Slippery plant solution*

A few years back I was talking to Angela Catterns on the 702 Weekday Breakfast Show about a new edition of Wildsolutions, a great little book by Andrew Beattie, Paul Ehrlich and Chris Turnbill. One of the fascinating stories in this book was about the, now trademarked, ‘Lotus Effect’.

Water doesn’t adhere to most leaf surfaces – generally it forms drops that roll off the leaf and hopefully onto the ground for the roots to take up – but some leaves are slipperier than others.

Even honey and glue won’t stick to a Lotus (Nelumbo) leaf. When a drop of water rolls around the leaf it picks up dirt and fungal spores and effectively cleans the leaf surface. So a Lotus leaf is always dry and clean.

Researchers in recent years have found that at a microscopic level, the leaf surface is covered in tiny irregular bumps topped by tinier spikes pointing upwards. Water drops only touch the top of the spikes and like a beach ball at the cricket seem to float over the surface.

Dew drops can condense on the leaves at night but a gentle vibration, such a morning gust of wind, causes the water to spring off the surface and roll off (tested by applying a lotus leaf to the woofer on a stereo speaker).

“Anti-dew superhydrophobicity” is now all the rage in physics and popular for self-cleaning glasses, water repellant paints and faster boats. It’s been suggested that one per cent of fuel consumption world-wide could be saved by applying a coating to ships similar to that on a lotus leaf or another slippery plant surface, the water fern Salvinia.

There are applications in space. A NASA team is looking at a lotus solution to stop dirt sticking to spaceflight equipment and bacteria from growing inside space ships.

Back on Planet Earth, a lot has happened in the Royal Botanic Gardens in 4-5 years since I spoke with Angela. Then we couldn’t get lotus to grow in our pond. The trick was to plant more lotus than the water hens could nibble, and eventually it took off to produce the spectacular display you see today.

*This Passion for Plants posting will also appear on the ABC Sydney website (under 'Weekends' or search 'gardening'), and is the gist of my 702AM radio interview with Simon Marnie on Saturday morning, between 9-10 am.


Image: Lotus, doing their thing in Adelaide's Botanic Garden, in 2005