Authors:Wang Mengyuan1,2,Yang Liangzhe1,2,Wang Dan1,2,Zhang Yangyang1,2,Duan Bihui1,2,Yuan Zhiyang1,2,Yan Jiali1,2*
Units: 1. Hubei Provincial Institute of Geological Sciences, 2. Hubei Provincial Selenium Ecological Environment Effect Testing Center
Introduction:Wang Mengyuan, female, from Zhijiang, Hubei Province, assistant engineer, master's degree, engaged in agricultural resources and ecological geochemistry research. *Corresponding author, engineer, engaged in agricultural geology and geochemistry research.
Funds: Hubei Provincial Bureau of Geology, "Hubei Province Selenium-rich Industry Development Targeted Poverty Alleviation Demonstration Project".
Source: Anhui Agricultural Sciences, Issue 6, 2024
Effect of foliar spraying of selenium fertilizer on the absorption of accumulated selenium and other mineral elements in rice[J].Anhui Agricultural Sciences,2024,52(6):150-154.
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Selenium can participate in the synthesis of a variety of enzymes and proteins in the human body, and is one of the indispensable beneficial trace elements in the human body, which has important values such as enhancing immunity, anti-oxidation, cancer prevention and anti-cancer. Due to the uneven distribution of selenium in the earth's crust, about three-quarters of the mainland is selenium-deficient, and selenium deficiency may lead to the occurrence of various diseases, such as cardiomyopathy, retinal spot degeneration, cataract and cerebral sclerosis and so on. Plant-based diets are the main source of human intake of selenium, but selenium levels in cereals such as rice and wheat, the main food crops, are generally low, and selenium deficiency is a long-term public health problem that needs to be addressed urgently. The application of exogenous selenium to increase the selenium content of crops is an important way to help the human body replenish selenium. The use of selenium fertilizer can promote the increase of selenium content in the edible part of crops, and the increase of selenium content in rice is more significant. In practical applications, the improvement of selenium content in rice can usually be done in three ways: selenium fertilizer seed dressing, soil selenium fertilizer application and foliar selenium fertilizer spraying. However, selenium fertilizer dressing has the disadvantages of low operability and difficult to grasp the dosage, and the utilization rate of soil selenium fertilizer is easy to occur in the application process, and it has the risk of soil pollution. For selenium-deficient areas, the use of foliar selenium fertilizer is a better choice to promote selenium enrichment in rice. Exogenous selenium fertilizer usually has two forms: inorganic and organic, the application of inorganic selenium fertilizer should control its application amount in the actual farmland production, otherwise it is easy to cause crop poisoning, affect the growth and development and yield, and may also lead to environmental pollution; organic selenium fertilizer can promote the growth of crops at the same time, improve the selenium content of crops, and avoid crops from being damaged due to high selenium fertilizer concentration. In addition, studies have shown that selenium has the effect of reducing heavy metal toxicity in plants due to antagonism, and some studies have shown that the application of exogenous selenium fertilizer has a certain effect on the absorption and accumulation of mineral elements in plants.
objective
To ensure the rational utilization of selenium fertilizer and the safe production of selenium-rich rice, and to explore the response degree of selenium and other mineral elements and heavy metal content in rice plants to exogenous selenium.
way
In this study, the rice variety "Ezhong No. 5" and the selenium fertilizer "Zhongdi Xineng" were used as the experimental objects, and four selenium fertilizer concentration treatments were set up by using a field random block design: CK treatment was blank control treatment, i.e., no selenium fertilizer treatment, T1 treatment was sprayed with selenium nutrient solution 15g/hm2, T2 treatment was sprayed with selenium nutrient solution 30g/hm2, and T3 treatment was sprayed with selenium nutrient solution 60g/hm2. The selenium content in each organ of rice plants, the content of different mineral elements in brown rice, and the content of different heavy metal elements in leaves were detected at the maturity stage, and the difficulty of selenium enrichment in brown rice and other organs was evaluated at the maturity stage.
outcome
◆Changes in selenium content in rice organs under different selenium fertilizer concentrations
It can be seen from Figure 1 that the selenium content of rice brown rice, chaff, roots, stems and leaves increased with the increase of selenium nutrient solution spraying concentration, and the increase of different organs was different, the largest increase was rice chaff, when the concentration of selenium nutrient solution sprayed was T3, the selenium content of rice chaff was as high as 5.41mg/kg, which increased by 1630.59% compared with the treatment without selenium fertilizer (CK), T1 (15g/hm2) and T2 (30g/ hm2) treatment increased by 250.50% and 567.47%, respectively, compared with the treatment without selenium fertilizer (CK), indicating that the chaff was the strongest selenium enrichment part in rice plant tissue under the treatment of foliar spray selenium fertilizer, and the selenium content of brown rice in T3 treatment was 1.63 mg/kg, which was significantly higher than that of other treatments (P<0.01), and the selenium content of all treatments was significantly higher than that of CK treatment (P<0.05); Compared with rice roots, the bioavailability of selenium in stems and leaves was greater, and with the increase of selenium fertilizer concentration, the highest selenium content in leaves was 3.33mg/kg, which increased by 510.21% compared with CK treatment, and the selenium content of rice stems increased first and then stabilized under different selenium fertilizer concentration gradients, and the selenium content of T3 treatment increased by only 12.65% compared with T2 treatment, while T2 treatment increased by 169.87% compared with T1 treatment. The increase of selenium content in the underground roots of rice was small, and only the maximum concentration of T3 treatment was significantly higher than that of CK treatment (P<0.05), and there was no significant difference between other treatments and CK treatment (P>0.05). Therefore, foliar spraying of selenium nutrient solution is an effective way to increase the selenium content of rice, and the selenium content in the aboveground part of rice is higher than that in the underground part, and the response ability of leaves and chaff to foliar selenium fertilizer is stronger.
Note: Different lowercase letters indicate significant differences between different treatments (P<0.05), while different uppercase letters indicate extremely significant differences (P<0.01).
Fig.1 Selenium content in each organ of rice plants under different treatments
◆Enrichment and transport of selenium in soil-rice system under different selenium concentrations
The Se bioenrichment coefficient (BCF) and the Se transfer coefficient (TF) of shoots in rice brown rice under different concentrations of selenium nutrient solution under foliar spraying are shown in Table 1, and the Se bioenrichment coefficient of rice brown rice is 0.77~6.68, indicating that the selenium polyglotation capacity of rice brown rice was weaker without spraying selenium nutrient solution, while the selenium nutrient solution treatment increased the selenium polygnosium capacity of rice brown rice (all greater than 1), and the BCF of rice brown rice was significantly different with the increase of selenium fertilizer spraying concentration (P<0.05), and the high concentration T2 and T3 treatments were significantly different from CK treatment (P<0.01), it can be seen that the spraying of foliar selenium fertilizer can promote the enrichment of Se in rice brown rice, and the higher the concentration of selenium nutrient solution, the greater the bioconcentration coefficient of Se in rice brown rice. Without selenium nutrient solution spraying, the transfer coefficient (TF) of selenium in each tissue of rice was as follows> chaff > stem > brown rice, and the transfer coefficient of selenium in each tissue was significantly different from that of the control when the selenium application rate was 30 g/hm2 (T2 treatment concentration) (P). <0.01）。 The transfer coefficients of brown rice, chaff and leaves increased with the increase of selenium nutrient solution concentration, and the T1 treatment significantly increased compared with the control group (CK) (P<0.05), it can be seen that the application of selenium nutrient solution can effectively promote the transport of selenium from roots to grains, thereby increasing the selenium enrichment of grains, while the selenium transfer coefficient of leaves increases with the increase of selenium fertilizer concentration, which may be related to the direct effect of selenium nutrient solution on leaves, and the transfer coefficient of stems increases first and then decreases with the increase of selenium spraying, which may be due to the transport of a large amount of selenium in plants to grains. Considering the enrichment and transfer capacity of rice selenium, the treatment without selenium fertilizer showed the characteristics of "low enrichment ability and low transfer ability", which was not conducive to the production and development of selenium-rich rice.
Note: Different lowercase letters in the same column indicate significant differences between different treatments (P<0.05), and different uppercase letters indicate extremely significant differences (P<0.01).
◆Effect of foliar spraying of selenium nutrient solution on various elements of root soil
The principal component analysis (Fig. 2) was performed with the content of each element in the soil as variables, in which the first principal coordinate explained 38.25%, the second principal coordinate explained 14.66%, and the two principal coordinate axes mainly explained 52.91% of the variables. It can be seen that the spraying of selenium nutrient solution has a certain effect on the elements in the soil. Compared with the CK treatment, the selenium nutrient solution spraying treatment mainly affected the content of some mineral elements and heavy metal elements, and it can be seen from the distribution characteristics of each element that the total Se content of soil was significantly correlated with the soil available state Zn, Cu, Fe, Cd, Pb, organic matter, There was a high positive correlation between the total nitrogen content, which may be due to the homologous Se element in the rock, and the exogenous organic matter may increase the soil Se content while increasing the soil organic matter, and the soil available Se content had a high positive correlation with the soil pH, exchangeable Ca, Mg, available Cr, Mo, Sn, As and available potassium content, which showed that the soil available Se content was closely related to soil pH and cation exchange capacity. On the whole, the foliar spray of selenium nutrient solution had little effect on the basic physical and chemical properties of soil, which may be due to the fact that selenium nutrient solution mainly enters the plant body through the foliar surface and directly participates in the circulation and distribution of various tissue elements in the plant body, and the effect on the soil can only be through the root system.
注：N为碱解氮，K为速效钾；P、Si、Se、Fe、Mn、S、B、Mo均为有效态；Ca、Mg为交换态；Cu、Zn、Ni、Pb、Cr、Cd、As、Sn均为浸提态。
Fig.2 Principal component analysis of soil element content under different selenium nutrient solution concentrations
◆Effect of selenium nutrient solution on selenium content in soil and plant tissues
The principal component analysis (Fig. 3) was performed with the selenium content of soil and plant tissues as variables, in which the first principal coordinate explained 72.23%, the second principal coordinate explained 14.53%, and the two principal coordinate axes mainly explained 86.76% of the variables. It can be seen that most of the variable factors are concentrated on the right side of the figure, and it can be seen that there is a strong positive correlation between the variables, and the selenium content of brown rice in rice plants almost overlaps with the variable axis of selenium content in chaff and leaves, indicating that there is a strong positive correlation between these three variables, and the correlation coefficient is close to 1, and the correlation between soil total selenium content, available selenium content and selenium content in plant tissues is weak. In addition, the CK treatments were all distributed on the left side, and the T1, T2 and T3 treatments gradually approached the variable axis of each tissue of the plant, which showed that the increase of selenium content in each tissue of rice was not related to the soil selenium content under the condition of spraying selenium nutrient solution, and the spraying of selenium nutrient solution 60g/ At hm2, the increase of selenium nutrient concentration can effectively promote the increase of selenium content in grains, rhizomes and leaves, and has little effect on soil selenium content.
Fig.3 Principal component analysis of selenium content in soil and plants under different selenium nutrient solution concentrations
◆Effect of selenium nutrient solution on the accumulation of various elements in rice grains
The principal component analysis (Fig. 4) was performed with the content of each element in brown rice as a variable, in which the first principal coordinate explained 44.95%, the second principal coordinate explained 21.10%, and the two principal axes mainly explained 66.05% of the variables. As can be seen from Fig. 4, most of the variables are gathered in the left part, the CK treatment is concentrated in the right part of the PCA diagram, and the selenium nutrient solution treatment is distributed in the middle of the axis of each variable, which shows that the spraying of selenium nutrient solution has a certain effect on the content of various elements in brown rice, and the increase of all mineral element content is related to the application of selenium nutrient solution, and other beneficial elements such as N, P, Ca, Zn, K, etc. Mg and others had a strong correlation with each other, which may be due to the fact that the selenium nutrient solution contains a small amount of beneficial trace elements that are transported to the grains, and the selenium nutrient solution has the effect of promoting the absorption and utilization of soil and exogenous mineral nutrients by plants. In addition, the optimal application rate of selenium nutrient solution to increase the content of beneficial mineral elements needs to be further studied.
Fig.4 Principal component analysis of each element in brown rice under different selenium nutrient solution concentrations
◆Effect of different concentrations of selenium nutrient solution on heavy metal accumulation in rice leaves
Different concentrations of selenium nutrient solution treatment had different effects on the absorption and accumulation of heavy metals in rice leaves (Fig. 5). It can be seen from Fig. 5 that with the increase of selenium nutrient solution application concentration, the content of Hg in leaves decreases first, then increases and then decreases, and the T1, T2 and T3 treatments decreased by 6.38%, 0.95% and 6.71%, respectively, compared with the CK treatment, respectively, and the Pb content in leaves increased first and then continued to decrease, with a decrease of 5.91%~14.03%. Compared with CK, the application of selenium nutrient solution also reduced the Cr content in leaves, with a decrease of 14.64%~44.36%, and the T3 treatment had the largest reduction, and there was no significant difference in the Cd content in leaves of each treatment, only T3 had a reduction effect of 3.63% compared with CK treatment. In conclusion, increasing the concentration of foliar selenium fertilizer can effectively reduce the contents of Hg, Pb, Cr and Cd in leaves, which is of great significance for reducing the toxicity of rice plants in heavy metal contaminated soil. The variation trend of the contents of the five heavy metal elements under different selenium nutrient solution treatments was inconsistent, and the optimal application rate and mechanism of foliar selenium fertilizer to reduce the content of heavy metal elements in plants need to be further studied.
Fig.5 The contents of heavy metals in leaves under different selenium nutrient solution concentrations
conclusion
The mechanism of selenium fertilizer to reduce the heavy metal content of crops is to reduce the content of reactive oxygen species in plants, improve the activity of hydrogen ions, and promote the binding and fixation of heavy metal ions in the cell wall, while the increase of heavy metal content in crops caused by selenium fertilizer is mainly due to the synergistic effect. Therefore, when selenium fertilizer is used to reduce heavy metal toxicity in practical production and application, the dosage and control measures should be comprehensively considered in combination with the source and degree of heavy metal pollution.
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