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Biology HL > Plant biology > Flashcards

Plant biology Flashcards

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1
Q

What plant consists of?

A
  • stem
  • leaf
  • root
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2
Q

What is the function of stem?

A

Supports the leaves in the sunlight and transports organic materials, ions, and water between the roots and leaves. It also storages nutrients.

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3
Q

Structure of the stem

A
  • At the top of the stem there is a terminal growing point
  • In the axil of each leaf there is an axillary bud (new cells are produced there)
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4
Q

What does leaf consists of and what is its function?

A

Consists of a leaf blade and it connected to the stem by the leaf stalk
- it is the organ specialized for photosynthesis

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5
Q

What is the function of root?

A
  • anchoring the plant
  • site of absorption of water and ions from the soil
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6
Q

What does the stem consists of?

A
  • vascular bundle (xylem and phloem)
  • cambium
  • cortex
  • epidermis
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7
Q

What is xylem?

A

Xylem is a dead tissue that has no cytoplasm.

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8
Q

Function of xylem

A

Transports nutrients and water from roots to stem and leaves.

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9
Q

Structure of xylem

A
  • vessel elements that allow for faster movement of water
  • tracheid that allows for exchange of water via pits and leads to slower rate of water movement
  • lignin thickening in its walls
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10
Q

What is the transport of water and minerals via the xylem called?

A

Bulk flow transport

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11
Q

Explain bulk flow via xylem

A

Water and minerals from the soil enter the plant through the epidermis of roots and pass into the vascular bundle. The water and dissolved minerals in the xylem are transported by bulk flow to the veins of the leaves.

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12
Q

What is phloem?

A

Living tissue that is responsible for active translocation of sucrose and amino acid from source to sink.

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13
Q

Difference between source and sink

A
  • source is a location in a plant where a resource is taken up
  • sink is a location where a resource is used.
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14
Q

What is the structure of phloem?

A
  • sieve tubes
  • companion cells
  • sieve plates
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15
Q

Sieve tubes

A

they do not have nucleus, mitochondrion, ribosomes and vacuoles. This reduction enables for nutrients to pass more easily through the cell

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16
Q

Sieve plates

A

They facilitate the flow of fluid from the cell to the sieve tube.

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17
Q

Companion cells

A

Located alongside each sieve tube element. They help to load sugars into the sieve tube elements and transport sugars to other parts of the plant.

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18
Q

What is the external structure of leaves?

A
  • leaf blade - flattened part of the leaf
  • petiole - leaf stalk
  • stipules - base of the leaf
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19
Q

What is the internal structure of the leaf?

A
  • upper epidermis
  • palisade mesophyll cells
  • spongy mesophyll cells
  • xylem and phloem
  • lower epidermis
  • stomata
  • guard cells
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20
Q

The function of upper and lower epidermis

A

protection of the leaf

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21
Q

function of palisade mesophyll cells

A

contain chloroplast for photosynthesis

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22
Q

function of spongy mesophyll cells

A

facilitates the movement of oxygen

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23
Q

guard cells and stomata function

A
  • guard cells - close stomata
  • stomata - opening in leaves that allow for gas exchange in leaf
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24
Q

2 main transports of water to xylem

A
  • mass flow - apoplastic pathway
  • diffusion - symplastic pathway
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25
Q

Apoplastic pathway (mass flow)

A

This involves the movement of water and solutes through the non-living spaces outside the plasma membranes of plant cells -> to xylem

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26
Q

Symplastic pathway (diffusion)

A

This involves the movement of water and solutes through the interconnected cytoplasm of plant cells via plasmodesmata. Substances can pass from cell to cell without crossing cell membranes directly -> to xylem

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27
Q

Plasmodesmata - meaning

A

channels that connect adjacent cells

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28
Q

Explain osmosis process

A

The transport of water from vacuole to vacuole of the cells driven by the gradient in osmotic pressure.

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29
Q

Casparian strip

A

Belt made out of waxy material that does not allow the water and dissolved materials to pass through. Thanks to it water and dissolved materials cannot cross the endodermis.

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30
Q

Cohesion tension theory

A

Water is pulled upward in plants due to the cohesive attraction between water molecules and the tension created by water loss through transpiration in leaves. This creates a continuous column of water in the xylem, facilitating upward movement from roots to leaves.

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31
Q

What are the process that allow the materials to pass from the soil to the roots?

A
  • diffusion and mass flow
  • aid provided by fungal hyphae
  • active transport
32
Q

Explain the mass flow and diffusion (soil -> roots)

A

It occurs when there is a higher concentration of mineral outside the root, the mineral moves into the root. They become dissolved and move via water.

33
Q

Aid provided by fungal hyphae (soil -> roots)

A

Fungal hyphae forms a cover over the surface of roots. This creates a large surface area available for water and mineral ion absorption.

34
Q

Active transport from soil to roots

A

It occurs when there is a higher concentration of mineral ions inside the plant. Proton pumps establish gradients and membrane transports particular materials into roots.

35
Q

Explain the bulk flow in xylem and phloem

A
  1. sugar is loaded to the sieve tubes and that reduces the water potential inside the sieve-tube elements. this causes the tube to take the water by osmosis.
  2. the uptake of water generates a positive pressure
  3. the pressure is relieved by the unloading sugar and water is lost at the sink
  4. xylem recycles water from the sink to source
36
Q

Explain the transpiration-translocation process

A
  1. leaf produces glucose that is converted to sucrose
  2. companion cells load the sucrose
  3. water follows from the xylem by osmosis
  4. organic molecules are unloaded by companion cells and sucrose is stored by starch
  5. water is released and recycled as the part of transpiration
37
Q

Translocation

A

movement of organic nutrients, primarily sugars, from sources to sinks within the plant.

38
Q

Transpiration

A

plants lose water vapor from their leaves and stems into the surrounding air through stomata.

39
Q

Factors affecting translocation rate

A
  • rate of photosynthesis
  • rate of transpiration
  • concentrations of sugars in phloem
40
Q

movement of water in plants

A
  1. Root Uptake - diffusion, mass flow, fungal hyphae, active transport
  2. Root to xylem - osmosis, mass flow, diffusion
  3. Translocation and transpiration
41
Q

What is the meristematic tissue in plants

A

it contains small unspecialized cells that can undergo mitosis. After cytokinesis one cell differentiates and the other one stays in the meristem

42
Q

Function of meristematic tissue

A

results in the growth of plants

43
Q

What is auxin?

A

It is the plant hormone that promotes a tissue growth and it is found in meristems

44
Q

What is the function of high auxin levels?

A

Promotes cell elongation in shoots (positive phototropism) and in roots it inhibits the elongation (negative phototropism)

45
Q

State the definition of tropism

A

growth toward or away from a directional stimulus in the environment

46
Q

Positive phototropism

A

Growth of plant towards the directional source of light. Shoots bend towards light and they become elongated.

47
Q

Negative phototropism

A

Growth of plant away from the directional source of light.

48
Q

Gravitropism

A

Growth of shoots and the downward growth of roots in response to gravity

49
Q

What was the Charles and Francis Darwin experiment on sensing light by plants?

A

They wanted to find out which part of the plant senses light
- They used oat seedlings and placed them in the dark for some time to ensure they were straight and vertically oriented.
- they exposed the seedlings to a unidirectional light source, such as sunlight or a lamp.
- Over time, they observed that the seedlings exhibited a bending response towards the light source.

50
Q

Structure of flowers

A
  • petal - attracts the insects to flower
  • anther - produces male sex cells
  • filament - holds anther
  • stigma - holds pollen
  • style - holds stigma
  • ovary - female sex cells
  • ovule
  • sepal - protects and holds flower
  • receptable - holds flower
51
Q

What is the pollination?

A

Transfer of pollen from a mature anther to a receptive stigma. We include:
- cross-pollination
- self-pollination

52
Q

Cross-pollination

A

pollen is delivered to a flower from a different plant

53
Q

Self-pollination

A

pollen from one flower pollinates the same flower or other flowers of the same individual

54
Q

What is the mutualistic relationship?

A

Two organisms of different species work together to benefit.
- example: bees and flower - they collect the nectar and flowers are pollination.

55
Q

Fertilization

A

Male and female gametes fuse to form a zygote. This occurs in the ovule of the flower.

56
Q

Structure of seeds

A
  • cotyledom (storage)
  • testa (protects the seed )
  • micropyle (scar caused by pollen entering the ovule)
  • embryonic root
  • embryonic shoot (becomes a new plant when the germination occurs)
57
Q

Double-fertilization

A

Fusion of gametes occurs after two sperm reach the female ovule.

58
Q

Seed dispersal

A

movement or transport of seeds away from the parent plant. The main modes include:
- gravity
- wind
- water
- animals

59
Q

Seed germination

A

Growth of an embryonic plant contained within a seed and it results in the formation of the seeding.

60
Q

Factors that influence germination

A
  • temperature
  • oxygen
  • water uptake
61
Q

Photoperiodism

A

refers to the physiological response of plants to the relative lengths of day and night.

62
Q

Short-day plants

A

flowers t night become longer and during the day they are shorter. they require a continuous period of darkness before flowering

63
Q

What is the phytochrome?

A

plants that respond to periods of darkness

64
Q

Where water evaporates?

A

mesophyll cells (water moves there from xylem)

65
Q

What is the potometer used for?

A

estimating transpiration rates by measuring the rate of water loss

66
Q

What are the environmental factors that affect the transpiration?

A
  • humidity
  • air movement
  • temperature
  • water supply
  • light intensity
67
Q

How humidity affects transpiration?

A

the lower the humidity outside of the leaf is, the faster the rate of transpiration.

68
Q

How air movement affects transpiration?

A

an increase in air movement increases transpiration

69
Q

How temperature affects transpiration?

A

increase in temperature increases transpiration

70
Q

How water supply affects transpiration?

A

transpiration is lower if there is a little water available as transpiration depends on the mesophyll walls being wet

71
Q

How light intensity affects transpiration?

A

greater light intensity increases the rate of transpiration because it opens stomata

72
Q

What are the guard cells?

A

They control the opening and closing of the stomata.

73
Q

What if the guard cells are flaccid ?

A

If the guard cells are flaccid, the stomatal pore closes, reducing water loss from the plant but also limiting the uptake of carbon dioxide for photosynthesis.

74
Q

What if the guard cells are turgid ?

A

If the guard cells are turgid, the stomatal pore opens, allowing for the exchange of gases such as carbon dioxide and oxygen between the plant and the atmosphere.

75
Q

Photosynthesis in C4 plants

A

stomata in C4 plants play a critical role in facilitating efficient gas exchange for photosynthesis while minimizing water loss, contributing to the plant’s ability to thrive in hot and arid environments.

76
Q

CAM plants

A

open their stomata during the night and close them during the day. closing it helps the desert plants conserve water and prevents from CO2 entering the leaves.

77
Q

What is the ABA?

A

Plant growth regulator that is contained in stems, leaves, and fruits. Its presence assists plant survival during the stress such as drought. In such conditions ABA levels are raised and the water loss is reduced.

Biology HL (8 decks)

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