The thinnest plastic film has a greater impact on

2022-07-25
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Thinner plastic film has a greater impact on plants Materials and methods

1.1 test materials

the test plant was triticumaestivuml, Purchased from Chinese Academy of Agricultural Sciences, variety name: rotation 987

1.2 soil for test

the soil was collected in Beijing Yuandu Ruins Park (n39 ° 54 ′ 27 ″, E116 ° 23 ′ 17 ″). After clearing the dead branches and leaves on the surface, the surface (2 ~ 20cm) soil was collected. After taking soil by multi-point sampling method, it was placed on the plastic cloth to mix evenly. After indoor natural air drying, impurity removal, mortar grinding, and 2mm screening for standby. The basic physical and chemical properties of soil were determined by conventional methods [12] (Table 1)

1.3 experimental design and methods

the limit tolerance range of wheat seeds obtained from the pre-test was set at 6 levels. Weigh 300.0g of the test soil and put it on the plastic cloth. Add 150, 300, 750, 1500, 4500mg of plastic film fragments and blank control to the soil respectively, mix them evenly with the soil, and then put them into a 500ml brown bottle to obtain the soil samples with the addition amount of 0, 500, 1000, 2500, 5000, -1. Deionized water was added to the soil to make the water content reach 75% of the field capacity, and each treatment was repeated three times. Add a cotton stopper to the brown bottle and put it into a 25 ℃ biochemical incubator for constant temperature culture. During the culture period, supplement water regularly every day to keep the water content at 75% of the field capacity. After balancing for one month, use the random sampling method to weigh soil samples from the brown bottle and put them into Petri dishes and disposable paper cups respectively for use

1.3.1 seed germination test

before the germination test, the surface of wheat seeds was disinfected with 3% H2O2 for 5min, and then washed with deionized water. Place the sterilized seeds in a Petri dish containing film covered soil and cover them with 2~3cm film covered soil. The control experiment was to fix the seeds on the soil without plastic film. Place 20 wheat seeds in each Petri dish, cover them, and incubate them in the incubator at (25 ± 5) ℃ in the dark for 48h. When the germ and radicle exceed 2mm, it can be considered as seed germination, and the seed germination rate is calculated. All tests were repeated 3 times to reduce the experimental error

1.3.2 experiment on root elongation and bud length of wheat seeds. During the cultivation period, water was supplemented at a fixed time every day to keep the soil water capacity at 75% of the field water capacity. After culture, measure and record the root length and bud length of wheat with different kinds of plastic mulch and different addition amounts with vernier caliper, calculate the average value and standard deviation of root length and bud length of wheat under each addition amount, and calculate the inhibition rate of root elongation and bud length of wheat under each addition amount. Compared with the control group, the bud length and root length of the seeds with plastic mulch were expressed by inhibition percentage

1.3.3 wheat seedling growth experiment

wheat seeds were cultured in the dark at (25 ± 5) ℃ for 7 days, and then further cultured in a constant temperature (25 ± 5) ℃ growth chamber, while maintaining 12h bright and 12h dark cycle in the growth chamber. Samples were collected and analyzed after 0, 7, 14 and 21 days of interval culture

take 500mg of the penultimate leaf and all roots, cool at 0 ~ 4 ℃ for 30min, cut them into pieces, and add 10ml of precooled 50mmol L-1 pH7.8 phosphoric acid buffer, ice bath grinding. 12000r/min freezing and centrifugation at 4 ℃ for 20min The supernatant is the extract of the enzyme. SOD activity was determined by nitrotetrazolium chloride blue photochemical reduction method [13], pod was determined by guaiacol spectrophotometry [14], and cat was determined by titration [14] The three antioxidant enzymes SOD, pod and cat in the leaves and roots of wheat seedlings were measured at 7, 14 and 21 days after emergence, and the control percentage was calculated by comparing with the blank enzyme activity

1.3.4 data system and accurate wiring analysis

all tests were repeated for 3 times, and three groups of parallel samples were measured by enzyme activity test. All data were analyzed by ANOVA, and the standard deviation was calculated. All data of the test were statistically processed and analyzed using microsoftexcel and SPSS13.0 software

II Results and discussion

2.1 the effect of two kinds of plastic film treatment on the germination rate of wheat seeds after 48 hours. Compared with the control, the treatment of 500 ~ -1 mulching film 1 had no effect on the germination rate. When the addition amount was -1, the germination rates of mulching film 1 and mulching film 2 were more than 97%. Compared with the control, it could be considered that there was almost no effect. It could be considered that the addition of low addition amount of plastic mulching film had little effect on the germination rate of seeds. With the increase of the addition amount, it gradually showed an inhibitory effect on the germination rate. When the addition amount was 5000 ~ -1, the germination rate after film 1 treatment was about 95.9% of the control, and the germination rate after film 2 treatment was about 91.8% of the control, which was lower than the control. In general, plastic film had little effect on the germination rate of wheat seeds. However, it can be seen that the effect of plastic film 2 on germination rate is greater than that of plastic film 1 under the condition of high addition (≥ -1), which indicates that the thinner film may have a greater impact on seed germination

loose, thus promoting the elongation of roots and buds. When the addition amount was -1, the inhibition rates of buds and roots were the highest. The inhibition rates of buds and roots were 16.7% and 19.95% respectively, and the inhibition rates of roots were 13.40% and 15.07% respectively This indicates that the addition of plastic mulch has an inhibitory effect on the elongation of malt and root under high addition, and this inhibition hinders the deep penetration of root system and the absorption of soil water and nutrients, which has a negative impact on plant growth

the comparative analysis shows that the elongation of roots and buds is more sensitive to the addition of plastic film than the germination rate of wheat, which indicates that the germination rate of seeds is a relatively insensitive index, which is consistent with the study of gong[15]. There are three reasons to explain this situation: first, plastic mulching has only affected soil physical properties, but this effect is not enough to have a chemical impact on wheat seed germination; Second, plastic mulch has only low toxicity in equilibrium time; Third, the toxicity of plastic mulch may be organic pollutants, while the seed coat can absorb organic pollutants, which constitutes a barrier between the embryo and the surrounding environment. Therefore, the addition of plastic film did not affect the germination of wheat seeds

2.2 effects of two kinds of plastic film on antioxidant enzyme system of Wheat Seedlings. The activity of SOD in leaves and roots decreased with the increase of adding amount. At the same time, with the extension of exposure time, the activity of SOD in leaves decreased with the time interval at the same adding amount, but there was no significant difference, but the activity of SOD in roots decreased significantly

when the dosage was -1, the SOD activity in roots on the 7th and 14th day was 189% and 145% of the control. However, when the dosage was high (-1), the SOD activity in roots was significantly inhibited, and the inhibition rates reached 39% and 29% respectively. On the 21st day, the inhibition rates even reached 95% In recent years, POD activity in leaves fluctuated irregularly with the increase of the amount of film 1. There was no significant difference in POD activity between the treatment of mulching film 1 and the extension of exposure time. However, with the extension of exposure time, the activity of pod in roots decreased at first and then increased at the same amount. After 14 days of exposure, the control percentage of pod was lower than 1, indicating that the treatment of film 1 had an inhibitory effect on POD activity

the treatment of plastic film 1 decreased the activity of cat enzyme in wheat seedlings after 7 days of exposure. With the extension of exposure time, the activity of cat in leaves increased at first and then decreased at the same dosage. However, the cat activity in roots did not change regularly with the addition amount

analysis showed that the treatment with different amount of mulching film 1 and the extension of exposure time had no significant effect on the cat activity of leaves, which was consistent with the change trend of pod. However, the treatment of plastic film 1 inhibited the cat activity of root system

the ratio of SOD, pod and cat activities in wheat leaves and roots treated with different amount of plastic film 2 to the control test. With the extension of exposure time, the SOD activity in leaves increased first and then decreased with the increase of the amount of mulch 2, but the SOD activity in roots did not change significantly. At the addition of 1000 ~ -1, the treatment of mulching film 2 induced the activity of SOD in leaves of wheat seedlings, while at the high addition (-1)

the treatment of mulching film 2 significantly inhibited the activity of SOD in leaves and roots. On the 7th, 14th and 21st days, the inhibition rates of SOD in leaves reached 48%, 20% and 51% respectively, and the inhibition rates of SOD in roots reached 57%, 69% and 78% respectively The activity of pod in leaves increased first and then decreased after 7 days of exposure, which was consistent with the change trend of SOD. There was no significant difference between POD activity and control after 7 and 14 days of exposure. After 7 days of exposure, POD activity in roots was significantly induced by film 2 treatment, but with the extension of exposure time, POD activity was significantly inhibited on the 14th and 21st days, but this inhibition had no significant difference with the extension of exposure time

there was no significant difference in CAT activity between leaves and control with different exposure time, which indicated that the treatment of plastic film 2 had little effect on CAT activity in leaves, but CAT activity in roots was inhibited after exposure. It can be seen from the figure that at -1, CAT activity has an obvious inducing effect, which is consistent with the changes of SOD activity and root elongation in the root system under this addition

although the production of active oxygen free radicals (AOS) in plants is inevitable without pollution, the synergistic effect of some enzymes in plants can eliminate AOS, which can help angstron materials company to expand the capacity of graphene to maintain a stable state for the production and elimination of AOS in plant cells [16] However, under environmental pressure, cells will produce too much AOS. When the production rate of AOS exceeds the elimination rate of antioxidant system, AOS will rapidly accumulate in cells. A large amount of AOS accumulation can lead to the oxidation of biological macromolecules (such as nucleic acids, membrane lipids, proteins, etc.) in the body. In serious cases, it can cause a series of oxidative stress, such as DNA breakage, membrane lipid peroxidation and enzyme inactivation, thus destroying the balance system in plants. SOD, pod and cat are three important protective enzymes for plants to scavenge reactive oxygen species. SOD can disproportionate superoxide anion (o2-) into O2 and H2O2. Pod and cat are H2O2 scavenging enzymes in plants. The three enzymes cooperate to prevent the damage of reactive oxygen species to cell membrane system and cell aging. Therefore, the changes of SOD, pod and cat activities can reflect the damage of plant antioxidant defense system under the pressure of pollutants

in this experiment, the SOD activity in wheat leaves and roots increased significantly in the early exposure stage after the treatment of low addition of film 1 and film 2 (≤ -1). The results showed that the environmental pressure caused by plastic mulching made plants produce more AOS, which induced the increase of SOD activity to eliminate excess aos According to the research results of mitter[18], it can be considered that wheat seedlings have strong ability to adapt to environmental pressure within a certain tolerance range. However, this tolerance is limited. Under the condition of high addition, the SOD activity in wheat leaves and roots was significantly lower than that in the control group. At the same time, the SOD activity in roots decreased significantly with the extension of exposure time. This showed that AOS accumulated rapidly with the extension of exposure time, and the remaining AOS could not be effectively removed by SOD. Whether in leaves or roots,

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