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(MY) BIOLOGY HL > Topic 9 - Plant biology > Flashcards

Topic 9 - Plant biology Flashcards

(87 cards)

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1
Q

Define transpiration

A

Water loss through leaves via evaporation and diffusion

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2
Q

Define transpiration stream

A

Flow of water within a plant from

roots -> leaves

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3
Q

Define cohesion

A

H bonds between water (same molecules) hold /stick together

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4
Q

Define adhesion

A

H bonds between water and the side of the xylem vessels help to counteract gravity

Provides force to pull water up sides of xylem tubes

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5
Q

What are stomata?

A

Pores in epidermis that allow movement + exchange of gases

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6
Q

What are guard cells?

A

Pair of curved cells that surround /are either side of stoma

Get small /big depending on pressure

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7
Q

How do stomata in the lead inevitably lead to transpiration?

A

CO2 required for photosynthesis and is acquired through gas exchange

For this to happen, stomata must open, and so water vapour is able to leave through these pores

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8
Q

Define diffusion

A

Net movement of particles from area of high conc -> area of low conc

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9
Q

Define active transport

A

Movement of ions /molecules from area of low conc -> area of high conc (against conc gradient)

Across cell membrane

Using energy from respiration

Assisted by enzymes

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10
Q

Define Osmosis

A

Movement of water from dilute solution -> conc solution

Across a pp membrane

(High water conc -> low water conc)

Water moves in plants via osmosis

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11
Q

Tension forces in leaf cell walls are generated due to the opposing forces of:

A

Water molecules evaporating from cell surfaces to move out of leaf by diffusion (down conc gradient)

Adhesion of water molecules to cell walls due to H bonding

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12
Q

Water is able to move through the plant under tension due to:

A

Thick walls of the xylem vessel elements, which are strengthened w/ lignin, preventing the vessels collapse

Pores on the end walls of xylem vessel elements allowing continuous columns of water molecules to form

Cohesion that holds water molecules in a column through H bonding

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13
Q

As water is removed from the surface of the spongy cells by evaporation, what will happen to the:

Water conc?

Pressure?

What part of the leaf supplies water to replace that which is lost?

Where will water flow from to counteract this change in pressure?

A

Both will decrease

Xylem supplies water

Water flows from lower down the xylem

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14
Q

Define xerophyte

A

A plant which requires very little water in order to survive

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15
Q

What are some adaptations of xerophytes?

A

Leaf hairs - trap moist air, reducing conc gradient, reducing diffusion from stomata

Reduces thick leaves - reduce sa

Spines - extreme reduction of sa

Rolled leaves + stomata in pits - traps moist air next to stomata, reducing conc gradient

Thickened waxy cuticle - reduces evaporation of water from the top surface of the leaves

Reduced stomata - decreases openings that water loss occurs through

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16
Q

Define halophtes

A

Plants that can survive in water with a high salt content

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17
Q

What are some adaptations of Halophytes?

A

Salt glands - secrete salt eg. Mangroves

Area - small

Lock away

Thick - cuticle

Sunken stomata - reduces water loss (high humidity around stomata)

Succulent - store water

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18
Q

How does temperature affect the rate of transpiration?

A

Temperature increases the rate of transpiration as more rapid evaporation + diffusion of water out of stomata. Evaporation etc takes place as higher amount of kinetic energy available to convert liquid water -> vapour

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19
Q

How does light intensity affect transpiration rate?

A

Plants respire (not directly) in light compared to in the dark. Light stimulates the opening of stomata and warms the leaf

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20
Q

How does humidity affect transpiration rate?

A

Rate of diffusion increases when the air is dry as there is a larger conc gradient for the vapour to move across

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21
Q

How does wind affect transpiration rate?

A

No breeze causes surrounding air to be humid, so less transpiration takes place

If there is a breeze then humid air is carried away and so transpiration rate increases

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22
Q

Define translocation

A

The transport of soluble food material from one plant to another via the phloem /xylem

Carries amino acids, DNA (nucleic acids) - dissolved in water as a solution

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23
Q

What does transpiration carry + in what direction?

What does translocation carry + in what direction

A

Transpiration carries minerals dissolved in water and carries it up

Translocation carries dissolved organic molecules in various directions

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24
Q

Plants transport organic compounds from ____ -> _____

A

Source -> sink

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25
What is a source
A plant organic that is a net producer of sucrose eg. Summer - leaves Spring - tubers /bulbs
26
What is a sink
A plant organ that (uses /stores) consumes sucrose eg. Summer - roots, seeds, flowers and fruits Spring - anywhere else: leaves, stems
27
Define intermediate
Not having all roots /branches ending in a flower bud + so potential for indefinite growth
28
What process is needed for stem extension to produce new cells?
Cell division (growth = division)
29
What process is needed for leaf development?
Differentiation (development = differentiation)
30
Apical meristem: Where is it found? What is it part of? (p /s growth) What does it add? What does it cause?
Found in tips of roots + stems Part of primary growth It adds length /height Causes herbaceous, non woody stems + roots (Following growth, differentiation occurs)
31
Lateral meristem: Where is it found? What is it part of? (p /s growth) What does it add? What does it cause?
It is found within stems /trunks Part of secondary growth It adds girth /breadth Causes thicker plants (Vascular cambium: xylem + phloem,, cork cambium = bark of plant)
32
# Define: Tropism Positive tropism Negative tropism
Growth in response to a stimulus Growth towards a stimulus Growth away a stimulus
33
# Define: Phototropism Geotropism
Growth in response to direction of light Growth in response to direction of gravity
34
What response occurs to the stimulus of light in the: Shoots Roots
Positive phototropism in shoots Negative phototropism in roots
35
What response occurs to the stimulus of gravity in the: Shoots Roots
Negative geotropism in shoots Positive geotropism in roots
36
What is auxin? Does it inhibit or stimulate growth in the: Shoots Roots
A plant hormone that causes cell elongation (aka indoleacetic acid) Stimulates growth in the shoots Inhibits growth in the roots
37
Define apex
The end, particularly suggesting a point
38
What are the 2 roles of auxin? What happens if auxin is removed by cutting off shoot tips?
Phototropic response Prevents lateral growth in buds ‘Bushy’ growth occurs if auxin is removed
39
How does auxin influence cell growth rates?
By changing the pattern of gene expression
40
What is the mechanism of auxin action? | 9 steps
1. Auxin produced in stem apex 2. Auxin efflux pimp removes auxin from cells on sunny side (active) 3. Auxin diffuses into cells on shaded side 4. Auxin enters nuclei of shaded cells 5. Auxin binds to a receptor 6. Auxin receptor compels activates proton pump from cytoplasm into cell wall 7. Drop in PH breaks H bonds between cellulose fibres 8. Also activates enzymes that break cellulose fibres 9. Turgor pressure against weakened cell wall causes elongation of cells
41
What does flowering allow for? When do flowers bloom?
Flowering allows for pollinators to be attracted to the plant Flowers bloom when conditions for germination are optimal
42
What is photoperiodism?
The process that controls flowering in plants
43
What is phytochrome?
A blue-green pigment in plants (in leaves)
44
What is: Pr? Pfr? What does pfr control? How does it control this?
Pr is the inactive form of phytochrome Pfr is the active form of phytochrome It controls flowering (inhibits or stimulates) Through a hormone called florigen)
45
Long day plant: Example When does it flower? Why does it flower at this time? Does pfr inhibit or promote the genes controlling flowering?
Irises Ldp flower when nights are short As less pfr is converted to pr, so high pfr levels are present at the end of the night Pfr promotes the genes controlling flowering
46
Short day plant: Example When does it flower? Why does it flower at this time? Does pfr inhibit or promote the genes controlling flowering?
Chrysanthemums Sdp flower when nights are long As more pfr is converted to pr, so low pfr levels present at the end of the night Pfr inhibits the genes that control flowering (Only flowers if darkness is longer than critical time)
47
What is the process of plant reproduction? (7 steps) Split into 3 categories: Pollination (2 /7 steps) Fertilisation (1 /7 steps) ``` Seed dispersal (2 /7 steps) How is seed dispersal aided? /what does it depend on? ```
Pollination: 1. Pollen carried from 1 plant to another by an animal eg. Insect 2. Pollen lands on stigma of 2nd flower (No category) 3. Pollen tube grows down stigma, through style, to ovary Fertilisation: 4. Pollen delivered to ovule, which fuse (No category) 5. Seed develops Seed dispersal: 6. Developed seed moves away from parent plant before germinating (eg. in fruit, wind, water and animals) 7. This process reduces competition for limited resources Seed dispersal depends on fruits produced from the ovaries - this is because the animals eat these fruits and then the seeds are later on dispersed.
48
What are the structures and functions of the phloem?
Companion cells connected to sieve tube members by plasmodesmata - provides sieve tube members w/ nutrients + ATP sieve plates have pores - allow movement of dissolved organic molecules along length of vessel Sieve tube members joined by sieve plates - forming sieve tubes, which allow bulk transport over large distances Sieve tube members have no nucleus + very little cytoplasm - allow transport of dissolved organic molecules to occur efficiently
49
What are the structures and functions of the xylem?
Ends of vessel elements have perforated cell walls - allowing water to move freely up plants in columns Log in is laid down in rings - as it allows flexibility of the tissue It is made of dead cells - allows transport of water + dissolved minerals to occur unimpressed by cell contents Sections of the vessel only containing primary cell wall w/ pits /pores in the sides - allows for lateral movement in water Thick lignified secondary walls - to provide strength to tissue Vessel elements attached end to end, forming continuous columns - to allow movements of water + dissolved minerals
50
What is a potometer?
A device used to measure transpiration rate
51
Describe the process of generating a transpiration steam
1. Water moves down conc gradient 2. Water lost by transpiration is replaced by water from vessels 3. Vessels water column is maintained by cohesion and adhesion 4. Tension occurs in the columns of water in the xylem 5. Water is pulled from the root cortex into the xylem cells 6. Water is pulled from soil -> roots
52
What are the adaptation of roots that allow for efficient take up or mineral ions and water from the soil?
They have an extensive branching pattern Have root hair cells that increase the sa by a factor of 3
53
How does lack of water in the soil affect transpiration rate?
Transpiration rate decreases as turgor loss occurs and so stomata close
54
How does high co2 conc affect transpiration rate?
Transpiration rate decreases as guard cells become turgor and so stomata close
55
Why is it important to take lead area /mass into account when calculating transpiration rate data?
As the larger the leaf, the more water is lost, even under the same conditions
56
What does the phloem do?
Transports food made from photosynthesis (glucose, sugar)
57
How did aphid stylets help improve our understanding of translocation?
Proved that the phloem sieve tubes are hollow, allowing phloem sap to move within plants
58
What is the process of translocation?
1. Active transport loads sugar into sieve tubes at source (reduces relative water conc) in tube members, causing osmosis from surrounding cells 2. Uptake of water at source causes positive hydrostatic pressure in sieve tube, resulting in bulk flow of phloem sap 3. Pressure is diminished by removal of sugar from sieve tube at sink (with help of active transport) to starch (is insoluble, no Aomori effects) 4. Xylem recycled relatively pure water by carrying f it from source back to sink
59
What characteristic of water causes hydrostatic pressure when water is added to sieve tube?
Water is incompressible, adding water or solute etc increases the pressure
60
What is the role of the: Sieve plates Companion cells? - in the phloem during translocation?
Sieve plates allow the phloem sap to travel along the phloem tubes Companion cells take part in loading and unloading of sugar into the sieve elements. They also regulate activity of adjacent sieve element
61
Define meristematic tissue
Area of active plant growth | Composed of aggregates of small cells that have the same function as stem cells in animals
62
What is micropropagation?
Technique used to produce large numbers of identical plants (clones) from a selected stock plant
63
Outline how plants can be cloned using micropropagation
1. Sterilise surface of the worktop 2. Cut part of the shoot apex from the plant (eg. cauliflower) sample around 5mm 3. Place the explant in disinfectant and shake every minute for 15 minutes 4. Remove explant from disinfectant and place in nutrient agar gel 5. Add growth hormone
64
What are the advantages of micropropagation
Rare + endangered species can be maintained eg. orchids w/ v small seeds Plants grown more reliably in sterile cultures Used to develop virus free strains of existing plants Ability to alter genome of existing plants to make them more beneficial to human kind Genetic modifications can be introduced to thousands quickly Plants can be produced any time of year
65
What are the disadvantages of micropropagation
Extremely expensive Difficult to maintain pathogen free environments essential for culturing meristematic tissue Infected plants may produce infected progeny Diseases can affect entire species Lack of overall resilience as all are clones
66
Define mutualistic
Relationship that benefits both organisms
67
Define germination
The emerging + growth of an embryonic plant from seed -> functioning plant
68
What is a pollinator
Animals that move pollen from the male anther of a flower to the female stigma
69
Examples of pollinators that have mutualistic relationships with plants in sexual reproduction
Bees - nectar for food (honey) Butterfly - nectar Humming bird - nectar (All help pollinate plants)
70
Explain how undifferentiated cells in the meristems of plants allow indeterminate growth When cells divide, how many remain meristematic?
Meristems are specialised tissues, which are regions of continuous cell division and growth, and so it allows plants to continue to grow indefinitely 1 remains meristematic (called initials) whilst the others differentiate
71
What is the plant hormone that controls growth in the shoot apex, in response to light?
Auxin
72
Explain how shoots grow towards a light source, using ideas of cell elongation
Auxin moves to the darker (shaded) side of the plant, so there is a greater conc. The cells there grow larger than those on the lighter, illuminated side. Elongation produces a curve, phototropism
73
Outline 3 conditions that must be fulfilled for a seed to germinate
Water - to rehydrate dried seed tissues Oxygen - to allow aerobic respiration to produce ATP Appropriate temp - for enzyme action
74
What is the plumule? (Internal view of a seed)
Embryonic shoot with embryonic leaves
75
What is the radicle? (Internal view of a seed)
Embryonic toot ending in an apex Remember: radish,, a root plant.. points down (When drawing as part of a diagram, the apex must be clearly pointy)
76
What is the testa? (Both internal + external view of a seed)
Tough, protective outer coat | When drawing as part of a diagram, ensure that it is shown as a double line
77
What is the cotydelon? (Internal view of a seed)
Internals of the seed, located within the testa
78
What is the micropyle? (External view of a seed)
Scar where the pollen tube entered the ovule at fertilisation
79
What is the hilum? (External view of a seed)
Where the seed was attached to the ovary wall
80
What is the germination process? (6 steps)
1. Seed /testa swells 2. Testa bursts 3. Root apex emerges /grows downward 4. Shoot apex grows 5. Cotydelons lifted /raised 6. New leaves emerge from between the cotydelons
81
What conditions are needed for a seed to germinate? What condition varies and is therefore not included?
Water Oxygen Warmth (optimum temperature) Testa erosion (eg. by fire or passing through the digestive tract of an animal) Light,, seeds vary in their light requirements Eg. Need light - lettuce, poppies Need darkness - parsley, pansies
82
Describe the metabolic events of germination in a typical starchy seed [5]
1. Absorption of water (through micropyle) 2. Gibberellic acid produced in embryo (GA = gibberellin) 3. This stimulates the production of amylase 4. Amylase catalysed the breakdown of starch (a carbohydrate) into maltose 5. Maltose diffuses to embryo (root + shoot) 6. Used for energy production respiration (hydrolysis to glucose) and growth (polymerisation to cellulose)
83
Explain the conditions needed for the germination of a typical seed [6]
- water Rehydrates dry cells causing swelling, which bursts testa Wash a hormone that inhibits germination out of seed Transports hydrolysed food /hormones - oxygen Used in aerobic respiration To release energy - temp Warmth required for enzyme catalysed reactions Increased temp = increased ke = increased collision rate - hormone Gibberellin stimulates (mitosis and) cell division Fire breaks down inhibitors or germination
84
What are the female reproductive organs in a plant?
The stigma and style
85
What are the male reproductive organs in a plant?
The anther and filament
86
What does the vascular bundle consist of?
The xylem and phloem
87
What are the limitations of using a potometer | Why the potometer itself does not accurately measure transpiration rate, rather than human error
The amount of water uptake is measured by a potometer, rather than the transpiration rate directly More water is uptaken by the plants than it is lost via transpiration This is because water is used by the plant to maintain turgor pressure, and to be used in photosynthesis

(MY) BIOLOGY HL (1 decks)

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