Section 3

Dispersal and Propagation

• Fruits and seeds are dispersed by animals, wind, water, forcible discharge, and gravity. Many fruits and seeds are adapted for a particular type of dispersal.

• The three major categories of fruits are simple, aggregate, and multiple.

• The structure of seeds differs among the major groups of seed plants. Seeds need water, oxygen, suitable

Vocabulary propagation (p. 618) seed coat (p. 620) plumule (p. 620) epicotyl (p. 620)

hypocotyl (p. 620) radicle (p. 620) hilum (p. 620) dormancy (p. 621)

temperatures, and sometimes light to germinate. Delayed germination often assures the survival of a plant.

• Asexual reproduction enables plants to spread rapidly in a favorable environment but can result in a lack of genetic variation among offspring.

• Human methods of plant propagation include using cuttings, layering, grafting, and tissue culture.

clone (p. 623) vegetative reproduction (p. 623) cutting (p. 624)

layering (p. 624) grafting (p. 624) tissue culture (p. 624)

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