Presentation Information
[O12-P49]The sea breeze blowing over the Izu Peninsula enriches the cherry blossom leaves with coumarin.
*Nana Kitamura1, *Soma Okawa1, *Haruka Sugiyama1, *Kanato Tsuchiya1, Hiroto Tsuchiya2, Tomomi Yamamoto2, Mimi Yamamoto2, Remi Watanabe2 (1. Nirayama high school, 2. Matsuzaki high school)
Keywords:
sea breeze,soil,Izu Peninsula,salt,Sea and land wind,Suruga Bay
1. Background and Purpose
Salt-pickled Oshima cherry (Prunus lannesiana var. speciosa) leaves, rich in the fragrant compound coumarin, are used in Japanese sweets. Matsuzaki Town (west coast of the Izu Peninsula) produces 70% of Japan's cherry leaves, benefiting from the warm, coastal-mountainous Oku-Izu climate. Over three years, we investigated why Matsuzaki and nearby areas excel in this production. We report our findings verifying the hypothesis that "Izu Peninsula sea breezes enrich coumarin in cherry leaves" and explore cultivation methods to maximize coumarin.
2. Methods
In Study 1, to assess regional and genetic factors, intact Prunus leaves (>6 cm) were collected from four eastern Shizuoka municipalities (Matsuzaki, Mishima, Izunokuni, Ito).
In Study 2, to test mechanical and salt stress, leaves were scratched with tweezers or sprayed with Suruga Bay seawater. Soil electrical conductivity (EC) was measured using a multi-sensor to assess soil salinity.
In Study 3, we tested whether Tengusa (red algae) residue—used in "Kawaura Hananoen's" premium cherry leaf compost—increases coumarin. We cultivated Oshima cherry clonal cuttings using this residue.
All leaves were pickled in 23% NaCl for three months, strictly following traditional methods from a specialty store. Coumarin content was calculated via liquid chromatography (LC) peak areas.
3. Results
LC analysis of 33 samples showed coumarin content (mg/g leaf) of 0.37–1.75 for Oshima cherry, 0.77–1.44 for Someiyoshino, and 0.85–1.23 for Kawazuzakura. Content varied 2-to-5-fold within cultivars, showing no statistically significant difference among the three. However, the maximum (1.75 mg) occurred in an Oshima cherry from Jogasaki (Ito City), just 52 m from the coast.
In stress experiments, coumarin increased 1.1–1.2 times with wounding and 1.1–1.5 times with salt stress. Soil EC measurements showed a positive correlation: higher soil salinity yielded higher coumarin.
Furthermore, a chi-square test on August meteorological data revealed a significant difference in wind direction between the west (Matsuzaki) and east (Ajiro) coasts. Matsuzaki experienced daytime westerly sea breezes 5.6 times more frequently than Ajiro.
In the Tengusa experiment, mixing residue into the soil increased coumarin more than surface application. This "mixed-in plot" reached 2.3 mg/g coumarin, the highest among all 54 samples tested historically.
4. Discussion and Future Tasks
We found no significant coumarin differences among cherry cultivars or regions. Since variation occurred even in asexually reproduced Someiyoshino, we conclude that the "growing environment" dictates coumarin levels more than genetics. Increased coumarin under wounding/salt stress and its strong positive correlation with soil salinity robustly support our hypothesis: "salt stress from sea breezes yields coumarin-rich leaves."
The coumarin increase in the Tengusa experiment likely occurred because Tengusa-derived minerals act as an environmental stressor similar to sea breezes, stimulating the production of the plant defense substance coumarin.
Future work will optimize cultivation using Tengusa compost. By analyzing soil EC and coumarin trends, we will determine the optimal conditions for coumarin maximization. We aim to apply these findings to produce highly fragrant leaves, contributing to Matsuzaki Town's regional revitalization.
Salt-pickled Oshima cherry (Prunus lannesiana var. speciosa) leaves, rich in the fragrant compound coumarin, are used in Japanese sweets. Matsuzaki Town (west coast of the Izu Peninsula) produces 70% of Japan's cherry leaves, benefiting from the warm, coastal-mountainous Oku-Izu climate. Over three years, we investigated why Matsuzaki and nearby areas excel in this production. We report our findings verifying the hypothesis that "Izu Peninsula sea breezes enrich coumarin in cherry leaves" and explore cultivation methods to maximize coumarin.
2. Methods
In Study 1, to assess regional and genetic factors, intact Prunus leaves (>6 cm) were collected from four eastern Shizuoka municipalities (Matsuzaki, Mishima, Izunokuni, Ito).
In Study 2, to test mechanical and salt stress, leaves were scratched with tweezers or sprayed with Suruga Bay seawater. Soil electrical conductivity (EC) was measured using a multi-sensor to assess soil salinity.
In Study 3, we tested whether Tengusa (red algae) residue—used in "Kawaura Hananoen's" premium cherry leaf compost—increases coumarin. We cultivated Oshima cherry clonal cuttings using this residue.
All leaves were pickled in 23% NaCl for three months, strictly following traditional methods from a specialty store. Coumarin content was calculated via liquid chromatography (LC) peak areas.
3. Results
LC analysis of 33 samples showed coumarin content (mg/g leaf) of 0.37–1.75 for Oshima cherry, 0.77–1.44 for Someiyoshino, and 0.85–1.23 for Kawazuzakura. Content varied 2-to-5-fold within cultivars, showing no statistically significant difference among the three. However, the maximum (1.75 mg) occurred in an Oshima cherry from Jogasaki (Ito City), just 52 m from the coast.
In stress experiments, coumarin increased 1.1–1.2 times with wounding and 1.1–1.5 times with salt stress. Soil EC measurements showed a positive correlation: higher soil salinity yielded higher coumarin.
Furthermore, a chi-square test on August meteorological data revealed a significant difference in wind direction between the west (Matsuzaki) and east (Ajiro) coasts. Matsuzaki experienced daytime westerly sea breezes 5.6 times more frequently than Ajiro.
In the Tengusa experiment, mixing residue into the soil increased coumarin more than surface application. This "mixed-in plot" reached 2.3 mg/g coumarin, the highest among all 54 samples tested historically.
4. Discussion and Future Tasks
We found no significant coumarin differences among cherry cultivars or regions. Since variation occurred even in asexually reproduced Someiyoshino, we conclude that the "growing environment" dictates coumarin levels more than genetics. Increased coumarin under wounding/salt stress and its strong positive correlation with soil salinity robustly support our hypothesis: "salt stress from sea breezes yields coumarin-rich leaves."
The coumarin increase in the Tengusa experiment likely occurred because Tengusa-derived minerals act as an environmental stressor similar to sea breezes, stimulating the production of the plant defense substance coumarin.
Future work will optimize cultivation using Tengusa compost. By analyzing soil EC and coumarin trends, we will determine the optimal conditions for coumarin maximization. We aim to apply these findings to produce highly fragrant leaves, contributing to Matsuzaki Town's regional revitalization.