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IB Biology > Plant Science > Flashcards

Plant Science Flashcards

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0
Q

Outline three differences between the structures of dicotyledonous and monocotyledonous plants

A

Monocots:

  • one cotyledon
  • veins parallel
  • vascular bundles random
  • floral organs on multiples of 3
  • fibrous roots

Dicots:

  • two cotyledons
  • veins form net-like pattern
  • vascular bundles in ring
  • floral organs in multiples of 4 or 5
  • taproot
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1
Q

Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant

A

Ex. Sunflower, bean

  • show distribution of tissues (xylem, phloem)
  • no individual cells
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2
Q

Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues

A

Upper Epidermis

  • upper surface of leaf (greatest heat/light intensity)
  • water conservation

Palisade Mesophyll

  • near upper surface
  • absorb light
  • photosynthesis

Spongy Mesophyll

  • near stomata in lower epidermis
  • gas exchange

Stoma

  • pore in lower epidermis
  • gas exchange (O2 + CO2)

Guard Cells

  • around stoma
  • control transpiration

Xylem

  • inside vein
  • transport water

Phloem

  • inside vein
  • transport products
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3
Q

Identify modifications of roots, stems, and leaves for different functions: bulbs, stem tubers, storage roots, and tendrils

A
  1. Bulbs
    - leaf bases (monocots) swell forming underground bulbs
    - food storage
  2. Stem Tubers
    - stems (dicots) swell underground forming tubers
    - food storage
  3. Storage Roots
    - swell from stores of food
  4. Tendrils
    - narrow outgrowths from leaves
    - attach to solid supports so plant can climb upwards
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4
Q

State that dicotyledonous plants have apical and lateral meristems

A

Dicots have apical (primary) and lateral (secondary) meristems.

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5
Q

Compare growth due to apical and lateral meristems

A 
Apical
- found at apex of root and stem
- primary growth
• roots/stems elongate 
• new leaves/flowers
Lateral
- found in young stems/old roots
- secondary growth (cambium)
• roots/stems thicken
• form bark/wood
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6
Q

Explain the role of auxin in phototropism as an example of the control of plant growth

A

Phototropism - directional growth in response to light
• shoot tips (containing apical meristems) detect light and produce auxin (phototropin binds to photoreceptor)
• auxin causes secretion of H+ ions into cell walls; loosens cellulose allowing growth (cell expansion)
• auxin receptors transcript specific genes
• auxin is transported from light to dark; more growth on shady side as shoot bends to light
• leaves receive more light; increased photosynthesis

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7
Q

Outline how the root system provides a large surface area for mineral ion and water uptake by means of branching and root hairs

A
  1. Branching
    - cortex walls increase surface area
    - fibrous roots (monocot) increase surface area
    - taproot (dicot) penetrates deeper
    - roots spread out to reach water/minerals
  2. Root Hairs
    - potassium, phosphate, nitrate are absorbed (active transport)
    - root hair cells contain mitochondria and protein pumps in cell membrane
    - require oxygen to produce ATP
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8
Q

Explain the process of mineral ion absorption from the soil into roots by active transport

A
  • high concentration (ions) in root; requires active transport
  • root hair cells contain mitochondria/protein pumps (in membrane)
  • mitochondria produce ATP through cellular respiration
  • apoplastic route through cell walls (intercellular space)
  • sympoplastic route through cytoplasm
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9
Q

List ways in which mineral ions in the soil move to the root

A

Diffusion: mineral ions follow concentration gradient
Fungal Hyphae (Mutualism): absorb ions from soil in exchange for sugars from root
Mass Flow: water-carrying ions drain through soil

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10
Q

State that terrestrial plants support themselves by means if thickened cellulose, cell turgor, and lignified xylem

A
  • terrestrial planter support by stem
    • thick cell wall
    • turgor pressure (cells absorb water; become rigid)
    • lignified xylem tissue
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11
Q

Define transpiration

A

Transpiration - loss of water vapour from leaves/stems of plants

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12
Q

Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion, and evaporation

A
  • water moves up from roots to leaves (transpiration stream)
  • heat allows water in spongy mesophyll to evaporate (replaced by water from xylem)
  • cellulose walls contain pores allowing water to pass through (capillary action)
  • low pressure in xylem when water is pulled out (transpiration pull)
  • columns of water (cohesion) are sucked from roots through xylem
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13
Q

State that guard cells can regulate transpiration by opening and closing stomata

A

Guard cells regulate transpiration by opening/closing stomata

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14
Q

State that the plant hormone abscisic acid causes the closing of stomata

A
  • plants produce abscisic acid (ABA) under water stress
  • ABA decreases potassium, leading to decreased water
  • lower pressure causes guard cells to be flaccid so stoma close
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15
Q

Explain how the abiotic factors light, temperature, wind, and humidity affect the rate of transpiration in a typical terrestrial plant

A
  1. Light
    - stoma close in darkness
    - greater transpiration in light
  2. Temperature
    - heat needed for evaporation
    - high temperature increases rate of diffusion and reduces humidity outside leaf
    - higher transpiration at higher temperatures
  3. Humidity
    - water vapour in air (follows concentration gradient)
    - higher transpiration at lower humidity outside leaf
  4. Wind
    - pockets of water-saturated air form around stoma
    - wind blows air away so higher transpiration
16
Q

Outline four adaptations of xerophytes that help to reduce transpiration

A

CAM (crassulacean acid metabolism) Physiology
- stoma open during cool nights instead of hot days

Spines (modified leaves)
- reduce surface area for transpiration

Thickened Waxy Cuticle
- covers stem with leathery consistency

Water Storage Tissue
- stored in fleshy stems during rainy season

17
Q

Outline the role of phloem in active translocation of sugars (sucrose) and amino acids from source (photosynthetic tissues and storage organs) to sink (fruit, seeds, roots)

A
  1. Sugar loads into sieve tube
  2. Sieve tube takes up water (osmosis)
  3. Water generates pressure forcing sap to flow
  4. Pressure gradient reinforced by sugar unload
  5. Xylem recycles water

Translocation - transportation of products through phloem
Source - plant organs that produce sugar (photosynthesis or breakdown of starch)
Sink - plant organs that consume/store sugar
Sieve Tube - carry food from source to sink

18
Q

Draw and label a diagram showing the structure of a dicotyledonous animal-pollinated flower

A

Sepal - enclose/protect floral bud
Petal - bright colour; attract insects/pollinators
Anther - contain chambers (pollen sacs) where pollen is produced
Filament - stalk of stamen holds up anther
Stigma - sticky structure; landing platform for pollen
Style - neck of carpel holds up stigma
Ovary - contain ovules and embryo sacs

19
Q

Distinguish between pollination, fertilization, and seed dispersal

A

Pollination - transfer of pollen from anther to stigma
Fertilization - fusion of male gamete (pollen grain) with female gamete (ovule)
Seed Dispersal - ovaries with fertilized ovules become fruits

20
Q

Draw and label a diagram showing the external and internal structure if a names dicotyledonous seed

A

Phasedus multiflorus

Testa - seed coat; protects seed
Micropyle - where seed attaches to ovary; water can enter
Radicle - embryo root; forms new roots
Plumule - embryo shoot; forms new shoots
Cotyledon - provide energy/nutrients for germination

21
Q

Explain the conditions needed for the germination of a typical seed

A
  1. Water
    - must be available to rehydrate dry tissues
  2. Oxygen
    - required for aerobic cell respiration
    - some seeds respire anaerobically but can produce toxic levels of ethanol
  3. Suitable Temperatures
    - enzyme activity at high/low temperatures is too slow
    - some seeds become dormant (only germinate during favourable times of year)
22
Q

Outline the metabolic processes during germination of a starchy seed

A
  • absorption of water rehydrates seed
  • gibberellin produced in cotyledons
  • stimulates production of amylase (catalyzes starch -> maltose)
  • maltose diffuses from food stores to growth regions (embryo)
  • converted to glucose
23
Q

Explain how flowering is controlled in long-day and short-day plants, including the role of phytochrome

A
  • flowering caused by change in gene expression in shoot apical meristem
  • trigger is length of darkness
    • long-day plants flower in summer (shorter nights) ie. petunias
    • short-day plants flower in fall (longer nights) ie. chrysanthemums

Pr (red absorbing) - stable/inactive form; converts to Pfr when absorbs red light or white light (400-700nm)
Pfr (far-red absorbing) - unstable/active form; concerts to Pr when absorbs far-red light (730nm)
- in sunlight, phytochromes convert quickly to Pfr
- in darkness, Pfr gradually changes back to Pr

  • Pfr promotes flowering in long-day plants
    • large amount of Pfr left at end of short nights to bind and cause transcription
  • Pfr inhibits flowering in short-day plants
    • small amount of Pfr left at end of long nights; Pr does not bind so inhibition fails (plant flowers)

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