ON LOCATION WATER WORLDS

Peter Bassett takes us beneath the surface, filming the extraordinary plants that live in lakes, rivers and streams

- Peter Bassett

What’s this episode’s theme?

How plants survive in one of the most challenging locations on Earth: in and underwater. If you’re on land, you’re rooted to the spot and your environment doesn’t change. If you live in, say, a mountain stream with a torrent of water cascading past, that presents a huge strain. So, we look at how plants feed and carve out niches in different watery worlds.

What particularly impressive plant behaviour do you show?

We’re all familiar with the Venus flytrap, but it’s a far more sophisticated plant than we realise. People think you simply flick the trigger hairs and the plant clamps shut. Not so. We take Sir David to Kew Gardens, where he shows that if you flick the hairs once, nothing happens; but if you flick them again within 20 seconds, the plant reacts. This is because Venus flytrap mechanisms use a lot of energy and the plant must be aware of false alarms: one ‘touch’ might just be a drop of water, but two in succession is more likely to be prey.

There’s more. The trap doesn’t seal completely, so tiny creatures can escape, which is fine as they’re not worth eating. If bigger insects, which can’t escape, trigger the hairs five more times, the plant starts the process of digestion. It’s amazing – in a way, the plant is counting.

What rarely seen behaviour is there?