CHAPTER 31 Plant Structure, Reproduction, and Development

1. CHAPTER 31Plant Structure, Reproduction, and Development

2. A Gentle Giant • This giant sequoia, the General Sherman, is the largest plant on Earth • It is 84 m (275 ft) tall • Its trunk is 10m in diameter

3. The General Sherman has been growing for about 2,500 years

4. Rings vary in thickness depending on weather conditions during the growing season • Growth rings mark each year in a tree's life

5. Lumber • Fabric • Paper • Food • Industrial chemicals • Humans depend on plant products

6. They provide food for land animals • They offer shelter and breeding areas for animals, fungi, and microorganisms • Their roots prevent soil erosion • Photosynthesis in plant leaves helps reduce carbon dioxide and adds oxygen to the air • Plants are vital to Earth's well-being

7. 31.1 Talking About Science: Plant scientist Katherine Esau was a preeminent student of plant structure and function • Katherine Esau was one of the twentieth century's most prolific plant scientists • Her early research on sugar beets led to important discoveries about • phloem • viral infections of plant tissue Figure 31.1A

8. Dr. Esau later used an electron microscope to continue studying the relationship between plant structure and function • She discovered that plant viruses are transmitted through plant tissues via plasmodesmata Figure 31.1B

9. PLANT STRUCTURE AND FUNCTION 31.2 The two main groups of angiosperms are the monocots and the dicots • Angiosperms, or flowering plants, are the most familiar and diverse plants • There are two main types of angiosperms • Monocots include orchids, bamboos, palms, lilies, grains, and other grasses • Dicots include shrubs, ornamental plants, most trees, and many food crops

10. Monocots and dicots differ in seed leaf number and in the structure of roots, stems, leaves, and flowers SEED LEAVES LEAF VEINS STEMS FLOWERS ROOTS MONOCOTS Onecotyledon Main veins usually parallel Vascular bundles incomplex arrangement Floral parts usuallyin multiples of three Fibrousroot system DICOTS Twocotyledons Main veins usually branched Vascular bundles arranged in ring Floral parts usually in multiples of four or five Taprootusually present Figure 31.2

11. 31.3 The plant body consists of roots and shoots • Root system • Provides anchorage • Absorbs and transports minerals and water • Stores food • Root hairs increase the surface area for absorption

12. Consists of stems, leaves, and flowers in angiosperms • Stems are located above the ground and support the leaves and flowers • Leaves are the main sites of photosynthesis in most plants • Shoot system

13. Terminal bud Blade Leaf Flower Petiole Axillary bud Stem SHOOTSYSTEM Node Internode Taproot Roothairs ROOTSYSTEM Figure 31.3

14. It is the growth point of the stem • Axillary buds can give rise to branches • In apical dominance, the terminal bud produces hormones that inhibit the growth of axillary buds • This results in a taller plant that has greater exposure to light • The terminal bud is located at the tip of a stem

15. 31.4 Many plants have modified roots and shoots • Roots and stems are adapted for a variety of functions • Storing food • Asexual reproduction • Protection • Plant breeders have improved the yields of root crops by selecting varieties, such as the sugar beet plant, with very large taproots Figure 31.4A

16. STRAWBERRYPLANT • runners, for asexual reproduction • rhizomes, for plant growth and food storage • tubers, for food storage in the form of starch Runner • Modified stems include POTATOPLANT Rhizome IRISPLANT Rhizome Tuber Taproot Root Figure 31.4B

17. Tendrils help plants to climb • Spines may protect the plant from plant-eating animals • Modified leaves include tendrils and spines Figure 31.4C

18. 31.5 Plant cells and tissues are diverse in structure and function Figure 31.5A

19. Parenchyma • Collenchyma • Sclerenchyma • Water-conducting cells • Food-conducting cells • There are five major types of plant cells

20. Parenchyma cells function in food storage, photosynthesis, and aerobic respiration Primarywall(thin) Pit Figure 31.5B

21. Collenchyma cells provide support in parts of the plant that are still growing Primarywall(thick) Figure 31.5C

22. Fiber cells • Sclerenchyma cells provide a rigid scaffold that supports the plant Pits Secondarywall Fibercells Primarywall FIBER Figure 31.5D

23. Sclereids (stone cells) Secondarywall Sclereidcells Primarywall Pits SCLEREID Figure 31.5D continued

24. Chains of tracheids or vessel elements form a system of tubes for water transport • Water-conducting cells convey water from the roots to the stems and leaves Pits Tracheids Vessel element Pits Openingsin end wall Figure 31.5E

25. Sieve-tube members are arranged end-to-end, forming tubes • Their end walls are perforated with plasmodesmata, forming sieve plates • At least one companion cell flanks each sieve-tube member • Food-conducting cells function in the transport of sugars, other compounds, and some mineral ions

26. Sieve plate Companioncell Cytoplasm Primarywall Figure 31.5F

27. Vascular tissues are complex tissues that conduct water and food • Xylem contains water-conducting cells that convey water and dissolved minerals • Phloem contains sieve-tube members that transport sugars • Complex tissues are composed of more than one type of plant cell

28. 31.6 Three tissue systems make up the plant body Leaf • Roots, stems, and leaves are made of three tissue systems • The epidermis • The vascular tissue system • The ground tissue system Stem Root Epidermis Groundtissue system Vasculartissue system Figure 31.6A

29. The cuticle is a waxy coating secreted by epidermal cells that helps the plant retain water • The vascular tissue contains xylem and phloem • It provides support and transports water and nutrients • The epidermis covers and protects the plant

30. It consists of parenchyma cells and supportive collenchyma and sclerenchyma cells • The ground tissue system functions mainly in storage and photosynthesis

31. The cortex consists mostly of parenchyma tissue • The selective barrier forming the innermost layer of the cortex is the endodermis • The ground tissue system of the root forms the cortex

32. Xylem VASCULARTISSUESYSTEM Phloem Epidermis GROUNDTISSUESYSTEM Cortex Endodermis Figure 31.6B

33. These microscopic cross sections of a dicot and a monocot indicate several differences in their tissue systems Figure 31.6C

34. The epidermis consist of pores called stomata (singular, stoma) flanked by regulatory guard cells • The three tissue systems in dicot leaves Figure 31.6D

35. The ground tissue system of a leaf is called mesophyll and is the site of photosynthesis Figure 31.6D

36. The vascular tissue consists of a network of veins composed of xylem and phloem Figure 31.6D

37. PLANT GROWTH 31.7 Primary growth lengthens roots and shoots • Most plants exhibit indeterminate growth • They continue to grow as long as they live • In contrast, animals are characterized by determinate growth • They cease growing after reaching a certain size

38. Examples: wheat, corn, rice, and most wildflowers • Biennials complete their life cycle in two years, with flowering occurring in the second year • Examples: beets and carrots • Perennials live and reproduce for many years • Examples: trees, shrubs, and some grasses • Annuals complete their life cycle in a single year or growing season

39. Meristems are areas of unspecialized, dividing cells • Apical meristems are located at the tips of roots and in the terminal buds and axillary buds of shoots • They initiate primary growth, lengthwise growth by the production of new cells • Roots and stems lengthen further as cells elongate and differentiate • Growth in all plants originates in tissues called meristems

40. Terminal bud Axillary buds Arrows =directionof growth Roottips Figure 31.7A

41. Vascularcylinder Cortex Epidermis DIFFERENTIATION Root hair ELONGATION Cellulosefibers CELLDIVISION Apical meristemregion Rootcap Figure 31.7B

42. Leaves Apicalmeristem Axillary budmeristems 1 2 Figure 31.7C

43. 31.8 Secondary growth increases the girth of woody plants • An increase in a plant's girth results from secondary growth • Secondary growth involves cell division in two cylindrical meristems • Vascular cambium • Cork cambium

44. Vascular cambium thickens a stem by adding layers of secondary xylem, or wood, next to its inner surface • It also produces the secondary phloem, which is a tissue of the bark • Cork cambium produces protective cork cells located in the bark

45. Figure 31.8A

46. Secondary phloem • Cork cambium • Protective cork cells • Heartwood in the center of the trunk consists of older, clogged layers of secondary xylem • Sapwood consists of younger, secondary xylem that still conducts water • Everything external to the vascular cambium is considered bark

47. A woody log is the result of several years of secondary growth Sapwood Rings Woodrays Heartwood Sapwood Vascular cambium Secondary phloem Cork cambium Bark Cork Heartwood Figure 31.8B

48. PLANT REPRODUCTION 31.9 Overview: The sexual life cycle of a flowering plant Anther • The angiosperm flower is a reproductive shoot consisting of • sepals • petals • stamen • carpels Carpel Stigma Ovary Stamen Ovule Sepal Petal Figure 31.9A

49. Sepals enclose and protect the flower bud before the flower opens • Petals are often bright and colorful • They attract insects (pollinators) • Sepals are usually green and resemble leaves in appearance

50. Pollen grains develop in anthers, at the tips of stamens • Carpels are the female reproductive organs of plants • The ovary at the base of the carpel houses the ovule • Stamens are the male reproductive organs of plants