Fig. 2

Pollen grain germination on the stigma and pollen tube growth in the style after self-pollination and cross-pollination of H. syriacus. a ~ e: Pollen grains on stigmas at 1, 2, 4, 6, and 8 h after pollination, respectively. Arrows indicate germinated pollen grains. f ~ i: Growth of pollen tubes in the style at 12, 24, 36, and 48 h after self-pollination, respectively. j ~ m: Growth of pollen tubes in the style at 12, 24, 36, and 48 h after cross-pollination, respectively. Arrows indicate the tip of the pollen tube in the style. n ~ o: At 24–48 h after pollination, some pollen tubes were distorted and twisted. p ~ q: At 24–48 h after pollination, callose had been deposited in the style and at pollen tube apices