Lecture 8 - Root Structure And Development Flashcards
(115 cards)
1
Q
The first structure to emerge from germinating seed.
A
Primary root
2
Q
Root functions
A
Anchorage, absorption, storage, hormone production, secondary metabolite production
3
Q
Anchorage
A
Holds plant in position and stabilizes it
4
Q
Absorption
A
Water, minerals, gas exchange
5
Q
Storage
A
Food from photosynthesizing parts moves through phloem to root
6
Q
Food is used by the root but also:
A
Digested and transported back aboveground
7
Q
Storage: Some roots are specialized for:
A
Overwinter storage
8
Q
What hormones are produced?
A
Cytokinins and gibberellins
9
Q
What do hormones do?
A
Stimulate growth and development
10
Q
Where are hormones made and where are they transported?
A
Made in meristematic regions of root and transported upward in xylem
11
Q
Secondary metabolite production example
A
Nicotine in tobacco
12
Q
What is the rhizosphere?
A
Layer of soil bound to the root by mucigel and root hairs
13
Q
What does the rhizosphere contain?
A
Micro-organisms and sloughed off rootcap cells
14
Q
Rhizosphere: what is mycorrhizae?
A
Mutually beneficial symbiotic associations between fungi and plant roots
15
Q
Plant benefit
A
Increased ability to get water and elements, protection
16
Q
Fungus benefit
A
Carbohydrates and vitamins
17
Q
Types of root systems
A
- Tap root
- fibrous root
18
Q
Tap roots are most common in?
A
Dicots
19
Q
What is the main component of taproots?
A
Primary root
20
Q
Lateral roots are common in what?
A
Tap roots and fibrous roots
21
Q
Fibrous roots are common in what?
A
Monocots
22
Q
No one root is prominent
A
Fibrous roots
23
Q
Describe the primary root of fibrous roots
A
Short and short-lived
24
Q
Root design is dependent on:
A
Moisture, temperature, soil composition
25
What do feeder roots do?
Most of the absorption
26
Where are feeder roots located?
Upper soil layers
27
Growth of roots is continuous unless:
Adverse conditions
28
Balance between surface area for photosynthesis and absorption of water and minerals is balance between:
The root and shoot
29
Damage to the root will cause:
Damage to the shoot (and vice versa)
30
What does lack of water cause?
Root-produced hormones that slow down shoot growth
31
What does reduced shoot growth cause?
Decreases available carbohydrates so root growth is limited.
32
What is the root apex made of?
Root apical meristem and rootcap
33
What is the rootcaps function?
Protection
34
Rootcap: cells produce a slimy polysaccharide called?
Mucigel
35
Mucigel function
Lubrication
36
What happens to sloughed off cells of the rootcap?
Replaced by new ones from the root apical meristem
37
root apical meristem is subterminal, meaning its
Under the root cap
38
In the root apical meristem, files of cells (initials) divide, but do not
Differentiate
39
root apical meristem: quiescent Center
Contains initials that are inactive and will replace injured regions
40
Zones of root growth
root apical meristem, region of elongation, region of maturation
41
root apical meristem is the region of:
Cell division
42
Region of elongation is the region of
Cell expansion
43
In the Region of elongation, root growth is towards:
The tip
44
The Region of elongation increases:
Root length
45
Region of maturation is the region of:
Cell differentiation
46
Root hairs are present in which growth zone?
Region of maturation
47
What are trichoblasts?
- Root hairs
- unicellular extensions of epidermal cells
48
What zone do root hairs form?
Absorption zone
49
Describe the life span of root hairs
Short-lived and replaced by new ones
50
Cuticle is _________ in root hairs
Absent
51
Primary meristems formed by the root apical meristem
Protoderm, ground meristem, procambium
52
What does the protoderm form?
Dermal tissues - epidermis, root hairs
53
What does the ground meristem form?
Ground tissue - cortex
54
What does the procambium form?
Vascular cylinder: primary vascular tissues, pericycle
55
What makes up most of the root?
The Cortex
56
Cortex is made of mostly:
Parenchyma
57
What are plastids (of the cortex) role?
Store starch
58
Cortex contains numerous:
Intercellular spaces
59
Intercellular spaces allow for:
Free flow of material through the symplast
60
In some plants, what is the outermost layer of the cortex?
Exodermis
61
What is the location of the endodermis?
Innermost layer of cortex
62
Describe the endodermis
Compact, lacks air spaces
63
Has a casparian strip
Endodermis
64
What does the casparian strip contain?
Suberin or lignin in anticlinal walls
65
casparian strip function
Apoplastic barrier
66
casparian strip: How do substances enter and leave the vascular cylinder? What does this allow for?
Through protoplasts. Allows for selectivity
67
What forms the stele?
Xylem and phloem
68
Stele does not include
Secondary vascular tissue
69
Outermost layer of stele and its location
Pericycle, below endodermis
70
Simplest and most primitive type of stele
Protostele
71
Describe the core of a protostele
Solid Xylem core, ridge like projections
- phloem surrounds Xylem
- no pith
72
What kind of roots have protostele?
Dicot roots
73
Xylem and phloem form concentric cylinders around a central pith
Siphonostele
74
Where is phloem located in Siphonostele?
Outer surface of Xylem only or on both inner and outer surface of xylem
75
What kind of roots have Siphonostele?
Monocot roots
76
How many cell layers does the pericycle have?
Single cell layer
77
Outermost layer of stele
Pericycle
78
What is the pericycle made of?
Parenchyma cells
79
Region where lateral roots begin
Pericycle
80
In roots that undergo secondary growth, what does the pericycle form?
Vascular cambium and cork cambium
81
Lateral roots are referred to as:
Secondary roots
82
How do lateral roots arise?
From pericycle by periclinal cell divisions
83
Several lateral roots initiate:
Simultaneously
84
Have their own root cap, root apical meristem, and absorption zone
Lateral roots
85
Lateral roots can produce:
New lateral roots
86
Secondary growth increases:
Width of root
87
What plant type is secondary growth common in?
Woody plants
88
Secondary growth is produced by:
Lateral meristems
89
Secondary growth: vascular cambium produces:
Secondary xylem (inside) and secondary phloem (outside)
90
What is the vascular cambium initiated from?
Procombial cells between primary phloem and primary Xylem
91
Also contributes to vascular cambium
Pericycle
92
Where are rays produced?
In the secondary xylem and secondary phloem
93
Secondary growth: cork cambium initiates from:
Pericycle
94
Cork is produced towards:
Outer surface
95
Phelloderm produced toward
Inner surface
96
What does the periderm consist of?
Phelloderm, cork cambium, and cork
97
Lenticels allow
Gas exchange
98
Secondary growth: At the end of first years growth, these tissues are present in a woody dicot root
- Remnants of epidermis
- remnants of cortex
- periderm
- pericycle
- primary phloem fibers and crushed phloem cells
- secondary phloem
- vascular cambium
- secondary xylem
- primary Xylem
99
Modified root types
Aerial, stilt, epiphytes, pneumatophores, fleshy
100
How are aerial roots produced?
From aboveground structures
101
Some aerial roots are prop roots that function in? What is their function after making contact with soil?
Supporting the plant. Then, Absorption
102
Stilt roots seen in tropical trees provide
Support
103
Some aerial roots cling to surfaces to provide:
Climbing support
104
Non-parasitic plants that grow on other plants
Epiphytes
105
Epiphytes: Root epidermis is:
Several layers thick
106
Epiphytes: root Epidermis function
Protection, may function in water absorption
107
Air roots
Pneumatophores
108
Pneumatophores allow plants to grow where?
Swampy habitats
109
Pneumatophores contain
Large air-filled cavities, may have lenticels
110
Grow upward against gravity
Pneumatophores
111
Fleshy roots are specialized for:
Food storage
112
Have Storage parenchyma in Xylem and phloem
Fleshy roots
113
What are root nodules?
Swellings on roots of legumes inhabited by symbiotic nitrogen-fixing bacteria (ex rhizobium)
114
Bacteria provides plant with nitrogen it can use
Fix atmospheric nitrogen
115
Root nodules: Plant provides bacteria with
Carbohydrates
