Effects of cadmium on the Amazonian tree species Virola surinamensis

Cadmium is a non-biodegradable and easily absorbed, translocated and accumulated element in plant tissues. This means that it is highly available to plant root systems and can be toxic even at low concentrations. Symptoms of cadmium toxicity include oxidative stress, inhibition of photosynthetic reactions and impaired root metabolism. Ever increasing cadmium levels are being detected in the environment from agricultural and industrial activities and have contributed to the degradation and contamination of soils, surface water and groundwater. In the Amazon, flooded ecosystems are constantly susceptible to contamination, as they are receptors for nutrients and organic and inorganic contaminants, including heavy metals. Identification of native Amazonian tree species with potential for phytoextraction and tolerance to cadmium could be used to direct studies and phytoremediation programs for the preservation of natural areas and recovery of environments contaminated by heavy metals.

(a) Leaves of the Amazonian tree Virola surinamensis. (b) Bioconcentration factor in young plants of V. surinamensis exposed to five concentrations of cadmium (0, 15, 30, 45, and 60 mg). ND = not detected. Different letters for concentrations of cadmium in solution indicate significant differences in the Kruskal Wallis test (P < 0.05). Mean ± SD, n = 7. Image credits: (a) Seuayan ravina via Wikimedia Commons; (b) Júnior et al.

In a recent study published in AoBP, Júnior et al. assess the physiological responses, phytoextraction and tolerance capacity of young Virola surinamensis plants subjected to varying cadmium concentrations. The authors measured a number of physiological processes and a tolerance index was determined to assess the plant ability to develop in the presence of cadmium. Leaf water potential, stomatal conductance and transpiration reduced in plants exposed to cadmium. Lower values of maximum photochemical efficiency of photosystem II, electron transport rate and photochemical quenching coefficient were accompanied by reduction of photosynthesis with increasing concentrations of cadmium. Despite negative impacts of cadmium on most measured physiological processes, the tolerance index indicated that V. surinamensis showed medium/high tolerance to cadmium suggesting that it may be promising for cadmium phytostabilisation purposes.

Researcher highlight

Waldemar Viana de Andrade Júnior holds a bachelor’s degree in Biological Sciences from the Federal University of Pará, Brazil (1996), Master’s degree in Biological Sciences (Tropical botany) from the Federal Rural University of Amazonia (UFRA), Brazil (2013). Currently Waldemar is PhD student in Forestry Sciences at UFRA, is a biologist at the Secretary of State for Environment and Sustainability (SEMAS) and is a Professor of the Secretary of State for Education (SEDUC-PA). He is part of the Study of the Biodiversity of Higher Plants Research Group.

Waldemar’s research focus is the ecophysiology of upper Amazon plants, with an emphasis on stress physiology and biochemistry. He is interested in identifying and understanding how Amazonian tree species adapt to water deficit and flooding, as well as plant responses to heavy metals, such as cadmium.

Further reading

Andrade Júnior, W. V., de Oliveira Neto, C. F., Santos Filho, B. G. dos, do Amarante, C. B., Cruz, E. D., Okumura, R. S., … Botelho, A. de S. (2019). Effect of cadmium on young plants of Virola surinamensis. AoB PLANTS, 11(3). https://doi.org/10.1093/aobpla/plz022