Effects of cycloheximide on photosynthetic abilities, reflectance spectra and fluorescence emission spectra in Phyllostachys edulis

KEY MESSAGE : CHX had remarkable inhibition on P. edulis photosynthesis, and the reflectance indexes and F ₆₈₅ / F ₇₃₅ had the potential value for quantifying the effects of antibiotics on trees. To reveal the effects of antibiotics on photosynthesis and provide help for remote sensing the influence of antibiotics on trees, we investigated the effects of cycloheximide (CHX) on Phyllostachys edulis. In CHX treatment, the photosynthetic pigment content in P. edulis was decreased markedly, which led to the increase in the reflectance spectra in visible region. CHX reduced the donor side and acceptor side of photosystem II (PSII), density of reaction centers, quantum production and electron transport in PSII, and raised the dissipation of absorbed light energy. Besides the dissipation, the absorbed light energy can be emitted as fluorescence with two main peaks in the red (685 nm) and far-red (735 nm) region, respectively. In 0.50 mM CHX treatment, a significant decline in the height and area of the peak at 685 nm might result from Chl loss reducing the light absorption and lower photochemical reaction in PSII. When fourth derivative analysis of fluorescence emission spectra was performed, the changes of the peaks at 718, 735 and 750 nm might result from the decline of absorbed solar radiation caused by the reduced pigment content and/or the damages to the PSI. In CHX treatment, a remarkable increase in intercellular CO₂ concentrations and light compensation point and decrease in light saturation point demonstrated that the CO₂ assimilation ability was decreased. Those results suggested that the photosynthesis in trees can be reduced after they were watered with wastewater containing CHX. The reflectance indexes and F ₆₈₅/F ₇₃₅ (H ₆₈₅/H ₇₃₅ and A ₆₈₅/A ₇₃₅) were markedly affected by CHX, demonstrating that they had the potential value for quantifying the effects of antibiotics on trees.