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Plant Structure, Growth, and Differentiation in Chapter 31

This chapter explores the structure, growth, and differentiation of plants, including herbaceous and woody plants, annuals, biennials, and perennials. It also covers the vascular plant body, tissue systems, and the process of growth in plants.

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Plant Structure, Growth, and Differentiation in Chapter 31

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  1. Chapter 31 Plant Structure, Growth, and Differentiation

  2. Plants • Herbaceous • In temperate climates, aerial parts die back • Annuals, biennials, perennials • Woody • In temperate climates, aerial parts persist • Perennials

  3. Annuals • Grow, reproduce, and die in one year or less • Corn • Geranium • Marigold

  4. Duckweeds, with Wolffia on frog’s back

  5. Biennials • Take two years to complete their life cycles before dying • Carrot • Queen Anne’s lace

  6. Perennials • Have the potential to live for more than two years • Asparagus • Oak trees

  7. Eucalyptus regnans

  8. Life history strategies • Long-lived trees compete successfully against smaller plants in favorable environments (e.g., tropical rain forests) • Small, short-lived plants thrive in unfavorable environments (e.g., deserts after a rainy spell)

  9. Vascular plant body • Root system • Generally underground • Obtains water and dissolved nutrient minerals • Anchor plant in place

  10. The plant body: Arabidopsis thaliana

  11. Vascular plant body, cont. • Shoot system consists of • A vertical stem bearing leaves (organs of photosynthesis) • Reproductive structures (flowers and fruits in flowering plants) • Buds (undeveloped embryonic shoots that develop on stems)

  12. Vascular plant body, shoot system, cont. • Generally aerial • Obtains sunlight and exchanges gases, such as CO2, oxygen, and water vapor

  13. Vascular plant body, cont. • Plant body is composed of • Ground tissue system • Vascular tissue system • Dermal tissue system • Although separate organs exist, tissue systems are integrated throughout plant body

  14. The three tissue systems in the plant body

  15. Ground tissue system • Parenchyma tissue • Collenchyma tissue • Sclerenchyma tissue

  16. Parenchyma cells

  17. Collenchyma cell Schlerenchyma cells

  18. Parenchyma tissue • Composed of living parenchyma cells with thin primary cell walls • Functions • Photosynthesis • Storage • Secretion

  19. Collenchyma tissue • Consists of collenchyma cells with unevenly thickened primary cell walls • Function is to provide flexible structural support

  20. Sclerenchyma tissue • Composed of sclerenchyma cells (sclereids or fibers) with • Primary cell walls • Secondary cell walls • Function is to provide structural support, although Sclerenchyma cells are often dead at maturity

  21. Parenchyma cell type Sclerenchyma cell type Collenchyma cell type

  22. Vascular tissue system • Conducts materials throughout plant body • Provides strength and support • Consists of • Xylem • Phloem

  23. Tracheid (xylem cell Sieve tube element Vessel element (xylem cell) Phloem tissue

  24. Vascular tissue system, cont. • Xylem • Complex tissue conducting water and dissolved nutrient minerals • Conducting cells are tracheids and vessel elements

  25. Vascular tissue system, cont. • Phloem • Complex tissue conducting sugar in solution • Conducting cells are sieve tube elements; they are assisted by companion cells

  26. Tracheid Vessel element

  27. Sieve tube element Companion cell

  28. Dermal tissue system • Outer protective covering of the plant body • Consists of • Epidermis • Periderm

  29. Dermal tissue system, cont. • Epidermis • Complex tissue covering herbaceous plant body • Epidermis of aerial parts secretes a waxy cuticle to reduce water loss • Stomata permit gas exchange • Trichomes (outgrowths or hairs)

  30. Dermal tissue system, cont. • Periderm • Complex tissue covering woody parts of plant body in woody plants

  31. Epidermal cell Guard cell

  32. Trichome Cork cell

  33. Growth in plants versus animals • Localized in meristems • Involves • Cell division • Cell elongation • Cell differentiation

  34. Primary growth • Increase in stem or root length • Occurs in all plants • Secondary growth • Increase in stem or root girth • Localized • Typically occurs in long cylinders of meristematic cells throughout length of older stems and roots

  35. Apical meristems • Localized • At tips of roots • At tips of shoots • Within buds of stems • Activity herein results in primary growth

  36. A root tip

  37. Lateral meristems • Vascular cambium • Cork cambium • Responsible for secondary growth

  38. Longitudinal section through shoot apex

  39. Secondary growth

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