Replicating how plants move

Recommendable! Fascinating!

"... the slow movement of a leaf as it turns towards the Sun, a plant might seem an unlikely choice given that such motion occurs at just a few microns per second. But plants can also act surprisingly quickly. They disperse seeds, for example, at tens of metres per second ...
Quite how plants make an array of movements over such varying timescales has long fascinated scientists. What’s more, lacking any of the muscles or joints found in animals, plants have to exploit other – often ingenious – methods to induce controlled, reliable motion. ...

The most striking example of a catapult is found on leptosporangiate ferns, which hold the spores on the underside of leaves in tiny spherical baskets, about 0.2 mm in diameter. Each basket, known as a “sporangium”, is ringed on one side by a series of cells arranged in a semi-circle. In summer, as the weather gets warmer and drier, water between the cells in this “annulus” starts to evaporate and it stretches out to form a straight arm, with the spores held at the tip. The arm then gets bent backwards, like a catapult primed for operation (figure 1).

At this point, so much energy is stored in the annulus that the pressure of the water falls below its vapour pressure, forming bubbles in the liquid. Known as cavitation, this process releases the stored energy and the arm swings back to its initial curved shape. ... discovered in 2012, this dramatic release of energy accelerates the seeds up to 105g, flinging them from their basket into the surrounding countryside at speeds of 10 m/s ...
A less-well-known carnivorous plant with interesting physics is the aquatic waterwheel (Aldrovanda vesiculosa). Native to Asia, Australia, Europe and Africa, it is an invasive, underwater plant that takes its name from the series of curved leaves arranged in a circle around the plant’s long, central stems. ...
Just like the Venus flytrap, the leaves have a set of trigger hairs on their surface, snapping the lobes together when an insect lands on them. And for this plant too, motion powered by hydraulics alone would not be fast enough for it to catch a meal. So to capture its prey ... the waterwheel uses the principle of “kinematic amplification”. This is where a small, controlled input motion in one part of a structure creates a larger displacement elsewhere. ...

Using an optical microscope, the upper and lower layers of cells in the Cape sundew leaf were found to have different shapes. The lower layer has elongated cells running down the length of the leaf, while the upper layer has more circular cells. When the plant is stimulated ... by an insect landing on its surface ..., the plant alters the internal pressure of its cells, which change size in response.

Much like a balloon, where the inflated shape depends a lot on its initial, deflated shape, the upper and lower cells respond differently to the pressure change, with the long cells on the bottom of the leaf extending much more than the rounder cells on the upper layer. This differential rate of growth changes the overall geometry of the leaf, which curls up around its prey like a forefinger on a hand beckoning inwards ..."

Replicating how plants move – Physics World Once studied by Charles Darwin, the Venus flytrap is perhaps the most famous plant that moves at high speed. ... researchers are still unearthing new scientific insights into plant motion, which could lead to novel, bio-inspired robotic structures