Effect of Vernalizing Conditions on the Concentrations of Endogenous Gibberellins in Wheat Seedlings

Abstract

In Chinese spring wheat (Triticum aestivum), GA₁, GA₃, GA₈, GA₉, GA₁₇, GA₁₉, GA₂₀, GA₂₉, GA₄₄, and GA₅₃ were identified in the mature leaves, GA₁, GA₃, GA₈, GA₁₉, GA₂₀, GA₂₉, GA₄₄, and GA₅₃ in the sheath segments, and GA₁, GA₃, GA₁₉, GA₂₀, GA₄₄, and GA₅₃ in the roots of seedlings, based on C₁₈ HPLC, GC-SIM and KRI data. Seven of these GAs were quantified by capillary GC-SIM, using deuterated GA₁, GA₃, GA₈, GA₉, GA₁₉, GA₂₀, and GA₅₃ as internal standards. The concentrations of these GAs tended to be highest in the sheath segments and lowest in the roots. In general, higher concentrations of GA₅₃, GA₁₉, and GA₃ were present in mature leaves, sheath segments, and roots of seedlings grown under vernalizing conditions (low temperature, short photoperiod, and low light intensity), while the concentrations of GA₂₀, GA₁, GA₈, and GA₉ were higher in seedlings grown under non-vernalizing conditions (higher temperature, longer photoperiod, and higher light intensity). The relative concentrations of GA₅₃, GA₁₉, GA₂₀, GA₁, and GA₈ from the two growing conditions lead us to infer that the conversion of GA₁₉ to GA₂₀ (C₂₀-GA to C₁₉-GA) would be a rate-limiting step for the biosynthesis of GA₁, this GA being apparently responsible for shoot elongation in wheat. This rate-limiting step may be associated with a short photoperiod and/or low light intensity.