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Lecture 19: Plant Structure and Function

Lecture 19: Plant Structure and Function. Plant structure can be divided into two systems: roots and shoots. Parts under ground Used for anchorage Used for absorption of water and nutrients. The Root System. Tap root. Fibrous root.

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Lecture 19: Plant Structure and Function

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  1. Lecture 19:Plant Structure and Function

  2. Plant structure can be divided into two systems: roots and shoots

  3. Parts under ground Used for anchorage Used for absorption of water and nutrients The Root System Tap root Fibrous root

  4. Roots are often covered with root hairs which increase the surface area for absorption Epidermal cell Root hair

  5. Modified roots

  6. Stems, leaves, buds Nodes are places on the stem where leaves are attached and buds form. The Shoot System

  7. Figure 35.5 Simple versus compound leaves

  8. Figure 35.19 Leaf anatomy

  9. Figure 35.6 Modified leaves: Tendrils, pea plant (top left); spines, cacti (top right); succulent (bottom left); brightly-colored leaves, poinsettia (bottom right)

  10. Figure 35.4 Modified shoots: Stolons, strawberry (top left); rhizomes, iris (top right); tubers, potato (bottom left); bulb, onion (bottom right)

  11. ground tissue -- bulk of plant body vascular tissue -- distribution of water and solutes dermal tissue -- covering, protection of plant surface. Plant structures are composed of 3 types of tissues

  12. Vascular tissue: xylem and phloem

  13. Meristem cells are undifferentiated and can divide through mitosis Continued divisions of meristem cells keeps a plant growing throughout it's life = indeterminate growth. apical meristems -- results in increase in length of stems and roots lateral meristems -- growth produces thickening of stems and roots Plant growth occurs at localized regions called meristems

  14. As a stem or root grows, primary meristems develop behind the growing tip These differentiate into the three tissue systems: Dermal tissue comes from: protoderm --> epidermis (waxy covering in shoots) Vascular tissue comes from: procambium --> vascular cambium--> primary xylem and phloem Ground tissue comes from: ground meristem -> ground tissues--> cork cambium Growth at apical meristems = primary growth

  15. Figure 35.17 The terminal bud and primary growth of a shoot

  16. In woody plants vascular cambium forms a ring each growing season a new layer of xylem is produced which pushes the cambium and all outer tissues further out. Old phloem cells are crushed and only a thin strip of newly- formed phloem remains alive. Growth at lateral meristems: Secondary growth

  17. Figure 35.22 Anatomy of a three-year-old stem

  18. As the stem expands, it ruptures the epidermis Bark is composed of phloem and ground issue cells called cork cells Figure 35.23 Anatomy of a tree trunk

  19. Tree Girdling

  20. If you hammer a nail into a tree 10 feet above the ground, and wait 20 years, where will the nail be? ? 10 feet

  21. Angiosperms are often divided into the monocots and dicots

  22. Monocots

  23. Dicots

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