Abstract:The paper focuses on the question if purple anthocyanin (PA) shields the photosynthetic apparatus of eggplant (Solanum melongena L.) leaves against excess light. Light response curves of photosynthetic activity of green-speckled parts (GSP) or purple-speckled parts (PSP) of the same leaf were measured with a CIRAS-2 instrument. Chlorophyll fluorescence transients were measured by two chlorophyll fluorometers (PEA and Dual-PAM-100) after illuminating with mixed spectrum (white light) or homo-chrome (red, blue or green) light produced by light-emitting diodes (LEDs) on GSP or PSP. The PA, which is localized in the epidermal cells of the leaves, mainly screens out green and yellow light (between 500 and 600 nm) removing 53.2% to 73.6% of the light in this range. The maximum net photosynthetic rate (Pnmax) of the PSP was smaller than that of the GSP, which may be caused not only by the smaller chlorophyll-a-content but also by the screening of 27% of the blue light between 400 and 480 nm and 10% of red light between 630 and 700 nm by PA. Increasing the intensity of the white light from 0 to 3000 μmol photons·m-2·s-1 photosynthetically active radiation (PAR), the maximum quantum yield of primary photochemistry of photosystem (PS) II (Fv/Fm), the density of reaction centers (RCs) per excited cross section (RC/CS0) and the driving force on absorption basis of antenna chlorophyll in PSII (DFABS) declined gradually, whereas the minimum fluorescence (Fo), the relative variable fluorescence at the J-step (VJ) and the dissipated energy flux per RC (DI0/RC) increased gradually in GSP and PSP. However, the change in the size of the parameters mentioned above was smaller in PSP than in GSP, implying that the susceptibility to photoinhibition was lower in PSP. After the GSP or PSP of eggplant were irradiated for 30 min with white, red, blue or green light of 2000 μmol photons μm-2·s-1, the Fv/Fm declined, but the Fv/Fm of PSP was significantly higher than that of GSP only in the case of an irradiation with white or green light. In addition, the decrease in the amplitude of the P700 (photosystem I) redox transients was bigger than that of PSII chlorophyll a fluorescence transient curves after irradiation with white light of GSP and PSP. However, the effect was smaller in PSP. We suggest that the RCs of PSI and PSII were effectively shielded by PA in the epidermal cells of the leaves. It prevents an excess reduction of electron transport chain and alleviates the need for a strong energy dissipation. It maintained the coordination between PS I and PS II. So, it is concluded that the protective effect of PA with respect to the photosynthetic apparatus is due to a screening of light in the visible spectrum between 500 and 600 nm. In other words PA is part of the biophysical defense system of the leaf.