| MadSci Network: Botany |
Plants have several ways to assure they don't pollinate themselves. However, not all species have these mechanisms. Species such as rice, wheat, tomato and pea are naturally self-pollinating. Some species are dioecious, which means they produce male and female flowers or cones on separate individuals. Dioecious species include holly, persimmon, fig, poplar, kiwi, ginkgo, cycads and date. Monoecious species bear separate female and male flowers or cones on the same plant. If they mature at different times, self-pollination is unlikely. Corn is an example. Female cones of wind-pollinated firs and Douglas fir develop in the top of the tree,but the male cones are on lower branches. This makes it unlikely pollen will reach female cones on the same tree. The shape of the flower may prevent self-pollination. For example, the stigma may be higher than the stamens so it would be unlikely for pollen to fall onto the stigma of the same flower. Probably the most common method to prevent self-pollinaion is self- incompatibility. The plant can recognize its own pollen because of a gene it carries. Pollen from the same plant is unable to fertilize an egg. References Self-Incompatibility: How Plants Avoid Inbreeding Flowering Plant Reproduction Dioecious Plant Species
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