The preservation of endangered plant species is critical to the survival of cultural legacy.
Historically, the color purple has been linked with nobility globally, and Japan is not an outlier in this regard. However, the distinctive murasaki shade is under threat due to the endangerment of the native gromwell plant, which is often synonymous with murasaki.
Factors such as disease and hybridization with non-native species are contributing to the escalating decline of murasaki.
Now, a research group including Kyoto University, is leading a movement to raise awareness of gromwell’s importance in preserving Japanese culture. For example, murasaki revival projects currently underway throughout Japan are investigating the seed’s origins and educating the public on the importance of protecting the plant’s homogeneity.
“Various non-profits involved in the revival of gromwell are also keen to maintain the silk staining technique through the collaboration with plant scientists,” says lead author Kazufumi Yazaki.
Purple gromwell — or Lithospermum erythrorhizon — contains shikonin derivatives in the plant’s root surfaces, which are red naphthoquinones. This natural pigment and medicinal properties are linked to ancient East Asian traditions. Among the range of hues, the most sought dye was the dark purple reserved for members in the top levels of government and the Imperial family, as well as the highest-ranking Buddhist monks.
“The purple color was also used for a national treasure called Koku-Bun-Ji Kyo, the ten-volume Buddhist scripture papers on which letters were written with gold,” says co-author Ryosuke Munakata of KyotoU’s Research Institute for Sustainable Humanosphere.
For medicinal purposes, the roots are prescribed in several remedies as an ointment called Shi-Un-Koh, which is still popular today in treating hemorrhoids, burns, frostbite, and other wounds.
Recovery initiatives, such as the Mitaka Gromwell Restoration Project, are focused on ensuring the native gromwell’s survival, impacted by the spread of cucumber mosaic virus and sudden environmental changes. Cross-breeding with the European species L officinale is another factor in this plant’s uncertain future.
Excavated official wooden documents from Kyushu — found to have been used to transport cargo during the Asuka dynasty — were unexpectedly related to gromwell, highlighting its purple dye’s crucial administrative role.
“We hope our research raises awareness of murasaki’s importance in Japanese history and culture,” comments co-author Emi Ito of Ochanomizu University.
Reference: “Letter to the Editor: Gromwell, a Purple Link between Traditional Japanese Culture and Plant Science ” by Emi Ito, Ryosuke Munakata and Kazufumi Yazaki, 28 April 2023, Plant and Cell Physiology.