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plant organisation Flashcards

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1
Q

active transport

definition

A

The transport of molecules against their concentration gradient from a region of low concentration to a region of high concentration.

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2
Q

companion cells

definition

A

Cells that help the phloem to transport substances by providing energy.

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3
Q

diffuse

definition

A

When particles spread out from a region of higher concentration to a region of lower concentration.

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4
Q

epidermal cells

definition

A

Cells of the epidermis, the outer covering layer of an organism.

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5
Q

eyepiece

definition

A

The eyepiece, or ocular, is the lens at the top of a compound microscope. It has a longer focal length than the objective lens and magnifies the image produced by the objective.

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6
Q

field of view

definition

A

The area seen when looking through a microscope.

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7
Q

flaccid

definition

A

Lacking turgor. Lacking in stiffness or strength. Soft and floppy.

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8
Q

graticule

definition

A

A glass or plastic disc fitted into the eyepiece of a microscope. The graticule has a scale ruled on it and is used to estimate the size of a specimen when viewed with a microscope.

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9
Q

hydrogen bonding

definition

A

The strongest type of van der Waals force that arises through a dipole-dipole attraction when hydrogen atoms are covalently bonded to highly electronegative nitrogen, oxygen or fluorine atoms.

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10
Q

lignin

definition

A

Carbohydrate material lining the xylem vessels providing strength and support.

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11
Q

mitochondria

definition

A

Structures in the cytoplasm of all cells where aerobic respiration takes place (singular is mitochondrion).

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12
Q

nuclei

definition

A

The nucleus controls what happens inside the cell. Chromosomes are structures found in the nucleus of most cells. The plural of nucleus is nuclei.

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13
Q

osmosis

definition

A

The movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration.

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14
Q

palisade mesophyll

definition

A

Plant tissue containing closely packed cells in the upper layer of a leaf.

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15
Q

phloem

definition

A

The tissue in plants that transports the products of photosynthesis, including sugars and amino acids.

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16
Q

photosynthesis

definition

A

A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.

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17
Q

representative sample

definition

A

A representative sample is one that accurately represents the whole of the group.

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18
Q

root hair cell

definition

A

A specialised cell that increases the surface area of the root epidermis to improve the uptake of water and minerals.

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19
Q

respiration

definition

A

The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration.

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20
Q

sieve tube

definition

A

Cells that have no nuclei and are connected to each other by their cytoplasm.

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21
Q

spongy mesophyll

definition

A

The plant tissue in a leaf which has loosely packed cells and air spaces between them to allow gas exchange.

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22
Q

stomata

definition

A

Tiny holes in the epidermis (skin) of a leaf. They control gas exchange by opening and closing and are involved in loss of water from leaves. Singular is stoma.

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23
Q

sucrose

definition

A

A disaccharide made from glucose and fructose. It is used as table sugar.

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24
Q

translocation

definition

A

The transport of dissolved material within a plant.

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25
Q

transpiration

definition

A

The loss of water from leaves by evaporation through the stomata.

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26
Q

tuber

definition

A

A swollen, fleshy underground stem of a plant, such as the potato, bearing buds from which new plant shoots arise.

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27
Q

turgid

definition

A

Having turgor - enlarged and swollen with water.

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28
Q

xylem vessels

definition

A

Narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants.

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29
Q

What are leaves adapted for?

A

Leaves are adapted for photosynthesis and gaseous exchange.

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30
Q

How are leaves adapted for photosynthesis and gaseous exchange?

A

They are adapted for photosynthesis by having a large surface area, and contain openings, called stomata to allow carbon dioxide into the leaf and oxygen out. Although these design features are good for photosynthesis, they can result in the leaf losing a lot of water. The cells inside the leaf have water on their surface. Some of this water evaporates, and the water vapour can then escape from inside the leaf.

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31
Q

Transpiration

A

When water evaporates from the leaves, resulting in more water being drawn up from the roots, it is called transpiration.

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32
Q

How are leaves adapted to reduce water loss?

A

To reduce water loss the leaf is coated in a waxy cuticle to stop the water vapour escaping through the epidermis. Leaves usually have fewer stomata on their top surface to reduce this water loss.

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33
Q

How are leaves adapted for photosynthesis?

A

Leaves enable photosynthesis to occur. Photosynthesis is the process by which leaves absorb light and carbon dioxide to produce glucose (food) for plants to grow. Leaves are adapted to perform their function, eg they have a large surface area to absorb sunlight.

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34
Q

What are the 2 different types of transport tissues in plants and what do they do?

A

Plants have two different types of ‘transport’ tissue, xylem and phloem. These specialised tissues move substances in and around the plant.

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35
Q

Functions of leaves.

Photosynthesis

A

The function of a leaf is photosynthesis - to absorb light and carbon dioxide to produce glucose (food). The equation for photosynthesis is:

carbon dioxide and water → glucose and oxygen

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36
Q

Functions of leaves.

Gas exchange in leaves.

A

Leaves are also involved in gas exchange. Carbon dioxide enters the leaf and oxygen and water vapour leave the plant through the stomata. Leaves are adapted in several ways to help them perform their functions.

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37
Q

Name the purpose of the adaptation large surface area of leaves.

A

To absorb more light

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38
Q

Name the purpose of the adaptation thin of leaves.

A

Short distance for carbon dioxide to diffuse into leaf cells

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39
Q

Name the purpose of the adaptation chlorophyll of leaves.

A

Absorbs sunlight to transfer energy into chemicals

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40
Q

Name the purpose of the adaptation network of veins of leaves.

A

To support the leaf and transport water, mineral ions and sucrose (sugar)

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41
Q

Name the purpose of the adaptation stomata of leaves.

A

Allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out

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42
Q

Functions of tissues of the leaf

Name the purpose of the adaptation epidermis is thin and transparent

A

To allow more light to reach the palisade cells

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43
Q

Functions of tissues of the leaf

Name the purpose of the adaptation thin cuticle made of wax

A

To protect the leaf from infection and prevent water loss without blocking out light

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44
Q

Functions of tissues of the leaf

Name the purpose of the adaptation palisade cell layer at top of leaf

A

To absorb more light and increase the rate of photosynthesis

45
Q

Functions of tissues of the leaf

Name the purpose of the adaptation spongy layer

A

Air spaces allow gases to diffuse through the leaf

46
Q

Functions of tissues of the leaf

Name the purpose of the adaptation palisade cells contain many chloroplasts

A

To absorb all the available light

47
Q

Gas exchange in plants

A

When a plant is carrying out photosynthesis carbon dioxide needs to move from the air into the leaf. It does this by diffusing through small pores called stomata.

At the same time oxygen moves out of the leaf through the stomata. This movement of gases in opposite directions is called gas exchange.

Water vapour also diffuses out of the stomata. The stomata are surrounded by guard cells, which control their opening and closing. Cells in the leaf are loosely packed.

48
Q

Plants absorbing light energy

A

Light absorption happens in the palisade mesophyll tissue of the leaf. Palisade cells are column shaped and packed with many chloroplasts. They are arranged closely together so that a lot of light energy can be absorbed.

49
Q

What does xylem move?

A

xylem moves water and mineral ions from the roots to the leaves

50
Q

What does phloem do?

A

phloem moves food substances such as sucrose (sugar) and amino acids from leaves to the rest of the plant. This movement of food is called translocation.

51
Q

Root hair cells

A

Plants absorb water from the soil by osmosis. They absorb mineral ions by active transport, against the concentration gradient. Root hair cells are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption. They also contain lots of mitochondria, which release energy from glucose during respiration in order to provide the energy needed for active transport.

52
Q

Root hair cell

The absorbed water is transported through the roots to the rest of the plant where it is used for different purposes:

A
  • it is a reactant used in photosynthesis
  • it supports leaves and shoots by keeping the cells rigid
  • it cools the leaves by evaporation
  • it transports dissolved minerals around the plant
53
Q

What are stomata?

A

Stomata are tiny holes found in the underside of leaves. They control water loss and gas exchange by opening and closing. They allow water vapour and oxygen out of the leaf and carbon dioxide into the leaf.

54
Q

Stomata

A

Plants growing in drier conditions tend to have small numbers of tiny stomata and only on their lower leaf surface, to save water loss. Most plants regulate the size of stomata with guard cells. Each stoma is surrounded by a pair of sausage-shaped guard cells. In bright light the guard cells take in water by osmosis and become plump and turgid. In low light the guard cells lose water and become flaccid, causing the stomata to close. They would normally only close in the dark when no carbon dioxide is needed for photosynthesis. Guard cells are adapted to their function by allowing gas exchange and controlling water loss within the leaf.

55
Q

Size of stomata

A

The size of the stomatal opening is used by the plant to control the rate of transpiration and therefore limit the levels of water loss from the leaf. This helps to stop the plant from wilting.

56
Q

Xylem consists of dead cells. The cells that make up the xylem are adapted to their function:

A
  • They lose their end walls so the xylem forms a continuous, hollow tube.
  • They become strengthened by a substance called lignin. Lignin gives strength and support to the plant. We call lignified cells wood.
57
Q

The phloem moves food substances that the plant has produced by photosynthesis to where they are needed for processes such as:

A
  • growing parts of the plant for immediate use
  • storage organs such as bulbs and tubers
  • developing seeds
58
Q

Transport in the phloem

A

Transport in the phloem is therefore both up and down the stem. Sucrose is the transport sugar in the phloem. Transport of substances in the phloem is called translocation. Translocation requires energy as it is an active process.

59
Q

Phloem consists of living cells. The cells that make up the phloem are adapted to their function:

A
  • Sieve tubes - specialised for transport and have no nuclei. Each sieve tube has a perforated end so its cytoplasm connects one cell to the next. Sucrose and amino acids are translocated within the living cytoplasm of the sieve tubes.
  • Companion cells - transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy. A sieve tube is completely dependent on its companion cell(s).
60
Q

Type of transport in xylem

A

Physical process

61
Q

Type of transport in phloem

A

Requires energy

62
Q

Substances transported in xylem

A

Water and minerals

63
Q

Substances transported in phloem

A

Products of photosynthesis; includes sucrose and amino acids dissolved in water

64
Q

Direction of transport in xylem

A

Upwards from roots to leaves

65
Q

Direction of transport in phloem.

A

Upwards and downwards

66
Q

Transpiration

A

When the plant opens its stomata to let in carbon dioxide, water on the surface of the cells of the spongy mesophyll and palisade mesophyll evaporates and diffuses out of the leaf. This process is called transpiration.

67
Q

Xylem
water molecules
hydrogen bonding

A

Water molecules inside the xylem cells are strongly attracted to other water molecules. There is strong cohesion between the molecules because of hydrogen bonding. A continuous column of water is therefore pulled up the stem in the transpiration stream by evaporation from the leaves.

68
Q

Transpiration is an unavoidable consequence of photosynthesis - only five per cent of the water taken up by the plant is used for photosynthesis - but does have its purposes:

A
  • provides the water for photosynthesis
  • transports mineral ions
  • cools the leaf as water evaporates
  • provides water that keeps the cells turgid, which supports herbaceous plants
69
Q

Water uptake and transport across the root

A

Root hairs are single-celled extensions of epidermal cells in the root. They grow between soil particles and absorb water and minerals from the soil.

Water enters the root hair cells by osmosis. This happens because soil water has a higher water potential than the cytoplasm of the root hair cell. Minerals enter by active transport.

70
Q

The rate of transpiration is affected by several factors. These include:

A
  • temperature
  • humidity
  • air movement
  • light intensity
71
Q

What is the change in factor that increases transpiration rate for the factor temperature

A

increase

72
Q

What is the change in factor that increases transpiration rate for the factor humidity

A

decrease

73
Q

What is the change in factor that increases transpiration rate for the factor air movement

A

increase

74
Q

What is the change in factor that increases transpiration rate for the factor light intensity

A

increase

75
Q

Explain how the factor temperature increases the transpiration rate

A

Increases molecular movement so that: more water molecules evaporate from cell surfaces; the rate of diffusion of water molecules from the leaf is increased

76
Q

Explain how the factor humidity increases the transpiration rate

A

Reduces the concentration of water molecules outside the leaf; diffusion of water from the leaf increases

77
Q

Explain how the factor air movement increases the transpiration rate

A

Removes water vapour from leaf surfaces; more water diffuses from the leaf because a high concentration gradient is maintained

78
Q

Explain how the factor light intensity increases the transpiration rate

A

Increases the rate of photosynthesis; stomata open so that water diffuses out of the leaf

79
Q

What conditions will decrease the rate of transpiration?

A

Decrease in temperature, increase in humidity, no or reduced air movement and low light intensity.

80
Q

What is a simple method for investigating water loss from plant leaves?

A

A simple method for investigating water loss from plant leaves is to measure their change in mass over a period of time.

81
Q

Various factors that affect water loss from the leaf can be investigated using this method, for instance:

A
  • air movement - direct a fan on the leaves
  • temperature
  • obstructing the stomata, eg. with petroleum jelly
82
Q

A simple method for investigating water loss from plant leaves is to measure their change in mass over a period of time.
Explain this method step by step.

A

1) Remove a number of leaves from a bush or tree.
2) Find the mass of each leaf.
3) Suspend each leaf from a piece of wire or string.
4) After a set period of time, re-measure the mass.

83
Q

Water loss through the stomata

A

Water is lost through open stomata. Scientists sometimes count all the stomata on a leaf surface, but usually, there are too many to count. In these instances, they take a sample. This must be a representative sample - it must give a true picture of the numbers of stomata on the leaf.

84
Q

To be representative of the whole leaf, the representative sample must:

A
  • include a sufficient number of counts - not just one or two - of stomata over different parts of the slide
  • must be random, and not select areas where there are many or few stomata
85
Q

Water loss through the stomata
sample
counting stomata

A

A number of random counts of stomata should be made with a microscope.

Count the number of stomata in the field of view. Then move the slide slightly and count the number of stomata in a different field of view.

Make at least five random counts, then calculate a mean.

Using this method, and a calibrated eyepiece graticule, you could estimate the number of stomata per unit area (mm2).

86
Q

Investigating transpiration

How to measure the uptake of water

A

The uptake of water can be measured using a potometer. Under normal circumstances, the rate of water uptake gives a measure of the rate of transpiration.

A simple potometer is a piece of capillary tubing to which a plant has been connected. The water uptake is measured by recording the time taken for a bubble in the tube to move a set distance.

87
Q

Measuring water uptake - Potometers
Investigating transpiration
step by step

A

1) The potometer is filed with water
2) A shoot is cut from a plant
3) The end of the shoot is cut under water to ensure the xylem remains water-filled and prevents air locks.
4) The shoot is inserted into the rubber tubing at the end of the potometer
5) The potometer is raised so that a bubble of air is taken up.
6) The potometer is lowered into the water. The distance travelled by the air bubble is recorded over a period of time.

88
Q

Investigating factors that affect the rate of transpiration

A

Insufficient water affects the yields of crops. Different factors affect transpiration and therefore water uptake. They can be investigated using a potometer.

89
Q

Laboratory experiments are designed to simulate conditions a plant may encounter such as:

A
  • air movement
  • coatings on leaves that block stomata
  • high light intensity
  • high temperature
90
Q

Laboratory experiments are designed to simulate conditions a plant may encounter such as air movement.
Explain when this is encountered by the plant and how the condition is produced in the laboratory.

A

When encountered by plant: Windy conditions

How the condition is produced in the laboratory: Fan

91
Q

Laboratory experiments are designed to simulate conditions a plant may encounter such as coatings on leaves that block stomata.
Explain when this is encountered by the plant and how the condition is produced in the laboratory.

A

When encountered by plant: Airborne pollution; horticultural use on cuttings and Christmas trees

How the condition is produced in the laboratory: Smear leaf surface(s) with petroleum jelly

92
Q

Laboratory experiments are designed to simulate conditions a plant may encounter such as High light intensity.
Explain when this is encountered by the plant and how the condition is produced in the laboratory.

A

When encountered by plant: Sunny climates; artificial lighting in greenhouses

How the condition is produced in the laboratory: Artificial lighting

93
Q

Laboratory experiments are designed to simulate conditions a plant may encounter such as High temperature.
Explain when this is encountered by the plant and how the condition is produced in the laboratory.

A

When encountered by plant: Warm and hot climates

How the condition is produced in the laboratory: Heater or greenhouse

94
Q

When investigating the effect of light intensity on water uptake, what are the control variables?

A

Temperature, no air movement or draughts. It is also important to use the same species of plant, and shoots with a similar leaf surface if different plant shoots are used.

95
Q

Under which conditions is the rate of transpiration greatest?

A

At high temperatures.

96
Q

Scientists use sampling and counting techniques to investigate the distribution of stomata on leaves. They count stomata to investigate:

A
  • their numbers, density and distribution on upper and lower surfaces
  • numbers that are open and closed at any time
  • adaptations of plants to environmental conditions, eg desert and water plants
  • effects of changing conditions such as increased carbon dioxide concentrations from climate change
97
Q

Give 2 methods (step by step) by which stomata can be counted.

A

Method 1

1) Put a small drop of water on a microscope slide.
2) Hold the leaf with the surface you want to examine uppermost.
3) Tear the leaf at an angle so as to reveal part of the epidermis.
4) Place the leaf on the microscope slide and examine.

Method 2

1) Paint the surface of the leaf with clear nail varnish.
2) Allow to dry.
3) Peel off the nail varnish with forceps.
4) Place on a dry microscope slide and examine

98
Q

Recording the distribution

A

The density of stomata on a leaf is recorded per unit area, usually the number per sq mm.

A microscope is calibrated so that its field of view is known.

99
Q

Adaptations of plants to extreme environments

Cacti are well adapted for survival in the desert. They have:

A
  • Stems that can store water.
  • Widespread or very deep root systems that can collect water from a large area or from very deep underground.
  • Spines which are modified leaves. These minimise the surface area and so reduce water loss. The spines also protect the cacti from animals that might eat them.
  • Very thick, waxy cuticle to reduce water loss by evaporation.
  • Reduced number of stomata to reduce water loss by transpiration.
100
Q

Which tissue in the leaf absorbs the most light for photosynthesis?

A

Palisade mesophyll

101
Q

Which tissue in the leaf is adapted for efficient gas exchange?

A

Spongy mesophyll

102
Q

Which tissue transports water and minerals from the root to the leaves?

A

Xylem

103
Q

Which tissue transports sugars from the leaves to other parts of the plant including roots for storage?

A

Phloem

104
Q

Translocation is the movement of which substance?

A

Sucrose

105
Q

Which cells control the stomata?

A

A pair of guard cells surround each stoma and when they are turgid, the stoma will be open.

106
Q

What sort of process is translocation?

A

active process

107
Q

What is the process which causes guard cells to become turgid?

A

Osmosis

108
Q

Which of these describes the stomata of a desert plant?

A

Reduced in number and mainly closed

1 BIOLOGY (36 decks)

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