Analysing cadmium uptake from root to shoot

Nilusha Ubeynarayana is undertaking research that could prove a game-changer for managing cadmium concentration in New Zealand soils.

The Sri Lankan PhD student, who began her research through Massey University in October 2017, says she is excited about the experiments she will be doing. She will use a range of advanced techniques, aimed at discovering how plants uptake cadmium from root to shoot.

Nilusha’s research builds on a recent PhD study by Aaron Stafford, which analysed the cadmium concentration of 12 forage species. This research showed that two popular supplementary feeds, chicory and plantain, accumulated significantly more cadmium than other forage species. These two plants are an important part of animal feed as they are a drought-tolerant, high nutrient food crop.

“The big question I’m seeking to answer is why chicory and plantain accumulate more cadmium,” says Nilusha.

Nilusha will commence her three-year project by analysing chemistry of the rhizosphere, the few millimetres of soil surrounding the plant roots that is influenced by the activity of soil microorganisms and plant roots. She will conduct experiments to study rhizosphere soil solution and root interaction. This will help her understand how this influences cadmium uptake of various forages when phosphate fertiliser has been applied on a long-term basis.

Nilusha plans to use advanced analytical techniques such as High-performance Liquid Chromatography and Cd Nuclear Magnetic Spectroscopy. This will provide valuable information on xylem sap ligands, which are involved in transporting cadmium in forage plants.

“An important part of my work will be developing a cadmium ion measuring electrode, because plant sap contains very low levels of cadmium concentration. This electrode will be able to measure very low levels of cadmium in plant saps.”

New Zealand soil is low in phosphorus, which is essential for plant growth. As a result, phosphorus fertiliser containing traces of cadmium is widely used on New Zealand farms.

“In New Zealand agricultural soils the cadmium concentration is more than double that of non-agricultural soil,” says Nilusha.

There are no indications for concern to human or animal health from the levels of contaminants currently in New Zealand soil. Nonetheless, phosphate fertiliser use must be actively managed and soils monitored to ensure that the risks from soil contaminants remain low over the long term.

“I’m really happy to be doing this work. If I can discover exactly how plants accumulate cadmium we will be able to develop remedies to stop high accumulation from happening.”

Nilusha’s research is funded by the Fertiliser Association of New Zealand and the Foundation of Arable Research. Her supervisors are Dr Paramsothy Jeyakumar (Jeya), Professor Chris Anderson, Dr Roberto Calvelo Pereira and Dr Peter Bishop.