Nav: Home

Plants are 'biting' back

May 19, 2016

Calcium phosphate is a widespread biomineral in the animal kingdom: Bones and teeth largely consist of this very tough mineral substance. Researchers from Bonn University could now for the first time demonstrate the presence of calcium phosphate as a structural biomineral in higher plants. The substance provides the necessary "bite" to the stinging hairs of representatives of the rock nettle family (Loasaceae). It hardens the trichomes, which serve as a herbivore defense. Conversely, our native stinging nettles have stinging hairs hardened by glass-like silica. The results of the study are now published in the journal Scientific Reports.

Animals only eat them once: When the tongue touches the minute trichomes of rock nettles (Loasaceae), the tips of the stinging hairs break off and a painful cocktail pours out into the sensitive tissue. These well-defended plants have their centre of diversity in the South American Andes. „The mechanism is very similar to that of our well-known stinging nettles", says Prof. Dr. Maximilian Weigend of the Nees-Institut for Biodiversity of Plants at Bonn University. There are additional differences between the only stinging nettles and rock nettles -- which are only distantly related -- apart from their different appearance: Native stinging nettles fortify their needle-like hairs with silica, while their spectacularly flowering South American counterparts employ calcium phosphate for that purpose.

Calcium phosphate has never previously been documented as a structural biomineral in higher plants. "The mineral composition of the stinging hairs is very smilar to that of human or animal teeth" says Prof. Weigend, who has been researching the highly diverse rock nettles for the past 25 years. Many scientists previously noted the strikingly rough hairs of this plant group, but nobody ended up researching their chemical composition. The botanists investigated the stinging hairs -- built like hypodermic syringes -- with their own electron microscope and in collaboration with colleagues from the Steinmann-Institute for Geology, Mineralogy and Paleontology and the Institute of Inorganic Chemistry of Bonn University.

Tips of the stinging hairs structurally similar to reinforced concrete

It could be shown that especially the mechanically highly stressed tips of the hairs are incrusted with calcium phosphate. „This is essentailly a composite material, structurally similar to reinforced concrete", explains Prof. Weigend. The fibrous cellulose as the typical material of plant cell walls provides the scaffolding and is densely incrusted with tiny crystals of calcium phosphate. The scientist of Bonn University is convinced „This renders the stinging hairs unusually rigid".

It is still unclear why rock nettles evolved this particular type of biomineralization, while most plants use silica or calcium carbonate as structural biominerals. „A common reason for any given solutions in evolution is that an organism possesses or lacks a particular metabolic pathway", says Prof. Weigend. However, rock nettles are able metabolize silica and use it as a structural biomineral -- side by side with calcium phosphate. It is not currently understood why it is particularly calcium phosphate that is used in the stinging hairs tips, the very substance that the mouthparts of their enemies also consist of. „At present we can only speculate about the adaptive reasons for this. But it seems that rock nettles pay back in kind - a tooth for a tooth" chuckles the biologist of Bonn University.

Bionics: plant trichomes as templates for bone substitutes

Additional research projects are directed towards investigating which other plants may use structural calcium phosphate to face challenges in their natural environment and which biomechanical advantages this material conveys to the plants. The discovery is also of potential relevance for bionic applications. „Surgical bone substitutes have to be highly tissue compatible, cellulose-composite are likely to meet that criterion", says Prof. Weigend. First attempts at producing artificial cellulose-calcium phosphate composite have been made by other researchers, but so far a natural template was unknown. The cellulose-calcium phosphate composite in rock nettles could be just such a template.
-end-
Publication: Hans-Jürgen Ensikat, Thorsten Geisler & Maximilian Weigend: A first report of hydroxylated apatite as structural biomineral in Loasaceae - plants' teeth against herbivoren, Scientific Reports, DOI: 10.1038/srep26073

Media contact:

Prof. Dr. Maximilian Weigend
Nees-Institut for Biodiversity of Plants
Bonn University
Tel. 49-0-228-732121
Email: mweigend@uni-bonn.de

University of Bonn

Related Plants Articles:

Transgenic plants against malaria
Scientists have discovered a gene that allows to double the production of artemisinin in the Artemisia annua plant.
How plants can tell friend from foe
The plant's immune system can recognize whether a piece of RNA is an invader or not based on whether the RNA has a threaded bead-like structure at the end, say University of Tokyo researchers.
Plants at the pump
Regular, unleaded or algae? That's a choice drivers could make at the pump one day.
How do people choose what plants to use?
There are about 400,000 species of plants in the world.
Defend or grow? These plants do both
From natural ecosystems to farmers' fields, plants face a dilemma of energy use: outgrow and outcompete their neighbors for light, or defend themselves against insects and disease.
How do plants protect themselves against sunburn?
To protect themselves against UV-B, which are highly harmful, plants have developed cellular tools to detect them and build biochemical defenses.
Pea plants demonstrate ability to 'gamble' -- a first in plants
An international team of scientists from Oxford University, UK, and Tel-Hai College, Israel, has shown that pea plants can demonstrate sensitivity to risk -- namely, that they can make adaptive choices that take into account environmental variance, an ability previously unknown outside the animal kingdom.
A 'Fitbit' for plants?
Knowing what physical traits a plant has is called phenotyping.
How plants conquered the land
Research at the University of Leeds has identified a key gene that assisted the transition of plants from water to the land around 500 million years ago.
Plants are 'biting' back
Calcium phosphate is a widespread biomineral in the animal kingdom: Bones and teeth largely consist of this very tough mineral substance.

Related Plants Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...