ABSTRACT
Objective::To study the forming process of the gynandrium-like in Amomum villosum. Method::The flowerets were divided into 8 growth periods from 0.5 cm in length to the day after flowering. Fresh sample were anatomized, and paraffin sectioning was performed on the flowerets. The height of anther chamber, the pollen sac angles, the width of anther gap, the diameter of style, the filament-labellum angle (α), and the filament-anther angle (β) were determined. Result::The angle of the pollen sac had no obvious change before flowering, but decreased from 32° to 17° after flowering. The width of anther gap increased to 0.29 mm in the 5th growth period, while the diameter of style was 0.32 mm in the same period, the ratio of them was 92%. Compared with the day before flowering, the angle α decreased from 83° to 42° during flowering, and the angle β decreased from 186° to 147°. In the filament, the abaxial side had 1 to 5 layers of cells more than the adaxial side. In the style, it was found that the adaxial side had 1 to 6 layers of cells more than the abaxial side. Conclusion::The asymmetry of the cell structure at abaxial and adaxial sides of the filament and style is the basis of the movement. In the 5th growth period, the width of anther gap increased almost to the size of style, so the style was able to slide in. When blossoming, the pollen sacs quickly squeezed to the gap in middle, and the entrance for style to access was blocked. Therefore, the style had to remain in the gap of the pollen sacs. Meanwhile, angles α and β drastically decreased, resulting in the stamen sandwiched the pistil and bending together toward the labellum. The gynandrium-like structure was formed.