David read the following link it gives details on what you are talking about.

http://cropwatch.unl.edu/archive/-/asset_publisher/VHeSpfv0Agju/content/factors-influencing-cold-stress-in-corn-and-soybean?redirect=http%3A%2F%2Fcropwatch.unl.edu%2Farchive%3Fp_p_id%3D101_INSTANCE_VHeSpfv0Agju%26p_p_lifecycle%3D0%26p_p_state%3Dnormal%26p_p_mode%3Dview%26p_p_col_id%3Dcolumn-1%26p_p_col_count%3D2