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chapter 3 Flashcards

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1
Q

What systems does the vascular plant consist of?

A

1) A root system

2) A shoot system

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2
Q

What does a root system do?

A

-anchors the plant
-absorbs water and ions from the soil

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3
Q

What does a shoot system do?

A

-consists of supporting stems, photosynthetic leaves, and reproductive flowers.
-the repetitive shoot units consist of internode, node, leaf, and axillary bud

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4
Q

What are the repetitive shoot units?

A

internode, node, leaf, axillary bud

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5
Q

What is the node?

A

area where leaf attaches

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6
Q

What is the internode?

A

area between 2 nodes

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7
Q

What is the axillary bud?

A

lateral shoot apex, found at a leaf axil (basis); it produces a new branch (stem) or a flower at the time of reproduction.

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8
Q

What is the shoot apex?

A

It bears the terminal bud.

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9
Q

What is the area where leaf attaches?

A

Node

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10
Q

What is the area between 2 nodes?

A

internode

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11
Q

What is the lateral shoot apex, found at the leaf axil, and which produces a new stem/flower at the time of reproduction?

A

axillary bud

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12
Q

What bears the terminal bud?

A

The shoot apex

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13
Q

What are the 3 types of tissues that the roots, shoots and leaves are comprised of?

A

Dermal tissue
ground tissue
Vascular tissue

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14
Q

Dermal tissue

A

epidermis and stomata forming the outer protective layer

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15
Q

Ground tissue

A

functions in storage, photosynthesis, and secretion. In addition to fibers that support the plant; structural support.
parenchyma collenchyma
and schlerenchyma.

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16
Q

Vascular tissue

A

conducts fluids and dissolved substances.

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17
Q

Why are these 3 tissues called the tissue system?

A

Because each of these tissue extends through the root and shoot systems.

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18
Q

What are tissues made of?

A

Cells

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19
Q

What is the 3 main factors that can help us differentiate between the plant cell types?

A

1-the size of their vacuole
2-the thickness of their cell walls (with secondary cell wall or not)
3-whether they are living or dead at maturity

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20
Q

What does the plant cell wall consist of?

A

cellulose

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21
Q

what is the primary cell wall of plant cells?

A

strong, protective, waterproof cover surrounding the cell

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22
Q

what is the position of microtubules wrt cellulose fibers?

A

parallel

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23
Q

Where is the secondary cell wall located?

A

It is laid in between the plasma membrane and the primary cell wall (outermost).

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24
Q

What does the secondary cell wall contain?

A

contains more layers of cellulose, in addition to other strengthening molecules, like lignin and pectin

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25
Q

lignin and pectin

A

strengthening molecules

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26
Q

Where does new plant growth occur?

A

Meristems

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27
Q

What are meristems?

A

Meristems are undifferentiated cells that can divide indefinitely to give rise to different types of cells.
Hence, they are cells that retained the ability to divide by mitosis or actively dividing embryonic tissues

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28
Q

What does each Meristematic cell give rise to?

A

Each meristematic cells gives rise to 2 daughter cells:
- 1 remains meristematic
- the other differentiate and contribute to the plant body

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29
Q

What does the meristem consist of?

A

Meristematic cells have dense cytoplasm and large nuclei.

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30
Q

What are the 2 types of meristems?

A

1)Apical meristems:
Responsible for the increase in length, called primary growth.
Extension of shoot and root produced by apical meristems.
Found in herbaceous and woody plants.
2)Lateral meristems:
Responsible for the increase in width (girth), called secondary growth.
Lateral meristems produce an increase in shoot and root diameter.
Found only in woody plants.

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31
Q

What are the tissues produced by the apical meristems?

A

primary tissues

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32
Q

primary tissues

A

The tissues produced by the apical meristem

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33
Q

What does the elongation of the shoot and root form?

A

primary plant body

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34
Q

What protects the root apical meristem?

A

Root cap

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35
Q

What protects the shoot apical meristem?

A

Leaf Primordia

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36
Q

Leaf primordia

A

Leaf primordia are embryonic leaves that protect the stem apical meristem.

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37
Q

Where is the bud primordia located? And what does it give rise to?

A

located at the base of a leaf axil (base), gives rise to a branch or a flower.

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38
Q

Where are root apical meristems found?

A

behind the root cap

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39
Q

What produces the root cap cells

A

Root cap cells are produced by the root meristem and are sloughed off and replaced as the root moves through the soil.

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40
Q

What are the 3 types of embryonic tissues that apical meristems give rise to?

A

The apical meristems gives rise to 3 types of embryonic tissues called primary meristems. The 3 primary meristems:
1.The protoderm: forms the epidermis.
2.The procambium: forms the primary vascular tissues(xylem and phloem)
3.The ground meristem: forms the ground tissue.
Few plants have an additional primary meristem:
4.intercalated meristems
Found in some plants only. Ex. corn and horsetails.
Found in the stem internodes
They add to internode length
(further increase in stem elongation in a short time).

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41
Q

Which embryonic tissue forms the epidermis?

A

the protoderm

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42
Q

Which embryonic tissue forms the primary vascular tissues(xylem and phloem)?

A

The procambium

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43
Q

What embryonic tissue forms the ground tissue?

A

the ground meristem

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44
Q

What does secondary growth result from?

A

Secondary growth results in the formation of the secondary tissues or secondary plant body.
Secondary growth results from the activity of lateral meristems.

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45
Q

What are the 2 types of lateral meristems?

A

a)CORK CAMBIUM: forms the outer bark
b)VASCULAR CAMBIUM: forms the secondary vascular tissues.
It divides to give 2⁰ xylem to its inside, known as wood,
and 2⁰ phloem to its outside, known as inner bark

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46
Q

What forms the outer bark?

A

cork cambium

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47
Q

What forms the 2ndary vascular tissues?

A

Vascular cambium

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48
Q

What is the secondary xylem known as?

A

wood

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49
Q

What is the secondary phloem known as?

A

inner bark

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50
Q

What type of growth do herbaceous plants exhibit? And what happens to them?

A

-Herbaceous plants exhibit only primary growth: increase in length.
-Some herbaceous plants become woody (ex. apple tree).

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51
Q

What type of growth do woody plants exhibit?

A

both primary and secondary growth

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52
Q

primary growth

A

Increase in length due to:
stem and root apical meristems

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53
Q

secondary growth

A

Two lateral meristems:
-Cork cambium:
forms the outer bark
-Vascular cambium:
inner bark (2⁰ phloem)
and wood (2⁰ xylem)

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54
Q

What is the epidermis?

A

the outer protective covering that covers all the surfaces in herbaceous plants.

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55
Q

How thick is the epidermis?

A

one cell-thick

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56
Q

What is the epidermis made of?

A

It is made of epidermal cells:
-transparent(and living) cells
-originating from the protoderm

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57
Q

What do the epidermal cells secrete?

A

a fatty and waxy cutin layer known as cuticle.
The cuticle is waterproof –> it prevents desiccation

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58
Q

What is the cuticle?

A

a fatty and waxy cutin layer; it is waterproof –> it prevents desiccation(drying out)

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59
Q

What are the specialized cells that the epidermis contains as well?

A

guard cells, trichomes and root hairs

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60
Q

Guard cells

A

—Are green, paired, sausage-shaped, and the only epidermal cells with chloroplasts.
—They allow gas exchange
-When they separate, they show an opening = stoma

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61
Q

Where are the guard cells found?

A

-In epidermis of leaves, sometimes stems and fruits.
-Usually more numerous on the lower leaf epidermis to decrease water loss.

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62
Q

Why are the guard cells more numerous on the lower leaf epidermis?

A

to decrease water loss

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63
Q

What happens when guard cells separate?

A

stoma shows=opening

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64
Q

Trichomes

A

-hair-like outgrowth of the epidermis
-unicellular/multicellular
-vary regarding the plant species
-found on leaves, stems, fruits.

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65
Q

What are the trichomes’ major functions?

A

—Reduce evaporation by covering stomatal openings
—Protect leaves from high-intensity light and ultraviolet radiation
—Can buffer against temperature fluctuations
—Some are glandular; secreting sticky or toxic substances to deter herbivory

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66
Q

Root hairs

A

are tubular extensions of epidermal cells. They increase the surface area for absorption of water and minerals.

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67
Q

Where are root hairs found?

A

in the zone of maturation, just behind the tip of a young root

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68
Q

Important notes about root hairs

A

-A root hair is not a cell!
-Root hairs are not lateral roots (/root branches).

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69
Q

What the cells that ground tissues primarily contain?

A

parenchyma cells
collenchyma cells
sclerenchyma cells,

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70
Q

Parenchyma cells

A

-most common and abundant
-thin walls and large vacuoles
-only have primary cell wall
-less specialized than the other cells
-Have a living protoplasm:
remain alive after they mature and may live for many years

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71
Q

What does having a protoplasm mean?

A

Have a living protoplasm:
remain alive after they mature and may live for many years

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72
Q

What are parenchyma cells’ major functions?

A

i) Storage(water; food; resins; nectar…)
ii)Photosynthesis: some are green and contain chloroplasts; they are also called chlorenchyma.
iii) Secretion(water; food; resins; nectar…)

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73
Q

Collenchyma cells

A

—Have a living protoplasm
—only have primary cell wall=lack secondary cell wall
—longer than wide with cell wall varying in thickness/ unevenly thickened 1°cell wall (thicker at the corners).

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74
Q

Where are collenchyma cells found?

A

—Not found everywhere in the plant.
—Found beneath the stem epidermis and along leaf veins
Ex. Found in celery strings

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75
Q

Sclerenchyma cells

A

*Have tough and thick walls.
*Have secondary cell wall with lignin —> rigid
*Are usually dead at maturity= NO protoplasm

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76
Q

What is the function of Sclerenchyma cells?

A

provide rigid and mechanical support and protection
—> strengthening the tissues

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77
Q

What are the 2 types of sclerenchyma cells?

A

i) FIBERS: long and slender cells, found in groups (strands).
Ex. Linen is woven from fibers of flax phloem
ii) SCLEREIDS: vary in shape, often branched (star-shaped).May occur singly or in groups.
Found in hard seed coats (pits of fruits)
Ex: In pear fruits: there is special type of sclereid in soft flesh giving the fruit its gritty texture.

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78
Q

What is the xylem tissue made of?

A

Tracheids
Vessel members
Fibers
Parenchyma

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78
Q

Vascular Tissues

A

a)XYLEM:
-conducts water and dissolved minerals
a)PHLOEM:
-conducts sugars (mainly sucrose) used by plants as food;
-also transports hormones, amino acids and other substances needed for plant growth.

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79
Q

Tracheids

A

1-Dead cells with tapered ends
2-Hollow
3-thick, lignified 2°cell wall (for support)
4-have pits(small areas with no 2°cell wall) to allow continuous water flow from one tracheid to another.
5-Found in clusters
6-Function in water conduction and support
7-Found in all vascular plants.

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80
Q

what are the pits in tracheids for?

A

(small areas with no 2°cell wall) to allow continuous water flow from one tracheid to another.

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81
Q

Vessel members

A

1-dead and hollow at maturity.
2-have a lignified 2°cell wall.
3-shorter and wider than tracheids
4-arranged end to end, forming tubes called vessels= a stack of vessel members.
5-have open ends (at the end of the cell), called perforation plates to allow for water to move up from cell to cell.
-have pits for lateral water transport
-more efficient in water conduction.
-ONLY found in angiosperms

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82
Q

Perforation plates

A

open ends at the end of the cell that allow water to move up from cell to cell.

83
Q

Fibers

A

1-Provide support
2-Dead and elongated cells with lignified 2°cell wall.

84
Q

Parenchyma

A

1-Function in storage(of food: starch, fats…)
2-In woody stems, the parenchyma also function in lateral water conduction and food storage.
3-They are usually found in horizontal rows called rays.
4-Rays are produced by ray initials in the vascular cambium.

85
Q

What is the phloem tissue made of?

A

Sieve cells
Sieve tube members
Companion cells
fibers
parenchyma

86
Q

Sieve cells

A

1-Function in food conduction
2-Found in ferns, horsetails, and gymnosperms.
3-Are living at maturity, but their nucleus dies.
4-Long cells with clusters of pores called sieve areas.
5-Unlike the pits of xylem cells, which contain 1mary cell walls, phloem pores are completely open.

87
Q

Sieve tube members

A

1-Function in food conduction
2-Found in angiosperms.
3-Are living at maturity, but their nucleus dies.
4-They are more efficient in food conduction.
5-The cells are arranged end to end forming continuous tubes called sieve tubes.
6-The pores at the end of the cells are larger, called sieve plates.

88
Q

Companion cells

A

-each sieve tube member is associated with an adjacent parenchyma cell called companion cell.
-Function: carry out some of the metabolic functions needed to maintain sieve-tube member (ex. Loading and unloading sugars).
-Living cells with many cytoplasmic connections called plasmodesmata (to connect to sieve tube members).
-They are found in angiosperms(only).

89
Q

Plasmodesmata

A

cytoplasmic connections; to connect to sieve tube members

90
Q

Fibers

A

provide support

91
Q

Parenchyma

A

function in storage

92
Q

What are roots adapted for?

A

Roots are adapted for growing underground and absorbing water and minerals.

93
Q

What is the root structure?

A

1.Root cap
2.Zone of cell division
3.Zone of cell elongation
4.Zone of maturation

94
Q

What is the root cap composed of?

A

a)The inner columella cells
b)The outer, lateral root cap cells
These cells are continuously being formed by the root apical meristem

95
Q

What are the main functions of the root cap?

A

-to protect the delicate tissues of the root apical meristem from abrasion with soil particles.

96
Q

What do outer root cap cells have?

A

-Golgi bodies that continuously secrete a slimy substance called mucigel that is released through the cell wall to the outside.
-Mucigel acts as lubricant, facilitating root movement through the soil.
-It also provides a medium for the growth of nitrogen-fixing bacteria in legume roots.

97
Q

How does the root cap function in the perception of gravity?

A

The root cap also functions in the perception of gravity. Columella cells contain amyloplasts (plastids with starch grains) that collect on the sides of cells facing the pull of gravity. Amyloplasts indicate the direction of gravity (so that roots bend toward gravity).

98
Q

what are amyloplasts?

A

plastids with starch grains that collect on the sides of cells facing the pull of gravity. They indicate the direction of gravity.

99
Q

What does the zone of cell division contain? And where is it located?

A

It contains the apical meristem and consists of actively dividing cells at a rate every 12-37 hours.
Most of the cells are cuboidal, with small vacuoles and large nuclei.
These rapidly dividing cells are daughter cells of the apical meristem.
In the center of the apical meristem, there is a quiescent center = a group of cells that divide infrequently.
—-It is located behind the root cap

100
Q

What do the apical meristem daughter cells subdivide in to?

A

The apical meristem daughter cells subdivide in to the 3 primary tissues: protoderm, procambium and ground meristem

101
Q

In Arabidopsis, what has been identified?

A

In Arabidopsis, 2 genes have been identified as regulating patterning of these 3 tissue systems (1°meristems).

102
Q

Where does the patterning of these cells begin?

A

The patterning of these cells begins in this zone of cell division, but the expression of this patterning is not fully revealed until the cells reach the zone of cell maturation.

103
Q

In Arabidopsis, What are the 2 genes that have been identified as regulating patterning of these 3 tissue systems (1°meristems)?

A

1)WEREWOLF (WER) GENE
-WER suppresses root hair development in nonhair and hair epidermal cells.
-Plant with the WER mutation have an excess of root hairs
2)SCARECROW (SCR) GENE
-is required for the differentiation of ground meristem cells into ground tissue cells and endodermis via asymmetrical cell division.
-SCR mutants form a single layer of cells that have both endodermal and ground cell traits (instead of forming an outer layer of ground tissue and inner layer of endodermis).

104
Q

Zone of cell elongation

A

*Roots lengthen in this zone, only!
*no cell division.
*The cells increase in size.
*Cells become longer than wide.

105
Q

Zone of cell maturation

A

*Cells differentiate into specific cell type.
*Cells at the surface become epidermal cells.
*Root hairs develop in this area.
*Other cells form: parenchyma (cortex); endodermis; and vascular tissue (to the center).

106
Q

Epidermis

A

-thin cuticle to allow water absorption
-Epidermal cells with root hairs or non-hair epidermal cells.
-Root hairs increase the surface area for water and mineral absorption

107
Q

Cortex

A

-It is made of parenchyma cells(produced in the ground meristem)
-Cortex functions in food storage.

108
Q

Endodermis

A

-The inner layer of the cortex differentiates into endodermis.
-Endodermal cells have a 1°cell wall impregnated with suberin, a fatty and water proof substance.
-Suberin is produced in bands called Casparian strips, surrounding every endodermal cell (at the end of the cell).
-Function of endodermis: controls what ions and other substances enter the core of the root (then xylem) —> regulates intercellular flow of water and solutes in the vascular core of the roots; blocks harmful and toxic substances.

109
Q

Suberin

A

a fatty and water proof substance impregnated in endodermal cells’ primary cell wall. It is produced in bands called casparian strips.

110
Q

Casparian strip

A

—fills the space between the cells of the endodermis.
—a waterproofing band that forces water and minerals to pass through the plasma membranes of endodermal cells, rather than through the spaces in the cell walls

111
Q

Where is the pericycle located?

A

behind (just after) the endodermis.

112
Q

Stele

A

-Is the tissues interior (after) to endodermis
-Inside the stele, there is a layer of parenchyma cells that can divide; it is the pericycle.

113
Q

What is the function of the pericycle?

A

–giving rise to lateral roots (root branches)
–giving rise in (woody) dicots to the lateral meristems: vascular cambium and cork cambium.
–After the pericycle, there are vascular tissues (xylem and phloem); but their arrangement differs in monocot and dicot roots.

114
Q

What happens in monocot roots?

A

–There is a pith made of parenchyma cells (storage function) at the core of the root.
–It is surrounded by a primary xylem found in discrete vascular bundles (veins) arranged in a ring.
–Phloem are found in patches in between the xylem

115
Q

What happens in dicot roots?

A

-There is no pith at the center of the root.
-Instead, xylem occupies the core of the root and it forms radiating arms, often star-shaped.
-Phloem is found in patches between the xylem arms

116
Q

Root cross section of monocots and dicots similarities

A

Both have epidermis, cortex, endodermis, and stele.
Inside the stele, there is a layer of pericycle.

117
Q

Root cross section of monocots and dicots differences

A

–There is a pith at core of a monocot root; surrounded by xylem veins in a circle, and phloem in patches.
-The xylem (radiating arms) is at the core of a dicot root, surrounded by phloem in patches between the xylem arms

118
Q

How is the root vascular cambium formed?

A

In woody dicots, some roots become woody (2ndary growth).
This involves the formation of a root vascular cambium from the pericycle and some parenchyma cells found in between xylem and phloem veins.

119
Q

What does the root vascular cambium form?

A

—The root vascular cambium forms 2ndary xylem (wood) to its inside and 2ndary phloem (inner bark) to its outside.
—The root increase in width.
—The outside of the pericycle will be lost and replaced with bark.

120
Q

What are the 2 types of roots that most plants produce?

A

Taproot or fibrous root

121
Q

Taproot system

A

Taproot system consists of a single large root with smaller branches. (ex. apple tree).

122
Q

Fibrous root system

A

Fibrous root system consists of many smaller roots of similar diameter. (ex. onion).

123
Q

What is an adventitious root?

A

—Any root that arises along a stem or in some other place than a root.
—Not all roots come from pre-existing roots.

124
Q

What are the roots modified for functions other than water and mineral absorption?

A

1.Prop roots
2.Aerial roots
3.Pneumatophores
4.Contractile roots
5.Parasitic roots
6.Food storage roots

125
Q

Prop roots

A

-Keep the plant upright
-Support the plant against wind
-are adventitious; thick roots emerging from lower part of stems;
-Found in some monocots like corn

126
Q

Aerial roots

A

-Obtain water from air
-Found in epiphytes (plants that grow attached on top of another plant); ex. orchids
-Have aerial roots for support
-Roots have a thick epidermis (many cell thick) to reduce water loss
-If aerial roots are green, like in vanilla orchids, they are photosynthetic.

127
Q

epiphytes

A

plants that grow attached on top of another plant

128
Q

Pneumatophores

A

-Are spongy outgrowths of roots
-Usually extend few cm above water surface
-Facilitate oxygen uptake to underwater roots
-Found in some plants growing in swamps
-ex. mangrove tree.

129
Q

Contractile roots

A

–Pull plant deeper in soil
–Roots from bulbs (lilies) and some plants (dandelion) form contractile roots that contract and push by spiraling new bulbs deep in the soil until they attain a suitable soil temperature for growth

130
Q

Parasitic roots

A

–Called haustoria
–Found in some plants that lack chlorophyll
Ex. Dodder
-Penetrate the host plant (to which they are attached to); they make contact with the conducting tissue of the host to steal carbohydrates.

131
Q

Food storage roots

A

—Store carbohydrates
—Root contain many parenchyma cells in the xylem of branch roots(storing starch).
Ex. Sweet potato; carrot; radish; turnip; beet; parsnip

132
Q

Water storage roots

A

—-Store water in roots
-Found in pumpkin family (Curcurbitaceae)
-In plants growing in arid (dry) regions.

133
Q

Buttress roots

A

-Huge (above ground) roots at the base of a tree trunk
-Give great stability and support
-Found in fig tree and other tropical trees

134
Q

Similarly to roots, what do stems contain?

A

Similar to roots, stems contain the 3 types of plant tissues.

135
Q

What are stems’ functions?

A

-the backbone of the shoot
-Transport nutrients and water
-Support the aerial plant parts (leaves, fruits…)

136
Q

What does the shoot apical meristem produce?

A

The shoot apical meristem produces new stem tissues and primordia.

137
Q

What does primordia produce?

A

Primordia produce leaves, other shoots or flowers

138
Q

What are the leaves attached to?

A

leaves are attached to the stem

139
Q

What is the pattern of leaf arrangement called?

A

phyllotaxy.

140
Q

What is the leaf arrangement designed for?

A

It is designed to optimize exposure of leaves to the sun.

141
Q

What are the 3 ways that leaves may be arranged around the stem?

A

-Alternate arrangement (spiral)
most common
1 leaf per node
-Opposite arrangement
2 leaves per node
-Whorled arrangement(in circle)
many leaves per node

142
Q

node

A

point of attachment of leaf to stem

143
Q

internode

A

area of stem between 2 nodes

144
Q

blade

A

flattened part of leaf

145
Q

petiole

A

stalk of leaf

146
Q

Axil

A

angle between petiole/blade and stem

147
Q

Axillary bud

A

develops into branches with leaves or may form flowers

148
Q

Terminal bud

A

extends the shoot system during the growing season

149
Q

What do Monocots and herbaceous dicots have in common?

A

Monocots and herbaceous dicots have the epidermis (with cuticle) as outermost layer.

150
Q

What does the stem epidermis commonly have?

A

The stem epidermis commonly have stomata, and sometimes trichomes.

151
Q

How do the stems of monocots and herbaceous dicots differ in the arrangement of their vascular tissues?

A

*In monocots (like grasses), the vascular bundles (veins) are scattered throughout the ground tissue.
*In dicots, the vascular bundles are arranged in a ring (circle), with internal ground tissue termed pith, and external ground tissue called cortex.
*Each vein in monocot stem contains xylem to the center and phloem to the outside.
*Each vein in dicot stem contains xylem to the center; a layer of vascular cambium, and phloem to the outside.

152
Q

What does the herbaceous dicot stem consist of?

A

–Epidermis
–Cortex (collenchyma and parenchyma)
–Veins in a circle (xylem to center; vascular cambium; phloem to outside)
–Pith (at the center): parenchyma (storage)

153
Q

What does the monocot stem consist of?

A

–Epidermis
–Veins scattered in ground tissue (parenchyma)
–Each vein: xylem to center; phloem to outside.

154
Q

How can the herbaceous stem become woody? What must develop in order for this to happen?

A

—-A herbaceous stem can become woody as the plant undergoes secondary growth (increase in width
—For this, the lateral meristems need to develop.

155
Q

The vascular cambium divides to give what?

A

-to the inside: 2dary xylem = wood
-to the outside: 2dary phloem = inner bark

156
Q

What happens as the secondary vascular tissue expands?

A

–the pith and the 1 ⁰ xylem at the center become crushed; the 1 ⁰ phloem breaks apart.
—The 1 ⁰ vascular tissues become non-functional and the 2⁰ xylem and 2⁰ phloem replace them in function.

157
Q

What happens when the stem increases in diameter?

A

the epidermis, cortex and 1⁰ phloem break apart/slough off

158
Q

What happens to the cork cambium when the stem increases in diameter?

A

The cork cambium develops in the outer cortex (from a few epidermal cells and cortex cells).

The cork cambium divides to give:
-To the inside: parenchyma-like cells called phelloderm cells.
-To the outside: cork cells.

159
Q

What do the cork cambium, cork cells and phelloderm cells form?

A

Periderm/outer bark

160
Q

What does the periderm replace?

A

The periderm replaces the epidermis and the cortex in function.

161
Q

What is the state of cork cells at maturation?

A

Cork cells are dead at maturity; they are impregnated with suberin, a water proof substance (replacing the cuticle).

162
Q

Lenticels

A

–located In the outer bark,
–unsuberized cork cells.
–allow for gas exchange; they replace the stomata.

163
Q

Why do the lenticels allow for gas exchange?

A

they replace the stomata

164
Q

What does the secondary growth involve?

A

The vascular cambium divides and connects to form a ring.
It divides to give to the inside 2 xylem and to the outside 2 phloem.The secondary vascular tissues replace the primary vascular tissues in function.
The cork cambium is formed and it divides to give to its inside phelloderm cells and to its outside cork cells.
The outer bark (or periderm) replaces the epidermis and cortex in functions.
Lenticels (unsuberized cork cells) replace the stomata.

165
Q

simple definition of periderm/outer bark

A

*Periderm or outer bark = cork cambium, cork, and phelloderm

166
Q

Simple definition of lenticels

A

Lenticels – Cork cambium produces unsuberized cells that permit gas exchange to continue

167
Q

In a cross-section of a woody tree trunk, what can we recognize?

A

Heartwood
sapwood
Springwood
Summer wood

168
Q

Heartwood

A

— inner, non-conducting primary xylem, which is darker and resistant to decay.
—Its function is support, only.

169
Q

Sapwood

A

—functional 2°xylem, which is lighter in color.
—Its functions are conduction and support.

170
Q

Springwood

A

—xylem cells are larger as there is plenty of
water in soil in spring; (also called earlywood)

171
Q

Summerwood

A

—xylem cells are smaller(less water in soil);
(also called latewood).

172
Q

Why ,in temperate regions, is annual growth of a tree (increase in width) is seen as annual rings?

A

because of springwood and summer wood

173
Q

Dendrochronology

A

Dendrochronology is the science of determining the age of trees.

174
Q

What are the 3 stem modifications?

A

—Most stems grow upright.
—Some grow horizontally. However, we can differentiate them from roots because (unlike roots) stems have leaves, nodes, internodes and buds in leaf axils.
—Some stems are modified for several purposes, such as vegetative reproduction(propagation).

175
Q

Bulbs

A

Ex. Onions, lilies, tulips.
—Are swollen, underground stems.
—produce adventitious roots at their base.
—consists of fleshy leaves (for storage) around a small knob-like stem.
—The fleshy leaves store carbohydrates.
—-They are surrounded by thin, papery brown leaves (protection).

176
Q

Corms

A

-they superficially resemble bulbs
-they lack fleshy leaves
-they are swollen, underground stems
-they produce adventitious roots
-they are protected by brown, papery leaves.
-Ex. Crocus, gladiolus

177
Q

Rhizomes

A

-are horizontal, underground stems, with adventitious roots.
-they produce a small scale-like leaf with an axillary bud at each node.
-ex. Perennial grasses; irises; ferns

178
Q

Runners and Stolons

A

-Runners are horizontal stems with long internodes that grow along the ground surface (above ground).
-At each node, a new plant is produced.
-Ex. Strawberries
-Some botanists refer to stolonsfor the underground stems with long internodes; such as in white potatoes.
(In potatoes, tuber develop at the end of stolons).

179
Q

Tubers

A

-are swollen, underground stems, that store carbohydrates;
or swollen tips of stolonsthat store carbohydrates.
-they form at the tip of stolons.
-they produce ‘eyes’ or axillary buds in the axils (base) of scale-like leaves.
-each ‘eye’ gives rise to new potato plant.

180
Q

Tendrils

A

-are modified stems that function in support and climbing.
-ex. Grapes and ivy.
-note: in peas and pumpkins, tendrils are modified leaves

181
Q

Cladophylls

A

-are flattened, green, photosynthetic stems of cacti.
-note: the spines of cacti are modified leaves.

182
Q

How do leaves start from primordia?

A

by apical meristems.

183
Q

What do leaves have unlike stems and roots?

A

Unlike stems and roots, leaves have determinate growth.
They stop growing at maturity.
They are the principal site of photosynthesis

184
Q

There are 2 types of leaves

A

Microphyll= leaf with 1 vein (only found in clubmosses/Lycophyta)
Megaphyll= leaf with many veins(found in seed plants and ferns

185
Q

How do leaves of monocots and dicots differ?

A

In monocots (ex. Grasses): leaves are long and narrow with parallel venation; lacking a petiole.

In dicots (ex. Sunflowers): leaves have a flat and expanded blade with netted (or branched) venation. Leaves are usually with a petiole; and sometimes they may have stipules (outgrowths at the base of the petiole in form of leaf-like or spine).

186
Q

Simple leaf

A

A simple leaf has an undivided blade.
The blade may have teeth, indentations, or lobes

187
Q

Compound leaf

A

A compound leaf has blade divided into leaflets.

188
Q

Summarize the internal leaf structure

A

A leaf is composed of an upper epidermis, lower epidermis, a photosynthetic tissue called mesophyll in between, and veins (vascular bundles

189
Q

Epidermis

A

EPIDERMIS
-it is the outside cover
-it is made of transparent cells with no chloroplasts.
-the epidermal cell secretes the waxy cuticle (waterproof)
-the epidermis may contain trichomes and glands.
-it has slit-like openings, stomata, for gas exchange.
-a stoma is found between guard cells (only epidermal cells with chloroplasts).
-stomata are more numerous in the lower epidermis (to reduce water loss).

190
Q

Mesophyll

A

MESOPHYLL
-Is the photosynthetic tissue between the upper and lower epidermis
-It is made of chlorenchyma cells(parenchyma with chloroplasts).
-In most dicots, it is differentiated into 2 regions:
a)Palissade mesophyll
-bellow the upper epidermis
-made of tightly packed (columnar) parenchyma cells (usually 2 rows)
b)Spongy mesophyll
-toward the lower epidermis
-chlorenchyma cells are loosely arranged
-there are many air spaces: help in gas exchange and exit of water vapor from leaves

191
Q

Palisside mesophyll

A

-bellow the upper epidermis
-made of tightly packed (columnar) parenchyma cells (usually 2 rows)

192
Q

Spongy mesophyll

A

-toward the lower epidermis
-chlorenchyma cells are loosely arranged
-there are many air spaces: help in gas exchange and exit of water vapor from leaves

193
Q

In monocots, what happens to the mesophyll?

A

In monocots, there is no differentiation of the mesophyll into palisade and spongy layers, and there is little distinction between the upper and lower epidermis.

194
Q

Veins(vascular bundles)

A

In both dicot and monocot leaves, there are veins (or vascular bundles/with xylem and phloem tissue) that run in the mesophyll

195
Q

Modified leaves

A

1)Floral leaves or bracts
2)Spines
3)Reproductive leaves
4)Window leaves
5)Shade leaves
6)Insectivorous leaves

196
Q

Floral leaves/bracts

A

-Leaves are large and colored; they surround tiny yellow flowers.
-They have the same function as petals (attract pollinators).
-Ex. Poinsettia

197
Q

Spines

A

-Sharp leaves with small surface area to reduce water loss and deter predators.
-Ex. Cacti

198
Q

Reproductive leaves

A

-Some plants produce plantlets along leaf margins.
-When plantlets fall, they give rise to new plants (propagation function).
-Ex. Kalanchoe plant; ferns.

199
Q

Window leaves

A

-Many plants in arid regions produce succulent, cone-shaped leaves with transparent tips.
-Leaves often become buried in sand (when blown by wind).
-Window leaves (with thick cuticle) allow light to pass so that photosynthesis can proceed below the soil surface

200
Q

Shade leaves

A

-When there is too much shade, the leaves become larger in surface area(to receive more light), but thinner as there is less mesophyll.

201
Q

Insectivorous leaves

A

*There are around 200 plants that have leaves to trap insects.
*These plants often grow in acid swamps and areas deficient in some minerals, mainly nitrogen.
*The plant catches and digests insects to supply the missing nutrients

202
Q

Pitcher plant

A

Have cone-shaped leaves in which rainwater accumulates; inside the leaves, there are stiff, down-oriented hairs.
Insect that drowns cannot escape.
Plant releases enzymes to digest insect

203
Q

Sundews

A

Have glandular trichomes on leaves that secrete sticky material to trap insects

204
Q

Venus fly trap

A

Leaf is made of 2 halves, with trigger hairs.
Hairs are stimulated when insects move.
The 2 halves snap shut, trapping insect

bio 202 (7 decks)

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