Distributions of PAR (a) and UV radiation (b) interceptions on the kales at different leaf orders in the control and UV-B treatments. PAR, photosynthetically active radiation in the range of 400–700 nm; UV, biological effective UV radiation in the range of 280–400 nm. The leaf order indicates the order from the oldest leaf at the bottom to the youngest leaf at the top in a whole plant. Based on kernel density estimation, the shape of the violin represents the frequencies of values. The boxes, horizontal lines, whiskers, and points indicate interquartile ranges, medians, 95% confidence intervals, and outliers, respectively.