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Biology > Topic 6 - Plant Structures and their Functions > Flashcards

Topic 6 - Plant Structures and their Functions Flashcards

1
Q

Phloem Tubes

A

They transport Food - Translocation
in both directions
Living cells

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2
Q

Xylem Tubes

A

Dead cells strengthened by a substance called lignin
Transport water - Transpiration

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3
Q

Stomata

A

tiny pores on the surface of the plant used for gas exchange

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4
Q

What is auxin?

A

A plant growth hormone that controls growth at the tips of roots and shoots. It moves through the plant in solution

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5
Q

What is a stimulus?

A

A change in environment

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6
Q

Response

A

A change made in an organism due to a stimulus

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7
Q

What do photosyntheic organisms do during photosynthesis

A

Photosyntheic organisms such as green plants and algae use sun to make glucose
-> They are the main producers of food for nearly all life on earth

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8
Q

what are the main uses of glucose in plants?

A

Cellular respiration - break down the glucose to release energy
Make cellulose - which is used to make strong cell walls
Make starch - which is used to store glucose for a later time
Make amino acids - which are used to make proteins
Make lipids - these store the energy as fats or oils for later use

Making larger, complex molecules the organism needs to grow

this makes up its biomass

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9
Q

What is the word equation for photosynthesis?

A

Carbon Dioxide + water -> Glucose + oxygen

-> Includes light and glucose

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10
Q

What is the enthalpy of photosynthesis?

A

Endothermic - energy is taken in during the reaction

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11
Q

What is the rate of Photosynthesis affected by?

A

Light intensity, the concentration of CO2 and the temperature - any of these can become a limiting factor

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12
Q

Why does not enough light slow down the rate of photosynthesis?

A

Light transfers the energy needed for photosynthesis
Rate of photosynthesis is directly proportional to light intensity

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13
Q

How does distance from lamp and light intensity relate?

A

They are inversely proportional to eachother
- As distance (squared proportion) increases, light intensity decreases

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14
Q

What is inverse square law?

A

Light intensity ∝ 1/ distance²

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15
Q

What does inverse square law mean?
Light intensity ∝ 1/ distance²

A

If you half the distance, the light intensity will be 4x greater
-> What ever happens to the distance, the opposite squared will happen to the light intensity

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16
Q

How does CO2 slow down light intensity?

A

it is a limiting factor

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17
Q

How does temperature affect photosynthesis?

A

Too Low - Limiting factor - The enzymes needed for photosynthesis work more slowly at lower tempertatures
Too hot - The enzymes it needs for photosynthesis and its other reactions will be de-natured

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18
Q

What temperature do the enzymes needed for photosyntheis de-nature?

A

45*C

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19
Q

What is the function of root hair cells?

A

To take in minerals and water

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20
Q

What is a root hair cell?

A

The cell on a surface of a plant root that grows into “hairs” and sticks out into the soil

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21
Q

How do plants take in mineral ions and water?

A

Each branch of their roots are covered in millions of root hair cells
-> This gives it a large surface area for absorbing water and mineral ions from the soil

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22
Q

How do root hair cells take in mineral ions and water?

A

The concentration of mineral ions is usually higher in root hair cells than the soil around them, so mineral ions are absorbed by active transport
Water is absorbed by osmosis

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23
Q

What are phloem cells?

A

columns of elongated living cells with small pores in the end walls to let stuff flow through

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24
Q

What do phloem cells do?

A

Translocation
-> They transport food substances (mainly sucrose) made in the leaves to the rest of the plant for immediate use (e.g. in growing regions) or for storage
-> This requires energy and respiration, and the transport can go both ways**

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25
What are xylem cells?
Dead cells joined end to end with no end walls between them and a hole down the middle -> Strengthened with a material called lignin
26
What do Xylem do?
**The transpiration stream** -> Carry water (and mineral ions dissolved in it) from the roots, through the xylem and out of the leaves
27
What is transpiration?
the loss of water from the/a plant
28
What is transpiration caused by and where does it happen?
Evaporation and diffusion of water from a plants surface (e.g. mostly occurs at the leaves)
29
How does the transpiration stream work?
Transpiration - The loss of water causes a slight shortage of water in the leaf, so more water is drawn up from the rest of the plant through the **xylem vessels** to replace it -> In turn this causes more water to be drawn up from the roots | This causes a constant transpiration stream throughout the plant
30
What are stomata?
Tiny pores on the surface of a plant, mostly found on the lower surface of leaves
31
What do stomata do?
Allow CO2 and oxygen to diffuse directly in and out of a leaf -> Also allow water vapour to escape during transpiration
32
How is transpiration a side effect of the way leaves are adapted for photosynthesis?
Leaves have stomata for easy gas exchange but due to there being more water inside the plant than outside, the water escapes from the leaves via the stomata due to diffusion
33
How are stomata controlled?
They are surrounded by guard cells which change shape to control the size of the pore When the guard cells are turgid (swollen with water) the stomata are open When the guard cells are flaccid (low on water and limp) the stomata are closed
34
What environmental factors affect transpiration rates?
Light intensity Temperature Air flow
35
How does light intensity affect the rate of transpiration?
The brighter the light, the greater the transpiration rate -> Stomata begin to close as it gets dark (no photosynth in dark so they dont have to be open to let CO2 in) -> When the stomata are closed, very little water can escape
36
How does temperature affect the rate of transpiration?
The warmer it is, the faster transpiration happens. -> When its warm the water particles have more energy to evaporate and diffuse out of the stomata
37
How does air flow affect the rate of transpiration?
The better air flow around the leaf (e.g. greater winds), the greater transpiration rate If airflow around the leaf if poor, the water vapour surrounds the leaf and doesnt move away. If theres a **high concentration of water particles outside the leaf as well as inside it**, diffusion doesnt happen as quickly | Diffusion happens quicker from an area of high conc to low conc
38
How are leaves adapted for plants?
They are adapted for photosynthesis and gas exchange -> Broas leaves = large surface area exposed to light = Better photosynthesis
39
# Leaf adaptations How is the palisade layer adapted for photosynthesis?
It has lots of chloroplasts - this means the leaf chloroplasts are near to the top of the cell and can get the most light
40
# Leaf adaptations How is the upper epidermis adapted for photosynthesis?
Its transparent so light can pass through it to the palisade layer
41
# Leaf Adaptations How are Xylem and Phloem adapted for photosynthesis?
The Xylem and Phloem form a network of vascular bundles, which provide the leaf with water for photosynthesis and take away the glucose produced | They also support the structure
42
# Leaf Adaptations How are the epidermal tissues adapted for gas exchange?
The epidermal tissues are covered in a waxy cuticle, which prevents water loss by evaporation
43
# Leaf adaptations How is the tissue of the leaf adapted for efficient gas exchange?
Lower epidermis - lots of stomata - lets CO2 diffuse directly into the leaf The spongy mesophyll tissue contains air spaces which increases the rate of diffusion of gases into and out of the leaf's cells
44
# Plant Adaptations What do extreme environment adaptations tend to affect?
The size/shape of plant's leaves Cuticle Number/Position of Stomata
45
# Plant Adaptations What plant adaptations to plants in the desert typically have?
- Smaller leaves or Spines instead - Curled leaves / hairs on the surface - Thick waxy cuticles - Thick, fleshy stem - Fewer stomata or stomata that only open at night - Stomata sunken in pits
46
# Desert plant adaptations How do smaller leaves or spines instead of leaves benefit a plant in the desert?
Reduces the surface area for water loss by evaporation and spines also help to stop animals eating the plant to get water
47
# Desert plant adaptations How do curled leaves or hairs on the surface of leaves benefit a plant in the desert?
Reduces airflow close to the leaf, trapping water vapour near the surface and reducing diffusion from the leaf to the air. | Spines also reduce airflow
48
# Desert plant adaptations How do thick waxy cuticles benefit a plant in the desert?
Reduce water loss by evaporation
49
# Desert plant adaptations How do thick, fleshy stems benefit a plant in the desert?
Store water
50
# Desert plant adaptations How do Fewer stomata or stomata that only open at night benefit a plant in the desert? | + stomata sunken in pits
Reduced water loss by evaporation Stomata sunken in pits - makes the stomata lower than the surface of the leaf which reduced airflow close to the stomata
51
What are auxins?
Plant hormones which control growth at the tips of roots and shoots
52
How do auxins move through the plant?
In solution
53
Where is auxin produced and how does this affect its job?
In the tips and diffuses backwards to stimulate the cell elongation process which occurs in the cells just behind the tips It **promotes growth in the shoot**, but **inhibits growth in the root**
54
What two tropisms does auxin growth respond to?
Phototropism (light) Gravitropism / Geotropism (Gravity)
55
How do shoots repond to light and gravity
They are **positively phototropic** - they grow towards light They are **negatively geotropic** - they grow away from gravity
56
# Auxin How does positive phototropism work in shoots?
1) When a shoot is exposed to light, it accumulates more auxin on the side thats in shade. 2) This makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light
57
# Auxin How is Positive Phototropism beneficial to plants?
- Absorb more light for photosynthesis - enables the plant to grow
58
# Auxin How does positive phototropism work on a plant completely in shade?
The auxin in the tips makes them quickly elongate on all sides - a taller shoot has a better chance at finding sunlight. This makes the shoot dark, tall and spindly
59
# Auxin How does negative Geotropism work in the shoots of plants?
1) When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side 2) This causes the lower side to grow faster, bending the shoot upwards
60
How do roots respond to light and gravity?
They are **negatively Phototropic** and **Positively Geotropic**
61
How does positive gravitropism work in roots?
1) A root growing sideways will have more auxin on its lower side 2) AUXIN INHIBITS GROWTH IN ROOTS, so the top cells will elongate faster, causing the roots to grow towards gravity
62
How are roots negatively phototropic? | Grow away from light
1) If a root starts being exposed to light, more auxin accumulates on the shaded side 2) Auxin inhibits cell elongation on the shaded side, so the root bends downwards, towards the light
63
# Investagating the effect of light on the growth of cress seeds How do you conduct a practical to investagate plant growth responses?
1) Put some seeds in a petri dish lined with moist filter paper 2) Surround the petri dish with black card , cut a hole in one side of the card only (box cover) 3) Shine a light into the box through the hole 4) Leave the cress seeds alone for one week then observe their response - the seedlings should have grown towards the light - can even mesure the angle theyre growing at
64
How can plant hormones function as selective weekkillers?
1) **Selective weedkillers have been developed from auxins and only target broad-leaved plants **(as weeds are more broadleaved compared to grasses/cereals which have narrow leaves) -> They disrupt the weed's normal growth patterns, which soon kills them but leaves the grass and crops untouched
65
How do plant hormones help growing plants from cutting with root powder? | Cuttings are parts of a plant that have been cut off
Without rooting power, cutting in soil will not grow. But with rooting powder (contains auxins), they will produce roots rapidly and start growing as new plants | This enables growers to produce clones of a good plant very quickly
66
How are plant hormones used to control flower and fruit formation?
**Gibberellins are used to make plants flower earlier** than they would usually do so, or under conditions in which they would'nt usually flower (e.g. when its warmer than usual) They can also be **used to reduce flower formation, which can improve fruit quality** (fruit grows from pollinated flowers) -> Less fruit = more support and minerals from tree = larger, higher quality fruit | Like quality>quantity type shit
67
What are gibberellins
Plant hormones that stimulate seed germination (growth of a seed into a plant), stem growth and flowering
68
How are plant hormones used to produce seedless fruit?
Fruit (with seeds in the middle) normally only grow on flowering plants which have been pollinated by insects. - If the flower doesnt get pollinated, seeds wont grow. Plant hormones (e.g. Gibberellins) are applied to the unpollinated flowers of some types of plant - the fruit will then grow but the seeds wont | Some seedless citrus fruits are grown this way
69
How can plant hormones control the ripening of fruits?
- Can control them whilst on plant or in transport -> Allows fruit to be picked unripe (therefore harder and less damageable) - A ripening hormone called ethene is then added and the fruit will ripen on the way to the supermarket and be perfect as it reaches the shelves
70
How can plant hormones control seed germination?
- Lots of seeds wont germiante untill they've been through certain conditions (e.g. a period of cold or dryness) - Seeds can be treated with gibberellin to make them germinate at times of year they wouldn't normally | It also can ensure all the seeds in a batch germinate at the same time

Biology (11 decks)

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