Ecophysiological responses of bryophytes and orchids to environmental pollution: an integrated approach

Environmental pollution is one of the largest threats to human societies. To deepen the relationships between plants and environmental pollution it is crucial to profit from plant biodiversity in the control and mitigation of environmental pollution whilst simultaneously preserving such biodiversity from the adverse effects of pollution. Plant–pollutant interactions are widely studied in the scientific literature. However, studies focusing on natural populations facing polluted environments are rare. In this scenario, mosses and orchids (the two groups discussed in the present thesis) are even less studied in their adaptive mechanisms for coping with environmental pollution. Mosses and orchids respectively belong to the Bryophyta (sensu lato) and Angiospermae taxa, the former being non-vascular cryptogams whilst the latter are vascular flowering plants. The two plants belong to phylogenetically distant groups (at the antipodes of the evolutionary path of land plants) and their ecophysiological relationships with environmental inorganic pollutants (i.e. heavy metals) and their survival strategies were studied herein. The two groups considered were found to occur naturally in environments featured by severe heavy metal pollution due to previous mining activity. The metallicolous populations of orchids and mosses were characterised by several morphometric, physiological and ecological parameters and then compared with unpolluted control populations. The studied metallicolous populations were found to be different from control populations due to the adaptive process that allowed the colonisation of such extreme environments. The observed differences between metallicolous and control populations are as follows: i) varying dimensions of adult individuals and seeds (orchids), ii) alterations in basal levels of metabolites and photosynthetic efficiency (mosses and orchids) and iii) differential early seed development. The present thesis also focused on the use of plants as biomonitors of environmental pollution. The reliability of the moss bag technique was evaluated by analysing accumulation values measured during an extensive biomonitoring campaign conducted in the vicinities of an oil refinery. Obtained results not only confirmed the reliability of the biomonitor species and the adopted biomonitoring technique but also provided evidence regarding the influence of several experiments and ecology-related factors on accumulation values. Both focal points of the present thesis (the study of naturally occurring metallicolous populations and the biomonitoring of environmental pollution) reveal that plants are extremely useful tools in the control of environmental pollution and the study of the biosphere–pollutant interaction at the individual and ecological levels.