ムラサキの根における表面積/重量比がエーテルエキス含有率へ及ぼす影響  [in Japanese] Effect of Surface Area/Dry Weight Ratio on Diethyl Ether-soluble Extract Content of Roots in Lithospermum erythrorhizon Siebold et Zucc., Boraginaceae  [in Japanese]

The supply of roots of Lithospermum erythrorhizon Siebold et Zucc., which have been used for a crude drug, depends almost entirely on the collection of wild plants in China. Unsustainable harvesting in the wild has reduced the plant resources and the demand for domestication has increased. However, in cultivated plants, the diethyl ether-soluble extract content, which is correlated with shikonin derivative content, is very low compared with that in the wild. Since the shikonin derivatives are distributed in the root periderm, the effects of the raising method of seedlings and plowing conditions of the cultivated field on tap root length, surface area of root/root dry weight ratio (S/W ratio) and diethyl ether-soluble extract content of one-year-old roots were investigated by transplanting. 1) The longest tap root length (13.1 to 15.6cm) was obtained from the plants whose seedlings were raised in paper pots and then transplanted to the deeply plowed field by trencher before transplanting (P-D plot). In contrast, the tap root elongation of the plants whose seedlings were raised in cell trays and then transplanted to the deeply plowed field by trencher (C-D plot), and raised in cell trays and then transplanted to the shallowly plowed field by tractor (C-S plot) were largely restricted (5.3 and 8.9cm, respectively). 2) The S/W ratio in the P-D plot was much larger than that in the C-S plot. 3) The diethyl ether-soluble extract content of roots in the P-D plot was significantly higher than that in the C-S plot, and the diethyl ether-soluble extract content was positively correlated with the S/W ratio (r=0.599, P<0.05). From those findings, we concluded that increasing the diethyl ether-soluble extract content of roots may be caused by the elongation of tap root in response to the S/W ratio.