| Activity of the Pollen Tube During the Penetration of the Style.
The chosen examples are grasses. The table compares the pollen
tube's activities in compatible and non-compatible situations.
In case of self-incompatibility (SI) occurs the rejection immediately
after the tube has begun to penetrate the style. Incongruent reactions
can manifest themselves later (according to J. HESLOP-HARRISON, 1982). |
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| 1. Contact of stigma surface and pollen. The pollen takes up water (hydration). | dependent on the surrounding and/ or the water content of the stigma's tissue | stage of rejection of strong SI-systems | rejection due to SI-reactions |
| 2. Pollen tube growth and subsequent penetration of the intercellular spaces | The tissue's architecture determines the direction of the pollen tube growth | stage of rejection of weak SI-systems | |
| 3. Penetration of the transfusion tissue of the style (stylodium) | The direction of growth is determined by the arrangement of the transfusion tissue's cells | delayed pollen tube growth. The tip of the tube does often swell and subsequently burst | |
| 4. Penetration of the gametophyte (ovary) | penetration of the cuticle of the inner ovary wall. The direction of growth is determined by the cortical cells of the embryo sac and presumably also chemotactically. | loss of orientation, no directed growth, missing of the micropylee | |
| 5. Penetration of the micropyle, fusion of the gametes, fusion of the nuclei | The micropyle accepts only such a pollen tube that has penetrated the nucellus and penetrates the embryo sac | ||