Chapter 40

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40.1 Plant embryo development establishes a basic body plan.
• Plant shape is determined by the direction of cell division and expansion. • Three tissue systems form radially through regulated cell division and differentiation. • Shoot and root apical meristems are established to continuously produce new tissues, which then differentiate into body parts. • Carbohydrates, lipids, and proteins are stored for germination in the endosperm or cotyledons.		1.  The pattern of cell division regulates the shape of an embryo. Describe the cell division pattern that results in the single, outer layer of protoderm in the globular stage embryo. 2.  What evidence supports the claim that the shoot meristem is genetically specified separately from the root?
40.2 The seed protects the dormant embryo from water loss.
• The ovule wall (integuments) around the embryo hardens to protect the embryo as embryogenesis ends. • Seed formation allows the embryo to enter a dormant state and continue growth under more optimal conditions.		3.  Why are seeds adaptively important? Why may a seed showing proper respiration and synthesis of proteins and nucleic acids and all other normal metabolic activities still fail to germinate?		•Corn Grain Structure •Garden Bean Seed Structure •Embryos and Seeds
40.3 Fruit formation enhances the dispersal of seeds.
• Fruits are an angiosperm innovation that develop from the ovary wall (a modified leaf) that surrounds the ovule(s). • Fruits are highly diverse in terms of their dispersal mechanisms, often displaying wings, barbs, or other structures that aid in their transport from place to place. Fruit dispersal methods are especially important in the colonization of islands or other distant patches of suitable habitat.		4.  Why is it advantageous for a plant to produce fruit? How does the genotype of the fruit compare with the genotype of the embryo? How does the genotype of the seed wall compare with the fruit wall?		•Fruits •Activity: Fruits
40.4 Germination initiates post-seed development.
• In a seed, the embryo with its food supply is encased within a sometimes rigid, relatively impermeable seed coat that may need to be abraded before germination can occur. Weather or passage through an animal's digestive tract may be necessary for germination to begin. • When temperature, light, and water conditions are appropriate, germination can begin. In some cases, a period of chilling is required prior to germination. This adaptation protects seeds from germinating until after the cold season. • At germination, the mobilization of the food reserves is critical. Hormones control this process.		5.  Explain how the embryo signals the endosperm to obtain sugars for growth during germination. 6.  Why does the root (actually the radicle) of the embryo emerge first?		•Germination •Activity: Germination

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