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By Narusa Yamato

The Reason Behind its Smell

Photo of the Gingko trees on the Komaba Campus. Photo by Yuki Iida

Photo of the Gingko trees on the Komaba Campus. Photo by Yuki Iida

One beautiful autumn day, you are walking around the Komaba campus, looking at the contrast between the blue sky and the golden Gingko tree leaves, and you suddenly notice a malodorous smell that destroys your pleasant walk. Have you ever had this kind of experience?

The cause of this smell is the rotten Ginkgo nut seed coat that contains certain acids. According to the book Chracteriztion of the purid aroma compunds of Gingko biloba fruits (1995) by T. Parliment, the Gingko nut consists of a seed coat called sarcotesta that contains 2 types of acid, butanoic and hexanoic acid. It is this combination that gives off this unpleasant smell, which is often described as a goat-like smell.

The smell is often worsened when pedestrians and vehicles crush the rotten nut. Moreover, this also leaves a nasty mess on the street, therefore ideally, the best way to prevent the smell will be to pick the nuts before they rot or get crushed. However, this may be very difficult because there are so many Gingko trees in the campus. Another solution might be to use the nuts for cooking, since they are very delicious.

Gingko nuts and leaves. Photo by Yuki Iida

Gingko nuts and leaves. Photo by Yuki Iida

Although this smell is certainly a negative consequence to us, it may have been one of the ways in which the Gingko tree has evolved to survive. Due to the impression of the odor, people might think that the smell has evolved to prevent animals from eating them. However, Peter Del Tredici, a botanist and a lecturer at Harvard University, suggested in the book Natural regeneration of Ginkgo biloba from downward growing cotyledonary buds (basal chichi)(1992) that the “existence of carnivores consuming the whole Gingko seed, and defecating intact nuts, raises a possibility that the foul smell sarcotesta may be attracting animals by mimicking the smell of rotten flesh”. Therefore, the smell of the might be a tool for seed dispersion.

Considering these reasons behind the smell, we may be able to perceive the smell of the odor of the Gingko nuts differently and enjoy the aesthetic beauty of the tinted autumnal leaves.

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