Fig. 2

Histological observation of PLB at different developmental stages. a Meristem mass. The meristem mass was induced from protocorms by half-strength MS medium containing 0.05 mg/L 2,4-D for 2 months. They composed of a small area of dense, small inner cells (red arrow) and compact aggregates of larger outside cells (Scale bar = 100 μm); b PLBs mass. The PLBs mass was induced from meristem mass by half-strength MS medium containing 0.05 mg/L 2,4-D for 2 months. The surface of the newly emerged PLBs mass was covered with small and compact meristem cells (S), which would subsequently develop into shoots. Small protrusions started to form at the surface of the PLB. Inner cells (I) remained larger (Scale bar = 500 μm). c-e Local PLBs development process. The compact small cells on the surface continued to divide, resulting in protuberances. They elongated and increased in size, eventually forming spheroids, which were the mature PLBs. The area in the red box depicted the development from a small protuberance to a mature PLB. (c-e. Scale bar = 200 μm); f Cluster shoots. The primordial and young leaves differentiated from PLBs (Scale bar = 500 μm)