The Effect of Composition of the Atmosphere and Duration of Exposure on Brown Stain of Lettuce1,2

The severity of brown stain on crisphead lettuce ( Lactuca sativa L., cvs. Calmar and Great Lakes 118) held at 0° or 2.5°C for 10 days increased with increasing CO 2 (1 to 5%) and decreasing O 2 (21 to 1%) levels. Very slight or no brown stain developed on lettuce subjected to 0, 1, or 2% CO 2 in combination with 10 or 21% O 2 for 10 days or on that held in 2.5 or 5% CO 2 + 2% O 2 for 4 days at 2.5°C. In 2.5 or 5% CO 2 + 2% O 2 , brown stain intensified with duration of exposure (2 to 30 days) at 0° or 2.5°C.