Environmental dependence of the metallicity, metallicity gradient and metallicity gradient residual (obtained by removing the best-fit linear relation between gradient and stellar mass) distributions. The gray shaded histograms represent the cluster subsample, and the open histograms represent the field subsample. The vertical black (gray) dashed line marks the median values of field (cluster) subsample. The value in the upper left corner corresponds to the p-value from the Kolmogorov-Smirnov tests conducted between galaxies in different environments.