Chapter 12: Nutrition and Transport in Flowering Plants Flashcards
(59 cards)
1
Q
What are the external structures of a leaf?
A
- Leaf blade
- Network of veins
- Leaf stalk
- Leaf arrangement
2
Q
Describe the structure-to-function adaptations of the leaf blade.
A
Structure: Large surface area
How it is adapted for its function: To obtain the maximum amount of light for photosynthesis
Structure: Large and thin
How it is adapted for its function: Allows carbon dioxide to rapidly reach the inner cells of the leaf
3
Q
Describe the structure-to-function adaptations of the leaf stalk.
A
Structure: Holds leaf blade away from stem
How it is adapted for its function: Ensures that the leaf obtains sufficient light and air
4
Q
What adaptation is present when the leaf stalk is absent in a leaf?
A
Long leaf blades
5
Q
Explain the significance of chloroplast distribution in a dicotyledonous leaf.
A
- Primarily located in the palisade mesophyll cells (main site of photosynthesis)
- Densely packed to maximize light absorption for photosynthesis
- Allows for efficient conversion of light energy into chemical energy, which is essential for carbohydrate formation
6
Q
Describe the function of the xylem.
A
The xylem conducts water and dissolved mineral salts from the roots to the stems and leaves.
7
Q
Describe the structure-to-function adaptations of the xylem.
A
Structure:
- Long and hollow tube made up of dead cells
- No cytoplasm
- No cross-walls
How it is adapted for its function:
- Reduces resistance to the water flowing through it
Structure:
- Inner walls of xylem vessels strengthened by deposits of lignin
How it is adapted for its function:
- Adds strength and rigidity
- Allows plant to withstand various environmental stresses
8
Q
Describe the function of the phloem.
A
The phloem carries manufactured food from cells in the leaf blade to other parts of the plant.
9
Q
Describe the structure-to-function adaptations of the phloem.
A
Structure:
- Sieve tubes (column of elongated, thin-walled living cells-> sieve tube cells/ elements)
- Sieve tube cells with minute pores separated by cross-walls (sieve plates)
- Sieve tube cells with a thin layer of cytoplasm connected to cells above and below
How it is adapted for its function: Allows for rapid flow of manufactured food through sieve tubes
Structure:
- Companion cells, located adjacent to sieve tube cells
How it is adapted for its function:
- Provides sieve tube with nutrients
- Assists in the transport of manufactured food
10
Q
Describe the typical leaf arrangement in a plant and its significance.
A
- Leaves arranged in a regular pattern around the stem
- Leaves either grow in pairs or singly
- This is so that the leaves do not block one another from light
11
Q
What are the internal features of a leaf?
(top to bottom, 6 excl. sub-cats.)
A
- Upper epidermis layer
- Mesophyll (palisade mesophyll and spongy mesophyll)
- Lower epidermis
- Cuticle
- Stoma
- Guard cell
12
Q
Describe the constituents of the upper epidermis layer.
A
- Single layer of closely-packed cells (upper epidermal cells)
- Covered by a waxy and transparent cuticle
13
Q
Describe the constituents of the mesophyll.
A
- Lies between upper and lower epidermis
- Main site of photosynthesis
- Comprises of:
(a) Palisade mesophyll
-Closely-packed, long and cylindrical cells
-Has most chloroplasts
-Specialised for photosynthesis
-More light can be absorbed near upper leaf surface
(b) Spongy mesophyll
-Loosely-packed, irregularly-shaped cells
-Many intercellular air spaces between cells
-Fewer chloroplasts than palisade mesophyll
-Contains vascular bundle
14
Q
Describe the constituents of the lower epidermis.
A
- Single layer of closely-packed cells (lower epidermal cells)
- Few or no chloroplasts
15
Q
Describe the cuticle.
A
- Outer layer
- Reduces water loss through evaporation from the epidermal cells
- Transparent, for light to enter the leaf
16
Q
Describe the constituents of the stoma.
A
- Opening
- Open in the presence of light
- Carbon dioxide diffuses in
- Oxygen diffuses out
17
Q
Describe the constituents of the guard cell.
A
- 1 pair surrounding each
- Has chloroplasts
- Controls the size of the stomata
- Regulates the passage of gases in and out of the leaf
- Regulates the rate of transpiration
18
Q
Describe how guard cells control the size of the stomata under typical sunlight.
A
- Guard cells manufacture glucose by photosynthesis
- ↑ in glucose conc. ↓ water potential of cell sap
- Water molecules enter guard cells by osmosis (across ppm of guard cells)
- Guard cells become turgid and more curved due to the thicker cell wall around the stoma
- Stoma opens
19
Q
Describe how guard cells control the size of the stomata during extremely hot and sunny days.
A
- Excess evaporation of water causes guard cells to become flaccid
- Stoma closes
- This prevents excessive water loss by the leaf
20
Q
Define photosynthesis.
A
Photosynthesis is a process whereby chlorophyll absorbs energy from light to synthesise glucose from carbon dioxide and water. Oxygen is released during the process.
21
Q
State the word equation for photosynthesis.
A
…………………………………….light…………………………………….
carbon dioxide + water → glucose + oxygen
………………………………..chlorophyll………………………………..
22
Q
State the chemical equation for photosynthesis.
A
…………………….light…………………….
6C02 + 6H2O → C6H12O6 + 6O2
…………………chlorophyll…………………
23
Q
What is the importance of photosynthesis?
A
- Converts energy from the sun to chemical energy
-energy from light is transferred to chemical stores of energy in carbohydrate molecules - Removes carbon dioxide from the atmosphere
- Provides oxygen
-used by living organisms for respiration to release energy - Contributes to energy stored in fossil fuels
24
Q
How do chloroplasts contribute to the process of photosynthesis in leaf cells?
A
- Contain chlorophyll
- Absorbs light energy, which is then transferred to chemical stores of energy in glucose molecules
25
Explain the significance of the interconnecting air spaces in spongy mesophyll.
-Facilitates efficient gas exchange within the leaf
- Allows for rapid diffusion of carbon dioxide and oxygen into and out of the mesophyll cells and the stomata
26
Explain how carbon dioxide enters the leaf cells
- When stomata open, carbon dioxide diffuses from the **atmosphere** into the **intercellular air spaces** within the spongy mesophyll.
- Moves through these air spaces
- **Dissolves** in the **thin film of moisture** on the surfaces of the mesophyll cells
- Carbon dioxide diffuses into cells
27
Describe test for presence of starch in a leaf.
1. Remove a green leaf from a plant and immediately place it in **boiling water** for **2 minutes**.
-high temperature will denature enzymes in the leaf and stop further chemical reactions.
2. Place the leaf in a boiling tube with some **alcohol/ ethanol**.
-alcohol/ ethanol removes chlorophyll from the leaf
-decolourising of the leaf so that the colour of iodine can be clearly observed
3. Gently remove the leaf as (it is now very brittle). Place the leaf in **hot water**.
-hot water will softens the leaf and makes it more permeable to iodine solution.
4. Remove the leaf and spread it evenly on a white tile. Add 1-2 drops of **iodine** on the leaf.
-test for presence of starch
(-ve-> iodine remains yellowish-brown)
(+ve-> iodine turns blue-black)
28
Explain the importance of de-starching a plant before conducting photosynthesis experiments.
- To ensure that any positive result for starch test is a direct result photosynthesis. - By placing the plant in the dark for two days, the stored starch is consumed, leaving the leaves free of starch
- This allows for a clear assessment of whether photosynthesis has occurred during the experiment, as any starch present afterward indicates successful glucose production.
29
Describe the investigation for whether plants use carbon dioxide in photosynthesis.
1. **De-starch** two potted plants by placing them in the dark for two days.
2. Enclose the pots in **polythene bags** and secure to the plant stems.
- to prevent any carbon dioxide released by microorganisms in the soil to enter the set-up
3. Place one pot in the set-up containing **potassium hydroxide and soda lime.**
- potassium hydroxide solution and soda lime rapidly absorbs carbon dioxide
- ensures that the plant does not have a supply of carbon dioxide
4. Place the other pot in the set up
containing **water and pebbles**.
- to serve as a control set-up
5. Leave both set ups in **strong light** for a few hours and **test the leaves for starch**.
- presence of strong light allows for photosynthesis to take place.
30
Describe the investigation for what gas is given off during photosynthesis.
1. Set up some freshwater plants and
dissolve 2 – 10 g of **sodium
hydrogencarbonate** in the water.
- sodium hydrogencarbonate provides dissolved carbon dioxide to the plant
2. Place the set up in **strong light **for a few hours. Gas bubbles will rise up the test tube and **displace the water** downwards. When the tube is about half-filled with gas, remove the tube by placing a thumb near its mouth.
- to collect sufficient gas for the test.
3. Test for gas with a **glowing splint**. To test for presence of oxygen.
- if the glowing splint relights, the gas is oxygen.
31
Define limiting factors.
A limiting factor is a factor that affects the rate of a reaction. The rate cannot increase unless the value of the limiting factor is increased.
32
How does light intensity affect the rate of photosynthesis?
(+set-up to investigate)
- As light intensity increases, the rate of photosynthesis increases until a constant rate is reached
- More light -> more energy for photosynthesis
- Set-up to investigate:
-vary power of lamp
(10W, 20W, 30W, 40W, 50W)/
-vary distance of lamp from plant
(10cm, 20cm, 30cm, 40cm, 50cm)
33
How does carbon dioxide concentration affect the rate of photosynthesis?
(+set-up to investigate)
- As carbon dioxide concentration increases, the rate of photosynthesis increases until a constant rate is reached
- More carbon dioxide -> more glucose can be produced
- Set-up to investigate:
-vary concentration of sodium hydrogencarbonate solution
34
How does temperature affect the rate of photosynthesis?
(+set-up to investigate)
- As temperature increases to the optimum temperature, the rate of photosynthesis increases
- As temperature increases beyond the optimum temperature, the rate of photosynthesis decreases due to enzyme denaturation
- Set-up to investigate:
-vary temperature of water bath
(10°C, 20°C, 30°C, 40°C, 50°C)
35
What happens to the glucose that is formed during photosynthesis?
(6 pts.)
1. Used _immediately_
- for **cellular aerobic respiration** in the **mitochondria** to provide energy for cellular activities
2. Conversion to _starch_, **stored** temporarily in **leaves**
- DAYTIME-> rate of photosynthesis is very high, excess glucose is formed
- excess glucose converted to starch for storage
- NIGHTTIME-> photosynthesis stops
- starch is converted back into glucose by enzymes
3. Conversion to _sucrose_, transported away via **phloem** for storage
- **stored** in other plant parts/ translocated to storage organs (e.g. seeds, stem tubers, root tubers)
- component of **nectar** (flowers)
- may be converted back into **glucose** for cellular respiration
4. Conversion into _amino acids_ in leaves, transported via **phloem**
- used to form proteins for **synthesis of new protoplasm**
- excess amino acids-> transported to other parts of the plant for synthesis of new protoplasm and storage as proteins
5. Forms _fats_
- used for storage, cellular respiration and synthesis of new protoplasm
6. Conversion into _cellulose_
- formation of **cell walls**
36
Define translocation.
Translocation is the transport of manufactured food substances, such as sugars (sucrose) and amino acids in plants.
37
State the three experiments used to study translocation.
1. The "Ringing" Experiment
2. Using Aphids
3. Using Isotopes (e.g. Carbon-14)
38
How is the root hair cell adapted to its function?
(chp 12.)
(structure to function)
Function: To absorb water & mineral salts from the soil into the roots
Structure:
1. Long and narrow extension/protrusion
- increases surface area to volume ratio, faster rate of absorption of water and mineral salts
2. More mitochondria (compare to general plant cells)
- higher rate of aerobic respiration for release of more energy to carry out active transport of mineral salts from soil sol. to root hair cell
3. Partially permeable membrane
- facilitates the movement of water through osmosis and ions via active transport
39
How does water enter a plant?
The cell sap of root hair cells contain a relatively concentrated solution of sugars and mineral salts. Thus, root hair cells have a lower water potential than the soil solution.
1. Each root hair is a narrow extension of an epidermal cell. It grows between the soil particles, coming into close contact with the soil solution surrounding it.
2. The thin film of liquid surrounding each soil particle is a dilute solution of mineral salts.
3. Water molecules move into the root hair cell by osmosis.
4. Water molecules move from the root hair cell to the inner cell by osmosis
5. Water molecules move from cell to cell until it reaches the xylem vessels
40
How do root hair cells absorb ions or mineral salts?
- By diffusion:
-occurs when conc. of certain ions in the soil solution is higher than in the root hair cell sap
-ions diffuse down conc. gradient
- By active transport:
-occurs when conc. of ions in the soil solution is lower than in the root hair cell sap
-ions absorbed against conc. gradient
-w/ the use of energy provided by cellular respiration that occurs in the root hair cell
41
Define transpiration.
Transpiration is the loss of water vapour from the aerial parts of a plant, mainly through the stomata of the leaves.
42
What is the main force that moves water and mineral salts up a plant?
Transpiration pull
43
Describe the steps involved in demonstrating transpiration in leaves and stems.
(+observations)
1. Wrap a polythene bag around the pot and stem of a plant
2. Place the pot on a glass plate and cover it with a dry bell jar
3. Set up a control without a plant
4. Place both setups side by side near an open window for two hours
Observations:
- Water droplets will be observed on the inner surface of the bell jar
- Testing the liquid with anhydrous copper (II) sulfate will show a colour change to blue, confirming the presence of water
44
How is transpiration involved in water movement in plants?
- Evaporation of water from the leaves removes water from the xylem vessels
- This results in a suction force (transpiration pull) which pulls water up the xylem vessels
45
What is the importance of transpiration?
- Transpiration pull draws water and mineral salts from the roots to the stems and leaves
- Evaporation of water from the surface of cells cools the plant, preventing it from being scorched by the hot sun
- Water transported to the leaves can be used for:
-photosynthesis
-keeping cells turgid (to keep leaves spread out widely to absorb light for photosynthesis)
-replacing water lost by cells
46
How does water movement occur inside a leaf during transpiration?
1. Water evaporates from the thin film of moisture covering the mesophyll cells
- water vapour is formed in the intercellular air spaces
2. Water vapour diffuses through the stomata to the drier air outside the leaf (transpiration)
3. More water moves out from mesophyll cells to replenish the thin film of moisture
- As water is lost from the mesophyll cells, the water potential of the mesophyll cell sap decreases, becoming lower than that of their neighbouring mesophyll cells
4. Mesophyll cells draw water from deeper inside the leaf by osmosis
5. Mesophyll cells deeper inside the leaf draw water from the xylem by osmosis
- suction force (transpiration pull) pulls the whole column of water up the xylem vessels
47
How do you measure the rate of transpiration using a spring balance?
1. Immerse the cut end of a leafy shoot in a test tube of water
2. Add a little oil to the surface to prevent evaporation
3. Attach a spring balance to the mouth of the test tube using a spring
4. Record the mass
5. Place the test tube near the window for five hours
6. Record the mass again
7. Calculate the rate of transpiration
48
What is the formula for rate of transpiration? (g/h)
Loss in mass (g)/
Time taken (hours)
49
What is a potometer?
- An instrument used to measure the rate of water absorption by a plant
- Rate of transpiration is assumed to be proportional to the rate of water absorption
- Determines the effect of different environmental conditions
50
What is the formula for rate of transpiration? (cm^3/min)
Difference in volume (cm^3)/
Time taken (min)
51
What are the factors that affect the rate of transpiration?
- Wind
- Temperature
- Light
- Humidity
52
How does wind affect the rate of transpiration?
- Wind blows away the water vapour that diffuses out of a leaf
- Rate of transpiration increases with more wind
53
How does temperature affect the rate of transpiration?
- When temperature increases, water evaporates from cell surfaces more quickly
- Rate of transpiration increases with higher temperature
54
How does light affect the rate of transpiration?
- When there is light, the stomata open and become wider
- Rate of transpiration increases with higher light intensity
55
How does humidity (conc. of water vapour in the air) affect the rate of transpiration?
- Amount of moisture in the surrounding air affects the concentration gradient of water vapour between the leaf and the surrounding air
-the higher the humidity, the less steep the water vapour conc. gradient (rate of transpiration decreases)
-the lower the humidity, the steeper the water vapour conc. gradient (rate of transpiration increases)
56
How does wilting occur?
Wilting occurs when the rate of transpiration is higher than the rate of absorption of water by the roots.
57
What is the advantage of wilting?
Rate of transpiration decreases
- folding of the leaf reduces the surface area exposed to light
- this reduces the rate of water loss through the stomata
- excessive loss of water causes guard cells to become flaccid
- stomata closes
58
What is the disadvantage of wilting?
Rate of photosynthesis decreases
- folding of the leaf reduces the surface area exposed to light
- as stomata are closed, the amount of carbon dioxide entering the leaf decreases
59
State the differences between transpiration and translocation.
Translocation: movement of manufactured food substances, such as sugars and amino acids, from the leaves to all parts of the plant
Transpiration: movement of water vapours through stomata of the leaves to the surroundings
Translocation: carried out by phloem tissue
Transpiration pull: carried out by xylem tissue
Translocation: direction is throughout the plant
Transpiration: direction of transpiration pull is upward and one-directional, against gravity
