Royal Institution Christmas Lectures 2009: The 300-Million-Year War

In this years Royal Institution Christmas Lectures ecologist Professor Sue Hartley - only the fourth woman to present the lectures since they began in 1825 - shows how the epic 300-million-year war between plants and animals has shaped us and the world we live in. Plants may seem harmless, but Professor Hartley reveals that the opposite is the case: they've had to develop terrifying and devious ways to defend themselves and attack their plant and animal enemies. Vicious poisons, lethal materials and even cunning forms of communicating with unlikely allies are just some of the weapons in their armoury that have seen off everything from dinosaurs to caterpillars. And Professor Hartley demonstrates how humans have turned plants into food, medicines and drugs and reveals what is likely to happen next in the epic struggle between plants and animals. In this first lecture Professor Hartley reveals how, despite animals attempts to destroy plants by eating them, plants are winning the war.

Ecologist Professor Sue Hartley continues to show how the epic 300-million-year war between plants and animals has shaped us and the world we live in. The life of a herbivore is not a happy one. For a start, plants are the wrong sort of food for animals: they are low in essential nutrients and getting any of those nutrients in the face of flora defences is even harder. In this programme, Professor Hartley reveals the many different ways plant-eating animals, from sloths to aphids, have evolved to overcome these problems. Herbivores use all sorts of tricks: they employ "friendly" bacteria in their gut to extract as many nutrients as possible from indigestible plants. They also have continuously growing teeth to grind down tough plants like grasses. Professor Hartley also reveals some of the many ways herbivores cope with plant poisons, and that some herbivores even steal plants' poisons to use in their own defence against their predators

Can a plant, something without a mouth, ears or eyes, communicate? Yes! Plants do communicate but not in ways that are obvious to humans. Instead of barking or shrieking when they are attacked, they release chemical ‘signals' into the air which can be detected by other plants. But these physical and chemical defences cost energy that could be used to grow instead of being used for protection. Do they protect themselves, or grow?

Lunch anyone? Human agriculture has usually tried to disarm plant defences and increase plant nutrient content. Our domestic varieties of wheat and cabbage now look, and taste, very different to their wild relatives. White carrots anyone? We cook, cure, freeze and otherwise process plants until they become edible and more nutritious. We grow them to epic proportions. And now, using the latest scientific research, we have the opportunity to grow them more efficiently and perhaps more healthily using genetic modification.

With changing climate it is difficult to predict who will win the 300 million year war. What has gone wrong when herbivores get the upper hand and strip plants bare? The battle ground is changing such that different conditions could favour either the plants or the herbivores. When the balance is broken we could have an ‘outbreak’, which is a situation where one side of the war gets an unfair advantage and grows unchecked. Will climate change compromise the abilities of plants, including our crops, to defend themselves?