Application and method of organic selenium fertilizer in improving yield, nutritional quality, antioxidant capacity and selenium content of lagenaria plants

Abstract

The application provides application of organic selenium fertilizer in improving at least one of yield, nutritional quality, antioxidant capacity and selenium content of lagenaria plant, and belongs to the field of agricultural technology. In the application, the application amount of selenium in the organic selenium fertilizer is 3.5-8.5 mg / plant / time. The application also provides a planting method of lagenaria plant, wherein organic selenium fertilizer is sprayed on the leaves of lagenaria plant during the reproductive growth period of lagenaria, and the application amount of selenium in the organic selenium fertilizer is 3.5-8.5 mg / plant / time; the spraying frequency is 1-2 times, and the interval between each spraying is 6-10 days. The application can effectively improve the yield, nutritional quality, antioxidant capacity and selenium content of lagenaria plant by controlling the application amount of organic selenium fertilizer. The method is simple in operation, low in cost and suitable for cultivation of lagenaria in facilities or open fields.

Description

Technical Field

[0001] This invention belongs to the field of agricultural technology, and specifically discloses the application and method of organic selenium fertilizer in improving the yield, nutritional quality, antioxidant capacity and selenium content of Luffa plants. Background Technology

[0002] Selenium is an essential micronutrient for the human body, possessing various physiological functions such as antioxidation, immune enhancement, and anti-cancer and anti-tumor effects. It is crucial for maintaining cell health and regulating metabolism. However, the human body cannot synthesize selenium and must obtain it continuously through daily diet. Currently, naturally selenium-rich agricultural products are extremely scarce, far from meeting the public's demand for selenium fortification. Summary of the Invention

[0003] The purpose of this invention is to provide a method for increasing the selenium content in the fruit of Luffa plants. By adjusting the amount of organic selenium fertilizer applied in a single application, the selenium content in the fruit of Luffa plants can be effectively increased. At the same time, it can also enhance the yield, nutritional quality and antioxidant capacity of the plant. It is characterized by simple operation and low cost.

[0004] This invention provides an application of organic selenium fertilizer in improving at least one of the following: fruit yield, fruit nutritional quality, fruit antioxidant capacity, and selenium content in the fruit of Luffa plants. The application amount of selenium in the organic selenium fertilizer is 3.5~8.5 mg / plant / time.

[0005] Preferably, increasing the fruit yield of Luffa plants includes increasing at least one of the following indicators: fruit length, fruit diameter, and single fruit weight.

[0006] Preferably, improving the nutritional quality of the fruit of the *Luffa* species includes increasing the content of vitamin C and / or total soluble sugars.

[0007] Preferably, improving the antioxidant capacity of the fruit of the Luffa species includes improving at least one of the following indicators: superoxide dismutase activity, catalase activity, and peroxidase activity.

[0008] This invention provides a method for cultivating Luffa plants, comprising the following steps: applying organic selenium fertilizer during the reproductive growth period of the plant, wherein the amount of selenium applied in the organic selenium fertilizer is 3.5~8.5 mg / plant / time.

[0009] Preferably, the plant reproductive growth period refers to the period starting from the initial flowering stage of the plant.

[0010] Preferably, the organic selenium fertilizer includes chelated selenium.

[0011] Preferably, the method of applying the organic selenium fertilizer includes foliar spraying.

[0012] Preferably, the organic selenium fertilizer is applied 1 to 2 times, with an interval of 6 to 10 days between each application.

[0013] Preferably, the fruit is harvested 8 days after the last application of the organic selenium fertilizer.

[0014] This invention provides the application of organic selenium fertilizer in improving fruit yield, nutritional quality, antioxidant capacity, and at least one of the following in the fruit of *Luffa* species: the application rate of selenium in the organic selenium fertilizer is 3.5–8.5 mg / plant / application. After application of the organic selenium fertilizer, compared with the water control group, the selenium content in the fruit significantly increased, demonstrating a significant selenium enrichment effect. Furthermore, because organic selenium is less toxic than inorganic selenium, its use is safer and more environmentally friendly. In addition, at the above-mentioned application rate of organic selenium fertilizer, the single fruit weight, fruit length, and fruit diameter all significantly increased, and the vitamin C content and total soluble sugar content increased. Simultaneously, the activities of superoxide dismutase, peroxidase, and catalase were also enhanced. This indicates that while increasing the selenium content of the fruit, it also improves the fruit yield, nutritional quality, and antioxidant capacity. Therefore, the application provided by this invention not only enriches the types of selenium-enriched agricultural products but also improves the yield and quality of agricultural products and enhances the plant's stress resistance.

[0015] This invention also provides a method for cultivating *Luffa* species, further specifying the application method, frequency, and interval of organic selenium fertilizer. Experimental results show that the method not only improves the utilization efficiency of organic selenium fertilizer and avoids fertilizer waste during the vegetative growth stage, but also ensures high levels of selenium content, fruit growth quality, and nutritional quality in the fruit, achieving simultaneous improvement in selenium enrichment and high yield and quality. The method is simple to operate, cost-controllable, and has a high input-output ratio, making it suitable for the cultivation of *Luffa* species in greenhouses or open fields. Detailed Implementation

[0016] This invention provides the application of organic selenium fertilizer in improving at least one of the following: fruit yield, fruit nutritional quality, fruit antioxidant capacity, and selenium content in fruit of Luffa plants. The application amount of selenium in the organic selenium fertilizer is 3.5~8.5 mg / plant / time.

[0017] In this invention, the *Luffa* species preferably include one or more common cultivated varieties such as ridged *Luffa*, common *Luffa*, snake-shaped *Luffa*, fragrant *Luffa*, and fleshy *Luffa*. This invention does not impose any special restrictions on the variety of *Luffa*; any *Luffa* variety well-known in the art can be used. In this embodiment of the invention, the 'Tai Xiang No. 1' fragrant *Luffa* variety was used as the planting object for the experiment, but this should not be construed as a limitation on the scope of protection of this invention.

[0018] In this invention, the application rate of the organic selenium fertilizer can be 4 mg / plant / time, 5 mg / plant / time, and 6 mg / plant / time. In the embodiments of this application, specific application rates of 3.75 mg / plant / time and 7.5 mg / plant / time are used. Using these application rates not only increases the selenium content in the fruit but also significantly promotes fruit growth. Applying the organic selenium fertilizer according to these rates during the growth process can simultaneously improve yield, quality, antioxidant capacity, and selenium content, offering advantages such as flexible operation, wide applicability, and controllable cost.

[0019] In this invention, the organic selenium fertilizer is preferably applied 1-2 times, with an interval of 6-10 days between each application. In this embodiment, the fertilizer is applied twice consecutively with an 8-day interval. Samples are taken and tested 8 days after the first and second applications. The results show that applying the organic selenium fertilizer once is superior to applying it twice in terms of selenium content, fruit quality, and antioxidant performance, but slightly lower in single fruit weight. Therefore, for the goal of achieving high selenium content, high quality, and high antioxidant activity, one application is sufficient and more effective; while for the goal of achieving high yield while simultaneously improving selenium content, fruit quality, and antioxidant performance, two applications are more advantageous.

[0020] In this invention, the selenium content in the fruit refers to the total selenium content in the fruit. Within an application range of 3.5–8.5 mg / plant / application, the total selenium content increases with increasing application rate. In the embodiments of this application, when the application rate of selenium in the organic selenium fertilizer is 3.75 mg / plant / application, after one application of the organic selenium fertilizer, the total selenium content of the fruit is 5.58 times that of the control; after two applications of the organic selenium fertilizer, the total selenium content of the fruit is 1.70 times that of the control. This indicates that if the goal is to achieve high selenium content in the fruit, a single application followed by harvesting approximately 8 days after application is more advantageous. If both yield and continuous selenium supply are considered, a two-application strategy can be adopted. When the application rate is increased to 7.5 mg / plant / application, the total selenium content of the fruit after one application is 7.79 times higher than the control; after two applications of the organic selenium fertilizer, it is 2.55 times higher than the control, indicating that this application rate has the strongest selenium enrichment effect. When the application rate was further increased to 11.25 mg / plant / time, the total selenium content of the fruit after one spray was lower than that of the control group, and after two sprays it was slightly higher than that of the control, but much lower than that of the 3.75 mg / plant / time and 7.5 mg / plant / time treatments, indicating that excessive application rate seriously inhibited the absorption and accumulation of selenium.

[0021] In this invention, increasing the fruit yield of *Luffa* plants preferably includes promoting the growth of individual fruits. Promoting the growth of individual fruits preferably includes increasing at least one of the following indicators: fruit length, fruit diameter, and fruit weight. Within an application range of 3.5–8.5 mg / plant / application, the fruit length, fruit diameter, and fruit weight all increase with increasing application amount. In an embodiment of this invention, when the application amount of selenium in the organic selenium fertilizer is 3.75 mg / plant / application, after one application, the fruit length, diameter, and fruit weight of *Luffa* plants significantly increased by 18.00%, 10.91%, and 41.54%, respectively, compared to the control; after two applications, although the fruit length, diameter, and fruit weight increased compared to the control, there was no significant difference. When the application rate of selenium in the organic selenium fertilizer was 7.5 mg / plant / application, after one application, the length, diameter, and weight of the loofah fruit increased significantly by 34.61%, 16.36%, and 50.39% respectively compared to the control. After two applications, the length, diameter, and weight of the fruit all increased compared to the control, with the length and diameter showing significant differences. When the application rate of selenium in the organic selenium fertilizer was further increased to 11.25 mg / plant / application, after one application, the length, diameter, and weight of the fruit all increased significantly compared to the control. However, after two applications, the length, diameter, and weight of the fruit decreased slightly compared to the control. This indicates that the above application rate can significantly promote fruit growth rate and improve fruit growth performance, with the effect becoming more significant with increasing concentration.

[0022] In this invention, improving the nutritional quality of *Luffa* fruits preferably includes increasing the content of vitamin C and / or total soluble sugars. Within an application range of 3.5–8.5 mg / plant / application, both vitamin C and total soluble sugar content increase with increasing application amount. In an embodiment of this invention, when the application amount of selenium in the organic selenium fertilizer is 3.75 mg / plant / application, after one application, the total soluble sugar content is significantly higher than the control; after two applications, the vitamin C content is significantly higher than the control. When the application amount of selenium in the organic selenium fertilizer is 7.5 mg / plant / application, after one application, both vitamin C and total soluble sugar content are significantly higher than the control; after two applications, the vitamin C and total soluble sugar content remain at a high level and are significantly different from the control group. This indicates that the aforementioned application amounts can significantly promote the improvement of fruit nutritional quality, and the improvement effect is stable and long-lasting, with the effect becoming more significant with increasing concentration. When the application rate of selenium in organic selenium fertilizer was further increased to 11.25 mg / plant / application, the vitamin C and soluble sugar contents were slightly lower than the control after one application, but the vitamin C content was slightly higher than the control after two applications. These results indicate that a single application is more effective in improving fruit quality; and within the application rate range of 3.5–8.5 mg / plant / application, a higher selenium application rate plays a crucial role in improving the sweetness and taste of loofah fruit, providing an optimal application rate for producing selenium-enriched loofah with high vitamin C content and high sweetness.

[0023] In this invention, improving the antioxidant capacity of *Luffa* fruits preferably includes increasing at least one of the following indicators: superoxide dismutase (SOD) activity, catalase activity, and peroxidase activity. In the embodiments of this application, when the application amount of selenium in the organic selenium fertilizer was 3.75 mg / plant / application and 7.5 mg / plant / application, regardless of whether the organic selenium fertilizer was sprayed once or twice, the activities of SOD, catalase, and peroxidase were significantly increased compared to the control. When the application amount was further increased to 11.25 mg / plant / application, the malondialdehyde (MDA) content was significantly higher than the control after both one and two applications, indicating that while excessive application could significantly activate some antioxidant enzymes, it induced membrane lipid peroxidation damage. The above results show that an application amount range of 3.5–8.5 mg / plant / application can increase the activities of SOD, catalase, and peroxidase without causing oxidative damage, thereby enhancing the overall antioxidant capacity of *Luffa* fruits. Antioxidant capacity is the core physiological mechanism for plants to cope with various abiotic stresses. Enhancing the antioxidant level of plants can improve their ability to scavenge reactive oxygen species and maintain cell homeostasis under stresses such as drought, salinity, and high and low temperatures, thereby comprehensively improving the overall stress resistance of plants.

[0024] This invention provides a method for cultivating Luffa plants, comprising the following steps: applying organic selenium fertilizer during the reproductive growth period of the plant, wherein the amount of selenium applied in the organic selenium fertilizer is 3.5~8.5 mg / plant / time.

[0025] In this invention, application during the reproductive growth period of plants refers to starting from the early flowering stage. Applying selenium fertilizer at the early flowering stage can timely supply the nutrients needed for reproductive growth, effectively enhance the plant's antioxidant capacity, strengthen the flower's resistance to damage and stress, reduce flower and bud drop, promote the steady development of flower buds, and thus increase the fruit set rate, laying a good foundation for subsequent fruit quality improvement and yield increase.

[0026] In this invention, the organic selenium fertilizer preferably comprises chelated selenium. The organic selenium fertilizer can also be other forms of organic selenium, such as yeast selenium, amino acid chelated selenium, etc., as long as the selenium element exists in an organic form and can be effectively absorbed and utilized by *Luffa* plants. In the embodiments of this application, the organic selenium fertilizer used is a chelated organic selenium fertilizer, specifically purchased from Henan Qianxiang Biotechnology Co., Ltd. The main advantages of using chelated selenium are: firstly, chelated selenium has higher stability and bioavailability, which can reduce the oxidative loss of selenium during application and improve the absorption efficiency of selenium by leaves; secondly, chelated selenium is less irritating to plants, less likely to cause leaf burn, and its organic form is more smoothly transported within the plant, which is conducive to the targeted accumulation of selenium in the fruit.

[0027] In this invention, the preferred method of applying the organic selenium fertilizer includes foliar spraying. The organic selenium fertilizer is prepared into a solution at an application rate of 3.5-8.5 mg / plant / application. The preferred application rate for foliar spraying is per 6 m². 2 The application rate for the planted area is 5-7 L, or up to 6 L. In this embodiment, the organic selenium fertilizer solution is evenly sprayed onto the leaves of the loofah using a foliar spraying method, ideally covering the leaf surface with uniform droplets without dripping. The spraying time is around 9:00 AM. If it rains within 12 hours after spraying, a second spraying is necessary to ensure effective selenium deposition and absorption. Compared with soil application, foliar spraying allows the selenium fertilizer to act directly on the plant's absorption organs, quickly entering the plant through the stomata and cuticle on the leaf surface. This avoids losses such as selenium fixation, leaching, or microbial transformation in the soil, thus significantly improving selenium utilization efficiency. In addition, foliar spraying has the advantages of low dosage, rapid effect, and simple operation, and the spraying concentration and frequency can be flexibly adjusted according to the growth stage of the loofah.

[0028] In this invention, the fruit is harvested 8 days after the last application of the organic selenium fertilizer. This harvesting timing is determined based on the dynamic changes in fruit selenium content, single fruit weight, antioxidant capacity, and nutritional quality at different time points. In the embodiments of this application, the total selenium content of the fruit reaches its peak after one application, with the most significant selenium enrichment effect; while after two applications, the yield indicator of single fruit weight reaches its optimal level, while the vitamin C content and total soluble sugar content remain at a high level. Harvesting the fruit 8 days after the last application allows for the full translocation, enrichment, and stable conversion of selenium, ensuring robust growth of the loofah fruit and achieving a significant increase in yield; it also maintains nutritional quality indicators such as total soluble sugar at a high level, effectively activates the antioxidant enzyme system, enhances the fruit's antioxidant and damage resistance, and reduces the risk of oxidative stress; and it ensures that the selenium content of the fruit reaches a stable and safe selenium enrichment standard, avoiding inhibition or toxicity caused by excessive concentration.

[0029] This invention provides an application of organic selenium fertilizer in improving at least one of the following aspects of luffa plants: yield, nutritional quality, antioxidant capacity, and selenium content. The application rate of selenium in the organic selenium fertilizer is 3.5–8.5 mg / plant / application. Within this application range, it can synergistically enhance several key traits of luffa fruits: promote fruit length and diameter, significantly increase single fruit weight, achieve yield increase, and shorten the growth cycle; increase vitamin C content and total soluble sugar content, improving fruit flavor; activate the activity of antioxidant enzymes such as superoxide dismutase, catalase, and peroxidase without causing membrane lipid peroxidation damage, enhancing the fruit's antioxidant defense capacity and stress resistance; most importantly, it can also achieve efficient selenium accumulation in the fruit, with a stable and long-lasting selenium enrichment effect. Exceeding this application range will result in negative effects such as growth inhibition or hindered selenium absorption. In summary, limiting the application rate of selenium in organic selenium fertilizer to 3.5–8.5 mg / plant / application can achieve multiple synergistic improvements in luffa yield, nutritional quality, antioxidant capacity, and selenium content under safe and environmentally friendly conditions.

[0030] This invention also provides a method for cultivating *Luffa* plants, further specifying the application method, frequency, and interval of organic selenium fertilizer, as well as the fruit harvesting period. This results in superior selenium content, single fruit weight, and nutritional quality, achieving a synergistic effect of selenium enrichment and high yield and quality. Furthermore, this method requires less fertilizer, has controllable costs, and a high input-output ratio, making it suitable for both greenhouse and open-field *Luffa* cultivation.

[0031] To further illustrate the present invention, the solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1 Application and methods of organic selenium fertilizer in improving the yield, nutritional quality, antioxidant capacity and selenium content of Luffa plants 1. Materials and Methods The experiment was conducted from April to July 2025 at an experimental base in Taizhou City, Jiangsu Province. The soil at the experimental site was loam, with an organic matter content of 1.21%, available nitrogen content of 11.8 mg / kg, available phosphorus content of 12.9 mg / kg, and available potassium content of 138.2 mg / kg. The tested loofah variety was 'Taixiang No. 1', provided by the Taizhou Agricultural Research Institute of Jiangsu Academy of Agricultural Sciences. The tested fertilizer was Bala organic selenium fertilizer produced by Henan Qianxiang Biotechnology Co., Ltd., which contained only chelated selenium with a selenium content ≥20 g / L.

[0033] A single-factor randomized block design experiment was conducted, with three treatment groups and one control group: treatment group T1 (sprayed with 10 mg / L selenium from exogenous organic selenium fertilizer), treatment group T2 (sprayed with 20 mg / L selenium from exogenous organic selenium fertilizer), treatment group T3 (sprayed with 30 mg / L selenium from exogenous organic selenium fertilizer), and a blank control group (CK) sprayed with water. The organic selenium fertilizer was prepared into a solution for spraying.

[0034] On March 10, 2025, the loofah seeds were germinated using the hot water soaking method. Seedlings were sown in plug trays on March 13 and transplanted on April 20 when the seedlings had two leaves and a central bud. A field plot experiment was conducted, with each treatment comprising one plot. Each plot was 4 m long, 1.5 m wide, and had an area of ​​6 m². 2 Sixteen loofah plants were planted in each plot, with three replicates per treatment. Starting from the early flowering stage, a selenium fertilizer solution was sprayed on the leaves at a rate of 6 liters per treatment: 3.75 mg selenium per plant per application for group T1, 7.5 mg per plant per application for group T2, and 11.25 mg per plant per application for group T3. Spraying was performed twice, once every 8 days. Samples were taken 8 days after the first and second applications, for a total of two samplings. Spraying was done around 9:00 AM each time, ensuring the leaves were evenly covered with droplets. If rainfall occurred within 12 hours, spraying was repeated. All cultivation and management methods were consistent throughout the loofah planting process.

[0035] The first fruit sampling was conducted 8 days after the first application of organic selenium fertilizer. Six loofah fruits of similar growth were collected from each plot and sealed in resealable bags. The second fruit sampling was conducted approximately 8 days after the second application of organic selenium fertilizer. Samples were immediately placed in dry ice for preservation after collection and brought back to the laboratory for subsequent indicator determination.

[0036] 2. Determination of growth indicators of loofah fruit The transverse diameter, longitudinal diameter, and single fruit weight of the two samples were measured. The transverse diameter was measured with a vernier caliper, the longitudinal diameter with a ruler, and the single fruit weight with a 0.1% balance. The measurement results are shown in Table 1 and Table 2.

[0037] Table 1. Effects of spraying different concentrations of organic selenium fertilizer on the growth of loofah fruit in one application.

[0038] Note: Different letters in the same column indicate P < 0.05.

[0039] Table 2. Effects of spraying different concentrations of organic selenium fertilizer twice on the growth of loofah fruit.

[0040] Note: Different letters in the same column indicate P < 0.05.

[0041] Samples were taken after the first application, and the results are shown in Table 1. Eight days after a single application of exogenous selenium fertilizer, the growth indicators of the loofah fruit were significantly improved. Treatment T2 showed the most outstanding performance, with loofah fruit length, diameter, and single fruit weight all significantly higher than other treatments, increasing by 34.61%, 16.36%, and 50.39% respectively compared to the control (CK). However, overall, the high concentration of selenium fertilizer in treatment T3, compared to T1 and T2, actually reduced the length, diameter, and single fruit weight of the loofah fruit, but still exceeded those of the control (CK).

[0042] Sampling was conducted after the second application, and the results are shown in Table 2. Significant differences were observed in the growth indicators of the loofah fruit after two consecutive applications of selenium fertilizer. After the second application, the longitudinal diameter of the fruit in each treatment ranged from 25.77 cm to 30.65 cm, with T2 having the longest at 30.65 cm. As the concentration of selenium fertilizer increased, the longitudinal diameter of the loofah fruit generally showed a trend of first increasing and then decreasing, with T3 showing the shortest fruit length, a significant difference compared to the control (CK). In terms of transverse diameter, T2 had the highest, while T3 had the lowest. Regarding single fruit weight, the trend was one of first increasing and then decreasing with increasing selenium concentration, with T2 showing the highest weight, increasing by 7.03% compared to the control (CK), while T3 had the lowest single fruit weight, decreasing by 3.39% compared to the control (CK).

[0043] In summary, appropriate concentrations of selenium treatment promote the growth of loofah fruits, while excessively high concentrations inhibit fruit growth.

[0044] 3. Quality determination of loofah fruit Nutritional quality was tested on the fruits sampled twice, and the content of vitamin C (VC) and total soluble sugar in the loofah fruits was determined. The VC content was determined using the 2,4-dinitrophenylhydrazine colorimetric method, and the total soluble sugar content was determined using the anthrone sulfate colorimetric method (Wang Xuekui. Principles and Techniques of Plant Physiology and Biochemistry Experiments [M]. Beijing: Higher Education Press, 2006). The test results are shown in Table 3.

[0045] Table 3. Effects of different application rates of selenium fertilizer on the quality of loofah fruit.

[0046] Note: Different letters in the same column represent... P <0.05.

[0047] Table 2 shows that after spraying selenium fertilizer, the vitamin C and total soluble sugar content of the fruit initially increased and then decreased with increasing selenium fertilizer concentration. Eight and sixteen days after spraying selenium fertilizer, the T2 treatment showed the highest vitamin C and total soluble sugar content in the loofah fruit, significantly higher than the control (CK). After one application of organic selenium fertilizer, the vitamin C content of each treatment was in the order T2 > T1 > CK > T3, with significant differences between T2 and both CK and T3 treatments. The T2 treatment had the highest total soluble sugar content (26.21 mg / g), showing a highly significant difference from both T3 and CK. After spraying different concentrations of organic selenium fertilizer twice, the VC content of each treatment was significantly different except for T1 and T2. Among them, the VC content and total soluble sugar content of loofah fruit in the T2 treatment were 63.73 μg / g and 24.32 mg / g, respectively, which were 57.83% and 15.90% higher than those in the CK. The total soluble sugar content of the T1 and T3 treatments did not differ significantly, but both were significantly higher than that of the CK (Table 2).

[0048] With the increase in the number of organic selenium fertilizer applications, the trends of vitamin C and total soluble sugar varied among the treatments. Except for the T3 treatment, which showed an increase in vitamin C and total soluble sugar content in loofah fruit after two applications, and the T2 treatment, which showed an increase in total soluble sugar content, the vitamin C and soluble sugar content in the other treatments all showed a decreasing trend with the increase in the number of selenium fertilizer applications.

[0049] The study indicates that spraying an appropriate concentration of organic selenium fertilizer is beneficial for increasing the vitamin C and total soluble sugar content of loofah fruit, but excessively high concentrations of selenium fertilizer will lead to a decrease in the vitamin C and total soluble sugar content of the fruit.

[0050] 4. Determination of antioxidant indexes in loofah fruit The fruits sampled twice were tested for superoxide dismutase (SOD), hydrogen peroxide (H2O2), peroxidase (POD), catalase (CAT), malondialdehyde (MDA), and other indicators. The test results are shown in Tables 4 and 5. Among the antioxidant system indicators, SOD activity was determined by the nitroblue tetrazolium photochemical reduction method (Wang Xuekui, "Principles and Techniques of Plant Physiological and Biochemical Experiments"); H2O2 content was determined by the ammonium molybdate method (Zhang Youshen, et al. Determination of ammonium molybdate peroxide in plasma free hemoglobin [J]. Journal of Clinical Laboratory Medicine, 1994, (04): 19); POD activity was determined by the guaiacol colorimetric method (Wang Xuekui, "Principles and Techniques of Plant Physiological and Biochemical Experiments"); CAT activity was determined by the ultraviolet absorption method (Wang Qun, et al. New progress in the determination of maize catalase activity by ultraviolet spectrophotometry [J]. Chinese Agricultural Science Bulletin, 2016, 32(15): 159-165); and MDA content was determined by the TBA colorimetric method (Wang Xuekui, "Principles and Techniques of Plant Physiological and Biochemical Experiments").

[0051] The test results are shown in Tables 4 and 5.

[0052] Table 4. Effects of spraying different concentrations of organic selenium fertilizer once on the antioxidant index of loofah fruit.

[0053] Note: Different letters in the same column indicate P < 0.05.

[0054] Table 5. Effects of two applications of different concentrations of organic selenium fertilizer on the antioxidant index of loofah fruit.

[0055] Note: Different letters in the same column indicate P < 0.05.

[0056] Foliar application of organic selenium fertilizer has a significant regulatory effect on the antioxidant system of loofah fruit. Regarding enzyme activity, all selenium treatments generally increased the activity of antioxidant enzymes. After two applications of organic selenium fertilizer, the SOD, CAT, and POD enzyme activities in treatments T1 and T2 were significantly higher than those in the control and T3 treatment groups. After two applications of organic selenium fertilizer, the SOD and POD enzyme activities in treatment T1 were significantly higher than those in the control T3 treatment group, while treatment T2 had the highest SOD, CAT, and POD enzyme activities, all higher than other treatment groups.

[0057] Regarding stress indicators, the H2O2 content in all treatments remained within the normal range of 0.11–0.12 mmol / g, indicating that selenium treatment did not cause significant oxidative stress. Except for treatment T3, which showed an increase after two applications of organic selenium fertilizer, the MDA content in the other treatments remained the same as the control. MDA is one of the core products of membrane lipid peroxidation, and its accumulation level indicates the degree of membrane damage, suggesting that excessive selenium application can damage the loofah membrane system.

[0058] In summary, treatment with appropriate concentrations of selenium fertilizer can effectively activate the antioxidant enzyme system of loofah fruit, improve the loofah's resistance to stress, and will not cause oxidative stress.

[0059] 5. Determination of selenium content in loofah fruit The total selenium content was determined by atomic fluorescence spectrometry, referring to GB 5009.93-2017 "National Food Safety Standard - Determination of Selenium in Food". The test results are shown in Table 6.

[0060] Table 6. Effects of spraying different concentrations of selenium fertilizer on the selenium content of loofah fruit.

[0061] Note: Different letters in the same column indicate P < 0.05.

[0062] Table 6 shows that foliar application of selenium fertilizer significantly increased the selenium content of loofah fruits. After one application of organic selenium fertilizer, the T2 treatment had the highest selenium content, reaching 1.67 mg / kg, which was 7.79 times higher than the control (CK). The T1 treatment was second highest at 1.06 mg / kg, while the T3 treatment had a selenium content of only 0.07 mg / kg, lower than the CK. This indicates that appropriate concentrations of selenium can significantly promote the accumulation of selenium in loofah fruits, but excessively high concentrations may inhibit selenium storage, possibly due to changes in the metabolic pathways of selenium in plants or feedback inhibition. After two applications of organic selenium fertilizer, the overall selenium content of each treatment decreased compared to the first application, but the T2 treatment still had the highest selenium content at 0.51 mg / kg, which was 1.55 times higher than the CK. The selenium contents of the T1 and T3 treatments were 0.34 mg / kg and 0.25 mg / kg, respectively.

[0063] The above results indicate that selenium accumulation in fruits is closely related to the spray concentration and sampling time. The low-concentration T1 treatment showed a significant selenium enrichment effect in the short term, but its sustainability was poor, possibly because its organic selenium form is more easily metabolized and utilized by the plant. The medium-concentration T2 treatment showed a stable and long-lasting selenium enrichment effect. The high-concentration T3 treatment, on the other hand, inhibited the effective absorption or transport of selenium due to excessive metabolic burden.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of organic selenium fertilizer in improving at least one of the following aspects of fruit yield, fruit nutritional quality, fruit antioxidant capacity, and selenium content in fruits of Luffa plants, wherein the application amount of selenium in the organic selenium fertilizer is 3.5~8.5 mg / plant / time.

2. The application according to claim 1, characterized in that, The improvement of fruit yield in Luffa species includes increasing at least one of the following indicators: fruit length, fruit diameter, and single fruit weight.

3. The application according to claim 1, characterized in that, Improving the nutritional quality of fruits from Luffa species includes increasing the content of vitamin C and / or total soluble sugars.

4. The application according to claim 1, characterized in that, The improvement of the antioxidant capacity of the fruits of the Luffa genus includes improving at least one of the following indicators: superoxide dismutase activity, catalase activity, and peroxidase activity.

5. A method for cultivating plants of the genus *Luffa*, characterized in that, Organic selenium fertilizer is applied during the reproductive growth period of plants, with the amount of selenium in the organic selenium fertilizer being 3.5~8.5 mg / plant / application.

6. The planting method according to claim 5, characterized in that, The reproductive growth period of a plant refers to the period starting from the early flowering stage.

7. The planting method according to claim 5, characterized in that, The organic selenium fertilizer includes chelated selenium.

8. The planting method according to claim 5, characterized in that, The application method of the organic selenium fertilizer includes foliar spraying.

9. The planting method according to claim 5, characterized in that, The organic selenium fertilizer is applied 1-2 times, with an interval of 6-10 days between each application.

10. The planting method according to any one of claims 5 to 9, characterized in that, The fruit was harvested 8 days after the last application of the organic selenium fertilizer.

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