Evidence for the Rapid Phytotoxicity and Environmental Stress Evaluation Using the PAM Fluorometric Method: Importance and Future Application

Abstract

Modulated fluorometry has opened new possibilities for the interpretation of photosynthetic parameters concerning the physiological state of plants. By exposing plant to continuous actinic light and to pulses of saturating light, it is possible to calculate from the Kautsky fluorescence transient four important values: ΦM, the maximum quantum yield as a measure of the maximum photosystem II (PSII) photochemistry; Φ′M, the steady state quantum yield as a real PSII photochemistry at the equilibrium state of electron transport; QP, the photochemical quenching as a measure of light-energy dissipation via photosynthetic electron transport; and QN, the non-photochemical quenching as a measure of dissipation of the absorbed light energy via non-photochemical processes. The change of these PAM-fluorescence parameters is related to the physiological state of the plant and therefore they can be used as reliable indicators of different environmental stress effects. However, these parameters have never been seen as useful standard tools for toxicological monitoring of ecosystems. Highly sensitive modulated fluorometers are today available which allow to measure the fluorescence parameters either in the lab or in the field. In this report we evaluate the use of these parameters in assessing the rapid environmental impact of mercury toxicity on Selenastrum capricornutum and of temperature stress on tomato plants. In interpreting our results, we suggest the utility of some of these parameters as technologically advanced tools in future bioassays.