Plant development and environmental perception Flashcards
plant development cellular aspects of development how cells respond to stimuli (198 cards)
1
Q
what are angiosperms
A
plants that have flowers and produce seeds enclosed within a carpel
2
Q
what are the two main groups of angiosperms
A
eudicots and monocots
3
Q
what is a cell
A
the fundamental unit of life
4
Q
what is a tissue
A
a group of cells consisting of one or more cell types that together perform a specialized function
5
Q
what is an organ
A
it consists of several types of tissues that together carry out particular functions
6
Q
what do plants absorb below the ground
A
water and minerals
7
Q
what do plants absorb above the ground
A
light and carbon dioxide
8
Q
what are the 3 basic organs of a plant
A
stems, leaves and roots
9
Q
what does the root system consist of
A
the roots
10
Q
what does the shoot system consist of
A
stems and leaves
11
Q
what is a root
A
an organ that anchors a vascular plant in the soil, absorbs minerals and water and often stores carbohydrates and other reserves
12
Q
what is the first organ to emerge from a germinating seed
A
the primary root
13
Q
what does the primary root branch into
A
lateral roots
14
Q
what is a taproot
A
the main vertical root that develops from the primary root and is exhibited in tall erect plants - facilitates anchorage
15
Q
what is a fibrous root system
A
a thick mat of slender roots spreading out below the soil surface
16
Q
what is an adventitious root
A
a root that grows in an unusual location e.g. roots arising from stems or leaves
17
Q
what are root hairs
A
thin finger like extensions of root epidermal cells
18
Q
what are mycorrhizal associations
A
root symbiotic interactions with soil and fungi that increase a plants ability to absorb minerals
19
Q
what is a stem
A
a plant organ bearing leaves and buds
its chief function is to elongate and orient the shoot in a way that maximises photosynthesis by the leaves
they also elevate reproductive structures, facilitating the dispersal of pollen and fruit
20
Q
can a green stem perform photosynthesis
A
yes but it is limited
21
Q
stems consist of nodes, what are these
A
the points at which leaves are attached
22
Q
stems consist of internodes, what are these
A
the stem segments between nodes (between the points where leaves are attached
23
Q
what is the main photosynthetic organ
A
the leaves
24
Q
how do monocots and eudicots differ
A
by the arrangement of veins ((the vascular tissue) in the leaves
- most monocots have parallel veins
- most eudicots have a branched network of veins arising from a major vein
25
what are the 3 fundamental tissue types of vascular plants
dermal, vascular and ground tissues
26
what is the function of the dermal tissue system
serves as an outer protective covering of the plant
27
what are the functions of trichomes
reduce water loss
reflect excess light
defend against insects
28
what is the function of the vascular tissue system
facilitates the transport of materials through the plant and provide mechanical support
29
what are the 2 types of vascular tissue
xylem and phloem
30
what is the function of xylem
conduct water and dissolved minerals upward from roots into the shoots
31
what is the function of phloem
transports sugars from where they are made to where they are needed or stored
32
what is ground tissue
tissue that is not vascular or dermal - it includes specialised cells for functions such as storage, photosynthesis, support and short distance transport
33
what is intermediate growth
the process of plants growing throughout their life
34
why can plants continually grow
because they have undifferentiated tissues called meristems, containing cells that can divide, leading to new cells that elongate and become differentiated
35
which type of plant does not grow continuously
dormant plants
36
describe the growth of most animals
determinate growth - they stop growing after they reach a certain size
37
what are the 2 main types of meristems and what type of growth do they enable
apical meristem - primary - length
| lateral meristems - secondary - thickness
38
roots and stems grow intermediately/determinately
intermediately
39
leaves grow intermediately/determinately
determinately - because the oldest leaves at the bottom of the plant would be large and heavily shaded, unable to photosynthesise maximally
40
what is the function of stomata
they are pores interrupting the leaf epidermis which allow exchange of carbon dioxide and oxygen between the surrounding air and the photosynthetic cells in side the leaf
they are also major avenues for the evaporative loss of water
41
what does the stomatal complex consist of
a stomatal pore flanked by 2 specialised epidermal cells known as guard cells which regulate the opening and closing of the pore
42
what is a parenchyma cell
a relatively unspecialised plant cell type that carries out most of the metabolism, synthesis and stores most of the organic products and develops into a more differentiated cell type
43
what type of cell does mesophyll mainly consist of
parenchyma
44
what is a bundle sheath
a layer of cells that encloses the veins and regulates the movement of substances between the vascular tissue and the mesophyll
(prominent in leaves that carry out C4 synthesis)
45
contrast primary growth in roots and shoots
roots - primary growth occurs in 3 successive stages, moving away from the tip of the root: the zones of cell division, elongation and differentiation
shoots - occurs at the tip of apical buds, with leaf primordia arising along the sides of an apical meristem - most growth in length occurs in older internodes below the shoot tip
46
what are leaf primordia
finger like projections along a shoot apical meristems from which a leaf arises
47
what is a lenticel
a small raised area in the bark of stems and roots that enabled gas exchange between living cells and the outside air
48
why do stomata need to be able to close but lenticel s do not
stomata need to close because water evaporation is much more intensive in leaves than from the trunks of woody trees as a result of higher SA to volume ratio in leaves
49
what is meant by plant growth being modular
it follows patterns that are repeated over and over again
50
what does morphogenesis (plant form) arise from and what is it dependent on
arises within cell walls and depends entirely on cell division and cell lineage
51
the first 4 divisions of embryogenesis give cell ……….
bulk
52
the fifth division (to 16 cell stage) results in what
cell layers
53
tripoblasts/atripoblasts form root hairs
triipoblasts
54
tripoblasts/atripoblasts do not form root hairs
atripoblasts
55
what happens to the fassiculated mutant of Arabidopsis
it has a loss of positional interactions - the cell walls become disorganised
56
what happens to the knolle mutant of Arabidopsis
it has a loss of cell division control - knolle is a structural protein needed to form the cell division plate - the mutant has irregular and incomplete cell divisions
57
simple rules of association provide guidelines for what
development
58
what is pattern formation
the development of specific structures in specific locations
59
where do plant developmental stages (phases) occur
the apical shoot meristem
60
what are phase changes
in plants it is a morphological change that arises from a transition in shoot apical meristem activity
61
what does GLABRA-2 do
if it is expressed the cell is hairless but if it isn't expressed then the cell will develop a root hair
62
do nodes and internodes maintain juvenile status even after the shoot apical meristem has changed to adult phase
yes - new leaves that develop at juvenile nodes will also be juvenile even though the apical meristem is producing mature nodes
63
describe 3 difference between animal and plant development
plants:
- intermediate growth
- juvenile and mature phases are found on the same plant
- cell differentiation is more dependent on final position
animals:
- determinate growth
- juvenile and mature phases not found on the same individual
- cell differentiation is more dependent on cell lineage
64
what phase change does flower formation involve
a change from vegetative growth to reproductive growth
65
is floral growth usually indeterminate or determinate
determinate
66
how does the production of a flower by a shoot apical meristem affect growth
it usually stops the primary growth of that shoot
67
which genes control the switch from vegetative growth to flowering
meristem identity genes
68
how do meristem identity genes affect flowering
their protein product acts as a transcription factor that regulates the genes required for the conversion of intermediate vegetative meristems to determinate floral meristems
69
what are the 4 floral organs
sepal, petal, stamen or carpel
70
what do organ identity genes belonging to the MADS-box family encode
transcription factors that regulate development of the characteristic floral pattern
71
what can a mutation in organ identity genes in plants cause
abnormal floral development such as petals growing in place of stamens
72
what process leads to polarisation
germination
73
what factors induce germination
- light (rhizoid grows on shaded side)
- heat (rhizoid grows on warm side)
- osmotic gradient (rhizoid grows towards water)
- pH (rhizoid grows towards alkaline pH)
- salt rhizoid grows towards salt)
- fertilization (rhizoid at entry point)
74
describe the steps in polarisation due to fertilisation
- in fertilisation, a calcium wave triggers secretion of cell wall material
- calcium current is initiated and enters at future rhizoid end
- actin is organised, and secretion is directed to future rhizoid
- polarity is fixed and the rhizoid tip is visible
- mitosis and cell division occur
75
what are rhizoids
long tubular single cells
76
what is the regulatory factor of polarity
calcium
77
root structure arises from ……….. divisions that initiate cell lineage
meristems
78
how is polarity controlled between cells in plants
Apical-basal polarity is maintained by hormonal gradients, especially auxin
79
Plant tissue structure arises from cell lineages with defined cell fates originating from established ...………...
cell polarity
80
what do pin proteins do
transport auxins out of cells (efflux carriers)
81
what happens to the pin-1 mutant
disturbs shoot form and root growth direction
82
what happens to the pin-2 mutant
mutant seedlings show loss of gravitropism (movement or growth in relation to gravity) in the root - they can't access nutrients and water from the soil as well
83
in signal transduction what is a receptor need for
to sense the stimulus - the receptor converts the signal into a biological meaningful form
84
what are second messengers
- they amplify the internal biochemical signal from the receptor
- they transfer the signal to the response mechanism
85
by opening and closing of stomata, what is balanced
the need for CO2 for photosynthesis against the prevention of water loss
86
abscisic acid is involved in which kind of tress
drought - drought stimulates roots to synthesise abscisic acid which then travels to the leaves with the transpiration stream
87
is abscisic acid a stimulus for stomatal closure or opening
closure
88
the abscisic acid stimulus overrides the need for ……….
CO2
89
what are the 3 main ion channels used by guard cells
Ca
Cl
K
90
how can we measure ion channels
using a method called clamping
| we can also measure how single proteins function using a method called patch lamp
91
ion channels are pores with ……….... gates
regulated
92
how does gating of ion channels arise
from changes in protein conformation in the channel
93
how does abscisic acid trigger closing of stomata
it triggers potassium and chlorine efflux and suppresses influx which triggers closing of the stomata
the abscisic acid affects the gating of the channels affecting their frequency of opening
94
what are jaffes laws
the laws for determining if something is a secondary messenger
1. the stimulus, second messenger and response must be related in time and space
2. blocking a signal or messenger must block the signal and response downstream
3. introducing a second messenger without a primary stimulus must give the response downstream
95
abscisic acid triggers a rise/decrease in Ca in the cytosol
rise
96
Ca is needed to regulate what
ion channels
97
Ca in the cytosol promotes/suppresses abscisic acid action on K and Cl channels
suppresses
98
is Ca sufficient to regulate ion channels without abscisic acid
yes
99
give examples of stimuli that trigger signal transduction pathways
light
hormones
physical environment
pathogens
100
signal transduction pathways link signal .......... to .............
reception to response
101
what is etiolation
morphological adaptations for growing in darkness
102
describe a dark grown potato
tall stems and unexpanded leaves - an adaptation enabling shoots to penetrate the soil
the roots are short as there is little need for water absorption due to the lack of water loss due to the lack of leaves
103
describe a potato grown in light
short sturdy stems
broad green leaves - to enhance photosynthesis
long roots - to enhance water absorption
104
what is de-etiolation
the changes a plant undergoes due to being exposed to light
| the light signal is transduced to de-etiolation response
105
what are the 3 main steps of a signal transduction pathway
reception
transduction
response
106
what are signals detected by
receptors
107
what is the receptor involved in de-etiolation
phytochrome
108
where is the phytochrome located
cytoplasm
109
where are the majority of photoreceptors found
the plasma membrane
110
what causes golden rice
it is an aurea mutant which has less phytochrome (this reduces the level of chlorophyll because phytochromes detect red light that chlorophyll absorbs)
in the absence of chlorophyll the yellow and orange accessory pigments become more prominent
111
cytosolic changes in calcium concentration play an important role in ............ signal transduction
phytochrome
112
how do phytochromes affect calcium concentration
- phytochrome activation leads to the opening of calcium channels increasing cytosolic levels of calcium
113
describe the role of phytochrome in de-etiolation
1. light signal is detected by the phytochrome receptor, activating 2 signal transduction pathways
2. a. one pathway uses cGMP as a second messenger that activates kinase
b. the other pathway increases the cytosolic level of calcium which activates another kinase
3. both pathways lead to the expression of genes (by transcription factors activated by kinase) for proteins that function in the de-etiolation response
114
what are the 2 main mechanisms by which a signalling pathway can enhance an enzymatic step in a biochemical pathway
transcriptional regulation
| post translational modification
115
what is transcriptional regulation
controlling the level of mRNA encoding a specific enzyme
116
what do post translational modifications do
activate pre-existing enzymes
117
give examples of post translational modifications
phosphorylation
118
what enzymes are important in stopping signal transduction pathways after the stimulus has faded
phosphatases - they dephosphorylate
119
what are the 2 types of transcription factors
activators (increase transcription) and suppressors (decrease transcription)
120
why is etiolation advantageous
etiolated growth is beneficial to seeds growing underground or under dark conditions.
by devoting more energy to stem elongation and less to leaf expansion and root growth, the plant increases the likelihood that the shoot will reach the sunlight before its stored food runs out
121
which hormones enhance stem elongation
auxin and brassinosteroids
122
what is a hormone
signalling molecule that is produced in low concentrations by one part of an organism and is transported to other parts triggering responses in target cells and tissues
123
what are plant growth regulators
plant hormones
124
where is auxin found
shoot apical meristems and young leaves
125
what is the function of auxin
simulates stem elongation
promotes formation of lateral and adventitious roots
regulates development of fruit
functions in phototropism and gravitropism
126
where are cytokinins found
mostly synthesised in the roots - and are transported in the xylem sap
127
what is the function of cytokinins
regulation of cell division in roots and shoots
promote movement of nutrients
stimulates seed germination
128
where is ABA found
almost all plant cells have the ability to produce ABA
129
what is the function of ABA
inhibits growth
promotes stomatal closure during drought stress
promotes seed dormancy and inhibits early germination
130
what is a tropism
any growth response that results in plant organs curving towards or away from light
131
what is phototropism
the growth of a shoot towards or away from light
132
why do high concentrations of auxin inhibit growth
high auxin concentrations may induce production of ethylene which hinders growth
133
explain how proton pumps play a major role in the growth response of cells to auxin
- in a shoots region of elongation, auxin stimulates the plasma membranes proton pumps pumping H from the cytoplasm
- H increases the voltage across the membrane and lowers the pH in the cell wall
- acidification of the cell wall activates proteins that break H bonds between cell wall constituents, making the cell wall more flexible
- increasing the membrane potential enhances ion uptake into the cell which causes osmotic uptake of water and increased turgor
- increased turgor and increased cell wall plasticity enable the cell to elongate
134
what is IBA used for
it is used in the vegetative propagation of plants by cuttings
treating a detached leaf or stem with IBA often causes adventitious roots to form near the cut surface
135
why are synthetic auxins used as herbicides
they can be quickly broken down by monocots but overdose eudicots, eliminating eudicot weeds
136
what is apical dominance
the ability of the apical bud to suppress development of auxiliary buds (controlled by various hormones including auxin and cytokinins)
137
how do cytokinins slow aging
they inhibit protein breakdown and stimulate RNA and protein synthesis
138
what is the role of gibberellins
stimulate stem elongation, pollen development, fruit growth, germination
139
what is the function of ethylene
promotes fruit ripening, leaf abscission, promotes root hair formation
induces triple response in seedlings
140
what is the function of brassinosteroids
promotes root growth at low concentrations but inhibits it at high concentrations
141
what is the ABA response to drought
- ABA accumulates in the leaves
- by affecting the second messenger, Ca, ABA cause potassium channels in the plasma membrane of guard cells to open leading to a massive loss of potassium ions from cells
- the accompanying osmotic loss of water reduces guard cell turgor and leads to the closing of the stomatal pores
- as a result less transpiration occurs
142
many plants prone to wilting are deficient in what
ABA - it acts as a drought signal
143
what is the triple response induced by ethylene
it enables seedling shoots too avid obstacles
the 3 parts of the response are:
- slowing of stem elongation
- thickening of stem
- stem curvature that causes it to start growing horizontally
the stem resumes regular growth after the ethylene pulse lessens
144
what is senescence
the programmed cell death of certain cells or organs or the entire plant - ethylene is almost always associated with apoptosis in senescence
145
what is abscission and what is it controlled by
the natural detachment of parts of a plant, typically dead leaves and ripe fruit
it is controlled by a change in the ratio of ethylene to auxin. an aging leaf produces less and less auxin rendering the abscission layer more sensitive to ethylene. when ethylene targets the abscission layer, the cells produce enzymes which digest cell wall components
146
what forms after leaf abscission to protect the plant from pathogens
a protective layer forms on the remaining twig to prevent pathogen entry
147
what triggers the ripening of fruit
a burst of ethylene - the enzymatic breakdown of cell wall components softens the fruit and conversion of starches and acids to sugars makes the fruit sweeter
148
how do gibberellins promote stem elongation
they enhance cell elongation and cell division
- they activate enzymes that loosen cell walls allowing the entry of expansins - which along with auxin promote cell elongation
149
in many plants, ………….. and …………. must be present to allow fruit to develop
auxin and gibberellins
150
which hormone signals seeds to break dormancy and germinate
gibberellins
151
what are brassinosteroids similar to in animals
sex hormones and cholesterol
152
which hormone slows leaf abscission
brassinosteroids
153
what are tumour growths on leaves caused by
uncontrolled cell division and cell differentiation - can be caused by pathogens interfering with the function of auxin and cytokinin
154
what are ein mutants
ethylene insensitive mutants - they fail to undergo the triple response - they lack the ethylene receptor
155
what are eto mutants
ethylene overproducing mutants - they undergo the triple response
156
what are ctr mutants
constitutive triple response mutants - they don't respond to inhibitors of ethylene synthesis so the ethylene signal transduction pathway is permanently turned on even id ethylene is absent
157
what is photomorphogenesis
the effects of light on plant morphology
158
what does an action spectrum show
the relative effectiveness of different wavelength of radiation in driving a particular process
159
what are the 2 major classes of light receptors
blue light photoreceptors - regulate phototropism, stomatal opening, slowing of hypocotyl elongation when a seedling breaks ground
phytochromes - regulate seed germination and shade avoidance
160
what is phototropism
growth of a plant shoot towards or away from light
161
which blue light photoreceptor is involved in mediating stomatal opening
phototropin (a protein kinase)
162
describe the role of phytochrome in the germination process
Pr in lettuce seeds exposed to red light is converted to Pfr stimulating germination.
when the red illuminated seeds are then exposed to far red light Pfr is converted back to Pr inhibiting germination
in nature the conversion to Pfr is faster than the conversion to Pr so germination is promoted
163
if a plant is exposed to multiple flashes of light, which flash will create the response
the last flash - the final light exposure is the determining factor
164
describe the role of phytochromes in shading avoidance
- if other trees in a forest shade a tree the phytochrome ratio will shift in favour of Pr because the - forest canopy screens out more red than far red light
- this is because pigments in the leaves of the canopy absorb red light and transmit far red light
- the shift in the ratio of red to far red light induces the tree allocates more of its resources to growing taller
- in contrast direct sunlight increases the proportion of Pfr which stimulates branching and inhibits vertical growth
165
what is a circadian rhythm
cycles with a frequency of 24 hours that are not directly controlled by an environmental variable
166
what is photoperiodism
a physiological response to specific night or day lengths e.g. flowering
167
what is a short day plant
they require a light period shorter than the critical length to flower (flower in winter instead of summer when light hours decrease)
168
what are long day plants
they require a light period longer than the critical length to flower (they flower in spring or early summer )when the photoperiod is long)
169
what are day neutral plants
they are unaffected by photoperiod and flower when they reach a certain stage of maturity
170
is flowering in short day and long day plants controlled by night length or day length
night length - so short day plants are actually long night plants and long day plants are actually short night plants
171
long day plants - maximum/minimum number of hours of darkness
maximum
172
short day plants - maximum/minimum number of hours of darkness
minimum
173
which colour of light is most effective in interrupting night length
red
174
where on the plant do flowers form
from apical or auxiliary bud meristems
175
which part of the plant detects changes in the photoperiod
leaves - they produce signalling molecules that cu bud to develop as flowers
176
how is flowering initiated
a gene called FT is activated in leaf cells in conditions favourable for flowering
the FT protein travels to the shoot apical meristem initiating the transition of a bud meristem from vegetative to flowering state
177
what is gravitropism
a plants response to gravity
roots display positive gravitropism (growing in direction of gravity) and shoots exhibit negative gravitropism (growing against gravity)
178
what is thigmomorphogenesis
changes in form that result from touch (mechanical perturbation)
179
what is thigmotropism
directional growth in response to touch
180
on a dry sunny day why does a plant wilt
it water loss by transpiration exceeds water absorption from the soil.
181
why may an overwatered house plant suffocate
the soil lack air spaces that provide oxygen for cellular respiration in the roots
- oxygen deprivation can induce ethylene production which causes some cells in the root cortex to die. this creates air space so oxygen can be taken up for respiration
182
how does salt affect plants
if plant soil is too salty this prevent water uptake into the plant
183
how do plants cope with cold stress
they alter their membrane lipid composition to keep it fluid - they increase the proportion of unsaturated fatty acid keeping the membrane fluid at low temperatures
184
how do plants cope with frost
when they freeze, water leaves the cytoplasm to go to the cell wall
the increase in the concentration of ions in the cytoplasm is harmful to the plant
plant have adapted by increasing cytoplasmic levels of specific solutes that are tolerated by the plant and help reduce the loss of water from the cell during extracellular freezing
unsaturation of membrane lipids is also increased helping to maintain fluidity
185
why are plant that are producing ABA warmer
because they cant undergo as much transpiration (evaporative cooling) due to stomatal closure
186
give an example of how plants can invade pathogens
by entering through openings in the epidermis e.g. the stomata
187
do plants have an adaptive immune system
no only an innate immune system
188
what are the 2 immune responses of plants to pathogens
1. PAMP - pathogen associated molecular patterns
| 2. effector triggered immunity
189
what is the hypersensitive response
a plants localised specific defence response to a pathogen, involving the death of cells around the site of infection, preventing the spread of the infection
190
what is systematic acquired resistance
a defensive response in infected plants that helps protect healthy tissue from pathogenic invasion -- a plant wide response (not localised)
191
what are the steps in defence responses of plants against pathogens
1. pathogens infect leaf cells and secrete effectors, proteins that bypass PAMP immunity
2. hypersensitive response occurs in response to effectors
3. before infected cell die they release a signalling molecule (methysalicylic acid) to the rest of the plant
4. the signalling molecule is converted to salicylic acid which induces systematic acquired resistance protecting the plant against many pathogens for several days
192
why is calcium effective as a second messenger in plants
because it is poorly mobile and largely bound in the cytosol
193
how many genes are involved in plant development
3
194
describe the mutant lacking the C gene in the ABC flower model
lacks stamen and carpel but has extra petals and sepals
195
describe the mutant lacking the B genes in the ABC flower model
lack stamen and petals but has extra sepals and carpels
196
describe the mutant lacking the A genes in the ABC flower model
lacks petals and sepals but has extra carpel and stamen
197
what is an apoprotein
photoreceptor protein
198
what is a chromophore
a small organic molecule that detects and absorbs light, attached to the apoprotein
