Predatory plant is more sensitive than we thought, new UoG research reveals

A species of predatory plant that has captivated scientists for centuries is more sensitive than previously thought, new research by University of Gloucestershire has revealed.

The great 19^th century naturalist Charles Darwin – author of On the Origin of Species – was so fascinated by sundews (scientific name Drosera rotundifolia) that he once remarked: “At this present moment I care more about Drosera than the origin of all the species in the world.”

The carnivorous round-leaved sundew – a deadly cousin of the Venus flytrap – is renowned for capturing and digesting small insects that are attracted to the sticky, sugary substance on the hair-like tentacles on its leaves.

Once the helpless insect is trapped by the sticky substance, the leaf of the sundew curls up to engulf and digest its victim, which provides the plant with vital nutrients that aren’t always readily available in the bogs where it typically lives.

But a groundbreaking study by University of Gloucestershire’s Dr Chris Hatcher has cast fresh light on sundews’ sensitivity to their surroundings after finding that they modify their carnivorous traits in response to changes to their local environment.

Dr Hatcher and Dr Jonathan Millett (Loughborough University) studied how sundews responded to differences in sunlight and the availability of nitrogen through rainfall – both vital for plant life – by measuring the density of tentacles on their leaves and the proportion of nutrients derived from prey, noting that the balance of water through rainfall and evaporation alters where nutrients accumulate in bogs.

A key finding of the research is that sundews are more carnivorous in high-sunlight bog microhabitats that are not rich in nutrients.

Where rainfall is higher, nitrogen accumulates in low-lying hollows and therefore the sundews’ reliance on carnivory is reduced.

In areas where rainfall and evaporation are more balanced, sundews are theoretically able to gain nutrients through their roots across hollows and hummocks (raised areas) in equal measure.

But the study found that in these same conditions, sundews are in fact more carnivorous when they grow in hollows, with their leaves having 50% more sticky tentacles to capture their luckless prey. This is because hollows gain more sunlight than hummocks, which shade the sundews.

Dr Hatcher, from the University’s School of Education and Science, said: “The resilience and adaptability of sundews that we have discovered could be key to their survival in changing environmental conditions, which is a fantastic breakthrough for all admirers of this popular predatory plant.

“By exploring these adaptive patterns in rainfall and sunlight, we have demonstrated how carnivorous plants can persist in nutrient-poor environments by responding flexibly to local conditions.

“This adaptability might allow sundews to survive in specific microhabitats by eating more prey where it is most advantageous, which is an important discovery for understanding how species can survive in a changing environment.”