Chronic toxicity of cadmium in Pteris vittata, a roadside fern.

: The effect of Cd at concentrations of 0.1, 1.0, 2.5, 5.0 and 10.0 ppm on Pteris vittata, a commonly occurring roadside fern was studied during the entire life cycle from spore germination to spore production. Light, fluorescence, scanning and transmission electron microscopy were used to study the structural changes due to Cd. With increasing Cd concentrations the following changes were observed: inhibition of first and second generation spores, abnormal development of protonema, disintegration of thylakoid organization, delayed formation of reproductive elements and abnormal sporangia. As the Cd content of the plants increased with increasing concentration in the medium, biomass-specific concentrations of chlorophyll and carotenoids decreased. The gametophytic phase was more sensitive than the sporophytic stage to Cd. The differences noticed during the three stages of development could be useful as markers for Cd contamination in the environment.