Under the Trafalgar Square Christmas tree

Trafalgar Square - Christmas Tree and Fountain (Image: MrT HK Flickr)

Trafalgar Square - Christmas Tree and Fountain (Image: MrT HK Flickr)

Tonight the crowds will gather in Trafalgar Square to see the lights on the world’s most famous Christmas tree switched on. But it’s the bits we can’t see that make the Norway Spruce ( Picea abies ) so magnificent.

CT scanning - X-Ray Computed Tomography (X-Ray CT) - is an imaging technique originally developed by Sir Godfrey Hounsfield for medical application. Plant and soil scientists at the University of Nottingham have branched out into other applications for non-destructive CT scanning - the study of soil and plants, including the Norway spruce!

Without removing the sapling from its pot they have revealed how the roots of a Norway Spruce slowly develop over two years of its early life - the Christmas baubles are seasonal extras!

These images were created by scientists in the Schools of Biosciences and Computer Science. They have designed a unique laboratory - the Hounsfield Facility - equipped with a range of CT scanners and computer technology that allows them to peer deep into the world of soil and roots and watch plants as they grow.

The ‘Hidden Half’ of plants

Their ’ Hidden Half ’ website gets to the root of what goes on below the surface as plants grow and develop.

The Norway Spruce, an annual gift from city of Oslo to the people of Britain, stands around 20 metres high and has taken between 50 and 60 years to reach its prime. At 45 cm tall the Nottingham sapling has a long way to go!

Sacha Mooney , Director of the Hounsfield Facility, said: “The big advantage of the X-ray CT approach is that it is non-invasive, so we can reveal exactly how roots and shoots develop over time to form recognisable shapes such as the Norway spruce. At the Hounsfield Facility, we have several X-Ray CT scanners capable of scanning plants over a range of growth stages and under different environmental conditions as revealed in the video clip.”

Malcolm Bennett , Professor of Plant Sciences in the School of Biosciences , said: “The X-ray scanning equipment allows us to understand how roots grow in the soil and identify specific features of crop roots - such as root depth, thickness, angle and numbers of root branches - that all help plants to efficiently forage for water or nutrients in the soil. In the forest, Norway spruce trees also form a mutually beneficial relationship with a special type of soil fungi, creating an even bigger root system to help forage for nutrients further from the main tree.”

The Norway Spruce

The Norway Spruce, is a conifer best known as a Christmas tree. It is native to most of Europe and up to the Arctic where it can survive in freezing temperatures. The thin needle leaves of the spruce are adapted to reduce water loss. As well as being an important part of Christmas, this tree has also contributed to science as it was the first non-flowering tree to have its genome sequenced.

The Hounsfield Facility

You can see more extra-ordinary images of other plants and trees on the ‘ Hidden Half ’ website. All the plant root systems on this website have been imaged at the Hounsfield Facility. These X-ray CT images showcase for the first time the beauty, diversity and complexity of plant root systems in their undisturbed soil environment.

Nottingham’s plant and soil scientists will continue to add species to this site as they scan them to highlight the amazing variety in root architecture across the plant kingdom. You can also follow them on twitter: @UoNHiddenHalf

And if you want to know more about Christmas trees and their links with the dinosaurs - check out Dr Susannah Lydon’s blog on the Guardian website. Susie is a palaeobotanist in the School of Biosciences at the University of Nottingham - @susieoftraken