Trees bleed ... metal?

Heavy metals like nickel and zinc are not what plants want to grow next to in high concentrations.

But a group of specialized plants, called hyperaccumulator plants , have evolved to absorb common toxic metals into stems, leaves and even seeds.

Researchers have been specifically investigating Pycnandra acuminate - a plant that grows on the island of New Caledonia in the southern Pacific Ocean.

They thought it might use nickel to defend against insects.

The sap is unusually green-blue because it contains up to 25% of nickel.

Dr. Antony van der Ent, a researcher at the University of Queensland studying this plant, said: 'Pycnandra acuminate is a rare and large tropical rainforest species (up to 20m high), restricted to the remaining tropical rainforest in New Caledonia. As an experimental object, it is quite difficult because this plant grows very slowly, and it takes several decades to flower and seed. It is threatened by deforestation due to mining operations and rapid fire fires'.

New Caledonia soil is mined because of the valuable nickel.

The unusual nickel love of this plant was first discovered in the 1970s, and the study of other super-accumulating plants has increased since then.

The particle of Alyssum murale, another super-accumulating plant, recorded by X-ray fluorescence. Nickel is shown in blue - (Photo by Antony van der Ent).

Look inside

How can you know what's going on inside these trees?

Pycnandra and other super-accumulating plants were analyzed at DESY National Research Center in Hamburg using X-ray techniques.

Dr. Kathryn Spiers, who also studied Pycnandra, explained: 'If you use a normal microscope, you can see the textures, but can't say what it is made of.'

Dr. Spiers used a technique that allowed to capture images and rotate the sample very quickly before it was destroyed by X-radiation.

'At the accelerator, the light source is very bright and the detectors are very fast, meaning you can scan it before you kill your sample. You see the samples; You really burned a hole through them. '

Researchers can then assemble a full picture of the plant experiment, with its various tangible element components.

Phyllanthus balgooyi plant of Borneo has nickel-rich green plastic - (Photo by Antony van der Ent).

Future uses

Researchers are still investigating exactly why these particular plants evolved in this way to cope in such harsh areas. But it is likely not because of human intervention into the environment.

Dr. van der Ent said: 'The evolution of the supercapacity plant group has occurred many times in very different lines, and is likely to take several million years. These plants were originally found in rich metal areas'.

However, some scientists hope that supercharged plants can be used to 'clean' the soil in areas where there is a buildup of toxic materials by human activity.

Other potential applications include phytomining - growing super-concentrated plants on nutrient-poor soil but rich in metals to extract the elements they absorb.