PhD project: Anne-Kristin Lenz

One effect of climate change is an increased frequency of extreme weather events. Hail, wind and heavy rain can cause considerable damage to plants, with devastating effects on agriculture, horticulture and forestry. However, not all plants (and growth stages) are affected equally. This project investigates the adaptations that allow plants to (1) avoid impacts, (2) dissipate impact energy or (3) utilize impacts to dislodge insects from their leaves. (4) Studying these adaptations in a broad range of plants will help to identify broadly valid key factors for impact resistance.

Using highspeed videography and 3D motion tracking to characterise the impact response of leaves in situ, in the Bristol Botanic Garden.

Physiological responses such as the touch-triggered leaf folding in Mimosa pudica (“Touch-Me-Not”) plants may provide a means to reduce the exposed area and avoid impacts. Adaptations of the leaf material properties and geometry may function to dissipate impact energy or result in spring-like properties that enable the plant to utilise the impact energy to dislodge insects or contaminating particles. For example, we are investigating the structural adaptations that enable a carnivorous Nepenthes pitcher plant to exploit the impacts of rain drops to capture insect prey. The roof-like ‘lid’ of the cup-shaped trapping leaf of this plant functions as rain-actuated spring that literally catapults sheltering insects from its underside into the deadly trap below. Understanding the properties underpinning the ‘lid spring’ or the remarkable impact resistance of some leaves may inspire novel approaches to energy harvesting from natural impact forces, or engineering solutions for improving the impact resistance of man-made buildings.

The spectacular lid trapping mechanism of Nepenthes gracilis can only be fully appreciated when viewed in super-slow motion (filmed here at 2,000 frames per second). In reality, it is over in the blink of an eye.