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

2. Plants are essential to human life.
Our use of plants parallels the growth of civilization.
Some plants, such as coastal redwoods, are among the largest and oldest organisms on earth.
Coast redwoods are gymnosperms, a kind of plant that bears seeds on cones

3. Man climbing a redwood tree.

4. Most plants are angiosperms which will be the focus of this discussion on plant structure.

5. Angiosperms
Angiosperms, or flowering plants, bear seeds in fruits.

6. Two Main Groups of Angiosperms
Monocots and Eudicots
They differ in:
number of seed leaves (cotyledons)
leaf venation
arrangement of vascular system in stems
number of flower parts
root structure

7. Lily – Monocot
Rose – Eudicot

9. parallel leaf venation scattered vascular bundles
Monocots
one cotyledon
parallel leaf venation
scattered vascular bundles
flower parts in 3s or multiples of 3
fibrous roots

10. Eudicots two cotyledons branched leaf venation
ring of vascular bundles
flower parts in 4s or 5s (or multiples)
taproot system

11. Monocot or Eudicot?

12. Typical Plant Body
Three basic organs – several types of tissues that perform a particular function.
Roots
Stems
Leaves

13. Plants must draw resources from two different environments.
They must draw water and minerals from the soil and CO2 and sunlight from aboveground.
Neither roots nor shoots can survive without the other.

14. Plants absorb water and minerals from soil through roots.
Plants absorb the sun’s energy and carbon dioxide from the air through shoots (stems and leaves).

15. Plant roots depend on shoots for carbohydrates produced via photosynthesis.
Plant shoots depend on roots for water and minerals.

17. Root System Anchors the plant in the soil.
Absorbs and transports minerals.
Stores food.

18. Monocots
Dicots

19. Root Hairs Found in both monocots and dicots.
Increase surface area enormously.
Cotyledons

20. Shoot System
Made up of stems, leaves, and adaptations for reproduction (flowers in angiosperms).
Stems – above ground and support the leaves and flowers.
Nodes – areas on the stems at which leaves are attached.

22. Two Types of Buds Terminal Bud – where a plant stem grows in length.
Produces hormones (auxins) that inhibit the growth of the lateral buds (apical dominance).

23. Apical Dominance Concentrates resources on height.
Evolutionary adaptation that increases the plant’s exposure to height.
Some axillary buds become flowers.

24. Modified Roots, Stems, and Leaves
Modified stems used for reproducing asexually.
Used for food storage and asexual reproduction.

25. Modified Leaves - Tendrils

26. Purposes of Leaf Modifications
Protection
Cactus spine or rose thorns.
Climbing
Tendrils on pea plants or clematis.

27. Three Tissue Systems – Plant Body
Dermal Tissue
Ground Tissue
Vascular Tissue

29. Dermal Tissue Forms an outer protective covering.
In many plants, it has a waxy covering to prevent water loss.
Acts as a first defense against damage and disease.
Usually a single layer of packed cells called the epidermis.

30. Stomata Openings in the epidermis (pores) that enable gas exchange.
Usually found on the underside of the leaf.
Are opened and closed by guard cells.

32. Vascular Tissue
Xylem and Phloem

33. Vascular System Analogous to our circulatory system.
Xylem – dead cells that function to transport water from the roots to the aboveground plant.
Phloem – living cells that function to transport sugars from the aboveground plant to the roots.

34. Phloem
Xylem

35. Ground Tissue Lies between dermal and vascular tissue.
Analogous to connective (muscle) tissue.
Eudicot ground tissue divided into pith and cortex.
Leaf ground tissue called mesophyll.

36. Three Structures that Distinguish Plant Cells from Animal Cells.
Chloroplast
Water-Filled
Vacuole
Cell Wall

37. Five Types of Plant Tissues
Parenchyma cells
Collenchyma cells
Sclerenchyma cells
Water-conducting cells (Xylem)
Food-conducting cells (Phloem)

38. Parenchyma Cells
Function in photosynthesis, metabolism, and food and water storage.

39. Have thick cells walls that give herbaceous plants their structure.
Collenchyma Cells
Have thick cells walls that give herbaceous plants their structure.

40. Sclerenchyma Cells Fibrous lignified cells.
Gives pears their grittiness.
Make up seed coats.

41. Sclerenchyma Sclerenchyma cells
Thick secondary cell wall containing lignin
Lignin is a main component of wood
Dead at maturity
Rigid support
Two types of sclerenchyma cells are fibers and sclereids
Fibers—long and thin, arranged in bundles
Sclereids—shorter than fibers, present in nut shells and pear tissue

42. Water-Conducting Cells
Tracheids and vessel elements that move water from the roots to the stomata in the leaves.
Both have thick secondary cell walls
Both are dead at maturity
Chains of tracheids and vessel elements form tubes that make up the vascular tissue called xylem

43. Xylem

44. Food Conduction Cells No secondary cell wall
—Sieve tube members – move nutrients both ways (roots to leaves and leaves to roots).
No secondary cell wall
Alive at maturity but lack most organelles
Companion cells
Contain organelles
Control operations of sieve tube members
Chains of sieve tube members, separated by porous sieve plates, form the vascular tissue called phloem

45. Phloem

46. Primary Growth Lengthen s Roots and Shoots
Unlike animals, plant growth is indeterminate
Growth occurs throughout a plant’s life
Plants are categorized based on how long they live
Annuals complete their life cycle in one year
Biennials complete their life cycle in two years
Perennials live for many years

47. Primary Growth Lengthen s Roots and Shoots
Plant growth occurs in specialized tissues called meristems
Meristems are regions of active cell division
Apical meristems are found at the tips of roots and shoots
Primary growth occurs at apical meristems
Primary growth allows roots to push downward through the soil and shoots to grow upward toward the sun

48. Primary – Getting Taller
Two Types of Growth
Going Deeper
Primary – Getting Taller

49. Primary Growth of a Root
Zone of Elongation
Cells can lengthen
by as much as 10 times.
Zone of Maturation
Cells differentiate into dermal, vascular, and ground tissue.

50. Primary Growth of a Shoot
The apical meristems of shoot tips occur as buds at the stem tip and at the base of leaves
Cells produced in the shoot apical meristem differentiate into dermal, vascular, and ground tissues
Vascular tissue produced from the apical meristem is called primary vascular tissue (primary xylem & primary phloem)

52. Secondary Growth Increases Girth
Secondary growth occurs at lateral meristems
Lateral meristems are areas of active cell division that exist in two cylinders that extend along the length of roots and shoots.
Vascular cambium is a lateral meristem that lies between primary xylem and phloem.
Cork cambium is a lateral meristem that lies at the outer edge of the stem cortex.

53. Secondary Growth Increases Girth

54. Sexual Reproduction of Flowering Plants
Flowers typically contain four types of highly modified leaves called floral organs
Sepals—enclose and protect flower bud
Petals—showy; attract pollinators
Stamens—male reproductive structures
Carpels—female reproductive structures
Memory Hint: Stamens - male

55. Anther - produces pollen which develops into sperm
Stigma - site of pollination
Ovary - houses ovules, which contain developing eggs

56. Angiosperm Life Cycle Overview
Fertilization occurs in the ovule; the fertilized egg develops into an embryo encased in a seed.
The ovary develops into a fruit, which protects the seed and aids in dispersal.
The seed germinates under suitable conditions to produce a seedling, which grows into a mature plant.

57. Life Cycle of a Angiosperm

58. Development of Pollen and Ovules Culminates in Fertilization
Plant life cycles involve alternating diploid (2n) and haploid (n) generations.
The diploid generation is called the sporophyte.
Specialized diploid cells in anthers and ovules undergo meiosis to produce haploid spores
The haploid spores undergo mitosis and produce the haploid generation
The haploid generation is called the gametophyte.
Gametophytes produce gametes via mitosis.

59. Male Gametophyte The male gametophyte is a pollen grain.
A cell in the anther undergoes meiosis to produce four haploid spores.
Each spore divides via mitosis to produce two cells called the tube cell and generative cell.
A tough wall forms around the cells to produce a pollen grain.
Pollen grains are released from the anther.

60. Female Gametophyte The female gametophyte is an embryo sac.
A cell in the ovule undergoes meiosis to produce four haploid spores
Three of the spores degenerate
The surviving spore undergoes a series of mitotic divisions to produce the embryo sac.
One cell within the embryo sac is an egg ready for fertilization.
One central cell within the embryo sac has two nuclei and will produce endosperm.

62. Development of pollen and ovules culminates in fertilization.
Pollination
Transfer of pollen from anther to stigma.
Pollen is carried by wind, water, and animals.
Pollen grain germination
Tube nucleus produces pollen tube, which grows down through the style to the ovary.
Generative nucleus divides to produce two sperm.

63. Double fertilization
One sperm fertilizes the egg to produce a zygote.
One sperm fuses with the central cell nuclei to produce 3n endosperm.
Endosperm (3n) nourishes the developing embryo.

65. The Ovule Develops into a Seed
The zygote divides many times via mitosis to produce the embryo.
The embryo consists of tiny root and shoot apical meristems and one or two cotyledons.
A tough seed coat develops.
Seed dormancy
Embryo growth and development are suspended
Allows delay of germination until conditions are favorable

66. Endosperm:
Food for the Embryo

67. Pea Flower to Peas Seeds

68. Seed Germination Completes the Life Cycle
Germination breaks seed dormancy.
Germination begins when water is taken up.
Eudicot seedling shoots emerge from the soil with the apical meristem “hooked” downward to protect it.
Monocot seedling shoots are covered by a protective sheath and emerge straight from the soil.