and increased the nitrogen content in the panicles of NJ9108 at HD; in MD, NT-MeJA reduced the nitrogen content in the panicles of the two varieties. HT treatment significantly increased the nitrogen content in leaves and stems of the two varieties at PS and ME periods. The effects of HT treatment on the nitrogen content in the panicles of the two varieties were inconsistent, as shown by HT significantly reducing the nitrogen content in the panicles of YD6 at HD and increasing the nitrogen content in the panicles of NJ9108; the nitrogen content in the panicles of the two varieties decreased significantly at MD. Compared with HT-CK, HT-MeJA had a trend of further reducing the nitrogen content in leaves, stems and panicles.

[0074]

[0075] Figure 6This is the effect of methyl jasmonate on nitrogen accumulation in the aboveground parts at different periods under high temperature stress during rice panicle differentiation. Figure 7 This is a diagram showing the effect of methyl jasmonate on nitrogen accumulation in different parts of rice during different periods under high temperature stress during rice panicle differentiation. Figure 6-7 It can be seen that NT-MeJA has different effects on the aboveground nitrogen accumulation of the two varieties. The aboveground nitrogen accumulation of YD6 during the panicle differentiation period (PS and ME) was significantly increased, and the aboveground nitrogen accumulation of NJ9108 during the PS period was significantly reduced. HT-CK significantly reduced the aboveground nitrogen accumulation of the two varieties at each growth period. HT-MeJA can alleviate the impact of high temperature and significantly increase the aboveground nitrogen accumulation. Compared with HT-CK, HT-MeJA can significantly increase the nitrogen accumulation of the nutritional organs (roots, stems and leaves) at each growth period, increase the nitrogen accumulation of the panicle ( Figure 7 ).

[0076] 6. Three pots of rice plants with the same growth were selected during the PS and ME periods. The rice leaves, root tips (3-4 cm) and young panicles were cut off and quickly wrapped in tin foil and placed in liquid nitrogen for 1-2 minutes. After being fully ground with a German RETSCHMM400 mixing ball grinder, they were transferred to a -80°C ultra-low temperature refrigerator for storage. The malondialdehyde test kit, catalase test kit, peroxidase test kit and superoxide dismutase test kit produced by Jiangsu Keming Biotechnology Co., Ltd. were used to determine the malondialdehyde content and antioxidant enzyme activity in the leaves and young panicles during the above periods according to the specific operating steps in the instructions of each test kit. The results are as follows Figure 8-11 Shown

[0077] Figure 8 This is the effect of methyl jasmonate on the content of malondialdehyde (MDA) in leaves and panicles under high temperature stress during rice panicle differentiation period. Figure 8 It can be seen that high temperature stress during panicle differentiation significantly increased the MDA content in PS and ME leaves and young panicles of the two varieties, and the reduction in NJ9108 was greater than that in YD6. Exogenous spraying of MeJA can alleviate the effect of high temperature on MDA content, and the overall performance is NJ9108>YD6.

[0078] Fig. 9 This is the effect of methyl jasmonate on the activity of peroxidase (POD) in leaves and young panicles under high temperature stress during rice panicle differentiation period. Fig.10 This is the effect of methyl jasmonate on catalase (CAT) activity in leaves and panicles under high temperature stress during rice panicle differentiation period. Fig.11 This is a graph showing the effect of methyl jasmonate on superoxide dismutase (SOD) activity in leaves and panicles under high temperature stress during rice panicle differentiation period. Figure 9-11It can be seen that high temperature stress significantly reduced the activities of antioxidant enzymes (POD, CAT, SOD), and HT-MeJA significantly increased the activities of CAT and SOD compared with HT-CK. Among them, HT-MeJA increased the activities of CAT and SOD in leaves or young panicles of YD6 more than NJ9108.

[0079] 7. During the PS and ME periods, three rice plants with the same growth were selected. The rice leaves and root tips (3-4 cm) were cut off, and the young panicles were peeled off and quickly wrapped in tin foil and placed in liquid nitrogen for 1-2 minutes. After being fully ground with a German RETSCHMM400 mixing ball grinder, they were transferred to a -80°C ultra-low temperature refrigerator for storage. The nitrate reductase kit, NADH-glutamate synthetase kit and glutamine synthetase kit produced by Jiangsu Keming Biotechnology Co., Ltd. were used, and the activities of nitrate reductase, NADH-glutamate synthetase and glutamine synthetase were determined according to the specific operating steps in the instructions of each kit. The results are as follows Figure 12-14 shown.

[0080] Fig.12 This is the effect of methyl jasmonate on nitrate reductase (NR) activity in leaves and panicles under high temperature stress during rice panicle differentiation period. Fig.13 This is the effect of methyl jasmonate on the activity of NADH-glutamate synthase (NADH-GOGAT) in leaves and young panicles under high temperature stress during rice panicle differentiation period. Fig.14 The figure shows the effect of methyl jasmonate on glutamine synthase (GS) activity in leaves and panicles under high temperature stress during rice panicle differentiation period. Figure 12-14 It can be seen that compared with NT-CK, NT-MeJA significantly increased the activity of NADH-GOGAT in leaves and panicles; HT-CK significantly increased the activity of NR and NADH-GOGAT in leaves of two varieties PS and ME, and reduced the activity of nitrogen metabolic enzymes (NR, NADH-GOGAT and GS) in panicles. Under high temperature stress, exogenous MeJA can increase the activity of nitrogen metabolic enzymes in panicles and significantly reduce the activity of NR and NADH-GOGAT in leaves.

[0081] 8. Three pots of rice plants with the same growth were selected during the PS and ME periods. The rice leaves, root tips (3-4 cm) and young panicles were cut off and quickly wrapped in tin foil and placed in liquid nitrogen for 1-2 minutes. After being fully ground with a German RETSCHMM400 mixing ball grinder, they were transferred to a -80°C ultra-low temperature refrigerator for storage. The sucrose synthase (decomposition direction; SS-I) kit, sucrose synthase (synthesis direction; SS-II) kit and sucrose phosphate synthase kit produced by Jiangsu Keming Biotechnology Co., Ltd. were used, and the SS-I, SS-II and SPS activities in the leaves and young panicles during the above periods were determined according to the specific operating steps in the instructions of each kit. The results are as follows Figure 15-17 Shown

[0082] Fig.15 This is the effect of methyl jasmonate on the activity of sucrose synthase (SS-I) in leaves and panicles under high temperature stress during rice panicle differentiation period. Fig.16 This is the effect of methyl jasmonate on the activity of sucrose synthase (SS-II) in leaves and panicles under high temperature stress during rice panicle differentiation period. Fig.17 The figure shows the effect of methyl jasmonate on the activity of sucrose phosphate synthase (SPS) in leaves and panicles under high temperature stress during the panicle differentiation period of rice. As shown in Figures 15-17, compared with NT-CK, exogenous MeJA can reduce the activity of SS-I (PS and ME periods) and SPS (PS period) in leaves, while SS-II (PS and ME periods) and SPS (ME period) increase significantly. High temperature stress during the panicle differentiation period significantly reduces the activities of SS-I, SS-II and SPS in leaves and panicles. Compared with HT-CK, HT-MeJA significantly increases the activity of SS-I in NJ9108 leaves during the PS and ME periods, and increases the activity of SS-II in both varieties, and only significantly increases the activity of SPS in leaves of both varieties during the ME period. HT-MeJA significantly increases the activities of SS-I, SS-II and SPS in panicles of both varieties at all periods, except for the activity of SS-II in panicles during the ME period.

[0083] 9. Three pots of rice plants with the same growth were selected during the PS and ME periods. The rice leaves, root tips (3-4 cm) and young panicles were cut off and quickly wrapped in tin foil and frozen in liquid nitrogen for 1-2 min. After being fully ground using a German RETSCH MM400 mixing ball grinder, the plants were transferred to a -80°C ultra-low temperature refrigerator for storage. About 0.5 g of samples were extracted according to the method of Pan et al. (see Pan, X., Welti, R., & Wang, X. (2010). Quantitative analysis of major plant hormones in crude plant extracts by high-performance liquid chromatography–mass spectrometry. Nature protocols, 5(6), 986-992). The extracted samples and standards were tested for zeatin and zeatin riboside content using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS / MS, TSQ Vantage, ThermoFisher Scientific, Waltham, MA, USA) according to the protocol of Pan et al. The results are as follows Figure 18-19 shown.

[0084] Fig.18This is the effect of methyl jasmonate on the content of zeatin + zeatin riboside (Z + ZR) in leaves and young panicles under high temperature stress during rice panicle differentiation period. Fig.19 This is a graph showing the effect of methyl jasmonate on the contents of jasmonic acid (JA) and methyl jasmonate (MeJA) in leaves and panicles under high temperature stress during rice panicle differentiation period. Figure 18-19 It can be seen that compared with NT-CK, NT-MeJA had no significant effect on the contents of Z+ZR, JA and MeJA in leaves and panicles of YD6 and NJ9108 during the panicle differentiation period (PS, ME), while HT-CK significantly reduced the contents of Z+ZR, JA and MeJA in leaves and panicles during the PS and ME periods. Compared with HT-CK, HT-MeJA could significantly increase the contents of endogenous Z+ZR, JA and MeJA.

[0085] 10. During the PS and ME periods, three pots of rice plants with the same growth were selected. The rice leaves, root tips (3-4 cm) and young panicles were cut off and quickly wrapped in tin foil and placed in liquid nitrogen for 1-2 minutes. After being fully ground with a German RETSCHMM400 mixing ball grinder, they were transferred to an ultra-low temperature refrigerator at -80°C for storage. The RNAsimple total RNA extraction kit produced by Tiangen Biochemical Technology (Beijing) Co., Ltd. was used to extract total RNA from leaves and young panicles according to the kit instructions. FastKingcDNA kit was used for reverse transcription and synthesis of cNDA. The fluorescence quantitative PCR kit was ThermoScientific DyNAmoColorFlash SYBR Green qPCR Kit. The instrument was Stratagene Mx3005P fluorescence quantitative PCR instrument. The reaction system and conditions were referred to the kit instructions. The rice Actin gene was used as the internal reference gene. Each sample was repeated 3 times. The primer sequences used for PCR were:

[0086] Lipoxygenase gene 8 (OsLOX8): F: 5′-GCGACAAGATCCTCCTCT-3′, R: 5′-GCGAACTCCTCATCTCTG-3′;

[0087] Allene oxide synthase gene 1 (OsAOS1): F: 5′-GCGTCCTCTCCTACCTTGAC-3′, R: 5′-CGGAACTTGGGGATCACCTG-3′;

[0088] 12-Oxo-phytodienoate reductase gene 7 (OsOPR7): F: 5′-CCTATGGCAAGTATCCTAA-3′, R: 5′-GGCTTGACGATATTGTTC-3′;

[0089] Jasmonic acid ZIM domain gene 9 (OsJAZ9): F: 5′-TCGACGGATCCCATGACC-3′, R: 5′-GGCCTTGACGTACTGGCTG-3′;

[0090] OsCOI1b: F: 5'-TCTGGGTAATGTTGGGGAAA-3', R: 5'-GCCCTGTACCCACACGTATC-3'.

[0091] result Fig. 20 As shown, Fig. 20 This is the effect of methyl jasmonate on the expression of genes related to jasmonic acid synthesis in young panicles under high temperature stress during panicle differentiation period. Fig. 20 It can be seen that under different temperature treatments, exogenous spraying of MeJA had inconsistent effects on jasmonic acid synthesis-related genes in the young panicles of the two varieties during the PS and ME periods. Compared with NT-CK, NT-MeJA significantly upregulated OsAOS1, OsLOX8 and OsJAZ9 in the young panicles of YD6 and NJ9108, while significantly downregulated OsCOI1b; HT-CK significantly downregulated the gene expression levels of OsOPR7, OsAOS1, OsLOX8 in the jasmonic acid synthesis pathway and OsJAZ9 and OsCOI1b in the jasmonic acid signal transduction pathway, and exogenous MeJA could significantly upregulate the expression levels of genes related to the jasmonic acid synthesis pathway and signal transduction pathway.

[0092] Example 2

[0093] The experimental process was the same as in Example 1, except that in step (2), a MeJA concentration gradient (0, 50, 100, 150 μmol L -1 ) and in different time periods (morning: 8:00-9:00; noon: 12:00-13:00; evening: 17:00-18:00) of the same day, spraying MeJA solutions of different concentrations. The test results are shown in Table 5.

[0094] As shown in Table 5, the total number of spikelets showed significant or extremely significant effects among temperature, MeJA concentration, temperature × spraying time / MeJA concentration, and temperature × spraying time × MeJA concentration. -1 Compared with MeJA (100 μmol L -1 , 150 μmol L -1 ), spraying MeJA (50 μmol L -1 , 100 μmol L -1 , 150 μmol L -1) significantly decreased, mainly due to the significant decrease in the number of spikelets on the primary and secondary branches. Compared with NT, HT caused a 46.3% decrease in the number of spikelets. Spraying 50 μmol L -1 , 100 μmol L -1 and 150 μmol L -1 The MeJA concentrations of 100 μmol L-1 and 20 μmol L-2 could alleviate the damage of high temperature stress on the total spikelet differentiation number by 10.0%, 22.1% and 15.5% respectively. Under HT conditions, spraying different concentrations of MeJA at noon had no significant effect on the total spikelet differentiation number, but spraying 100 μmol L-1 in the evening had a significant effect on the total spikelet differentiation number. -1 The MeJA increased the total spikelet differentiation number by 10.1%. Based on the above results, it can be seen that the total spikelet differentiation number of rice under high temperature stress responds to the spraying of MeJA in the order of morning > evening > mid-morning, and the effect of spraying MeJA in the morning is 100 μmol L -1 >150μmol L -1 ≥50 μmol L -1 .

[0095] Example 3

[0096] The experimental process is the same as that of Example 1, except that in step (2), a MeJA concentration gradient (0, 50, 100, 150 μmol L -1 ) and different spraying methods in the same time period are specifically: continuous spraying: spraying on the first day + the second day + the third day; spraying with one day interval: spraying on the first day + the third day + the fifth day; spraying with two days interval: spraying on the first day + the fourth day + the seventh day, spraying different concentrations of MeJA. The test results are shown in Table 6.

[0097] As shown in Table 6, the total spikelet differentiation number showed significant or extremely significant effects among temperature, spraying method, MeJA concentration, temperature × spraying method / MeJA concentration, and spraying method × MeJA concentration. Under NT treatment, different concentrations of MeJA had a downward trend on the total spikelet differentiation number, and increased with the increase of concentration gradient. High temperature stress (0 μmol L -1 ) compared with the room temperature control (0 μmol L -1 ) The existing number of primary and secondary branch spikelets decreased, and the number of degenerate spikelets increased, resulting in a decrease in the total number of spikelets differentiation. However, spraying MeJA alleviated the high temperature damage and increased the total number of spikelets differentiation. Under HT conditions, compared with no spraying of 0 μmol L -1 Compared with continuous spraying, one-day spraying and two-day spraying, the number of total spikelet differentiation of rice was effectively increased by spraying 100 μmol L MeJA at different concentrations. Further analysis showed that the total spikelet differentiation number of rice under high temperature stress was significantly increased by spraying 100 μmol L MeJA at different concentrations. -1The response effect of MeJA was the best, and spraying at intervals of one day > spraying at intervals of two days = continuous spraying.

[0098] Example 4

[0099] According to the analysis of the results of Examples 2 and 3, the best spraying method (spraying every other day) and spraying time period (morning: 8:00-9:00) for the number of spikelet differentiation can be determined, but the effects of different concentrations of MeJA on yield and its components need to be further clarified. The specific steps are the same as those of Example 1, except that a MeJA concentration gradient (0, 50, 100, 150 μmol L -1 ). The test results are shown in Table 7.

[0100] It can be seen from Table 7 that under normal temperature conditions, compared with 0 μmol L -1 Treatment, 50 μmol L -1 , 100 μmol L -1 and 150 μmol L -1 The spraying dose of MeJA had no significant effect on rice yield. The reason why HT significantly reduced rice yield was attributed to the significant reduction in the number of grains per panicle, fruit setting rate and 1000-grain weight, which was similar to 0 μmol L -1 In comparison, 50 μmol L -1 , 100μmolL -1 and 150 μmol L -1 Reducing the damage of high temperature stress on the number of grains per panicle, fruit setting rate and 1000-grain weight led to a significant increase in rice yield by 14.7%, 48.0% and 37.9%, respectively.

[0101] Comparative Example 1

[0102] In order to clarify the effects of different hormones at the same concentration on spikelet differentiation and degradation under high temperature during panicle differentiation period. The specific steps of this comparative example are the same as those of Example 1, except that MeJA is replaced by other growth-promoting plant hormones (auxin (IAA), cytokinin (GA), gibberellin (CTK)). Compared with the results of Example 1, the test results are shown in Table 8.

[0103] As shown in Table 8, under normal temperature conditions, spraying growth-promoting plant hormones (IAA, CTK, GA) increased the number of spikelet differentiation by increasing the existing number of spikelets, while the spraying effect of MeJA was opposite to that of growth-promoting plant hormones, reducing the number of spikelet differentiation. Under high temperature conditions, compared with CK, the total number of spikelet differentiation of exogenous spraying of IAA, CTK, GA and MeJA increased significantly by 15.5%, 10.3%, 10.7% and 23.1%, respectively (MeJA>CTK>IAA / GA). It can be seen that exogenous plant hormones can alleviate the effect of high temperature stress on the number of spikelet differentiation, but MeJA has the best effect in alleviating high temperature adversity.

[0104]

[0105]

[0106]

[0107]

Claims

1. A plant growth regulator for use in the rice panicle differentiation period under high temperature stress, characterized in that: The plant growth regulator comprises methyl jasmonate.

2. The plant growth regulator for rice panicle differentiation period under high temperature stress according to claim 1, characterized in that: The plant growth regulator further comprises ethanol, acetone, ether, chloroform and / or water.

3. The plant growth regulator for rice panicle differentiation period under high temperature stress according to claim 1, characterized in that: The plant growth regulator is an ethanol aqueous solution of methyl jasmonate.

4. The plant growth regulator for rice panicle differentiation period under high temperature stress according to claim 3, characterized in that: The concentration of methyl jasmonate in plant growth regulators is 10-200 μmol L -1 .

5. The plant growth regulator for rice panicle differentiation period under high temperature stress according to claim 1, characterized in that: The rice is Yangdao 6 and / or Nanjing 9108.

6. The plant growth regulator for rice panicle differentiation period under high temperature stress according to claim 1, characterized in that: The high temperature is above 35°C.

7. The method for using the plant growth regulator for promoting rice growth during the rice panicle differentiation period under high temperature stress according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Fertilizers were applied to rice during the tillering stage and panicle differentiation stage after transplanting, and a shallow water layer was maintained after transplanting; (2) spraying the plant growth regulator for rice panicle differentiation under high temperature stress according to any one of claims 1 to 3 at the beginning of rice panicle differentiation; (3) The rest of the management is carried out according to conventional field high-yield cultivation management.

8. The method of use according to claim 7, characterized in that: In step (1), the fertilizer is urea, potassium dihydrogen phosphate, or superphosphate and potassium chloride. During transplanting, double seedlings are planted in each hole. 0.2-0.4g of fertilizer is applied to each hole during the tillering stage, and 0.1-0.2g of fertilizer is applied to each hole during the ear differentiation stage. The shallow water layer is 2-3cm.

9. The method of use according to claim 7, characterized in that: In step (2), the initial stage of rice panicle differentiation is when the panicle primordium at the top of the stem tip is visible, and the plant growth regulator is sprayed each time until beads are attached to the surface of the rice leaves and do not fall off, and the spraying is performed more than three times in total.

10. The method of use according to claim 7, characterized in that: In step (2), the spraying method is to spray continuously for more than three times, or spray once every one day, or spray once every two days.

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