This post was contributed by Tony Boniface – a member of the University of the Third Age.
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On 3 July, Dr Martin Ingrouille, of Birkbeck’s Department of Biological Sciences, began his talk by pointing out that Darwin had studied plants for 40 years and had published books on pollination. However, Darwin knew nothing of genes and chromosomes and could not explain the rapid origin of flowering plants in the Cretaceous period.
Dr Ingrouille continued by emphasising that garden plants are sterile and exotic plants without their natural pollinators. They have been selected for showiness, many being artificial hybrids. He referred to Goethe, who stressed the essential unity of floral parts, which have all evolved from leaves.
Dr Ingrouille explained how genetic control, in its simplest form, consists of three classes of genes: A, B and C. Class A genes control sepals and petals, class B genes control petals and stamens, and class C genes control stamens and carpels. Mutations of these genes result in parts being converted into others.
Floral evolution in plants could have been the result of duplication of basic genes allowing one to perform its normal function while the other could give rise to a novel structure or function. New plant species have often arisen by chromosome doubling in a sterile hybrid as seen in the formation of Primula kewensis.
Dr Ingrouille then explained how much insight into plant evolution arose from the work of John Gerard (gardener to William Cecil), John Ray (author of the first modern text book of botany) and the Jussieus family (three generations of gardeners to the king of France). These people put plants into groups that were the first natural classification of the angiosperms.
Now DNA sequencing has resulted in a detailed understanding of the phylogeny or evolutionary history of these plants in which many of the families have survived such as the umbellifers and legumes but some such as the figwort family have been split. The result was the arrangement of the plants into two main groups namely the Eudicots, with three grooves on their pollen grains, and the Basal Angiosperms, with only one groove. Within the Eudicots are the Core Eudicots including the Rosids and the Asterids whilst the Monocots are within the Basal Angiosperms. The first ancestor was Amborella trichopoda, a weedy shrub from New Caledonia in the Pacific – a place Dr Ingrouille hopes to visit on his retirement.
Dr Ingrouille finished by urging his audience – all members of the University of the Third Age (a movement for retired and semi-retired people to come together and learn together) – to examine their garden plants in detail to look for the variations, which suggest their origins.
