1. 9.1 Plant Organs Vegetative Organs Reproductive Structures Roots Stems
Leaves
Reproductive Structures
Flowers
Seeds
Fruits

2. Organization of a Plant Body

3. Organization of a Plant Body

4. 9.1 Plant Organs
Roots
Generally, the root system is at least equivalent in size and extent to the shoot system
Anchors plant in soil
Absorbs water and minerals
Produces hormones
Root hairs:
Projections from epidermal root hair cells
Greatly increase absorptive capacity of root

5. 9.1 Plant Organs
Stems
The main axis of a plant that elongates and produces leaves
Nodes occur where leaves are attached to the stem
Internode is region between nodes
Stems have vascular tissue that transports water and minerals
In some plants, stems carry on photosynthesis, or store water and nutrients.

6. 9.1 Plant Organs
Leaves
Major part of the plant that carries on photosynthesis
Deciduous plants are those that lose their leaves every year.
Evergreens retain their leaves for two to seven years.
Foliage leaves are usually broad and thin
Blade - Wide portion of foliage leaf
Petiole - Stalk attaches blade to stem
Leaf Axil - Axillary bud originates

7. 9.1 Plant Organs Some Specialized Types of Leaves
Tendrils - Leaves that attach to objects
Bulbs - Leaves that store food
Some leaves are designed to protect buds, and in some cases leaves capture insects.

8. 9.2 Monocot Versus Eudicot Plants

9. 9.2 Monocot Versus Eudicot Plants
Cotyledons = seed leaves.
Flowering plants are divided into two groups dependent upon the number of cotyledons are present in the embryonic plant.
Monocots (one cotyledon)
Eudicots (two cotyledons)

10. Structural Differences in Monocots and Dicots

11. 9.3 Plant Tissue
Meristematic tissue allows plants to grow their entire lives.
Apical meristems are located at or near the tip of stem and roots, increasing the length of these structures.

12. 9.3 Plant Tissue Meristematic tissue gives rise to: Epidermal tissue
Ground tissue
Vascular tissue

13. 9.3 Plant Tissue Epidermal Tissue Specialized Epidermal Cells
Contains closely packed epidermal cells
Specialized Epidermal Cells
Epidermal cells exposed to air have a waxy cuticle
Minimizes water loss
Protection from disease
Root epidermis has root hairs
Absorb water
Anchor the plant

14. 9.3 Plant Tissue Specialized Epidermal Cells Trichomes Stomata
Protect the plant from too much sun
Produce toxic substances
Stomata
Gas exchange
Periderm contains cork cells
Protect the plant

15. Modification of Epidermal Tissue

16. 9.3 Plant Tissue Ground Tissue Ground tissue forms the bulk of a plant
Parenchyma cells
Collenchyma cells
Sclerenchyma

17. 9.3 Plant Tissue Parenchyma cells: Collenchyma cells:
Least specialized and are found in all organs of plant
Can divide and give rise to more specialized cells
Collenchyma cells:
Have thicker primary walls
Form bundles underneath epidermis
Flexible support to immature regions of the plant

18. 9.3 Plant Tissue Sclerenchyma cells:
Have thick secondary walls impregnated with lignin
Most are nonliving
Primary function is to support mature regions of the plant
Two types of sclerenchyma cells
Fibers
Sclereids

19. Ground Tissue Cells

20. 9.3 Plant Tissue Vascular Tissue Vascular tissue is for transport
Xylem transports water and minerals form the roots to the leaves
Phloem transports sucrose and other organic compounds (including hormones) from the leaves to the roots).
Xylem and phloem are complex tissues because they are composed of two or more types of cells.

21. 9.3 Plant Tissue Xylem has two types of conducting cells
Vessel Elements
Larger, with perforated plates in their end walls
Tracheids
Long, with tapered ends
Pits in end walls
Vascular rays
Fibers

22. Xylem Structure

23. 9.3 Plant Tissue Phloem Sieve-Tube Members Are the conducting cells,
Arranged to form a continuous sieve tube
Contain cytoplasm but no nuclei
Have a nucleated companion cell
Plasmodesmata extend from one cell to another through sieve plates

24. Phloem Structure

25. 9.4 Organization of Leaves

26. 9.4 Organization of Leaves

27. 9.4 Organization of Leaves
Leaf Diversity

28. Classification of Leaves

29. Leaf Diversity

30. 9.5 Organization of Stems

31. 9.5 Organization of Stems
Woody twigs provide a good example for studying stem organization.
Terminal Buds
Leaf Scars and Bundle Scars
Axillary Buds

32. Stem of a Woody Twig

33. 9.5 Organization of Stems Shoot Apical Meristem
Produces new cells for growth
Protected by leaf primordia
Primary Meristems
Protoderm
Ground Meristem
Parenchyma tissue

34. Shoot Tip and Primary Meristems

35. 9.5 Organization of Stems Herbaceous Stems
Mature nonwoody stems exhibit only primary growth
Outermost tissue covered with waxy cuticle
Stems have distinctive vascular bundles
Herbaceous eudicots - Vascular bundles arranged in distinct ring
Monocots - Vascular bundles scattered throughout stem

36. Herbaceous Stems

37. 9.5 Organization of Stems Woody Stems
Woody plants have both primary and secondary tissues
Primary tissues formed each year from primary meristems
Secondary tissues develop during first and subsequent years from lateral meristems

38. 9.5 Organization of Stems Woody Stems
Woody stems have no vascular tissue, and instead have three distinct regions
Bark
Wood
Pith

39. Secondary Growth of Stems

40. 9.5 Organization of Stems Bark
Bark of a tree contains cork, cork cambium, and phloem
Cork cambium produces tissue that disrupts the epidermis and replaces it with cork cells.
Cork cells provide waterproofing
Lenticels are pockets of loosely arranged cork cells that allow gas exchange
Phloem transports organic nutrients

41. 9.5 Organization of Stems Wood
Wood is secondary xylem that builds up year after year
Vascular cambium dormant during winter
Annual ring is made up of spring wood and summer wood
In older trees, inner annual rings no longer function in water transport
Annual rings can provide a growth record.

42. Three-Year-Old Woody Twig

43. Tree Trunk

44. 9.5 Organization of Stems Stem Diversity Stolons: Rhizomes:
Above-ground horizontal stems
Produce new plants when nodes touch the ground
Rhizomes:
Underground horizontal stems
Contribute to asexual reproduction
Variations:
Tubers - Enlarged portions functioning in food storage
Corms - Underground stems that produce new plants during the next season

45. Stem Diversity

46. 9.6 Organization of Roots Root Apical Meristem
Protected by the root cap
Three Regions
Zone of Cell Division
Zone of Elongation
Zone of Maturation

47. Eudicot Root Tip

48. 9.6 Organization of Roots Tissue of a Eudicot Root Epidermis Cortex
Endodermis
Casparian Strip
Vascular Tissue
Pericycle

49. Branching of A Eudicot Root

50. 9.6 Organization of Roots Monocot Roots
Ground tissue of root’s pith is surrounded by vascular ring
Have the same growth zones as eudicot roots, but do not undergo secondary growth

51. Monocot Root

52. Root Diversity
Primary root (taproot) - Fleshy, long single root, that grows straight down
Stores food
Fibrous root system - Slender roots and lateral branches
Anchors plant to the soil

53. Root Diversity Root Specializations
Adventitious roots - Roots develop from organs of the shoot system
Prop roots
Haustoria:
Rootlike projections that grow into host plant
Make contact with vascular tissue and extract water and nutrients
Mycorrhizas:
Associations between roots and fungi
Assist in water and mineral extraction
Root Nodules - Contain nitrogen-fixing bacteria

54. Root Diversity

55. 9.7 Uptake and Transport of Nutrients

56. 9.7 Uptake
Water moves into root cells by osmosis; minerals by diffusion and active transport
Water can enter directly into as cell using symplastic route OR it can move between the cell walls using the apoplastic route. Minerals cannot not enter the xylem using the apoplastic route due to the Casparian Strip. This helps to regulate ion concentration
H+ ion is actively pumped out of the cell. This disrupts the cations within the soil and they inturn will diffuse into the cells taking with them negative anions. Active transport is sometimes also used to bring in specific ions such as potassium
Root pressure is generated by water moving into the roots - pushes xylem sap

57. 9.7 Uptake and Transport of Nutrients
Cohesion-Tension Model of Xylem Transport
Relies on the properties of water
Transpiration-evaporation from the leaves creates a “sucking” force that pulls water upward through the xylem
Adhesion-water molecules interact with the walls of the xylem vessels to reinforce strength of column
Cohesion-water molecules are attracted to each other and form a continuous column within xylem from leaves to roots
Tension-created by transpiration; reaches from the leaves to the roots as long as column is continuous

58. Cohesion Tension Theory
1. Light absorbed by leaf increases the temperature within
2. Water in the spongy mesophyll enters vapour phase
3. Water vapours evaporates through the stomata (plural of stomate) to a lower water concentration
4. Loss of water due to evaporation creates a tension within the xylem so water is replaced due to adhesion and cohesion
5. Water enters the xylem cells from the root – there is transpirational pull as well as root pressure of water
6. Due to the transpirational pull- water is pulled into the roots from soil. Of course osmosis assists as well

59. Cohesion-Tension Model of Xylem Transport

60. Conducting Cells of Xylem

61. 9.7 Uptake and Transport of Nutrients
Opening and Closing of Stomata
Each stoma in leaf epidermis is bordered by guard cells
Increased turgor pressure in guard cells opens stoma
Caused by active transport of K+ into guard cells

62. Opening and Closing of Stomata

63. 9.7 Uptake and Transport of Nutrients
Mineral Uptake and Transport
Epiphytes- “air plants” that grow on larger plants; absorb moisture from the air
Parasitic plants have haustoria that tap into the xylem and phloem of hosts
Carnivorous plants have various adaptations for catching insects
Root nodules- in leguminous plants, house nitrogen-fixing bacteria
Mycorrhizae - symbiotic relationship between roots and fungi that increases surface area for absorption and the fungi break down organic matter for the plant to absorb

64. Root Nodules

65. Mycorrhizae

66. 9.7 Uptake and Transport of Nutrients
Organic Nutrient Transport
Role of Phloem
Transports products of photosynthesis from the leaves to the site of storage
Pressure-flow Model of Phloem Transport
Sugars produced in the leaves are actively transported into sieve tubes; water follows by osmosis
The buildup of water in the sieve tubes creates pressure that starts the phloem sap flowing
Other plant organs serve as the “sink”- sugars are actively transported out for use or storage and water follows by osmosis
Phloem sap always flows from source to sink

67. Pressure-flow Model of Phloem Transport