Q.Describe three devices by which cross pollination is encouraged in Angiosperms by avoiding self pollination.

Outbreeding devices such as unisexuality, dichogamy, and self-incompatibility each structurally or genetically prevent self-pollination, so cross-pollination becomes the only route to fertilization. …

Step 1 -- Unisexuality (dioecism): Some plants bear only male flowers or only female flowers, either on separate individual plants (dioecious, e.g., papaya, mulberry) or as separate male and female flowers on the same plant (monoecious, e.g., maize). Because no single flower carries both a functional androecium and gynoecium, self-pollination within one flower is structurally impossible, forcing pollen transfer between different plants or different flowers.

Step 2 -- Dichogamy: In a bisexual flower, the androecium and gynoecium mature at different times, so a flower's own pollen is never available at the same time as its own receptive stigma. In protandry, the anthers mature first (as in sunflower); in protogyny, the stigma matures first (as in Gloriosa). Either way, self-pollen and the flower's own stigma are never simultaneously ready, favouring pollen arriving from another flower. …

Select and explain three distinct outbreeding devices, describing the mechanism by …

• Describing only pollination types (autogamy/xenogamy) instead of the structural/genetic devices that prevent self …