Figure 1

Core sampling device. Core sampling device (CSD) (A). The CSD handle is lifted-up (the white arrow indicates the direction of the handle) and the maize main stalk internode is placed on the rubber mat (B and C). Once the internode is in the right position (center of rubber mat), the handle is pulled down (D) and the cork borer begins to penetrate the internode (E) until both sides of the internode (rind) are cut (F). The handle is lifted up again (G) and the core is released by a core extractor mechanism (H, I, and J). A tube is placed over the end of the cork borer before the sample is released (K). The sample consists of a complete cross-section of the stalk internode composed of both rind sections as well as the pith (L, M). Note: in E-H, the separation plate was removed to facilitate visualization.