Effect of Heavy Metals on the Photophysical Properties of Planta Leaves

TELLERÍA, D.; LAGORIO, M.G.

La Serena

Congreso; X Encuentro Latinoamericano de Fotoquímica y Fotobiología; 2010

Universidad de Santiago de Chile

Copper is an essential micronutrient for higher plants but excess concentration of copper in the environment may induce significant toxic effects. In the present work, changes in photophysical properties of leaves exposed to copper were analyzed and compared to control ?non-stressed? leaves. Potus species was used in the study.   The maximum quantum yield of photosystem II (Fv/Fm), the quantum yield of photosystem II (FPSII), the proportion of open PSII (qP), and the non-photochemical quenching coefficient (qNP) were determined using a Pulse Amplitude Modulated fluorometer Hansatech FMS1. Results are summarized in table 1.   Fv/Fm FPSII qP qNP Copper stressed leaves 0.40 ± 0.15 0.12 ± 0.02 0.53 ± 0.11 0.34 ± 0.10 Control leaves 0.795 ± 0.004 0.50 ± 0.02 0.85 ± 0.09 0.64 ± 0.07 Table 1. Photosynthesis parameters obtained from variable Chlorophyll-a fluorescence.   Fluorescence spectra under low flux of light irradiation were also recorded using a PTI steady-state fluorometer. Values for the fluorescence ratio at 685 and 735 nm (F685/F735) are shown at table 2.   F685/F735 Copper stressed leaves 0.72 ± 0.11 Control leaves 0.51 ± 0.05 Table 2. Fluorescence ratio F685/F735 obtained from initial fluorescence spectra. The absorption and the scattering of light coefficients were determined from transmittance and reflectance values of single leaves (obtained with a spectrophotometer Shimadzu 3101 equipped with an integrating sphere) and using the Pile of Plates model. The absorption coefficient decreased in copper-stressed leaves showing a destruction of photosynthetic pigments. The scattering coefficient, on the other hand, remained almost unchanged.   It was shown that the most sensitive parameter in this work for copper toxicity was the quantum yield of PSII (FPSII).