stem-length group 25.2 control 29.5 control 30.1 control 30.1 control 30.2 control 30.2 control 30.3 control 30.6 control 31.1 control 31.2 control 31.4 control 33.5 control 34.3 control 24.7 stress 25.7 stress 26.5 stress 27.0 stress 27.1 stress 27.2 stress 27.3 stress 27.7 stress 28.7 stress 28.9 stress 29.7 stress 30.0 stress 30.6 stress