Application of rutile type nano titanium dioxide in relieving thallium stress of rice

Abstract

The invention belongs to the technical field of crop planting, and particularly relates to application of rutile type nano titanium dioxide in relieving thallium stress of rice. According to the application, rutile type nano titanium dioxide is applied to a thallium-stressed rice growth environment, and the application concentration is 30 mg / L-300 mg / L. Hydroponic experiments prove that rutile type nano titanium dioxide can effectively relieve inhibition of thallium stress on rice growth and remarkably improve root length, stem length and biomass accumulation of thallium-stressed rice, and rutile type nano titanium dioxide can enhance stress resistance of rice to thallium stress by adjusting chlorophyll fluorescence parameters. More technical schemes are provided for rice field thallium pollution treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of crop planting, and particularly relates to application of rutile-type nano titanium dioxide in relieving thallium stress of rice. BACKGROUND

[0002] Thallium (Tl) is a highly toxic heavy metal, which can affect the germination and growth of plants, and can also be enriched in the human body through the underground water-soil-plant pathway to cause harm.

[0003] Current thallium pollution control in rice fields mainly relies on agronomic measures such as soil deep ploughing, lime acid adjustment, organic fertilizer cultivation, selenium application at the tillering stage, and waterlogging control at the booting stage. For example, 100-150 kg / mu of lime needs to be applied to the pollution field with pH < 5.0 to reduce the bioavailability of thallium; shortening the drying field time at the tillering stage and maintaining a 3-5 cm water layer at the booting stage can reduce the translocation of thallium to grains. However, at present, the effect of a single technology is limited, and more technical solutions are urgently needed to relieve thallium stress of rice.

[0004] Nano titanium dioxide has unique potential in heavy metal pollution control due to its photocatalytic activity, large specific surface area, and surface modifiability, but its specific mechanism in thallium stress rice still needs to be further explored. Existing studies have shown that the combined use of TiO2 and silicon nanoparticles can synergistically reduce cadmium toxicity, but the chemical behavior of thallium and cadmium is significantly different, and it is not known whether TiO2 can be applied to reduce thallium toxicity, so it is of great research value to study the mechanism of TiO2 in thallium stress. SUMMARY

[0005] To solve the above technical problems, the application establishes a plant model under different concentrations of thallium stress, and further studies the effects of rutile-type nano titanium dioxide and anatase-type nano titanium dioxide on thallium absorption, metabolism and stress resistance gene expression of rice, and finds that rutile-type nano titanium dioxide effectively relieves the inhibition of thallium stress on the growth of rice, significantly improves the root length, stem length and biomass accumulation of thallium stress rice, and adjusts the chlorophyll fluorescence parameters of rice to enhance the stress resistance of rice to thallium stress. The application provides more solutions for thallium pollution control in rice fields.

[0006] On the one hand, the application provides a preparation for relieving thallium stress of rice, and the active ingredient of the preparation is rutile-type nano titanium dioxide, and the concentration of the rutile-type nano titanium dioxide is 30 mg / L-300 mg / L.

[0007] Further, in the preparation, the concentration of the rutile-type nano titanium dioxide is 30 mg / L.

[0008] Further, the preparation is a water culture solution.

[0009] In a second aspect, the present application also provides use of the rutile type nano-titanium dioxide in preparation of a preparation for relieving thallium stress of rice, which relieves the thallium stress by improving photosynthetic performance of the rice under the thallium stress.

[0010] Further, in the use, the photosynthetic performance is the maximum photochemical efficiency and / or apparent photosynthetic electron transport rate.

[0011] Further, in the use, the preparation is applied to the rice seedling in a hydroponic mode.

[0012] In a third aspect, a method for relieving thallium stress of rice is also provided, which comprises applying the rutile type nano-titanium dioxide with a concentration of 30 mg / L-300 mg / L to the rice seedling under the thallium stress in a hydroponic mode.

[0013] Further, in the method, the rutile type nano-titanium dioxide is applied at a concentration of 30 mg / L.

[0014] Compared with the prior art, the technical solution provided by the present application has at least the following beneficial effects or advantages: (1) The present application finds and confirms that the rutile type nano-titanium dioxide can relieve thallium stress of rice. The experimental results show that applying 30 mg / L of the rutile type nano-titanium dioxide can restore the stem length and root length of the rice under the thallium stress to a level close to the normal level, which is only 5.88% and 9.60% lower than the blank control group, respectively, which is significantly better than the single thallium stress group, and effectively relieves the growth inhibition and biomass decrease of the rice caused by the thallium stress.

[0015] (2) The thallium stress seriously damages the photosynthetic system of the rice, and the present application confirms that the rutile type nano-titanium dioxide significantly improves the photosynthetic performance under the thallium stress, which is specifically manifested in that the maximum photochemical efficiency (Fv / Fm) and the apparent photosynthetic electron transport rate (ETR) are greatly restored, and the Fv / Fm is increased by 151.2% compared with the thallium stress group, which guarantees the energy source of the plant and promotes the healthy growth of the plant.

[0016] (3) The present application finds, through systematic comparative tests, that there is an essential difference between the rutile type nano-titanium dioxide and the common anatase type nano-titanium dioxide in relieving the thallium stress of rice, and even the anatase type may exacerbate the damage to the photosynthetic system under certain conditions. This discovery breaks through the conventional cognition of the technical personnel in the field on the application of nano-titanium dioxide. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Figure 2 is a diagram of the agronomic traits of the rice treated with different concentrations of thallium.

[0018] Figure 2 Figure 3 is a statistical result of the physiological indexes and Tl enrichment differences of the rice under different treatment conditions. (a) is root length and stem length; (b) is Tl content; (c) is fresh weight and dry weight; (d) is BCF index.

[0019] Figure 3 Figures are CAT enzyme and POD enzyme activity determination results of rice roots and leaves treated with different treatments. Among them (a) is the CAT enzyme activity determination results of rice roots and leaves treated with anatase type nano titanium dioxide and thallium; (b) is the CAT enzyme activity determination results of rice roots and leaves treated with rutile type nano titanium dioxide and thallium; (c) is the POD enzyme activity determination results of rice roots and leaves treated with anatase type nano titanium dioxide and thallium; (d) is the POD enzyme activity determination results of rice roots and leaves treated with rutile type nano titanium dioxide and thallium.

[0020] Figure 4 Figures are chlorophyll fluorescence parameter radar plots of rice treated with different treatments. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described below in conjunction with examples, but the present application is not limited to the following examples.

[0022] In order to enable those skilled in the art to better understand the technical solutions of the present application and to implement them, the present application will be further described below in conjunction with specific examples and drawings, but the examples are not limiting to the present application.

[0023] The experimental methods and detection methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0024] EXAMPLE This example is a water culture test of nano titanium dioxide relieving thallium stress of rice.

[0025] Tested rice variety: indica two-season hybrid rice Y Liangyou 1148.

[0026] The rice of indica two-season hybrid rice Y Liangyou 1148 was selected for water culture, and different concentrations of thallium (0 µM, 1 µM, 5 µM, 10 µM) stress was applied when the rice grew into seedling form, 3 replicates were set for each treatment, and the agronomic traits of rice under different concentrations of thallium stress were as shown in Table 1. Figure 1 The growth inhibition of Y Liangyou 1148 became more and more obvious with the increase of thallium concentration, and the leaves of the high concentration group turned yellow and withered, indicating that the rice seedlings were obviously affected by thallium stress treatment.

[0027] Rice seedlings under 1.02 mg / L (5 µM) thallium stress were treated with 30 mg / L rutile titanium dioxide (TR30), 300 mg / L rutile titanium dioxide (TR300), 30 mg / L anatase titanium dioxide (TA30), and 300 mg / L anatase titanium dioxide (TA300), respectively. A blank control group (BK) without thallium treatment and titanium dioxide application and a thallium treatment group (TL) without titanium dioxide application were also set up.

[0028] The stem length, root length, fresh weight, and dry weight of rice under different treatments were measured 14 days after the addition of anatase titanium dioxide and rutile titanium dioxide. The thallium concentration in the hydroponics solution and different parts of the rice was measured, and the biological enrichment coefficient (BCF) and transport coefficient (TF) were calculated to evaluate the migration of thallium in the environment and the plant body. The results are shown in Figure 2 The calculation formulas for BCF and TF are as follows: BCF = Thallium concentration in rice roots or leaves / Thallium concentration in hydroponics solution TF = Thallium concentration in aboveground parts of rice / Thallium concentration in roots of rice The catalase (CAT) activity and peroxidase (POD) activity of leaves under different treatments were measured, and the test results are shown in Figure 3

[0029] The chlorophyll expression of different treatment groups was analyzed. The specific test process is as follows: Prepare the leaf samples to be tested, and dark adapt for 2h before measurement to ensure that the chlorophyll is in the best state. Ensure that the leaf surface is dry, and there is no obvious damage or disease. Set the PAM chlorophyll fluorometer to an excitation light intensity of 179 µmoL photons m -2 s⁻¹, measure each sample for 287 s, and perform the test. Place the sample to be tested in the measurement chamber of the chlorophyll fluorometer, ensure that the sample leaves are evenly covered on the measurement window, start the instrument for measurement, and record the ETR, qP, NPQ, and Fv / Fm obtained by measurement to evaluate the photosynthetic efficiency and light protection ability of chlorophyll. The results are shown in Figure 4

[0030] The results are shown in Figure 2 ​​It can be seen that compared with the control group (BK), the stem length of rice in TL, TA30, TA300, TR30 and TR300 treatment groups decreased by 21.35%, 16.39%, 17.37%, 6.87% and 4.95% (p<0.05), respectively, and the root length was shortened by 13.13%, 6.86%, 12.73%, 4.81% and 2.23% compared with the control group (BK). It is shown that both anatase type nano-titanium dioxide and rutile type nano-titanium dioxide can greatly improve the growth retardation, dwarfing and dry matter accumulation reduction of rice seedlings caused by thallium stress. Among all the treatments, rutile type nano-titanium dioxide (TR300 group) performs best, and its stem length and root length are closest to the BK control group, which shows that rutile type nano-titanium dioxide is a more effective thallium stress reliever than anatase type nano-titanium dioxide.

[0031] Figure 2 Fig. 6 (d) shows that the BCF of leaves and roots of anatase type nano-titanium dioxide (TA30 group) decreased by 20.5% and 37.9%, respectively, indicating that it effectively inhibited the absorption of thallium by rice. Rutile type nano-titanium dioxide (TR30 group) can effectively inhibit the absorption of leaves and roots, and the BCF decreases by 28.8% and 43.8%, respectively, which is the best in all treatments. The BCF of leaves and roots of anatase type nano-titanium dioxide (TA300 group) increased sharply by 72.3% and 175.5%, respectively, and the TF value decreased by 37.4%, indicating that high concentration of anatase type nano-titanium dioxide greatly promoted the absorption of thallium by rice roots. The BCF of leaves of rutile type nano-titanium dioxide (TR300 group) increased by 122.8%, and the BCF of roots decreased slightly by 7.6%, which slightly inhibited the absorption of thallium by roots and could transfer thallium pollutants from roots to aboveground parts for harvesting treatment.

[0032] From the above, it can be seen that the rutile type nano-titanium dioxide is the best thallium stress reliever among all the treatments, and the anatase type nano-titanium dioxide is the worst. The rutile type nano-titanium dioxide can effectively inhibit the absorption of thallium by rice, and the anatase type nano-titanium dioxide can promote the absorption of thallium by rice roots. The rutile type nano-titanium dioxide can effectively reduce the thallium content in rice, and the anatase type nano-titanium dioxide can increase the thallium content in rice. The rutile type nano-titanium dioxide can effectively reduce the thallium content in rice shoots, and the anatase type nano-titanium dioxide can increase the thallium content in rice shoots. The rutile type nano-titanium dioxide can effectively reduce the thallium content in rice roots, and the anatase type nano-titanium dioxide can increase the thallium content in rice roots. Figure 3It can be seen that the CAT enzyme activity of the blank group (BK) rice leaves was the highest, and the CAT enzyme activity of the single thallium treatment (TL) group decreased by 15.2%. The addition of 30 mg / L rutile type nano-titanium dioxide (TR30) decreased by 10.9% compared with the TL group, and the addition of 30 mg / L anatase type nano-titanium dioxide (TA30) decreased by 22.0%. When the concentration increased to 300 mg / L, the activity of the TR300 group increased to 1387.68 U / g (3.6% higher than TL), and the activity of the TA300 group remained at 1354.97 U / g. The CAT activity in rice leaves showed a significant dose-effect difference. The root CAT activity showed a biphasic regulation feature. Thallium stress (TL) reduced the activity by 30.7%, and the TR30 activity in the low concentration treatment group continued to decrease to 107.83 U / g, while the TA30 group increased to 149.10 U / g. High concentration treatment showed a significant recovery effect: the TR300 group reached 183.19 U / g (17.1% higher than TL), and the TA300 group even exceeded the blank group by 3.6% (229.36 U / g).

[0033] Compared with the BK group, the POD activity of the TL group increased by 15.4%, and the TR30 group further increased to 69233.99 U / g (22.7% higher than BK). However, the TA30 group showed abnormal inhibition (19342.56 U / g, decreased by 65.7%), and the high concentration treatment TR300 and TA300 recovered to 83.1% and 59.4% of the BK group, respectively. The leaf POD activity showed obvious crystal-specificity.

[0034] Thallium stress (TL) led to a 12.3% decrease in leaf POD activity. The group treated with 30 mg / L rutile nano-titanium dioxide (TR30) maintained a similar level to TL (1313.82 U / g), while the group treated with 30 mg / L anatase nano-titanium dioxide (TA30) significantly increased it to 1695.75 U / g (29.5% higher than TL). High concentration treatments showed an inhibitory effect, with TR300 and TA300 decreasing by 21.4% and 18.7% respectively compared to BK. The significant difference in the mitigating effects of rutile and anatase nano-titanium dioxide on thallium stress may be closely related to the surface chemical properties of the two crystal forms. Anatase TiO2 exhibits a higher hydroxyl (-OH) density (approximately 3.5–5.0 OH / nm²), significantly higher than rutile TiO2 (1.5–3.0 OH / nm²), enabling more efficient adsorption of Tl⁺ through surface complexation at low concentrations (TA30), reducing thallium ion entry into rice cells and thus alleviating oxidative stress. Anatase TiO2 also possesses a higher photogenerated electron-hole pair yield (quantum efficiency 30–40% higher than rutile TiO2), which may have led to an abnormal decrease in POD activity in the leaves of the TA30 group. It is speculated that the ·OH free radicals generated by its photocatalysis exacerbate membrane lipid peroxidation, triggering negative feedback regulation to inhibit POD synthesis.

[0035] The CAT activity in the TA300 group was significantly higher than that in the control group, which may be related to the activation of the jasmonic acid signaling pathway induced by nano-TiO2, promoting the growth of antioxidant enzyme genes ( OsCAT1 / 2 Leaf response is limited by the transport efficiency of nanomaterials, therefore, POD activity is more significantly affected by the photocatalytic side effects of anatase (TA30 leaf POD activity is only 34.3% of that of the BK group), suggesting that mesophyll cells rely more on non-enzymatic antioxidant systems (such as the GSH-AsA cycle) to cope with oxidative damage. In general, anatase reduces thallium uptake at low concentrations through high adsorption, while rutile maintains free radical scavenging ability at high concentrations due to its stability advantage.

[0036] Depend on Figure 4It was found that the Fv / Fm (maximum photochemical efficiency) of the blank group (BK) was maintained at a normal level, while the single thallium treatment (TL) caused a sharp decrease of 83.0% in Fv / Fm, indicating that the PSII reaction center was severely damaged. The addition of 30 mg / L rutile-type nano-TiO2 (TR30) restored Fv / Fm, which was 151.2% higher than that of TL, but the anatase-type treatment (TA30) aggravated the damage, which was 92.6% lower than that of TL, suggesting that there were essential differences in the regulation of thallium toxicity by different crystal forms of nano-materials. The ETR (apparent photosynthetic electron transport rate) of the TL group was only 27.4% of that of the BK group, and the TR30 group partially recovered, which was 25.8% higher than that of TL, while the ETR of the TA30 group was almost completely inhibited, which was 0.3% of that of the BK group, indicating that the anatase-type nano-materials might trigger a secondary light inhibition effect. The NPQ (non-photochemical quenching) of the TL group increased by 10.1 times compared with the BK group, and the TR30 group maintained a similar level, while the NPQ of the TA30 group further increased to 21.7 times of that of the BK group, indicating that the anatase-type treatment triggered an abnormal light protection response. There was no significant difference in Y (NPQ) between the TL group and the TR30 group, but the Y (NPQ) of the TA30 group was 87.5% higher than that of the TL group, suggesting that the PSII reaction center of the TA30 group relied excessively on the heat dissipation pathway, and the photochemical energy conversion efficiency was severely damaged.

[0037] The phenomenon that the anatase-type TiO2 (TA30) aggravated the damage of PSII might be related to the induction of ROS explosion by photocatalytic activity. The hydroxyl radicals generated by the anatase-type TiO2 under light caused the lipid peroxidation of the chloroplast thylakoid membrane of the TA30 group to be aggravated, directly damaged the D1 protein repair cycle of PSII, interfered with the light energy transmission pathway, and caused the ETR to approach zero.

[0038] The rutile-type TiO2 had a higher reflectivity than the anatase-type TiO2 by 15–20% in the visible light region (400–500 nm), reduced the stress of light energy input, and alleviated the pressure of PSII over-excitation, so the NPQ was not further increased.

[0039] As described above, the basic principles, main features and advantages of the present application are better described. The above examples and descriptions only describe the preferred embodiments of the present application, and the present application is not limited by the above examples. Various changes and improvements to the technical solutions of the present application made by those skilled in the art without departing from the spirit and scope of the present application shall fall within the scope of protection of the present application.

Claims

1. A formulation for alleviating thallium stress in rice, characterized by, The active ingredient of the preparation is rutile type nano titanium dioxide, and the concentration of the rutile type nano titanium dioxide is 30 mg / L-300 mg / L.

2. The preparation according to claim 1, characterized in that, The concentration of the rutile type nano titanium dioxide is 30 mg / L.

3. The preparation according to claim 1 or 2, characterized in that, The preparation is a hydroponic solution.

4. Use of nanometric titanium dioxide in rutile form in the preparation of a formulation for the mitigation of the stress of thallium in rice, characterized in that, The preparation relieves thallium stress by improving the photosynthetic performance of rice under thallium stress.

5. Use according to claim 4, characterized in that, The photosynthetic performance is the maximum photochemical efficiency and / or apparent photosynthetic electron transport rate.

6. Use according to claim 5, characterized in that, The preparation is applied to rice seedlings by a hydroponic method.

7. A method of alleviating thallium stress in rice, characterized by, The method is to apply rutile type nano titanium dioxide with a concentration of 30 mg / L-300 mg / L to rice seedlings under thallium stress by a hydroponic method.

8. The method of claim 7, wherein, The application concentration of the rutile type nano titanium dioxide is 30 mg / L.

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