Photosynthesizing while hyperaccumulating nickel: insights into the genus Odontarrhena

Title : Photosynthesizing while hyperaccumulating nickel: insights into the genus Odontarrhena

Abstract:

Nickel (Ni)-induced changes in photosynthetic activity in edaphically contrasting species of Odontarrhena were investigated. Two Ni-hyperaccumulators (O. chalcidica and O. moravensis) and one non-accumulator (O. muralis) were grown in hydroponics and exposed to NiSO₄ treatments (0.250 and 1 mM) for one week. Nickel effects on growth, root and shoot Ni accumulation and several photosynthetic parameters, through gas exchange and chlorophyll fluorescence analyses, were measured. The Ni-hyperaccumulators accessions showed a more efficient photosynthesis under Ni excess in respect to the non-accumulating species, at both the metal concentrations used in the case of O. chalcidica and at the lowest one in O. moravensis. Unexpectedly, Ni treatments in O. chalcidica increased not only the photochemical efficiency of PSII and the CO₂ assimilation rate, but also the stomatal conductance. Moreover, the changes in the concentration of photosynthetic pigments was species-dependent in the two hyperaccumulators in response to the different Ni treatments. The increased efficiency in photosynthetic activity under high Ni levels was more striking in O. chalcidica, that also displayed the highest Ni tolerance and accumulation in respect of O. moravensis. Odontarrhena muralis showed reduced growth in the presence of Ni with the lowest levels of the metal in roots and shoots, thus underlining its higher sensitivity to this element; in the same condition, the decrease in the photosynthetic performance, already at the lower concentration used, was due to a combination of both stomatal and non-stomatal factors.

Our data represent the first report on the Ni effects on photosynthetic activity in Ni-hyperaccumulating plants. An unexpected positive effect of the metal excess on the photosynthetic performance was found in O. chalcidica and, to a lower extent, in O. moravensis. Therefore, beyond the already known Ni functions in plant nutrition, new research possibilities could be opened concerning the role of the metal in the photosynthetic machinery of hyperaccumulators.

Biography:

Ilaria Colzi obtained a second level degree in Environmental Biology in 2008 and a European PhD in “Biosystematics and Plant Ecology” in 2012 at University of Florence, Italy. Between 2012 and 20218 she continued her research activity as research fellow at Department of Biology and DISPAA at University of Florence, and as post-doc fellow at London Institute for Mathematical Sciences. From 2018 she is a Temporary Researcher at the Department of Biology, University of Florence and she is lecturer of the course “Applied Plant Physiology” for the Master degree in Biology. She is author of 31 publications in referred international journals.