Greta Jimenez
Air pollution is a pressing issue that has detrimental effects on the environment, human health, and crop growth. While plants are capable of removing pollutants from the environment, they are also vulnerable to the harmful effects of pollutants. The negative impacts of air pollution on crops are far-reaching, ranging from visible markings on foliage to reduced growth, yield losses, and even premature death.
Various air pollutants, such as nitrogen oxides, ozone, and particulate matter, can directly or indirectly affect crop growth and productivity. These pollutants interfere with the metabolic function of leaves, disrupt root functioning, and alter soil chemistry, ultimately hindering the ability of crops to photosynthesize and grow optimally.
The effects of air pollution on crop growth are influenced by factors such as pollutant concentration, length of exposure, plant species, developmental stage, and environmental conditions. As air pollution continues to pose a significant challenge, understanding its impact on crop growth is crucial for ensuring food security and maintaining the health of our planet's ecosystems.
| Characteristics | Values |
|---|---|
| Type of pollution | Air pollution, water pollution, soil pollution, noise pollution |
| Sources of air pollution | Smokestacks from factories, burning of fossil fuels, transport emissions, agriculture, paints, varnishes, VOCs, waste incineration, landfill gas leakage |
| Effects of air pollution | Direct: toxins deposit on plants and affect leaf metabolism and carbon uptake; Indirect: air pollutants fall on the ground and change soil chemistry and pH, preventing plants from obtaining enough nutrients |
| Effects of water pollution | Water becomes toxic for plants, preventing them from absorbing nutrients and water; excess nutrients in water cause an excess in plant growth, making plants weak and vulnerable |
| Effects of soil pollution | Toxic chemicals strip the soil of nutritional content, change its chemical properties, and prevent plants from obtaining nutrients and thriving |
| Effects of noise pollution | Reduction in the number of pine seedlings due to the absence of birds and pollinators |
| Visible effects of pollution on plants | Leaf damage (yellowing, falling leaves, injuries), reduced growth, root damage, necrotic lesions, chlorosis (yellowing leaves), reddening, bronzing, mottling |
| Pollutants | Nitrogen oxides, ozone, particulate matter, heavy metals, acid rain, pesticides, fertilizers, cement dust, fluorides, ammonia, sulphur dioxide |
What You'll Learn
Nitrogen oxides damage crops directly and indirectly
Nitrogen oxides (NOx) are among the most widely emitted pollutants in the world. They are found in car exhaust and industrial emissions. NOx can directly damage crop cells and also affect them indirectly through their role in the formation of ozone and particulate matter aerosols.
The direct damage to crop cells occurs because NOx is a phytotoxin, meaning it is toxic to plants. It can reduce plant growth and yields, and in some cases, cause the premature death of the plant. The severity of the damage depends on factors such as the length of exposure, the plant species, and its stage of development.
The indirect damage occurs through NOx's role in the formation of:
- Ozone: NOx is a key precursor to the formation of ozone in the troposphere. Ozone is a phytotoxin known to reduce crop yields.
- Particulate matter aerosols: NOx can react with ammonia, often present in agricultural regions due to the use of nitrogenous fertilizers, to form ammonium nitrate aerosols. These aerosols, along with ammonium sulfate aerosols formed through the oxidation of sulfur dioxide, can reflect and scatter sunlight away from crops, reducing the amount of light available for photosynthesis.
Overall, the effects of NOx on crop growth are complex and depend on various factors, including the local pollution regime. However, reducing NOx emissions can have significant benefits for crop production and food security.
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Ozone is a major pollutant that harms plant growth
Ozone enters plants through the stomata, the microscopic pores on the bottoms of leaves that allow the plant to breathe. Once inside the plant, ozone dissolves in the water and reacts with other chemicals, causing a variety of problems. For example, some cell membranes become leaky, possibly due to ozone's ability to interact with lipid (fatty) components and/or membrane proteins. This leads to slower photosynthesis, which results in slower plant growth and a decrease in the amount of carbon stored in plant tissues.
Compounds resulting from oxidation by ozone interfere with the cell's energy production in the mitochondria. These compounds also decrease the number of flowers and fruits a plant will produce and impair water use efficiency and other functions. Plants weakened by ozone may be more susceptible to pests, diseases, and droughts.
Ozone can also affect soil fertility. Plants exposed to high ozone concentrations metabolize less carbon dioxide, so less carbon is available in the soil for microbes to grow and thrive. This results in a decrease in microbial activities that contribute to soil enrichment and carbon processing, ultimately diminishing soil fertility.
The effects of ozone on individual plants can have negative consequences for entire ecosystems. For example, ozone can cause changes to the specific assortment of plants present in a forest, habitat quality, and water and nutrient cycles.
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Particulate matter can cause mechanical harm to plants
Furthermore, particulate matter can enter the stomata and interfere with the biochemistry of plant metabolism. This can disrupt the plant's ability to photosynthesize, affecting its growth and survival. The accumulation of particles on leaves can also cause chemical injuries or lesions, especially when the deposited dust reacts with water from the environment. For example, alkaline dust becomes toxic to plants when it comes into contact with water.
In addition to the direct effects on leaves, particulate matter can also settle on the soil, altering its chemistry and pH to levels that are detrimental to plant growth. For instance, alkaline dust can increase soil pH, affecting the ability of plants to utilize nutrients effectively. These changes in soil conditions can have a significant impact on the growth of crops, as they typically consist of a single plant species (monoculture) cultivated over a large area.
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Soil pollution can change soil chemistry and pH
For example, alkaline dust, which is a type of particulate matter, increases soil pH and changes its chemistry. This affects the ability of plants to utilize nutrients. Such profound changes in the environment can affect the growth of entire crops, as they usually consist of one type of plant grown over a large surface area.
Similarly, acid rain, which is formed when sulphur dioxide and/or nitrogen oxides react with water, oxygen, and other chemicals in the atmosphere, damages the soil and indirectly harms plants by dissolving and washing away the nutrients and minerals they need. Acid rain can also impair the efficiency of nutrient and water uptake by plants, changing the chemistry of soils and mobilizing metals like toxic aluminium, which affects plant metabolism.
Soil pollution can also come from direct sources such as oil spills, landfills, pesticides, or illegal dumping of toxic chemicals. These harmful substances often accumulate in the soil, changing its chemical properties and the availability of other elements, which damages plant cells and prevents them from obtaining the nutrients necessary for growth.
Soil pollution, by altering the chemistry and pH of the soil, can have far-reaching consequences for plant health and crop productivity.
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Water pollution can cause an excess of nutrients in water
The growth of aquatic plants and algae is also influenced by the increased supply of nutrients, particularly nitrogen and phosphorus. While these nutrients are essential for crop growth, their excess availability in water bodies can lead to eutrophication, a process where a water body becomes abundant in aquatic plants and depleted in oxygen. As aquatic plants die, they serve as a food source for microorganisms, further reducing the oxygen levels in the water. This can ultimately suffocate fish and other aquatic life, negatively impacting the ecosystem.
Furthermore, high levels of nitrates in water, resulting from the mismanagement of manure or nitrogen fertilisers, can have toxic effects on both livestock and humans. Nitrate poisoning can occur in animals and methemoglobinemia, or blue-baby syndrome, in human infants and other warm-blooded animals. Nitrates interfere with oxygen uptake in the circulatory system, posing significant health risks.
Water pollution, including excess nutrients, can also impact crops directly. High soluble salt levels in water can damage roots, interfering with water and nutrient uptake. This, in turn, affects crop growth and yield. Additionally, water with high alkalinity can adversely affect the pH of the growing medium, disrupting nutrient uptake and causing nutrient deficiencies that compromise plant health and aesthetics.
Overall, water pollution causing an excess of nutrients in water can have far-reaching consequences, affecting both aquatic ecosystems and agricultural crops. Proper management of fertilisers and manure is essential to mitigate these negative impacts and ensure the health and productivity of both natural environments and agricultural systems.
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Frequently asked questions
Pollution can affect crop growth in several ways, including direct and indirect effects. Direct effects include toxins such as ozone and nitrogen oxides harming plants by depositing on them directly from the air and affecting their leaf metabolism and uptake of carbon, which they need to build their bodies and get energy to live. Indirect effects happen via the soil and start at the roots. Some air pollutants, like heavy metals from industrial activities, fall on the ground and change soil chemistry and pH, which in turn affects plants' ability to obtain enough nutrients to thrive.
Some of the recognizable signs of pollution damage on crops include leaf damage (yellowing, falling leaves or injuries), poor growth, root damage, and inability to photosynthesize properly, which results in stunted growth and diminishing productivity.
Air pollution comes from many sources, including smokestacks from factories, burning of fossil fuels for energy, emissions from transport, agriculture (livestock), and fumes from paints, varnish, VOCs, or during the solid waste management such as waste incineration or gas leakage from landfills.
Nitrogen oxides, which are found in car exhaust and industrial emissions, can directly damage crop cells and also affect them indirectly through their role as precursors to the formation of ozone, an airborne toxin known to reduce crop yields.
Air pollution can have significant economic impacts on crop growth and productivity. For example, in India, air pollution is cutting yields of wheat and rice crops in half, resulting in losses worth around $5 billion per year.
