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Fig. 1. Growth of sorghum and alien species' pollen tubes in sorghum pistils stained with aniline blue and observed with fluorescent microscopy. (A) Sorghum pollen tubes in stigmas at 1 h post-pollination; (B) Sorghum pollen tubes that have grown into the ovary at 1 h post-pollination; (C) Germinated pollen grain of S. interjectum with a pollen tube that has not penetrated the stigma branch at 24 h post-pollination; (D) A germinated pollen grain of S. nitidum that grew in a convoluted fashion without entering the stigma branch at 24 h post-pollination; (E) Pollen tubes of S. ecarinatum in the stigma and style at 6 h post-pollination; (F) Stigma branches with an ungerminated pollen grain and a pollen tube of S. interjectum in the stigma branch at 24 h post-pollination; (G) Sorghum ecarinatum pollen tubes in the style and ovary at 24 h post-pollination; (H) Pollen tube of S. plumosum growing outside and parallel to the stigma branch; (I) Pollen tube of S. intrans that has grown out of and back into a stigma branch; (J) A pollen tube of S. interjectum in the stigma axis that reversed its direction and grew toward the apex of the stigma; (K) Pollen tube of S. purpureo-sericeum with a swollen tip; (L) Pollen tube of S. timorense terminating at accumulated callose in the stigma axis. Scale bars are 100 µm, except when designated otherwise.
