Boxplot of M-values in response to heat stress. Q1 (−0.392) and Q3 (0.432) represented the lower quartile and the upper quartile, respectively. The interval equaled 1.5× the interquartile range (IQR). The upper fence lay at Q3 + 1.5×IQR (1.668), while the lower fence lay at Q1-1.5×IQR (−1.628). The outliers represented observations that fell beyond the upper and lower fences.