I’ve always enjoyed the Systematic Beds at the Cambridge Botanic Gardens. Now they are in the process of being completely overhauled, not because of the drought this summer or because the plants need replacing, but because of DNA.
Cambridge University Botanic Garden is a listed heritage garden in the centre of Cambridge. It maintains the University’s study collection of living plants, which number 8,000 species, across 40 acres. It is the most visited university botanic garden in the UK. The Systematic Beds are completely unique in their design concept and the intellectual idea which led to them.
The Beds were originally laid out in 1845 by Andrew Murray. His intention was to group together plants which were of the same botanical families in order that the groupings could be studied by comparing and contrasting them. For thousands of years, humans have grouped plants into families based on observation made using the naked eye. This included comparing leaf shapes, roots, flowers, seeds and stems. Vast collections of pressed plant material were store in Herbariums at Cambridge and other universities. All of this research was drawn together by the magnificently named Augustin Pyramus De Candolle in his definitive work Principes Élémentaires de Botanique, in which he proposed a natural method of plant classification. It was a work which profoundly influence Charles Darwin, and it was using De Candolle’s classifications that Murray laid out the Systematic Beds at Cambridge. And so they stayed for nearly 175 years
However over that period science has advanced, not least in botanical taxonomy. Once the genome had been cracked scientists could compare the DNA of plants as well as their stems and seeds and it has turned botany upside down. As a result, all of the Systematic Beds at Cambridge are being replanted to demonstrate the DNA links and not their visual characteristics. It is going to lead to some strange combinations.
This only the latest change at Cambridge. The first mention of a garden for study in Cambridge goes back to 1597, but it wasn’t until 1696 that plans were drawn up for a Physic Garden in the grounds of the former Augustine monastery. Basically it was intended for the teaching of medicinal uses of herbs. By 1825 the University had given up teaching that subject and the garden had fallen into disrepair. However in that year John Henslow was appointed Professor of Botany. He pushed for the restoration of the garden, but it was too small on the monastery site. In 1831 forty acres of land were bought from Trinity Hall to created a new garden for the intensive study of botanical specimens by the students. In 1845 Andrew Murray laid out the Systematic Beds.
The Chronological Beds followed. They display the plants in a timeline, showing when each species was introduced to Britain. Woad and almonds are some of the first, while the sixteenth century discovery of potatoes is perhaps the most important. They provide a way of understanding how our diets and medicines changed, as well as tracking the UK’s growing global interaction with the world. The latter point led to a vast collection of plants from what was the British Empire. In recent years the gardens have increasingly focused on sustainability as the issues of global warming escalate, looking after numerous endangered plant species. This in turn has led to the garden being used for study by students from disciplines as diverse as Archaeology, Architecture, Computer Science, Earth Science, Engineering, Oriental Studies and Zoology as well as Plant Science.
Over the last decade a group of scientists led by Dr Mark Chase, head of the molecular systematic section of Kew’s Jodrell Laboratory, have been reclassifying plants by their DNA. The process involved the detailed comparison of three genes for each of the 565 family representatives of flowering plants. The first and most important being the gene responsible for controlling photosynthesis, the essential process by which plants convert sunlight into energy. The relationship between plant families indicated by that gene was exactly repeated with the next two genes, convincing Dr Chase and his colleagues that they now have the true picture of how all plants are related. Discoveries at the molecular level have resulted in new families being formed, families being renamed and plant species changing families. Plants which De Candolle put into entirely different classifications turn out to be directly linked through their DNA, such as nettles sharing most of their DNA with roses; peonies turning out not to be related to buttercups but to saxifrage; orchids not related to lilies but to yellow star grass; papaya not related to the passion flower, its closest relative being the cabbage family. The research has been accepted by the wider botanical community and is now the standard way of classifying plants.
The Systematic Beds cover three acres of the gardens. In his design, Murray used hedges as structural elements to express de Candolle’s way of organising the plant families. Plants which germinate with one seed leaf were placed in the centre. Around them were plants which developed with two seed leaves. Radial hedges then divided the beds into sections to demonstrate De Candolle’s groupings. With his book in hand you could literally ‘read’ the book through the Beds starting on page one with the buttercups and ending on the last, with the American Pokeweed.
The Post-DNA understanding of how plants are related has changed that irrevocably. If students are to continue studying the plants, then having the beds laid out on the old system was no longer fit for purpose. To stay true to Murray’s intent of only ever putting one plant family in a bed, things have to change. For a garden that is listed as being of historic interest that poses interesting challenges of how to be both guardian of a historic landscape and keeping it relevant to contemporary research.
Work on changing the beds began in 2016. When the renovation is complete in 2019, the Systematic Beds will represent 1,600 plant species across 119 beds, demonstrating about 78 DNA groupings. Go and have a look.