Guy Padgett | 8/20/2011 12:23:37 AM
In this article:
Ozone is the most widespread air pollutant that damages plants, including soybeans. Ozone is generated fro the reaction of sunlight with nitrous oxides and oxygen in the presence of hydrocarbons. Such a mixture is commonly referred to as smog and arises primarily from automobile exhausts in urban areas. Most damage occurs when contaminated air stagnates over soybean fields.
Prolonged exposure may result in reduced growth and yields depending on the cultivar and the stage of plant growth. Damage is most severe when plants are growing under optimal conditions. Drought-stressed plants are resistant. Soybeans exposed over a long period (several days or more) to low ozone levels of 0.06 ppm or greater, although damage and symptom development vary depending on the cultivar.
Leaves are most sensistive during the later stages of leaf expansion and symptoms appear 48 hours or more after exposure. For this reason, symptoms are first observed on older leaves. Symptoms often referred to as leaf stippling or bronzing, include small cream to bronze colored lesions on upper leaf surfaces between the veins. Injured leaves may ultimately exhibit chlorosis and die prematurely.
Examination of local air-quality data in addition to symptom appearance will help confirm ozone injury.