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Biology 2 > Plant Bio 2 > Flashcards

Plant Bio 2 Flashcards

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1
Q

What are the Vegetative organs?

A

Roots, Stems and Leaves

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2
Q

What are modules?

A

Internode, Leaf and Axillary buds

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3
Q

What are the Reproductive organs?

A

Flowers and Seeds

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4
Q

what are the Three Tissue systems?

A

Dermal, Ground and Vascular

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5
Q

Dermal tissue systems

A

Outer layer of the plant - Epidermal cells and cuticles

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6
Q

Ground tissue systems

A

Cells which carry out photosynthesis/hold photosynthetic products, supports the plant

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7
Q

Vascular tissue systems

A

Cells which conduct water and solutes through the plant

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8
Q

Key features of plant organisation

A

Organs made up from three tissue systems.

Modular construction.

Growth from meristems.

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9
Q

what is the Structure of dicot embryo?

A

L1 – epidermal cells (protoderm)
L2 – cortical cells (ground meristem)
L3 – vascular tissue (procambium)

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10
Q

what is the model plant used? why is it a good model plant?

A

Arabidopsis thaliana

Compact plants with a short life cycle, self fertile and has a small genome

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11
Q

what were the two factors that were found during experiments with Arabidopsis thaliana?

A

There are distinct regions in the embryo that develop independantly
Radial organisation is untouched

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12
Q

what are root apical meristems?

A

branch roots arise back from root cap

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13
Q

what are root caps?

A

mechanical protection for meristem – mucigel aids movement and gravity perception

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14
Q

what is the Quiescent zone?

A

slowly dividing cells – production of new tissues for elongation and regeneration of root cap

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15
Q

how is height added to the plant?

A

by adding new nodes and elongation of the internodes

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16
Q

which hormones regulate growth?

A

Auxins, cytokins and gibberellins

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17
Q

why are rosette plants different?

A

they’re radially symmetrical and growth is intermediate

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18
Q

what are lateral meristems used for?

A

Lateral meristems are cylindrical and are used for secondary growth, thickening roots and stems

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19
Q

what are the key features of cell enlargement?

A

Uptake of water into vacuole.
Expansins unlock linkages between cell wall components.
Cell wall can stretch and expand.

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20
Q

what is the equation for water uptake?

A

Rate of water uptake measured by increase in cell volume over time = LΔΨW = L(ΔΨS + P)
L = hydraulic conductance (property of membrane)
ΔΨW = water potential difference between cell and surroundings (must be negative for net movement).
ΔΨS = gradient in osmotic pressure between cell & surroundings (normally negative).
P = turgor pressure of cell (normally positive)
Higher conductance implies faster water uptake.

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21
Q

what is the equation for plant growth?

A 
RGR = LAR x NAR
RGR = Relative growth rate
LAR = Leaf area ratio
NAR = Net assimilation rate
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22
Q

how do you work out LAR?

A 
LAR = SLA x LMR
SLA = specific leaf area
LMR = leaf mass ratio
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23
Q

what are the factors affecting growth?

A

Rate of photosynthesis
Water availability
Nutrition
Genetic factors

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24
Q

how is cell specialisation controlled?

A

Hormones and external signals (e.g light) changing genetic expression

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25
Q

what is the function of a pavement cell?

A

Structure and spacing, morphologically unspecialised

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26
Q

what is the function of stomata?

A

Regulation of water loss and gas exchange, distribution is affected by the environment

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27
Q

what is the function of root hair cells?

A

Nutrients uptake, increase root surface area, unicellular

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28
Q

what is the function of Trichomes?

A

Protection from predators via the production of specialised chemicals, physical barriers, reduces transpiration and UV light

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29
Q

what are the two processes of development?

A
  • Unequal cell division
    plant cells cannot move relative to one another
    -Position effects
    differences in exposure to chemical signals or physical influences associated with cell position, stomatal formation involves peptide signal molecules
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30
Q

How is flowering initiated?

A
  • A development switch occurs, where vegetative development is switched to reproductive.
  • Meristems stop producing leaves and produce flowers
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31
Q

What external factors effect flowering?

A
  • Age
  • Temperature (vernalisation)
  • Day length (photoperiod)
  • Combination
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32
Q

Give two examples of photoperiodism

A

-Mutant tobacco (Maryland Mammoth) – tall, large leaves but no flowering in field. In greenhouse, even small plants flowered in winter.
-Soybeans sown over a 3 month period all flower within a
3 week period in September.

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33
Q

What are the types of photoperiodism shown in plants?

A
  • Short-day plants - Henbane - Spring/early summer
  • Long-day plants - Maryland Mammoth - late summer/autumn
  • Day neutral - Maize/ tomatoes - use age/temp
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34
Q

Where and how is the signal perceived?

A
  • Signal called florigen and is produced by leaves, due to grafting experiments.
  • Detached leaves can be induced to flower and can ‘pass on’ the flowering signal when grafted.
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35
Q

Describe the function of phytochrome

A
  • Photoreceptor for red light in plants

- Red light more present in daylight (stimulates flowering in short day plants)

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36
Q

What is phytochrome?

A
  • Photoreceptor for red light in plants
  • Soluble protein, ~120 KDa (~1100 AA)
  • Has tetrapyrrole chromophore
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37
Q

Why is length of night important for flowering?

A

-Xanthium strumarium would only flower after a 9H continuous night, which is required for short day plants

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38
Q

What are the three classes of genes involved in flower initiation?

A
  • Flowering time genes – determine when flowers are initiated. Example: FLOWERING LOCUS T (FT) gene codes for florigen protein.
  • Floral identity genes – commit meristems to production of floral rather than vegetative structures. Examples: LEAFY (LFY), APETALA1 (AP1).
  • Organ-identity genes – control development of floral parts (sepals, petals, stamens, carpels). Mutations cause abnormal flower development.
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39
Q

List the signalling pathway for florigen

A
  • Photoperiodic stimulus at leaf companion cell stablises CO, which acts as a TF
  • FT is made and enters sieve tube element through plasmodesmata
  • FT is transported through the phloem up to apical bud
  • FT combines with FD, and the complex acts as a TF for AP1
  • AP1 is made and initiates flowering
40
Q

List the 4 whorls of a plant

A
  • Stamens
  • Carpels
  • Petals
  • Sepals
41
Q

Describe the ABC table?

A

Gene class A B C
Gene name APETALA1 APETALA3 Agamous
APETALA2 PISTILLATA
-Sepals + - -
-Petals + + -
-Stamens - + +
-Carpels - - +

  • Loss of B - no stamens or petals
  • Loss of C - no carpel or stamens
  • A and C antagonistic - inhibit each other
42
Q

Define endogenous clocks and give two examples of clocks

A
  • Rhythmic leaf and flower movements are quite common in plants
  • Linnaeus (1751) - Floral clock
  • Jean-Jacques (1729) - Circadian rhythm (24 hr clock)
43
Q

List 5 things the circadian rhythm controls

A
  • Leaf movements
  • Stomatal opening
  • Stem growth
  • Membrane potential
  • Transcription
44
Q

What three criteria are required for clock controlled rhythms?

A
  • Rhythm persists in absence of external cues
  • Rhythm can be reset by external signals (e.g. light)
  • No lasting effect of temperature on timing of rhythm
45
Q

What is a zeitgeber?

A

-A signal synchronising rhythms, E.g when bean plants are in continuous light, the period increases to 25.7 hrs

46
Q

Describe the oscillator

A
  • The oscillator is the clock and it contains a lot of negative feedback, mainly between the TOC1 (early evening gene) and the CCA (early morning gene)
  • The oscillator produces overt rhythms that activate genes at different times of the day
47
Q

Describe senescence

A

-When cells undergo cell death and are dismantled and redistributed

48
Q

Define Carbon allocation

A

-The trade-off between growth and persistence

49
Q

What is the Harvest index ratio?

A

–Ratio of useable biomass : total biomass

50
Q

Describe what photo-assimilates are

A
  • Primary compounds that conserve fixed carbons and energy: Sucrose in cytosol and vacuole, Starch in the chloroplast
  • Species differ in proportions of starch:sucrose.
  • Exported photo-assimilates are transported in phloem, most commonly as sucrose.
51
Q

What are photo-assimilates used for?

A

Used for:

  • Growth and maintenance of leaf.
  • Local storage in leaf.
  • Export to other tissues for growth or storage.
52
Q

How is Sucrose synthesised in the cytosol?

A

-Triose-P translocator exchanges triose-P for phosphate, which then forms sucrose.

53
Q

Describe photo-assimilate exportation

A
  • From source to sinks
  • Can be used for growth or stored
  • Transportation occurs in the phloem, as phloem gridling blocks translocation
54
Q

Describe the phloem anatomy

A
  • Transportation occurs in the sieve tubes, supported by the companion cells
  • Phloem also contains phloem parenchyma cells
  • Sieve cells lack nucleus and most organelles
55
Q

Explain the Pressure flow model

A
  • Sugar loading into sieve element causes osmotic uptake of water from xylem.
  • Water pressure forces sap flow through sieve tubes.
  • Hydrostatic pressure lowered at sink end as sugar unloaded – pressure difference causes mass flow of solute from source to sink.
  • Xylem recycles water from sink to source leaf.
56
Q

What are the effects of translocation from source to sink?

A
  • Minimal energy is required for translocation
  • Direction is from source to sink
  • Loading and unloading regulate translocation and partitioning
57
Q

List the 3 routes of loading

A
  • Symplastic - Passive movements between cells through plasmodesmata requires high conc of sucrose in mesophyll than phloem
  • Apoplastic - Active movement of sucrose from mesophyll to companion cells, requires energy
  • Polymer-trapping model
58
Q

List the 3 methods of phloem unloading

A
  • Sucrose moving down a conc gradient in symplast
  • Sucrose released into apoplast, then hydrolysed by acid invertase and take up via active transport
  • Energy-dependent export into apoplast
59
Q

Give the equation form sink strength

A

-Sink strength = Sink size X Sink Activity

60
Q

List feature of a stomata

A
  • Two guard cells
  • Subsidiary cells
  • Stomatal cavity
61
Q

How do stomata vary?

A
  • Shape

- Distrubution - Aligned, Random and clustered

62
Q

What is the stomatal index?

A

-Number of stomata in relation to total number of epidermal cells.

63
Q

What is the function of the stomata?

A

-Guard cells function as hydraulic values that open and close to limit water loss

64
Q

How does a stomata open?

A
  • K+ enters guard cells driven by a electrochemical gradient caused by H+ ATPase
  • Cl- also enter the cell and both ions are transported into the vacuole
  • Malate ppt are used as a counter ion to increase water potenial, therefor water moves into the cell (can also be sucrose)
65
Q

How do stomata close?

A

-Movement of Ca2+ into the guard cell leading to k+ efflux and reduction of osmotic pressure

66
Q

What is a patch clamp?

A

-A piece of equipment that allows measurement of ions movement in a channel protein

67
Q

How can pharmacology interfere with the putative processes in guard cells?

A
  • Fusicoccin - stimulates H+ ATPase

- Vanadate and cccp - inhibit H+ ATPase

68
Q

How can genetics interfere with the putative processes in guard cells?

A

-ABi, mutant that can never close it’s stomata therefore wilting occurs. Due to ABA being non-functional

69
Q

List and describe the factors effecting the regulation of stomata

A
  • Internal CO2 conc - high conc will cause stomatal closure, even under high light
  • Light - blue light opens stomata, light effects mediated by phytochrome, CAM plants respond differently to blue light
  • Water vapour - Hydropassive closure: as a result of direct water loss by evapotranspiration by guard cells. Hydroactive closure: as a result of induced Ca2+ ion influx into guard cells
  • Abscisic acid (ABA) - Mediator of stomata water stress, produced in guard cells or surrounding cells
  • Circadian control - C3/C4 have stomata open during day, CAM have stomata open during night
70
Q

Describe the Transpiration ratio and reasons for it

A

-Water loss and carbon gain - CO2 is a heavier molecule and has to cross more membranes.

71
Q

Why does stress affect plants so much?

A
  • Plants are immobile and sessile, therefore cannot escape stress and must adjust their physiology.
  • Stress is either continuous or chronic
72
Q

What are the three ways plants can respond to stress?

A

-Specific or generalistic
-Localised or systemic
-Short-term, Mid-term and long-term
(some environmental signals are intergrated)

73
Q

Define ‘Resistance’ and ‘Avoidance’

A
  • The plant changes it’s physiology and adapts it’s metabolism to alleviate stress effects
  • The plant perceives the stress signal but ignores it and accepts the costs in terms of growth
74
Q

Describe Water deficit stress effects

A
  • Osmotic imbalances in cell
  • Cellular membranes become porous to solutes upon rehydration
  • Reduced photosynthesis caused by limited CO2 uptake due to stomatal closure
  • Changed root and shoot growth
  • Accelerates ‘ageing’
75
Q

Describe Water deficit stress biochemical responses

A
  • Production of compatible solutes: AA - Proline and betaine, sugar alcohols - sorbitol, pinitol, ononitol and myoinositol
  • Increase osmotic force to drive water into the cell
  • Production of hydrophilic proteins
76
Q

Describe Water deficit stress morphological responses

A
  • Rapid stomatal closure to limit evapotranspiration
  • Lower stomatal density on new leaves
  • Leaf expansion is reduced
  • Leaves produce more wax on surface
  • Plants show enhanced root extension into soil
  • Old leaves are rapidly lost
77
Q

Describe Water deficit stress adaptations

A
  • Reduced metabolism - only metabolise when water present
  • Evasion - short life cycles
  • Opportune leaf production - only reproduce leaves when there is sufficient H2O for photosynthesis
  • Extended roots - some roots can go as deep as 50M
78
Q

Describe Water excess stress effects

A

-Hypoxia and anoxia can occur, cutting a plants respiration and nutrient uptake

79
Q

Describe Water excess stress metabolic responses

A
  • Reduced metabolism

- Production of alcohol fermenting enzymes to produce ATP from sugar degradation

80
Q

Describe Water excess stress morphological responses

A 
-Pneumatophores - root extensions in the
air used to take up O2. 
-Aerenchyma - large parenchymatic cells 
around the vascular system used to transport 
O2 from the shoots to the roots.
81
Q

Describe Salt stress effects

A
  • Changes in the soils properties to have less aeration and hydraulic conductance
  • Low water potential causing reduced water and nutrient uptake
  • Inhibits cellular enzymes inducing cellular toxicity
  • Causes ionic imbalances in cellular compartments
82
Q

List 4 areas where salt stress present

A
  • Costal salinity marshes
  • Lakes where evaporation exceeds precipitation
  • Excessively irrigated soils
  • Groundwater under reduced rainfall
83
Q

Describe Salt stress physiological responses

A
  • Glycophytes - Plants which are sensitive to salt stress, usually die around 100mM NaCl
  • Salt-tolerant non halophytes - Plants that tolerate relatively high salt conc >200mM NaCl
  • Halophytes - Plants adapted to salinity and that can resit conc <500mM NaCl
84
Q

Describe mechanisms used to escape/alleviate Salt stress

A
  • Production of compatible solutes to increase the osmotic force driving water into the cell.
  • High ion selectivity, toxic ions are not taken up by the roots.
  • These roots have high capacities of ion extrusion that allow the removal of any toxic ions taken up.
  • The cell have ion transporters that allow the sequestration of ions in the vacuole.
85
Q

Describe Salt stress adaptations

A
  • Osmoregulation - produces high levels of proline
  • Bladder cells - Mesembryanthemum crystallium has specialised epidermal cells with massive vacuoles called bladder cells, store a lot of salt
  • Glands - used to excrete salt onto the surface of the leaf
86
Q

Describe High temperature effects

A
  • Increased evaporation and induced wilting of the plant
  • Increased respiration and photorespiration
  • Reduced photosynthesis: enzyme inhibition and excessive membrane fluidity
87
Q

Describe Low temperature effects

A
  • Reduced metabolism - reduced enzyme activities
  • Reduced membrane fluidity and even crystallisation
  • Reduced water availability in free form in the cell
  • Reduced photosynthesis and growth
88
Q

Describe High temperature physiological responses (>35)

A
  • Closure of stomata to reduce water loss
  • Synthesis of protective proteins like heat shock proteins
  • Production of saturated fatty acids to stabilise membranes
89
Q

Describe Low temperature physiological responses (<15)

A
  • Synthesis of compatible solutes to prevent freezing
  • Uptake of ions from soils to decrease the freezing point
  • Synthesis of unsaturated fatty acids to stabilise membranes
90
Q

Describe High temperature adaptations

A
  • Formation of radiation reflective and waxes on the leaves
  • Leaf rolling and vertical leaf orientation
  • Formation of small thin dissected leaves to maximise heat dissipation
91
Q

Describe Low temperature adaptations

A
  • Induction of dormancy by change in the photoperiod
  • Production of organic phosphates, conversation of starch into soluble sugars
  • Accumulation of glycoproteins and LEA proteins
92
Q

List the toxins which cause Air pollution

A
  • SO2
  • NO/NO2
  • Peroxyacetyl
  • CO
  • O3
  • Heavy metals
93
Q

Describe Air pollution effects

A
  • Inhibition of stomatal movement
  • Reduced photosynthesis and growth
  • Lesion caused by the high oxidative potential of these pollutants
  • Induction of necrosis and eventually plant death
94
Q

Describe Air pollution physiological responses

A
  • Stomatal closure
  • Production of detoxication enzymes like catalases, peroxidases, superoxide dismutases
  • Production of ROS-scavanging compounds like glutathione and ascorbic acid (Vitamin C),
95
Q

Describe Air pollution adaptations

A
  • Selective uptake of nutrients
  • Uptake of heavy metals by combining them with organic compounds
  • Phytoremediation - removal of toxic elements using metal-hyperaccumlating plants
96
Q

Define ‘Transducer’

A

-Any device by which variations in one physical quanity are quantitatively converted into variations in another

Biology 2 (10 decks)

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