X-ray photoelectron spectroscopy surface analysis of fluoride stress in tea (Camellia sinensis (L.) O. Kuntze) leaves

• Hydroponics and XPS were applied to study.
• Chemical form of fluoride in abaxial and adaxial surfaces was identified.
• AlF3 and trace amounts of MgF2 or CaF2 existed in the adaxial surface, only MgF2 for the abaxial surface.
• Tea leaf surface changes under F treatment were analyzed.

X-ray photoelectron spectroscopy (XPS) was applied to analyze the chemical form of fluoride and tea leaf surface changes. It was found that the leaf surface was mainly composed of C and O with some Si, N, and Al, besides a small amount of P and Ca in the adaxial surface. There was a tendency that Al was transferred from the abaxial surface to the adaxial surface with fluoride treatment. Under fluoride treatment, the content of C increased and O decreased in abaxial surface, while the opposite performance occurred in the adaxial surface. Meanwhile, the content of N of both the adaxial and abaxial surfaces decreased, suggesting a decreased nitrogen-fixation capacity. The results showed that fluoride treatment made cuticle thinner, and cutinized layer thicker and more active with a higher organic acid concentration for the adaxial surface, while both cuticle and cutinized layer got thicker and less active with a lower organic acid concentration for the abaxial surface. The content of protein decreased with fluoride treatment, causing tea leaf surface moisture loss. The ratio of O2/O1 was greater than 1 for untreated leaves, and the ratio dropped under treatment. AlF3 and trace amounts of MgF2 or CaF2 existed in the adaxial surface, however, only MgF2 for the abaxial surface.

X-ray photoelectron spectroscopy (XPS) and hydroponic experiments were applied to analyze the chemical form of fluoride and tea leaf surface changes. And fluoride species present in tea leaves was identified.Figure optionsDownload as PowerPoint slide