Which of the following outbreeding devices prevents both Autogamy and Geitonogamy?
Dioecy (e.g., in Papaya) means male and female flowers are on separate plants. This prevents both autogamy (same flower) and geitonogamy (same plant). Self-incompatibility prevents fertilization but not the arrival of pollen. Monoecy prevents autogamy but not geitonogamy.
Ref: Diagram comparing Monoecious (Castor/Maize) and Dioecious (Papaya) plants.