Effect of MCP on lettuce russet spotting.A small amount of RS developed in the midribs of lettuce during incubation at 6 °C in the absence of ethylene (Fig. 2). Exposure to eth-ylene stimulated RS development, while MCP treatment before exposure to ethylene pre-vented the increase. Treatment with MCP also prevented an ethylene-induced increase in res-piration rate (data not shown).