Chapter 31

1. Chapter 31 0 Plant Structure, Reproduction, and Development

2. 0 • A Gentle Giant • Gymnosperms • Are one of two groups of seed plants • Bear seeds in cones

3. 0 • Angiosperms, or flowering plants • Are the most familiar and diverse group of plants

4. TALKING ABOUT SCIENCE • 31.1 Plant scientist Natasha Raikhel studies the Arabidopsis plant as a model biological system • Natasha Raikhel • Is one of America’s most prominent plant biologists Figure 31.1A

5. Dr. Raikhel works with Arabidopsis • A popular model organism for studying biological systems Figure 31.1B

6. Leaf veins Flowers Roots Stems Seed leaves MONOCOTS Fibrous root system Floral parts usually in multiples of three One cotyledon Vascular bundles in complex arrangement Main veins usually parallel DICOTS Taproot usually present Floral parts usually in multiples of four or five Two cotyledons Vascular bundles arranged in ring Main veins usually branched PLANT STRUCTURE AND FUNCTION • 31.2 The two main groups of angiosperms are the monocots and the dicots • Monocots and dicots differ in • The number of seed leaves and in the structure of roots, stems, leaves, and flowers Figure 31.2

7. 31.3 A typical plant body consists of roots and shoots • A plant’s root system • Anchors it in the soil • Absorbs and transports minerals and water and stores food

8. The shoot system of a plant • Is made up of stems, leaves, and adaptations for reproduction, flowers

9. Terminal bud Blade Leaf Flower Petiole Axillary bud Stem Shoot system Node Internode Root hair Taproot Root hairs Root system Epidermal cell • The body of a dicot Figure 31.3

10. 31.4 Many plants have modified roots, stems, and leaves • Some plants have unusually large taproots • That store food in the form of carbohydrates Figure 31.4A

11. Strawberry plant Potato plant Stolon (runner) Ginger plant Taproot Rhizome Rhizome Tuber Root • Many plants have modified stems • That store food or function in asexual reproduction Figure 31.4B

12. Other types of plants have modified leaves • That function in protection or climbing Figure 31.4C

13. Central vacuole Chloroplast Nucleus Cell walls Primary cell wall Endoplasmic reticulum Secondary cell wall Middle lamella Mitochondrion Golgi apparatus Cell walls of adjoining cells Ribosomes Plasma membrane Microtubules Plasmodesmata Pit Plasma membrane • 31.5 Plant cells and tissues are diverse in structure and function • Most plant cells have three unique structures • Chloroplasts, the sites of photosynthesis • A central vacuole containing fluid • A cell wall that surrounds the plasma membrane Figure 31.5A

14. Primary cell wall (thin) LM 270 Pit Starch-storing vesicles Primary cell wall (thick) LM 270 • Plants have five major types of cells • Parenchyma, which perform most of the metabolic functions • Collenchyma, which provide support Figure 31.5B Figure 31.5C

15. Secondary cell wall Sclereid cells Pits Secondary cell wall Fiber cells Primary cell wall Primary cell wall Pits LM 266 LM 200 Fiber Sclereid • Sclerenchyma, the main component of wood Figure 31.5D

16. Pits Tracheids Vessel element Pits Openings in end wall Colorized SEM 150 • Angiosperms have water-conducting cells • Tracheids and vessel elements Figure 31.5E

17. Sieve plate Companion cell Primary cell wall Cytoplasm • Sieve-tube members • Are food-conducting cells Figure 31.5F

18. Two kinds of vascular tissue are • Xylem, which conveys water and minerals • Phloem, which transports sugars

19. Dicot leaf Cuticle Upper epidermis Xylem Phloem Vein Mesophyll Guard cells Lower epidermis Stoma Sheath Dicot stem Monocot stem Vascular bundle Vascular bundle Cortex Pith Epidermis Epidermis Xylem Phloem Vascular cylinder Key Epidermis Dermal tissue system Ground tissue system Vascular tissue system Cortex Endodermis Dicot root • 31.6 Three tissue systems make up the plant body • Each plant organ is made up of threetissue systems • The dermal,vascular, and ground tissue systems Figure 31.6

20. The dermal tissue system • Covers and protects the plant • The vascular tissue system • Contains xylem and phloem and provides long-distance transport and support • The ground tissue system • Consists of parenchyma cells and supportive collenchyma and sclerenchyma cells

21. PLANT GROWTH • 31.7 Primary growth lengthens roots and shoots • Meristems, areas of unspecialized, dividing cells • Are where plant growth originates

22. Terminal bud Axillary buds Arrows = direction of growth Root tips Figure 31.7A • Apical meristems • Are located in the tips of roots and in the terminal and axillary buds of shoots • Initiate primary (lengthwise) growth by producing new cells

23. Vascular cylinder Cortex Root hair Epidermis Zone of maturation Zone of elongation Cellulose fibers Zone of cell division Apical meristem region Key Root cap Dermal tissue system Ground tissue system Vascular tissue system • Roots are covered with a root cap • That protects the cells of the apical meristem Figure 31.7B

24. Leaves Apical meristem Axillary bud meristems LM 103 2 1 • Axillary bud meristems • Are found near the apical meristems Figure 31.7C

25. 31.8 Secondary growth increases the girth of woody plants • Secondary growth arises from cell division • In a cylindrical meristem called the vascular cambium

26. Year 2 Late Summer Year 1 Early Spring Year 1 Late Summer Key Dermal tissue system Ground tissue system Vascular tissue system Shed epidermis Growth Growth Growth Primary xylem Epidermis Cork Secondary xylem (wood) Vascular cambium Secondary xylem (2 years’ growth) Cortex Cork cambium Bark Primary phloem Secondary phloem • The vascular cambium thickens a stem • By adding layers of secondary xylem, or wood, next to its inner surface Figure 31.8A

27. Sapwood Rings Wood rays Heartwood Sapwood Vascular cambium Secondary phloem Heartwood Bark Cork cambium Cork • The heartwood and sapwood • Consist of different layers of xylem • Outside the vascular cambium, the bark consists mainly of • Secondary phloem, cork cambium, and protective cork cells Figure 31.8B

28. Stigma Carpel Anther Stamen Style Filament Ovary Ovule Sepal Petal REPRODUCTION OF FLOWERING PLANTS • 31.9 Overview: The sexual life cycle of a flowering plant • The angiosperm flower consists of • Sepals, petals, stamens, and carpals Figure 31.9A

29. Pollen grains develop in anthers • At the tip of stamens

30. Ovary, containing ovule Embryo Fruit, (mature ovary), containing seed Seed Mature plant with flowers, where fertilization occurs Seedling Germinating seed • The tip of the carpel, the stigma • Receives pollen grains • The ovary, at the base of the carpel • Houses the egg-producing structure, the ovule Figure 31.9B

31. 31.10 The development of pollen and ovules culminates in fertilization • In the diploid sporophyte of an angiosperm • Haploid spores are formed within ovules and anthers

32. The spores in the anthers • Give rise to male gametophytes, pollen grains, which produce sperm • A spore in an ovule • Produces the embryo sac, the female gametophyte, which contains an egg cell

33. Pollination • Is the arrival of pollen grains onto a stigma • A pollen tube grows into the ovule • And sperm pass through it and fertilize both the egg and a second cell in a process called double fertilization

34. Development of male gametophyte (pollen grain) Development of female gametophyte (embryo sac) Anther Ovule Cell within anther Ovary Meiosis Meiosis Surviving cell (haploid spore) Four haploid spores Pollen germinates Single spore Mitosis Wall forms Mitosis (of each spore) Pollination Two cells Pollen grain released from anther Embryo sac Egg cell Two sperm in pollen tube Triploid (3n) endosperm nucleus Pollen tube enters embryo sac Two sperm discharged Diploid (2n) zygote (egg plus sperm) Double fertilization occurs • Gametophyte development and fertilization in an angiosperm Figure 31.10

35. Triploid cell Ovule Shed epidermis Growth Cotyledons Zygote Endosperm Seed coat Two cells Shoot Cork Secondary xylem (wood) Cork cambium Secondary phloem Embryo Root Seed • 31.11 The ovule develops into a seed • After fertilization, the ovule becomes a seed • And the fertilized egg within it divides and becomes an embryo Figure 31. 11A

36. The other fertilized cell • Develops into the endosperm, which stores food for the embryo

37. Embryonic leaves Embryonic shoot Embryonic root Cotyledons Seed coat Common bean (dicot) Fruit tissue Cotyledon Seed coat Endosperm Embryonic leaf Embryonic Shoot Sheath Embryonic root Figure 31.11B Corn (monocot) • The internal structures of dicot and monocot seeds • Differ in a variety of ways

38. Upper part of carpel Ovule Seed Pod (opened) Ovary wall Sepal • 31.12 The ovary develops into a fruit • Angiosperms form fruits • Which help protect and disperse the seeds 1 3 2 Figure 31.12A Figure 31.12B

39. Angiosperm fruits • May differ in size and development Figure 31.12C

40. 31.13 Seed germination continues the life cycle • A seed starts to germinate • When it takes up water and starts to expand • The embryo resumes growth • And absorbs nutrients from the endosperm • An embryonic root emerges • And a shoot pushes upward and expands its leaves

41. Foliage leaves Embryonic shoot Cotyledons Embryonic root • In dicot germination, the root emerges first • Followed by the shoot, which is covered by a protective hook Figure 31.13A

42. Foliage leaves Protective sheath enclosing shoot Embryonic root Cotyledon • In monocot germination • A protective sheath surrounding the shoot breaks the soil Figure 31.13B

43. Figure 31.14A Figure 31.14B Figure 31.14C Figure 31.14D • 31.14 Asexual reproduction produces plant clones • Asexual reproduction can be achieved via • Bulbs, sprouts, or runners

44. CONNECTION • 1.15 Asexual reproduction is a mainstay of modern agriculture • Propagating plants asexually from cuttings or bits of tissue • Can increase productivity but can also reduce genetic diversity Figure 31.15