Scanning Cadmium Photosynthetic Responses of Elephantopus mollis for Potential Phytoremediation Practices
2015
Silveira, Fernanda Schmidt | Azzolini, Marisa | Divan, Armando Molina, Jr
Photosynthetic process is a good approach to discriminate cadmium-tolerant species, because it is reported as one of the most sensitive processes. Our goal was to measure Elephantopus mollis Kunth (Asteraceae) tolerance, determining the interference of Cd on the photosynthetic process. For this, a hydroponic experiment design was conducted in nutrition solution with concentrations of 0 (control), 10, 50, and 100 μM of cadmium (Cd). Measures of photosynthesis performance were obtained, for example, gas exchange, photosystem integrity, chlorophyll content, leaf growth rate, root length, and dry weight. In addition, cadmium and zinc concentrations were measured. Furthermore, results were linked to phytoremediation potential. Our specific questions were as follows: (1) Can the photosynthetic apparatus of E. mollis deal with cadmium stress? (2) Is E. mollis able to accumulate cadmium and maintain zinc level? (3) Is E. mollis a tolerant or sensitive species? (4) Can any phytoremediation practice be suggested from these results? Our results showed that E. mollis can deal with cadmium toxicity up to 10 μM Cd. Moreover, this plant is a potential hyperaccumulator, which can accumulate 248 mg Cd kg⁻¹ dry weight. However, at concentrations of 50 and 100 μM Cd, this species was sensitive and cadmium toxicity affected both biochemistry and photochemistry phases of photosynthesis on account of negative changes on gas exchange, fluorescence chlorophyll, and chlorophyll content. Nevertheless, these results did not compromise the research about its tolerance at lower concentrations of cadmium.
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