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Plant systems Flashcards

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1
Q

Explain the structures and adaptations of the cuticle

A
  • Waxy
  • Transparent
  • No chloroplasts
  • Reduces water loss by evaporation
  • Prevents invasion of bacteria
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2
Q

Explain the structures and adaptations of the upper and lower epidermis

A
  • Single layer of closely packed cells
  • No chloroplasts
  • Protects inner cells
  • Allows light to pass through to reach the palisade mesophyll
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3
Q

Explain the structures and adaptations of the palisade mesophyll

A
  • Long, cylindrical, and closely packed cells
  • Contain largest number of chloroplasts in leaf
  • Largest number of chloroplasts allow for the most light to be absorbed to increase rate of photosynthesis
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4
Q

Explain the structures and adaptations of the spongy mesophyll

A
  • Irregularly-shaped
  • Loosely packed
  • Filled with large intercellular air spaces
  • Covered with a thin film of moisture
  • Contains chloroplasts
  • Contains vascular bundle
  • Large intercellular air spaces allow for circulation of air within leaf and rapid diffusion of gases in/out of cells
  • Thin film of moisture allows gases to dissolve to increase diffusion rate
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5
Q

Explain the structures and adaptations of the vascular bundle

A
  • Contains xylem and phloem
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6
Q

Explain the structures and adaptations of the guard cells

A
  • Contains chloroplasts
  • Cell wall nearer to stomata is thicker than anywhere else of the cell
  • Regulates size of stomata for gaseous exchange and transpiration
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7
Q

How do guard cells control size of stomata in the day

A
  • Guard cells photosynthesise in the day
  • Chemical energy is used to pump potassium ions into guard cells from neighbouring epidermal cells
  • Water potential of guard cells decrease
  • Water enters guard cells by osmosis
  • Guard cells swell and become turgid
  • Due to difference in cell wall thickness, one side expands more than the other
  • Stomata open
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8
Q

How do guard cells control size of stomata at night

A
  • Potassium move out of guard cells by diffusion
  • Water moves out of guard cells by osmosis
  • Water potential of guard cells increase
  • Guard cells become flaccid
  • Stomata close
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9
Q

Define cambium

A

Cambium consists of undifferentiated cells which can divide to form new xylem and phloem

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10
Q

From side-view of leaf, describe position of xylem and phloem

A
  • Xylem on top
  • Phloem below
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11
Q

Describe the structure of xylem

A
  • Xylem vessels formed from cells arranged end-to-end
  • Cross wall in adjacent cells is removed when mature
  • Cell membranes and cellular contents break down
  • Long, hollow tubes are formed
  • Inner walls of xylem vessels are strengthened by lignin deposits
  • Lignin can deposit in different directions
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12
Q

Explain how the structure of xylem is adapted to its function

A
  • Empty lumen reduces resistance to water flow which is vital as transport of water and mineral salts is a passive process
  • Lignin strengthens xylem walls, preventing the collapse of the vessel and provides mechanical support for the plant
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12
Q

Define translocation

A

Translocation is the process of transporting manufactured food substances like sucrose and amino acids throughout the plant via phloem

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12
Q

Describe how phloem is formed

A
  • Phloem is composed of sieve tubes, which are columns of sieve tube cells
  • Sieve tube cells are separated by sieve plates
  • Sieve tube cells are also closely associated with companion cells
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13
Q

Why is glucose converted to sucrose for translocation

A
  • Sucrose is not as readily metabolised as glucose in respiration during transport
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14
Q

Explain the adaptations and functions of phloem

A

1) Sieve tube cells are living
- Need to be living as translocation is an active process

2) Sieve tube cells are living with reduced quantities of cytoplasm, no nucleus and presence of sieve plates
- Decreases resistance to flow of food substances

3) Companion cells contain many mitochondria
- Mitochondria in companion cells provide energy needed by sieve tube cells for translocation

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15
Q

What are thylakoids

A
  • System of interconnected membranous sacs
  • Separates stroma from interior of thylakoids
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16
Q

Define photosynthesis

A

Photosynthesis is the process in which light energy absorbed by chlorophyll is converted to ATP, which is used to synthesise glucose from water and carbon dioxide while oxygen is released during the process

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17
Q

Where does the light-dependent stage occur

A

Thylakoids

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18
Q

Where does the light-independent stage occur

A

Stroma

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19
Q

What are the requirements in the light-dependent stage

A
  • Light energy
  • Water
  • Chlorophyll
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20
Q

What are the requirements in the light-independent stage

A
  • Carbon dioxide
  • Chemical energy
  • Hydrogen ions
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21
Q

What is photolysis

A

When light energy is used to split water molecules into oxygen and hydrogen ions

22
Q

What are the products of the light-dependent stage

A
  • Hydrogen ions
  • Oxygen
  • ATP
23
Q

What are the products of the light-independent stage

A
  • Water
  • Glucose
24
Q

What happens in the light-dependent stage

A
  • Light energy is used to split 12 water molecules into 6 oxygen molecules and 24 hydrogen ions
  • Oxygen is released out of leaf via stomata
24
Q

What is the overall chemical equation of photosynthesis

A

6CO2+12H2O –> C6H12O6+6O2+6H2O

24
Q

What happens in the light-independent stage

A
  • 24 hydrogen ions produced in the light-dependent stage are used to reduce 6 carbon dioxide molecules to form 1 glucose molecule
24
Q

What happens to glucose formed during photosynthesis

A
  • Used during respiration to produce ATP
  • Used to form cellulose cell wall
  • Excess glucose converted to starch for storage
  • Converted to lipids for synthesis of cell membranes
  • Converted to sucrose for translocation
  • Reacts with nitrates and mineral salts to form amino acids
25
Q

What are the factors affecting rate of photosynthesis

A
  • Temperature
  • CO2 concentration
  • Light intensity
25
Q

Why is water not a limiting factor of the rate of photosynthesis

A

Less than 1% of water taken into the plant is used for photosynthesis

25
Q

What are the importances of photosynthesis

A
  • Makes chemical energy available to other organisms
  • Removes carbon dioxide and provides oxygen
  • Allows energy to be stored in fossil fuels
26
Q

Explain how temperature affects rate of photosynthesis

A
  • Photosynthesis is dependent on temperature as it is catalysed by enzymes
  • As temperature increases, kinetic energy of reacting particles increases, so frequency of effective collisions between enzymes and substrates increases
  • Rate of photosynthesis increases
  • Rate of photosynthesis is at the max at enzymes’ optimal temperature
  • Rate of photosynthesis decreases as temperature increases beyond enzymes’ optimal temperature
  • Photosynthesis stops when enzymes are denatured
27
Q

Explain how CO2 concentration affects rate of photosynthesis

A
  • Increase in CO2 concentration increases the rate of photosynthesis up to a point
  • Beyond this point, rate of photosynthesis remains constant even with further increase in CO2 concentration
  • It is limited by another factor
27
Q

Explain how light intensity affects rate of photosynthesis

A
  • Increase in light intensity increases rate of photosynthesis up to a certain point
  • Beyond this point, rate of photosynthesis remains constant even with further increase in light intensity
  • Rate of photosynthesis is limited by another factor
28
Q

Define compensation point

A

Compensation point is when rate of photosynthesis is the same as the rate of respiration

29
Q

Explain the entry of water into plant

A
  • Each root hair cell comes into close contact with soil solution
  • Cell sap in root hair cell is concentrated with sugars and mineral salts
  • Water potential of cell sap is lower than that of soil solution
  • Water enters root hair cell by osmosis
  • Root hair cell now has a higher water potential than neighbouring cell
  • Water moves into next cell by osmosis
  • Water travels cell to cell by osmosis until it reaches the xylem
29
Q

Describe the intake of CO2 in a plant

A
  • CO2 in leaf is used up due to photosynthesis
  • CO2 concentration in leaf is lower than that of surrounding air
  • CO2 enters the leaf by diffusion via the stomata
  • CO2 dissolves in thin film of moisture around mesophyll cells
  • Dissolved CO2 diffuses into mesophyll cells
30
Q

Explain the adaptations and functions of a root hair cell

A
  • Long narrow extension increases SA:V ratio for faster rate of water absorption
  • Cell sap maintaining a low water potential allows water to continuously enter the root hair cell
  • Contains mitochondria to provide energy for active transport of mineral salts into root hair cell
31
Q

Define transpiration

A

Transpiration is the loss of water vapour from the leaves via the stomata

32
Q

Define root pressure

A

Root pressure is the pressure resulting from the constant entry of water into the roots

32
Q

Define cohesion

A

Cohesion is when the partial negative charge on an oxygen atom in 1 water molecule attracts the hydrogen atom in a neighbouring water molecule

33
Q

Explain how capillary action works

A
  • Cohesion between water molecules and adhesion between water molecules and xylem walls allows for water to be pulled up the xylem in a continuous stream
34
Q

Explain how root pressure occurs

A
  • Respiring cells around xylem use active transport to pump mineral salts into xylem
  • Water potential of xylem decreases
  • Water enters xylem by osmosis
  • This pushes water into and up the xylem vessels, resulting in root pressure
35
Q

Explain how transpiration pull works

A
  • Water evaporates from thin film of moisture around mesophyll cells
  • Water vapour diffuses out of leaf by transpiration via stomata
  • Water leaves mesophyll cells to replenish thin film of moisture, decreasing water potential of mesophyll cells
  • Water moves from neighbouring cells into mesophyll cells by osmosis
  • Water is drawn from cells deeper within leaf and eventually the xylem
  • This results in a transpiration pull, a suction force that pulls the entire column of water up the xylem
36
Q

Define adhesion

A

Adhesion is when water is attracted to hydrophilic parts of the xylem walls

37
Q

Explain importances of transpiration

A
  • Creates transpiration pull
  • Removes latent heat which cools the plant, preventing it from being scorched
38
Q

What are the factors affecting rate of transpiration

A
  • Wind speed
  • Humidity
  • Temperature
  • Light intensity
39
Q

When does wilting occur

A

Wilting occurs when rate of transpiration exceeds rate of water absorption

40
Q

What is a disadvantage of wiling

A

Leaves droop, less surface area exposed to sunlight, rate of photosynthesis decreases

41
Q

What is an advantage of wilting

A

Leaves droop, less surface area exposed to sunlight, rate of transpiration decreases

42
Q

Explain how humidity affects rate of transpiration

A
  • As humidity increases, water vapour concentration in environment increases
  • Water vapour concentration gradient decreases
  • Water vapour diffuses out of leaf at a slower rate
  • Rate of transpiration decreases
43
Q

Explain how wind speed affects rate of transpiration

A
  • As wind speed increases, water vapour surrounding the leaf is blown away faster
  • Water vapour concentration gradient increases
  • Water vapour diffuses out of leaf at a faster rate
  • Rate of transpiration increases
44
Q

Explain how temperature affects rate of transpiration

A
  • As temperature increases, rate of evaporation increases
  • Concentration of water vapour in intercellular air spaces increases
  • Water vapour concentration increases
  • Water diffuses out of leaf at a faster rate
  • Rate of transpiration increases
45
Q

Explain how light intensity affects rate of transpiration

A
  • Higher light intensity causes stomata to open wider
  • Rate of transpiration increases
46
Q

What can remove carbon dioxide

A
  • Soda lime
  • Sodium hydroxide solution

Biology (20 decks)

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