1. Biology, 9th ed, Sylvia Mader
Chapter 25
Chapter 25
Structure and Organization of Plants
Plant Structure and Organization

2. Outline Plant Organs Roots Stems Monocots vs. Eudicots Leaves
Epidermal Tissue
Vascular Tissue
Roots
Organization
Diversity
Stems
Leaves

3. 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

4. Organization of Plant Body
Biology, 9th ed, Sylvia Mader
Organization of Plant Body
Chapter 25
Structure and Organization of Plants
4.A.4: Root, stem, and leaf

5. Vegetative Organs of Several Eudicots

6. Shoot system of a plant is composed of the stem, branches, and leaves
Stems
Shoot system of a plant is composed of the stem, branches, and leaves
Stem is 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
Stem also has vascular tissue that transports water and minerals

7. Leaves are the major part of the plant that carries on photosynthesis
Foliage leaves are usually broad and thin
Blade - Wide portion of foliage leaf
Petiole - Stalk attaches blade to stem
Leaf Axil - Axillary bud originates
Tendrils - Leaves that attach to objects
Bulbs - Leaves that store food

8. Monocots (Single cotyledon)
Monocot vs. Eudicot
Monocots (Single cotyledon)
Cotyledons act as transfer tissue
Root vascular tissue occurs in ring
Parallel leaf venation
Eudicots (Two cotyledons)
Cotyledons supply nutrients to seedlings
Root phloem located between xylem arms
Netted leaf venation

9. Flowering Plants: Monocots or Eudicots

10. Plant Tissues Epidermal Tissues Contain closely packed epidermal cells
Covered with waxy cuticle
Roots contain root hairs
Lower leaf surface contain stomata
Woody plants covered by cork

11. Modifications of Epidermal Tissue
Biology, 9th ed, Sylvia Mader
Modifications of Epidermal Tissue
Chapter 25
Structure and Organization of Plants
4.A.4: Root, stem, and leaf

12. Ground tissue forms bulk of a plant
Parenchyma 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

13. Biology, 9th ed, Sylvia Mader
Ground Tissue Cells
Chapter 25
Structure and Organization of Plants
4.A.4: Plant vascular and leaf

14. Ground Tissue Sclerenchyma cells:
Have thick secondary walls impregnated with lignin
Most are nonliving
Primary function is to support mature regions of the plant
Fibers
Sclereids

15. Survival Mechanisms of Plants
Biology, 9th ed, Sylvia Mader
Survival Mechanisms of Plants
Chapter 25
Structure and Organization of Plants
Thorns and spines to repel large herbivores; if injured, tracheids and vessel elements of xylem plug up with chemicals to block above and below injured site
Toxins or sticky secretions to deter predators, such as poison ivy and pine sap
Indigestible cellulose makes it difficult to obtain nutrients from eating leaves
Dormancy allows survival in seasonal environments
Seed dormancy allows growth when conditions are optimal
2.D.4: Plant defenses against pathogens include molecular recognition systems with systemic responses; infection triggers chemical responses that destroy infected and adjacent cells by apoptosis, thus localizing the effects.

16. Xylem transports water and minerals from the roots to the leaves
Vascular Tissue
Xylem transports water and minerals from the roots to the leaves
Tracheids
Long, with tapered ends
Pits in end walls
Vascular rays
Fibers
Vessel Elements
Larger, with perforated plates in their end walls

17. Biology, 9th ed, Sylvia Mader
Chapter 25
Xylem Structure
Structure and Organization of Plants
4.A.4: Plant vascular and leaf
4.B.2: Circulation of fluids

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

19. Vascular Tissue
Phloem transports sucrose and other organic compounds from the leaves to the roots
Sieve-tube members are conducting cells
Contain cytoplasm but no nuclei
Channels in end walls
Plasmodesmata extend from one cell to another through sieve plate

20. Biology, 9th ed, Sylvia Mader
Chapter 25
Phloem Structure
Structure and Organization of Plants
4.B.2: Circulation of fluids

21. Biology, 9th ed, Sylvia Mader
Organization of Roots
Chapter 25
Structure and Organization of Plants
Root apical meristem
Located in the root tip
Protected by root cap
Primary meristems are in the zone of cell division
Zone of maturation contains fully differentiated cells
4.A.4: Root, stem, and leaf
4.A.4: Plant vascular and leaf

22. Tissues of Eudicot Root
Epidermis
Cortex
Endodermis
Casparian Strip
Vascular Tissue
Pericycle

23. Eudicot Roots

24. Organization of Monocots 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

25. Monocot Root

26. 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 soil)
Adventitous 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

27. Biology, 9th ed, Sylvia Mader
Organization of Stems
Chapter 25
Structure and Organization of Plants
Shoot apical meristem
Produces new cells that elongate and increase stem length
Protected by terminal bud
Enveloped by leaf primordia
Specialized primary meristems
Protoderm
Ground Meristem
Procambium
4.A.4: Root, stem, and leaf
4.A.4: Plant vascular and leaf

28. Woody Twig

29. Shoot tip and Primary Meristems

30. Mature nonwoody stems exhibit only primary growth
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

31. Herbaceous Eudicot Stem

32. Monocot Stem

33. Woody plants have both primary and secondary tissues
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

34. Secondary Growth of Stems
Biology, 9th ed, Sylvia Mader
Secondary Growth of Stems
Chapter 25
Structure and Organization of Plants
Woody stems have no vascular tissue, and instead have three distinct regions
Bark
Wood
Pith

35. Bark of a tree contains cork, cork cambium, and phloem
Bark can be removed, but it is harmful to the plant due to lack of organic nutrient transport
Cork cells are impregnated with suberin
Gas exchange is impeded except at lenticels

36. 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, heartwood, no longer function in water transport

37. Three-year-old Woody Twig

38. Tree Trunk

39. Biology, 9th ed, Sylvia Mader
Chapter 25
Stem Diversity
Structure and Organization of Plants
Stolons:
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

40. Leaf Structure

41. Classification of Leaves
Biology, 9th ed, Sylvia Mader
Classification of Leaves
Chapter 25
Structure and Organization of Plants
Blade of a leaf can be simple or compound
Leaves are adapted to environmental conditions.
Shade leaves
Spines
Climbing leaves

42. Leaf Diversity

43. Biology, 9th ed, Sylvia Mader
Chapter 25
Ending Slide Chapter 25
Structure and Organization of Plants
Plant Structure and Organization