1. Roots, Stems, Leaves and Flowers
Plant Physiology
Roots, Stems,
Leaves and Flowers

2. Plant Physiology
Physiology – understanding how parts of an organism work
We will learn how roots, stems, leaves and flowers all work together to keep a plant alive

3. Plant Identification There are two main categories of angiosperms.
Monocots – grasses, grain crops, lilies, gladiolas, and palm trees

4. Monocots Mono = Single Cot = Short for cotyledon
Cotyledon = embryonic leaf
Embryo = developing plant offspring located in the seed

5. Monocots Have four distinct features
Veins in leaves are parallel to each other
Flower parts are arranged in groups of three
Xylem and phloem are arranged in bundles
Single embryonic leaf

6. Vascular System Xylem Phloem Cambium
Transports water throughout the plant
Phloem
Transports food (sugars) throughout the plant
Cambium
Layer of cells that creates new xylem and phloem

7. Monocot
Vein arrangement
Convallaria majalis (lily of the valley)
The major veins of monocot leaves are generally arranged parallel to each other along the length of the leaf blade.

8. Plant Identification
Dicots - most of the other plants such as the shrubs, trees, and flowers.
Veins in leaves are branched
Flower parts are arranged in groups of four or five
Xylem and phloem are arranged in layers
Two embryonic leaves

9. Dicot Leaf Venation
Helianthus (sunflower)
The major veins of dicot leaves are generally arranged in a netted (reticulate) pattern that extends across and down the leaf.

10. Parallel Leaf Venation
Monocot and Dicot Leaf Venation
Convallaria majalis (lily of the valley)
Helianthus (sunflower)
Monocot
Parallel Leaf Venation
Dicot
Netted Leaf Venation

11. Monocot
Flower Parts
sepal
petal
stigma
stamen
Trillium
In most monocots, the flower parts are arranged in multiples of three. This trillium flower has three sepals, three petals, six stamens, and three stigmas on the pistil.

12. Dicot Flower Parts
petal
stamen
pistil
Cydonia oblonga (quince)
In most dicots, the flower parts are arranged in multiples of four or five. These quince flowers have five petals, twenty stamens, and five pistils. The stamens are too numerous to count in this image.

13. Monocot and Dicot Flower Parts
petal
sepal
stamen
petal
stigma
stamen
pistil
Trillium
Cydonia oblonga (quince)
Monocot
Flower Parts in Multiples
of Three
Dicot
Flower Parts in Multiples
of Four or Five

14. Roots

15. Functions of a root Water Absorption Anchorage Reproduction
Most water enters the plant through the roots
Anchorage
Holds the plant in one place
Reproduction
Some roots allow for asexual reproduction
Food Storage
Store sugars for later use

16. Roots
The type of root will normally help you identify the plant. It will place the plant into a monocot or dicot category.

17. Types of Roots
Tap Root
Have a main central root and may have some lateral branching
E.g. Carrots
e.g. = exempli gratia = for the sake of example

18. Tap Roots
Penetrate the soil to various depths - some only a few inches, others like the mesquite to as deep as 114 ft.

19. Tap Roots Benefits of a tap root Access deep water
Hold plant in more securely
Store larger quantities of sugars

20. Types of Roots
Fibrous
Have many roots of equal size and a lot of lateral branching
Fibrous roots are generally much more dense and closer to the surface

22. Types of Roots
This root system can effectively prevent any other plant from becoming established – e.g.: grasses - idea of a healthy lawn is to compete with weeds

23. Types of Roots
Prop Roots - augment regular roots for anchorage aid - ex: corn - roots come out above soil and help hold plant up

24. Parts of Roots
Epidermis – Outer layer of cells, protecting inner cells
Root Hairs – Small hairs that grow from the epidermis, helping water absorption and holding root in place

25. Parts of Roots Cortex – Area of storage in the root
Vascular Cylinder – area that contains xylem and phloem tissues

26. Parts of a root
Root Cap – Layer of cells that protect the growing area of a root
Apical Meristem –
Meristem – point of new cell development
Apical – Tip (end of a branch)

27. Why Different Types of Roots
All plants are in competition with each other for water and nutrients
By having different types of roots, the plants can reach different depths in the soil and still live side by side with other plants

28. Stems

29. Stems
For identification: type of stem (woody or herbaceous), monocot or dicot,

30. Monocot stem Dicot stem
phloem
xylem
Dicot stem
cortex

31. Primary vs Secondary growth
Primary Growth
Growing from a specific location
In woody stems, often at the ends of the branches (apical meristem)
In herbaceous stems, can be at end or at the surface of the soil (e.g. grasses)
Secondary growth
Growing wider around a trunk

32. Mature Structure of Woody vs Herbaceous Stems
Lack secondary growth - plants only live above ground during the growing season
Annuals – plants that live only one growing season

33. Mature Structure of Woody vs Herbaceous Stems
Stems remain soft and flexible.
Buds lack protective scales (don’t need to survive harsh conditions)

34. Mature Structure of Woody vs Herbaceous Stems
Woody stems
Plants living and growing over multiple seasons have secondary growth (xylem, phloem) increasing diameter of the stems

35. Mature Structure of Woody vs Herbaceous Stems
Annuals – Die at the end of the growing season
Fast, frequent reproduction, with many seeds
Perennials – Live several growing seasons
Slower, less frequent reproduction

36. Growing season
- The time of the year in which most of the plant’s growth occurs
- usually in the summer
- can be other times
Wet season
Spring
Fall

37. Specialized Stems
Rhizomes - underground horizontal stems (ex: perennial grasses, bamboo) - will grow a plant and roots at a node.
Node – Any growth point on a stem or root
E.g. ‘eyes’ of a potato.

39. Specialized Stems
Stolons - runners - usually above ground, horizontal stems; will grow a plant and roots at a node - ex: strawberries

41. Specialized Stems
Tubers - several nodes at the end of a rhizome (ex: potatoes) - eyes are axillary buds – where the tuber will grow a plant

43. Specialized Stems
Bulbs - large bud with small stem at lower end - storage in the form of numerous, fleshy leaves - ex: onion, lily, tulip
Corms - look like bulbs, but are mostly stem tissue with a few, papery leaves on the outside - ex: gladiolus, crocus

46. Leaves

47. Leaves
Leaves are where plants conduct photosynthesis to produce most of it’s food.
Leaves come in many shapes and sizes

48. Parts of a Dicot Leaf
Leaf blade – expanded, usually flat portion of a leaf
Petiole – connects the blade of a leaf to a stem or branch – holds leaf up for better air flow and to catch the light

49. Parts of a Dicot Leaf
Veins – threads of vascular tissue (xylem & phloem)
Node – place on a stem where leaves or branches normally attach

50. Parts of a Leaf
Midrib– the primary vein that is seen from the petiole to the tip
Spine– Large veins that branch from the midrib
Margin– the edge of the leaf blade
Base – The lower part of the blade, where the petiole attaches

51. Tip
Midrib
Spines
Blade
Margin
Veins
Base
Petiole

52. Parts of a Monocot Leaf
Sheath – part of leaf that holds leaf to stem – encases stem
Ligule – membrane-like tissue extending up from the sheath (on inside) – keeps dirt and moisture out – clear membrane on leaf where attaches to stem

53. Monocot Leaf
Blade
Sheath
Node
Collar
Auricle
Stem
Ligule

54. Picture showing parts of a grass plant.

55. Two Types of Leaves
Simple leaves – composed of a single blade and a petiole

56. Two Types of Leaves
Compound leaves – are composed of a blade that includes several leaflets and a petiole
Two types:

57. Two Types of Leaves
Palmately Compound – (chestnut) – the lobes or divisions come together and are attached at one place at the base

58. Leaf Blade
Palmately Compound Leaf
Petiole

59. Two Types of Leaves
Pinnately Compound – compound leaf with the leaflets on two sides, usually along a central vein – ex: ferns, ash, hickory

60. Leaflets
Leaf Blade
Pinnately Compound Leaf
Petiole

61. Leaf Arrangement
Monocots – have only one type of arrangement – leaf comes off of a node – ex: grasses and grain crops

62. Leaf Arrangement Dicots – flowering plants
Alternate – one leaf per node
Opposite – two leaves per node
Whorled – three or more leaves per node

63. Leaf Arrangements

64. Arrangement of Veins Four types of vein arrangements:
Parallel veins – veins are small and run more or less parallel – most are long and narrow – ex: Buckhorn Plantain, grasses and Iris – mostly monocots

65. Arrangement of Veins
Netted veins – are large and small – the small ones connecting to each other to form a net – mostly dicots

66. Arrangement of Veins
Pinnately veined – with one larger midvein and smaller veins coming off along its length – mostly dicots

67. Arrangement of Veins
Palmately veined- with two or more large veins arising at or near the base of the leaf blade (palm) – leaves are usually broad or fat – mostly dicots

68. Parallel Veins
Netted Veins
Palmately Veined
Pinnately Veined

69. Monocot Leaf -Vein Arrangement
Dicot Leaf – Vein Arrangement
Smaller lateral vein
Midvein

70. Leaf Structure

71. Leaf Structure
Epidermis – Tough outside layer of cells that protect the inner cells
Divided into Upper epidermis and Lower Epidermis

72. Leaf Structure
Upper Epidermis
Lower Epidermis

73. Leaf Structure
Stomata – Openings in the leaf that allow the passage of CO2 and water
Stomata can open and close based on the needs of the plant
They will typically stay closed when the plant needs to retain moisture, and will open up when there is enough water available

74. Leaf Structure
Stomata open and close due to cells on the edge of the stomata called guard cells
Guard cells open and close the stomata by allowing water to enter and leave, causing them to swell or shrink

75. Leaf Structure
Upper Epidermis
Guard Cells
Lower Epidermis
Stomata

76. Leaf Structure Palisade Cells
Elongated cells where most photosynthesis takes place
Why are they elongated vertically, and not horizontally?

77. Leaf Structure Upper Epidermis Palisade Cells Guard Cells
Lower Epidermis
Stomata

78. Leaf Structure Spongy Mesophyll Water storage area of the leaf
Helps to transport wastes out of the leaf through the stomata

79. Leaf Structure Upper Epidermis Palisade Cells Spongy Mesophyll
Guard Cells
Lower Epidermis
Stomata

80. Leaf Structure Vascular System
Xylem – Transports water from roots to the leaves (water is necessary for photosynthesis)
Phloem – Transports sugars from the leaves to the rest of the plant

81. Leaf Structure Upper Epidermis Palisade Cells Spongy Mesophyll
Vascular System
Guard Cells
Lower Epidermis
Stomata

83. Flowers
Petals – are highly colored portions of the flower.
May contain perfume (rose) or nectar glands –to attract pollinators.
Number of petals on a flower is often used in the identification of plant families and genera.

84. Flowers Dicots –have sepals and/or petals in multiples of four or five
Monocots – have sepals in multiples of threes

85. Parts of a Flower
Sepals
Petals
Stamens (anther & filaments)
Pedicel
Pistil (stigma,style & ovaries)

86. Seeds

87. Monocot seeds Contain the embryo (infant plant)
Cotyledon (part of the embryo)
Seed Coat (protects the embryo)
Endosperm (provides nutrients to the embryo )
Radicle – The embryonic root tip

88. Monocot Seed

89. Dicot Seed