It was observed that some dark and gray osmiophilic materials coalesced to vacuoles in the cytoplasm.In stage 2, a lamellated suberin layer accumulated inside the primary cellulose layer.

• 阶段2：木栓质化壁层的形成，片层状木栓质不断叠加在初生纤维素壁内侧，其细胞结构与前期相似。