Chlorophyll a fluorescence as indicator of atmospheric pollutant effects

Abstract

Chlorophyll a fluorescence is a measurement of the changes in photosystem II (PSII) activity. Damage to PSII will often be the first manifestation of atmospheric pollutant stress in a plant. When atmospheric pollutants are absorbed by a leaf, the induction curve of chlorophyll a fluorescence and its measured parameters show alterations that can be used to determine the PSII damage. Generally, under atmospheric pollutant stress, maximal PSII photochemical efficiency, the PSII-mediated electron flow and the capacity to reduce the quinone pool are decreased. The non-photochemical quenching (NPQ) constitutes an important protective response which could dissipate excitation energy in light-harvesting antenna systems. At the beginning of stress, increase in NPQ correlated with decrease in photosynthetic quantum conversion may be associated with several mechanisms in photoprotective process. On long-time pollutant exposure, the capacity to NPQ formation can be reduced because the protective mechanisms are exhausted. The changes in chlorophyll a fluorescence can be observed in the absence of visual injuries and constitute an important technique for evaluation and diagnosis of negative effects on photosynthesis.

Keywords:

• Chl fluorescence
• non-photochemical quenching
• ozone
• oxides of nitrogen
• photochemical quenching
• sulphur dioxide