Acid rain with a pH of 1.0 and lower affects seed germination by delaying the germination process. Some seeds are more resistant to the effect of acid rain than others.
Acid rain is harmful to plants through all stages of growth. The germination rate, germination velocity, root length and many other measures of growth are negatively affected by acid rain. Acid rain increases the amount of toxins in the soil and the surrounding atmosphere. Free lead, aluminum, copper and other toxic metals are more prevalent in the soil with the presence of acid rain. Acid rain also lowers the pH balance of soil, which affects the population of microorganisms that break down organic material. Since this process is necessary for releasing nutrients into the soil, it results in fewer nutrients for the plant to grow. Additionally, acid rain causes damage to the protective waxy coating on leaves. When the protective coating is damaged, valuable moisture is lost. Acid takes the place of some of the water in the plant, damaging the ability of the plant to photosynthesize efficiently. The damage to the waxy coating on the leaves of the plant caused by acid rain also makes a plant more susceptible to cold weather.