Quantification of endogenous gibberellins in leaves and tubers of Chinese yam, Dioscorea opposita Thunb. cv. Tsukune during tuber enlargement

Eleven gibberellins (GAs) were identified and quantified in extracts of leaves and tubers of the Chinese yam, Dioscorea opposita Thunb. cv. Tsukune by GC-MS-SIM and Kovats retention indices. Five of these gibberellins are members of the early-13-hydroxylation pathway (GA₅₃, GA₄₄, GA₁₉, GA₂₀ and GA₁), and six are members of the non-13-hydroxylation pathway (GA₁₂, GA₁₅, GA₂₄, GA₉, GA₃₆ and GA₄). Of these eleven, GA₄₄, GA₁₅ and GA₁ were detected for the first time in Dioscorea opposita leaf tissues. The major biosynthetic GA pathway in leaves of Chinese yam was non C-13 hydroxylation (NCH). In addition, the active GA₄ content for all harvest dates was greater than that of GA₁ in the leaves and tubers during tuber development. It is suggested that the higher level of GA₄ in the leaves and tubers may be closely related to tuber enlargement.