Flipping on a light switch or starting your vehicle creates pollution that could indirectly harm or kill plants from your garden or yard. Some pollutants kill insects that benefit plants, but others reduce crop yields. Not all pollution effects are found with the naked eye however; some are disguised in the plant. Pollution harm to plants is common near cities but could occur anywhere.
Bees, butterflies and other beneficial insects spread pollen so plants may produce seeds and fruit. Air pollution harms plants since it masks the scent trails that lure pollinators to blossoms. Urban light pollution, from street lights and lights, draws night pollinators to the open, making them easy prey for bats. The more bats that eat night pollinators, the fewer pollinators you will find to pollinate plants, resulting in fewer plants. For example, if bats are eating additional sphinx moths (Eumorpha typhon), which pollinate evening primrose (Oenothera speciosa; U.S. Department of Agriculture plant hardiness zones 5 to 9), the outcome will be fewer night primrose plants since the plants wo not be able to reproduce.
Pollutants from lawnmower exhausts, in addition to discharge from coal-burning power plants, mix with sunlight to create ozone. This is highly poisonous to several plants. Ground-level ozone stunts development, reduces budding and lessens flowering in many species of trees in addition to edible and flowering plants when exposed over long periods. Young plants will be the most susceptible with old leaves affected first, followed by pathogens attacking the damaged location. Some plants susceptible to ozone damage are green beans (Phaseolus vulgaris); begonia (Begonia [Tuberosa Group]), hardy in USDA zones 9 through 11; white pine (Pinus strobus), hardy in USDA zones 3 through 8; and grapes (Vitis spp.) That develop year round in USDA zones 2 through 10. Cucumbers (Cucumis sativus) and white oak (Quercus alba), hardy in USDA zones 3 through 9, are immune to ozone pollution harm.
Exactly how much a plant is affect by pollution is dependent upon how close it is to the pollution source and the amount of pollution contacting the plant. Many pollutants only affect plants in the immediate area, but acid rain may travel hundreds of miles. It forms when sulfur dioxide, released from power plant stacks, and nitrogen oxides, from car exhaust, combine with components in the air. Ongoing exposure damages bud, turning it brown. Trees die from indirect effects of acid rain since it washes nutrients from the soil before the trees may take up them, leaving the tree with no adequate nutrition. Garden crops that are fertilized often aren’t affected by acid rain.
Not all plants harmed by indirect pollution show physical signs that something is wrong. Vegetable crops grown in soil contaminated with heavy metals, such as copper or lead, take the steel into their leaves and roots, but exhibit no indication of it. The Ohio State University claims a 2003 study from Northwestern University of 75 plants showed that 100 percent of root crops, and over 38 percent of herbs and leafy greens, contained lead when grown in soil contaminated with lead. Lead can occur naturally in soil, but a great deal of lead also gets to the soil from artificial substances. For example, when lead-based paint peels from buildings and falls upon the soil, rain leaches lead into the upper layer of this soil in which it might be taken plants. Eating vegetables contaminated with lead is harmful to humans.