By Jody Bourton
Earth News reporter
English ivy reaches out
English ivy can climb up almost anything, from the trunks of enormous trees to the smooth walls of houses.
Now scientists have found out exactly how the plant does it.
Rather than simply using a glue-like substance to attach itself to vertical surfaces, ivy uses a complex, energy-efficient system to anchor itself onto house fronts, tree bark and rocks.
Details of the discovery are published in the Journal of the Royal Society Interface.
"Formerly it was believed that English ivy just glues itself with its roots onto substrates and that was the whole story," says PhD student Bjorn Melzer who undertook the study as a member of the plant biomechanics group at the University of Freiburg, Freiburg, Germany.
The researchers, from the University of Freiburg and the Karlsruhe Institute for Technology, Germany, used new imaging techniques to analyse the attachment process of English ivy in detail for the first time.
They found the plant uses a more complex system, climbing in multiple phases.
First, the plant makes initial contact with the object it will climb.
This then triggers the second phase, when the plant's roots change shape to fit the surface of the structure they will climb.
The roots alter their arrangement to increase their area of contact with the wall.
Small structures called root hairs grow out from the root, coming into contact with the climbing surface.
The plant then excretes a glue to anchor it to the substrate.
Finally, the tiny root hairs fit into tiny cavities within the climbing surface.
There, they dry out, scrunching into a spiral-shape that locks the root hair into place.
The ivy's attachment is further strengthened by hook-like structures that grow on the tips of the root hairs.
Diagram of a fresh root hair and drying root hair in climbing surface cavity.
"Because the hairs are fixed on both ends the shortening process pulls the root a bit further towards the climbing surface and fastens the connection," Mr Melzer explains.
"This attachment system also works if the plant is dead," he says.
"Therefore it makes no sense to cut ivy, wait for a while and then pull it off your house front, the plaster will still be ruined."
The team used an environmental scanning electron microscope (ESEM) to observe how live root hairs shortened into a spiral as they dried.
"Our study is the first which had a look at the complete form, structure, and functional relationship of the English ivy attachment process," Mr Melze told the BBC.
"The plant actually uses a quite complex and energy-efficient system to anchor itself."
"There are many more plant attachment systems to understand and there are many more details to be worked out in the plants we are already studying."