Physiological effects of arsenate on transplant thalli of the lichen Pyxine cocoes (Sw.) Nyl

Introduction

The changes in photosynthetic pigments, chlorophyll fluorescence, protein content, and antioxidant enzymes were investigated in a foliose lichen Pyxine cocoes, which was subjected to increasing concentrations of arsenate.

Methods

The arsenate concentrations of 10, 25, 50, 75, 100, and 200???M were sprayed every alternate day on the lichen thallus. The thalli were then harvested on 10, 20, 30, and 45?days.

Results

The quantity of photosynthetic pigments exhibited a decreasing trend till 20?days but increased from 30?days onwards. Concomitantly, chlorophyll fluorescence also showed a decreasing trend with increasing arsenic treatment duration as well as concentration. The higher concentration of arsenate was found to be deleterious to the photosynthesis of lichen as the chlorophyll fluorescence and the amount of pigments decreased significantly. The protein content of lichen increased uninterruptedly as the concentration of arsenate as well as duration of treatment increased. The activities of superoxide dismutase and ascorbate peroxide increased initially at lower concentration of arsenate but declined at higher concentrations and longer duration of treatment.

Conclusions

The catalase activity was found to be most susceptible to arsenate stress as its activity started declining from very beginning of the experiment. P. cocoes also proved to be an excellent accumulator of arsenate whose concentration increased in the thallus corresponding to its increase in the treatment and duration. Thus, it can be utilized for active biomonitoring of arsenic pollution.