Acid rain and other acid precipitation forms when polluted air mixes with rain, snow and fog. It's destructive to buildings and monuments made of limestone and marble, it's devastating to sea life and it's not that good for animal or plant health either. Acid rain effects on plants, be they farmland crops or old growth forests, are a hard-to-ignore warning that the chemical and fuel industries need to clean up their acts.
Delayed Seed Germination
John H. Reynolds and Jeff D. Wolt investigated the effects of simulated acid rain on various stages of the life cycle of cool-season forage grasses. Their 10-day exposure of seeds to the simulated acid precipitation resulted inhibited radicle elongation and delayed seed germination, which effects increased with increasing acidity. (The radicle is the first part of the embryo to emerge from the seed; it develops into a main root.)
Toxins in the Environment
Increased acid rain leads to increased toxins in the atmosphere and the soil. Free lead, zinc, copper, chromium and aluminum become plentiful. These toxic metals in the air, soil and water result in stunted plant growth as well as reduced populations of nitrogen-fixing bacteria.
Denied Plant Nutrients
Acid rain can lead to plants losing access to essential nutrients. Sulfates and hydrogen sulfates in acid precipitation can leach calcium and magnesium out of the soil. The lowered pH can reduce populations of those microorganisms whose ability to break down decaying organic matter puts the necessary nutrients back into the soil.
Damage to Plant Tissue
Acid rain falling on living plants is destructive to their leaves. Specifically, the waxy protective coating on each leaf becomes damaged, allowing water to escape and acid to get in. The acid in the plant's system displaces the water, prevents carbon dioxide intake and retards or even disrupts photosynthesis.
Damaged leaves also don't do a good job of withstanding the cold, making trees more likely to die in the winter.
What Can Be Done
The National Acid Precipitation Assessment Program (NAPAP) has sponsored studies on the formation of acid rain, along with its effects on lakes, crops and forests. The Program is studying various strategies to combat acid rain, such as limiting emissions from power plants and automobiles and enacting legal regulations on the production of air pollution.