Figure 4

Pollen development of ‘Qx-097’ by paraffin section method. (A) Early microspores, tapetal layer cells condensed. (B) Middle microspores stage, showing germ pores, thickening cell walls and radial thinning of tapetal layer cells. (C) Late microspores stage, showing mononuclear microspores against the anther wall and degradation of tapetal layer. (D) Early bicellular pollen stage, showing nuclei divide excentrically to form a large central vegetative nucleus and a small generative nucleus, the tapetal cells only have residue and endothecium layer cells enlarge in volume. (E) Late bicellular pollen stage, contents such as starch began to accumulate in cytoplasm, but the two nuclei can be observed still and vacuoles gradually disappeared. (F) Mature pollen stage, contents such as starch fills the whole cell and the nuclei are hard to be observed. BP: Bicellular pollen; EM: Early microspore; GN: Generative nucleus; GP: Germ pore; LM: Late microspore; MaP: Mature pollen; MM: Middle microspore; Ta: Tapetum; TaD: Tapetum debris; VN: Vegetative nucleus.