Common Duckweeds as a Model System for Climate Change Impact Assessment

Common duckweeds – Lemna – are free-floating aquatic macrophytes belonging to Lemnaceae family. They occur universally, in tropical and temperate zones and are enabled to grow in stagnant, slow-flowing, nutrient-enriched waters. They have an ability to grow over a wide range of temperatures (6 – 33 0C) and pH (optimum 5.5 – 7.5). Lemna species also manifest a characteristic macrophyte community in association with plants functioning as a dominant primary producer. Asexual mode of reproduction is exclusive and therefore, all resources are directed towards vegetative growth. Structure wise they show leaflets (frond) and root-like diffuse form. This simple morphological and physiological form offers special scientific and engineering properties – reflected in easy handling and manipulation under laboratory conditions. As a result they are regarded as a model plant system for a number of chemical and biogeochemical studies. Climate change affects plant growth and physiology. For example, increasing atmospheric concentrations of carbon dioxide (CO2) and ozone (O3) or increase in ultraviolet (UV) radiation (due to the thinning of the ozone layer) can have pronounced effects on the growth and development of plants. In many instances the decrease in growth rate can create disturbances in photosynthetic processes. In the recent past there has been a surge in the interest in looking for alternative remediation technologies to meet formidable demands of polluting materials and situations. One such approach is phytoremediation – the use of plants and associated microbes for environmental cleanup. Cardinal points in favour of such an approach are – cost-effectiveness, natural energy-driven and minimal capital and running costs. Potency of Lemna spp. as a phytoremediation agent as well as its limitations haven dealt with in details in literature. Moreover, Lemna spp. are accepted and highly standardized as test organisms in aquatic ecotoxicology. The authors have shown earlier that Lemna spp. can play a vital role in combating pollution burden in a glaring local situation of river pollution. However, the recent trend in research indicates that Lemna spp (duckweeds at large) can play a critical and sensitive role in being an indicator of overt and subtle climate change. The following is an attempt to take a review of such recent trends.