2020 年 32 巻 4 号 p. 89-96
Wasabi (Eutrema japonicum (Miq.) Koidz.) was grown in a traditional cultivation field using spring water in Izu peninsula for 12 months. Four different shading nets were applied to the cultivation field to reduce sun light during the whole period. Among 4 nets, white-colored net transmitted photosynthetic active radiation (PAR) most abundantly (64%), whereas black-colored net did least abundantly (22%). Blue-colored and red-colored nets had similar values of PAR transmittance (58%). Transmittance of shortwave radiation including PAR and near infrared (NIR) was almost same among white-colored, blue-colored, and red-colored nets. As a result, temperature of black-painted brass boards placed horizontally was almost same under the three nets, suggesting that white-colored net can effectively reduce NIR and transmit PAR abundantly. Whole plant fresh weight and rhizome weight of wasabi were highest under white-colored nets. Pungent components such as allyl isothiocyanate were not significantly different among the four nets. Our result suggests that white-colored net can enhance wasabi growth compared with the other three nets, probably owing to abundant PAR and suppressed NIR reaching the plant surface.