Ginkgo: An Evolutionary and Cultural Biography

AbstractPerhaps the world’s most distinctive tree, living Ginkgo biloba is a botanical oddity that has remained little changed for at least 55 million years, and is also very similar to plants that flourished in the late Triassic and Jurassic over 200 million years ago. First brought to the attention of western science by Kaempfer, and named by Linnaeus only shortly before his death, Ginkgo was initially regarded as a conifer. It was later recognized as distinct in plant classifications of the early nineteenth century, a conclusion underlined subsequently by the remarkable discovery in Ginkgo (and also in cycads) of motile sperm cells. The precise phylogenetic position of Ginkgo among living and fossil seed plants remains uncertain, although most analyses using molecular data, as well as many morphological analyses that include fossils, associate Ginkgo with conifers. Classic work by Zhou Zhiyan has demonstrated that diverse Ginkgo-like plants existed during the Jurassic in China, and recent paleobotanical discoveries hint even greater diversity through the Jurassic and Early Cretaceous, as well as intriguing similarities to certain groups of Mesozoic “seed ferns”. For much of the Mesozoic Ginkgo-like plants were widespread in both hemispheres, but their diversity declined during the mid-Cretaceous. They disappeared from the Southern Hemisphere early in the Cenozoic. In the Northern Hemisphere Ginkgo remained widely distributed through the Late Cretaceous and early Cenozoic, including at high paleolatitudes. Ultimately, however, Ginkgo barely survived the marked climatic changes of the later Cenozoic. It is last recorded in western North America about 15 million years before present. It disappeared still more recently from Europe, parts of Asia and Japan, and apparently survived the Pleistocene Ice Ages only in China. The only remaining putatively wild populations exist as relics in central-western and eastern China and recent research suggests that all living Ginkgo trees were ultimately derived from these two relictual populations. Despite its near extinction Ginkgo began its remarkable contemporary renewal and resurgence when people in China first found it useful as a “nut tree” about a thousand years ago. Subsequently Ginkgo was grown widely in China and appears to have been introduced into Korea and Japan in medieval times. In the mid-seventeenth century Ginkgo was introduced into Europe and by 1784 it was being grown outside of Philadelphia in North America. Today Ginkgo is an increasingly familiar living link to landscapes of the distant past. Its “nuts” are still enjoyed in the cuisines of eastern Asia, but it is also revered for its longevity, beloved for the elegance of its leaves, valued as a medicinal, and widely cultivated as one of the world’s most popular street trees. In both the East and the West Ginkgo is also a source of artistic and spiritual inspiration. Ginkgo remains of great scientific importance and may provide our best window into the lives of diverse ancient seed plants that flourished between about 200 and 100 million years ago. The recent sequencing of the Ginkgo genome, and discoveries of new and exceptionally well-preserved fossil material, both offer exciting possibilities for a deeper insights into the life story of this remarkable tree, as well as its broader significance for understanding plant evolution.

People and Plants – the Unbreakable Bond

Abstract

Plants form the scaffold for Earth’s green ecosystems, but they are also essential for human survival. Plants provide most of the food we eat (directly or indirectly), our medicines, clothes, buildings, and even the air we breathe; they also beautify our daily lives. So we need plants, but do they need us? In this time of increasing human impact on plants, animals and natural habitats, our actions can make a big difference in whether plants are a part of an ecological civilisation for the future. Plants do in fact need us - they need us to study and use them responsibly, both as scientists and as members of human societies. So what can plant science contribute to the survival of these species on which we depend? I will draw on my own experiences as a scientist working on a flowering plant family of enormous economic importance, the Solanaceae, to explore how basic science can become part of many different aspects of people’s use of plants. Members of the Solanaceae have uses in horticulture (petunias), medicines (mandrakes, tobacco, and henbane), and they are among our most important foods (potatoes, tomatoes, and eggplants). I will look at how people have changed and modified these species, and explore the changes that have driven the use of some species and not others. The journeys taken by plants in the company of people involve many changes, on both sides. It could be said that rather than domesticating plants for our own use, plants are in fact domesticating people! So our relationship with plants is deep and complex – but what should it be in the future? Should we confine plant species to wild areas where we can see them, but not interact or use them? Or should we manage plant diversity strictly for human use and enjoyment by bringing more plants into cultivation and into close relationships with us? Or perhaps something in between? I will argue that to really develop the bonds that link plants to people and create a society in harmony with nature all of use, not just scientists, must work together in order to maintain these relationships now and for future generations.

Saving Plants to Save Ourselves: The Shenzhen Declaration

Abstract

Our planet consolidated into its present form about 4.5 billion years ago, with life appearing at least 3.9 billion years ago.  The photosynthetic group of bacteria known as Cyanobacteria began producing oxygen about 2.7 billion years ago, with oxygen reaching present or even higher levels around the start of the Cambrian Period, 541 million years ago, about the same time that multicellular life first appeared.  Animals, plants, and fungi colonized the land and began to diversify about 450 million years ago, with seed plants appearing about 370 million years ago and angiosperms some 135 million years ago.  The ancestors of both dinosaurs and mammals appeared about 200 million years ago.  The fourth great extinction occurred at about the time dinosaurs and mammals first appeared, with the last dinosaurs disappearing at the time of the fifth and last great extinction, at the end of the Cretaceous Period about 66 million years ago.  Mammals then began to diversity, with primates, the mammalian order of which we are members, appearing about 55 million years ago.  It is estimated that about 99% of all kinds of organisms that ever existed on earth are extinct, but when our ancestors diverged from the African apes about 6-8 million years ago, they did so in a world of biological richness, with perhaps 12 million species of eukaryotes and countless millions of species of prokaryotes supporting the functioning of the global ecosystem.  The oldest fossils we know of our genus, Homo, date from about 2.8 million years ago, the oldest of our species, Homo sapiens, from about 200,000 years ago; these are both from Africa, with Homo sapiens migrating to Eurasia about 60,000 years ago. Therefore we are very new on Earth, but our activities have become devastating to our continued existence and that of other organisms as well.

The human development of agriculture as a main source of food about 10,000 years ago led to an explosion of our numbers from about 1 million people then to 7.4 billion today, projected to grow to 9.9 billion by mid-century, 33 years from now.  This has made us an ecological force so great that we can be said to have entered the Anthropocene Period, one in which our actions will determined the fate of everything on Earth.  For example, our bodies and those of our domestic animals now constitute 95% of all mammalian biomass on our planet.  We are estimated to be consuming on a continuing basis about 164% of the planet’s sustainable productivity, with some of us rich and many poor (www.footprintnetwork.org) .  Like all organisms, we depend on the functioning of the global ecosystem for every aspect of our lives, and yet we are currently tearing it apart.  Extinction is currently taking place at a rate 1,000 times or more greater than it has since the end of the Cretaceous Period 66 million years ago, so that as many as half of the estimated 12 million species of eukaryotes existing now are likely to have disappeared from nature by the end of the 21st Century, and we shall not even have recorded most of them.

Plants, and photosynthesis in general, do not receive the attention they deserve, and if we want to attain global sustainability, we shall have to work much harder to gain the knowledge that we need to save ourselves and to apply it to the maintenance of a sustainable world.  We shall need to emphasize field studies in order to understand better the functioning of our globe.  We have little or no knowledge about the majority of species of plants or other organisms on earth, despite our living during the last decades when many of them will exist.  Nations and peoples have become starkly unequal, women and children often neglected or suppressed, and yet we are in danger of perishing together unless we do much better in these respects.  We need to learn to cooperate with and love one another while there is still time to do so.  We must attain a level population, equality between peoples, and better technologies while we still can do so.  Plants, the subject of this Congress, and agriculture must receive greater attention since we depend so clearly and completely on them.  Let us make this Congress a time of commitment to do better and resolutely seek a sound and sustainable future for all people.

Plants and People: History and Future

Abstract

The relationship between humans and plants extends far back into hominid history.  Plants have shaped our evolutionary past, adapting humans to a series of diet changes by alterations in morphological traits such as the structure of teeth, biochemical adaptations to novel foods and plant secondary compounds, and even alterations in our taste receptors.  Humans early on have used plants as part of their culture, their medicine and their religion, forming a deep bond with native species.  In turn, humans, with the advent of plant domestication and agriculture, have changed plants, altering them to increase yield, to simplify cultivation, and to modify their basic biochemistry for enhanced taste, and reduction in noxious compounds.   This evolutionary dance between humans and plants has been central for the development and flourishing of agriculture. Agriculture, in turn, allowed humans to settle in towns and fostered the subsequent development of more complex civilizations. This legacy has persisted for at least 10,000 years with plants providing fiber and food for both people and animals.  The complexity of our modern cities and cultures rests in part on the reliable production and transportation of food.  

But, what is the future?  How do we provide food security and proper nutrition to a growing global population?  How do we grow more food on less land and reduce the environmental footprint of agriculture? Can plants be part of the new bio-economy, providing income to farmers in both developed and developing countries?  And how do we affect all of these advances in the face of a rapidly changing climate?  These are monumental changes facing the entire globe and they present both a challenge and an opportunity for plant science.

Green Life, Beautiful Genes

Abstract

We have all the reasons to sing praises for plants: We survive by take-in plants everyday, and we, together with all other animals, breath with the oxygen made by plants every minute.  We live in a world to which plants contribute so much to its sustainability and balanced ecological environment.

Plants do not only teach us the sense of harmony and colorfulness, but also help us open the doors to understanding the secrets of all life.  It is the plant that provided the tools to discover the genetic rules of genes; t is the plant that helped us find out the genes are even able to “jump”; it is the plant, listed as one of the model organisms of the International Human Genome Project (HGP), helped understand ourselves, as well as providing the new strategy to understand plants.

The discovery of DNA double helix structure opened a new epoch of life sciences and biotechnologies，which revolutionized our understanding of the life and diversity of plants.  The HGP, with its belief that “Life is of Sequences, Life is Digital”, provides a now concept of genomics and all other omics, a new technology of sequencing, and a new culture of globalized collaboration under the HGP Spirit, “needed by all, owned by all, done by all, and shared by all”.

The Earth BioGenome Project (EBP), which was announced in February this year, has the ambitious missions to sequence “all life on Earth”, and plants accounting for a major part. We call again for international collaboration, especially all those working on plant sciences and omics-based breeding.