Speaker: Charles Stirton
When the booked speaker who was to talk about Harvest Mice failed to arrive, Charles Stirton, founding director of The National Botanical Garden of Wales, kindly stepped in and told us about his work with plants and the teaching of Botany. He explained how botanists use all their senses to understand plants, how they grow, and why. In the Kirstenbosch Botanical Gardens, Mutaru, he had a strip cut in the meadow and asked the students to walk through it and record what they saw. He then asked them to walk again and write down what didn’t move. The list was completely different. He told us how he could stand with the students under a tree and study the bark for an hour to discuss various aspects, for example why it was green on one side.
We were shown how different sizes and structures of leaves provide plants with what they require in the absorption of water and sunlight and protection from predators. He gave a few examples. Some leaves are purple and contain a chemical that protects the plant from attacks, broad leaves follow the light during the day, others have needles that can deter caterpillars or even impale them. Bright flowers are full of toxins so animals won’t eat them. If a tree is attacked it will send out pheromones to other trees through mycorrhizal networks. The warning prompts trees to produce chemicals poisonous to the predator, thus protecting themselves.
He pointed out how all animals are dependent on plants. Plants will adapt through evolution but require differing bacteria in the soil to thrive. There are so many bacteria in any small amount of soil that many of them don’t have a name.
The evening was concluded with Alan Feest leading a discussion on the difficulties of defining bio-diversity. After a shaky start it was a fruitful evening.
Steve Harper
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