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Types of inflorescences
Some plants bear only one flower per stem, which is called a solitary flower. Other plants produce an inflorescence--a cluster of flowers. Each flower in an inflorescence is called a floret.
Most inflorescences belong to one of two groups: racemes and cymes. In the racemose group, the florets start blooming from the bottom of the stem and progress toward the top. In a cyme, the top floret opens first and blooms progress downward along the peduncle. Detailed discussions of flower types are found in many botany textbooks.
How seeds form
Pollination is the transfer of pollen from an anther to a stigma, either by wind or by pollinators. Species pollinated by insects, animals, or birds often have brightly colored or patterned flowers that contain fragrance or nectar. While searching for nectar, pollinators transfer pollen from flower to flower, either on the same plant or on different plants. Plants evolved this ingenious mechanism in order to ensure their species' survival. Wind-pollinated flowers often lack showy floral parts and nectar because they don't need to attract pollinators.
A chemical in the stigma stimulates pollen to grow a long tube down the style to the ovules inside the ovary. When pollen reaches the ovules, it releases sperm, and fertilization typically occurs. Fertilization is the union of a male sperm nucleus from a pollen grain with a female egg. If fertilization is successful, the ovule develops into a seed. It is important to remember that pollination is no guarantee that fertilization will occur.
Cross-fertilization combines genetic material from two parent plants. The resulting seed has a broader genetic base, which may enable the population to survive under a wider range of environmental conditions. Cross-pollinated plants usually are more successful than self-pollinated plants. Consequently, more plants reproduce by cross-pollination than by self-pollination.
View the pollination/fertilization process in illustrated form as a mini-movie
or slide set.
