Fig. 3.

Representative high performance liquid chromatography (HPLC)‐DAD chromatograms of different tissue layers of 3‐month‐old Phyllirea latifolia leaves newly developed in partial shading (25% full sunlight, a) or in full sunlight (b), showing large light‐induced changes in phenylpropanoid composition. While hydroxycinnamic acid (HCA) and apigenin (Api) derivatives mostly contribute to the phenylpropanoid pool in shaded leaves, quercetin (Que) and luteolin (Lut) derivatives largely represent the phenylpropanoids synthesized by full‐sun exposed leaves. Of note, HCAs accumulate poorly in the mostly light‐exposed adaxial epidermis in leaves exposed to the greatest UV‐B irradiance (b), despite their greatest ability to absorb solar UV‐B wavelengths. Longitudinal sections were cut with a cryo‐microtome following the protocols of Ålenius et al. (1995) and Tattini et al. (2015) from leaves sampled at midday. The quali‐ and quantitative analysis of phenylpropanoids were performed using the protocol of Tattini et al. (2015) and chromatograms (recorded at 350 nm) were normalized based on the fresh weight of different tissue layers.