Influence of the nitrogen form on in vitro organogenesis in Equisetum arvense

The physiological and biochemical mechanisms of organogenesis in Equisetum arvense have not been clarified yet. However, high concentrations of nitrogen have been shown to exert an inhibitory effect on in vitro tuber formation in E. arvense. The aim of this study was to clarify the influence of the form of nitrogen in a medium on in vitro organogenesis in E. arvense. Single-node segments of E. arvense rhizomes were cultured in the test medium. The NH4-N and NO3-N concentrations of the test medium, respectively, were adjusted by adding NH4H2PO4 and KNO3 to the basal medium. The basal medium was a nitrogen-free, modified form of White's medium. Vegetative shoots were newly formed in the test tubes for concentrations of NO3-N and NH4-N that exceeded 56 mg L−1. However, no rhizome was formed at NH4-N concentrations exceeding 28 mg L−1. The number of newly formed tubers decreased at an NH4-N concentration of 28 mg L−1 and no tuber was formed at NH4-N concentrations exceeding 56 mg L−1. In summary, although the presence of NO3-N in the medium did not inhibit in vitro rhizome or tuber formation in E. arvense, the presence of NH4-N in the medium exerted a strong inhibitory effect on the in vitro formation of both of these organs.