Cover stories: Ginkgo biloba

The cover image for our April issue shows the diversity of leaf morphology from the fallen leaves of a single Ginkgo biloba tree, located in monitored plots at the Zijingang Campus, Zhejiang University, China. The image relates to the International Biological Flora: Ginkgo biloba, by Han-Yang Lin et al.

✏️A note from the Editor, Anthony Davy:

The April cover image (110:4) celebrates the second account in our new International Series of Biological Flora articles. Anybody who has ever done even a basic course on plant evolution will have heard of Ginkgo. G. biloba, the classic ‘living fossil’, is the sole survivor of an important lineage of gymnosperm (plants with naked seeds); its leaves are hardly different from fossil impressions of its predecessors some 100-200 million years ago. Having survived predation by the great herbivorous dinosaurs, mass extinctions and glaciations, the formerly global distribution of Ginkgo had shrunk to just a few refugia in China – but now it has again attained a worldwide reach as a tree widely planted in cities and gardens. It continues to shrug off environmental challenges into the Anthropocene. Ginkgo, however, is not just a botanical curiosity but now enjoys great cultural significance (see Crane, 2019) and some medical interest (many are the students who have resorted to the leaf extract as a putative memory stimulant in times of stress!). Moreover, its unique role in unravelling plant evolution is by no means complete, as a draft genome and transcriptomic and metabolomic studies are brought into play. Could there be a more appropriate species for an International Biological Flora account?

🔎The story behind the image, from the author Yun-Peng Zhao:

This image was taken on December 10, 2019, illustrating the remarkable diversity of leaf morphology from a single Ginkgo biloba tree. The tree is located in one of the ten 20 m×20 m plots which we established for long-term monitoring of ginkgo forests planted at the Zijingang Campus of Zhejiang University. This ginkgo forest is an on-campus hotspot, especially in autumn when the ginkgo leaves turn fully golden on and beneath the trees, which attracts numerous visitors with cameras. The golden season of this ginkgo forest was in early December 2019, and I went to take photos to record the phenology. When I observed the fallen leaves on the ground, I was immediately aware of the immense variation of leaf morphology. The prototype of the cover image appeared in my mind, so I tried to pick representative leaves on the morphological spectrum along multiple axis’s.

I returned to my office and arranged the leaves on my desk to photograph them. Although I have been observing and researching ginkgo for 15 years, I was still impressed by the prominent variation of leaf morphology for a single tree. The differences were even more pronounced by the big, deep-lobed leaves on the young vegetative tillers sprouted from the basal trunk. Such variation might result from plasticity in response to environmental changes on a developmental trajectory, and thus elicits questions about the underlying regulatory mechanisms of leaf development. The focal image also reminds me of the figure in Smarda et al. 2018 (Horticultural Research), which demonstrated the association between leaf size and ploidy level. Furthermore, a new thought occurred to me that such variation is likely to substantially affect the measurement of functional traits of leaves. It may prevent the detection of significant signature, leading to biased or controversial conclusions.

I used to collect plant specimens in the field and curate the Herbarium of Zhejiang University (HZU). My interest in collecting and preserving ginkgo leaves was initiated after one of my previous undergraduate students finished her project exploring the evolution of genome size in ginkgoalean. The project focused on testing the relationship between species diversity and genome size represented by stomatal size, using both fossil and dried leaves. To exclude the potential effect of environments on stomatal size, we collected dried leaves from 28 cities in China with the help from colleagues and students. I travel a lot due to field work and academic meetings, and I take photos and collect leaves of local ginkgo trees along the way. Now, we also have a dry pressed leaf collection of ginkgo in our herbarium, together with herbarium sheets, seeds, leaf DNA samples, seedlings, field plots and a comprehensive database, composing a unique Ginkgo Gene Bank.

I enjoy observing and researching trees like ginkgo. It’s not only my work, but also my hobby, and it has shaped the way I view nature and world, and in turn how I educate my students. Finally, I’d like to share a saying from the French novelist, Marcel Proust, ‘The only real voyage of discovery consists not in seeking new landscapes but in having new eyes‘.

Yun-Peng Zhao, Zhejiang University, China.

Read the full article here: International Biological Flora: Ginkgo biloba

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