Primary Plant Body Flashcards
(49 cards)
1
Q
what is the main function of the root?
A
- to anchor the plant
- the absorb nutrients and water from the soil
2
Q
What is cytokinin?
A
a hormone for shoot development ( stimulates germination)
3
Q
What are some hormones released by roots?
A
- ethylene, cytokinin, ABA (absicic acid)
4
Q
What are the two main patterns of root growth?
A
- tap root system
-adventitious (fibrous root) system
5
Q
How deep in the soil to roots generally reside? Why?
A
- 50-90% of root remains in the top 30 cm of soil because that is where the nutrients are
6
Q
Which plants are known to have a taproot system?
A
- most dicots and gymnosperms have a taproot system
7
Q
Describe the tap root?
A
- one main root, derived from the radicle , and develops lateral roots which develop their own branched roots
- taproots generally penetrate very deeply
8
Q
what is gravitropism?
A
- plant growth responds to gravity: roots show positive gravitropism
9
Q
What is responsible for gravitropism?
A
- amyloplasts : a different type of plastid, stores starch and acts as a gravity sensor to grow downward
10
Q
Describe the fibrous root system?
A
- most monocots and seedless vascular plants
- numerous roots emerge from lower part of the stem
- known as adventitious roots
- no single root stands out as the largest
- can hold many soil particle, shallower roots than taproot
11
Q
What is SALT?
A
- sloping agricultural land technology
- only fibrous roots can be grown because they hold more soil particles
12
Q
what are prop roots?
A
provide additional support
13
Q
Describe the aerial roots of mangrove plants
A
- these contain many aerenchyma to absorb oxygen and aid in support in the water
14
Q
what is the zone of cell division? Where does root development occur?
A
- zone of cell division: root apical meristem and the 3 primary meristems
- cell division occurs near the root tip: root apical meristem produces a root cap
15
Q
what does the root cap do?
A
- protects the root apical meristem
- replaced by new cells
- the outer cell of root cap produces a slimy polysaccharide called mucigel
16
Q
What is mucigel?
A
- a slimy polysaccharide on the outside of the root cap
17
Q
Describe the life span of the root cap
A
- lives 3-4 days, wears down fast because it goes through tough soil particles
- plants naturally removes the cap via programmed cell death
18
Q
what are root hairs?
A
small hair like extensions produced by the root epidermal cells
- help absorb water and minerals from the soil
- primarily within zone of maturation
- branched to provide a dense chamber for protection
19
Q
what is the main function of the epidermis?
A
- protection! - but it does have other functions
20
Q
what are some of the epidermal functions?
A
- protection from dessication and excess light and UV radiation
- attracts pollinators
- regulates uptake of water and nutrients
- regulates gas exchange
21
Q
Is the epidermis photosynthetic?
A
no! but the guard cells are
22
Q
describe the stomatal complex
A
- epidermis regulates gas exchange because of stomata
- two guard cells have chloroplasts: the only photosynthetic part of the epidermis
- guard cells open and close
- lower epidermis contains more
23
Q
Which part of the epidermis contains more stomata?
A
the lower part
24
Q
what are trichomes? Describe them
A
- stems and leaves
- serve to reflect excess light and UV radiation
- leaves don’t have hair because it blocks photosynthesis, and they are short lived because they are damaged by the sun
25
What else are trichome useful for aside from UV protection?
- dispersal and defense
26
how are trichomes involved in defense?
- release of terpenoids repel herbivores and attract predators of plant feeding insects
-trichomes often protect the shore apical meristem form pathogens, UV, and predators
27
describe the tissue layers of the primary mature root
- epidermis, cortex, endodermis, pericycle, vascular tissue (xylem and phloem)
28
what is the endodermis? what is the pericycle?
- regulates the flow of substances from the cortex to the vascular tissue
- pericycle: consist of meristematic cells which give rise to lateral roots : grow through cortex and epidermis (they are NOT root hairs)
29
what are the spaces in a root cross section called?
- aerenchyma
30
what are root aerenchyma
- gas spaces in root cortex caused b controlled collapse and death of certain cortical cells
- another example of programmed cell death
31
describe the structure of the endodermis
- arises from the inner most layer of the cortex, a single ring of cells
- surrounded on 4 of its 6 sides by the casparian strip
32
what is the casparian strip?
- forces water and mineral to pass across cell membranes and through cytoplasm, rather than between the cell walls
-
33
what is Suberin?
endodermis controls water usage Suberin: impermeable to water
34
what is the correct order of water flow from the soil to the xylem?
epidermis, cortex, endodermis, pericycle, vascular tissue (xylem)
35
what are some basic features of the stem?
- node, internode, axillary buds
36
what is the point called where leaves are attached to the stem? What about between them?
- the node
- the internode
37
why are axillary buds
embryonic shoot that lies dormant at the junction between stem and petiole (the stalk of branch)
38
Describe the tissue structure of a leaf
1) upper epidermis - protection
2) mesophyll cells
- palisade mesophyll
spongey mesophyll
3) lower epidermis
39
what allows the epidermis to remain impermeable to water?
- it produces a layer of wax and cutin (no waxy layers on top of pores)
40
what gases do stomata regulate the exchange of?
- water, Co2, O2
41
Where are most stomata found?
- on the underside of the leaf (less dust/exposure)
42
Describe the structure of stomata ? what conditions are they closed?
- 1 pore and 2 guard cells (guard cells have chloroplasts)
- closed during high temp/high wind, or high concentration of Co2 within the plant
43
what causes the opening and closing of the stomata
- turgid: open
- flaccid: closed
when photosynthesizing it is product a lot of sugars: water flows in, guard cells turgid and open
- no sun/night: they deflate
44
What are mesophyll cells?
- photosynthesis in the lead occurs in the mesophyll
- located between lower and upper epidermis
- mesophyll cells contain chloroplast and are specialized for photosynthesis
45
what are palisade cells?
- sometime mesophyll cells are long and line up beneath the epidermis: palisade
- usually one cell thick
46
what is the spongy mesophyll?
- below palisade mesophyll
- consists of loosely organized photosynethtic cells
- space allows for diffusion of Co2 from stomata to other parts of the leaf
-
47
where do palisade and spongy mesophyll cells occur?
- sometimes palisade occurs on both sides of the leaf, song mesophyll is in the centre or not at all
48
What are the two forms of leaves? Which is the advanced characteristic?
- netted and parallel
- netted is the advanced characteristic (in ferns, dicots, eg)
49
what wax does the endodermis use? what wax does the epidermis use? What are their functions?
endodermis: suberin
epidermis: cutin and wax
for water impermeability
