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Heinemann Senior Science 1
Chapter 2 Plants
2.1 Plant function
Questions
1
Phloem, xylem, guard cells.
2
They can convert carbon dioxide and oxygen with sunlight into a food source.
3
The stem holds plant upright. The roots absorb water and dissolved nutrients
from the soil and anchor the plant. Leaves capture sunlight for photosynthesis.
4
Yellowing of leaves, stunted growth.
5
Macrominerals: nitrogen, important for leaf growth; phosphorus, promotes
root growth and flowering; potassium, increases disease resistance.
Trace elements: iron, required by chloroplasts for functioning; copper,
required by plant enzymes; zinc, used in the production of the plant hormone
auxin.
6
Further questions
1
Spray a small amount of the liquid fertiliser into a flame and observe the
colours given off; compare to the known colours of metal salts.
2
3
a
carrot
b
spinach
Vegetables do not contain seeds; fruit do.
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Plants absorb oxygen and carbon dioxide from the air and these react in the
presence of sunlight and water to form glucose, a substance that supplies food
for the growing plant.
5
A farmer can observe plant growth for signs such as yellowing of leaves,
mottling and stunted growth. From the signs, he or she can determine which
mineral element is lacking and apply the appropriate fertiliser.
2.2 Seed germination and requirements
Questions
1
To germinate seeds under conditions generally seen as unfavourable, for
consumers, home gardeners and nurseries to keep up with supply.
2
Water, oxygen, warmth.
3
25–30C
4
Growth is slowed and a food supply is maintained for the following growing
season.
5
When a seed absorbs water the seed coat bursts, allowing oxygen into the seed
and respiration to start.
6
a
[top to bottom]
b
lateral bud
c
[top to bottom]
root/shoot
swollen stem
seed coat
lateral bud
cotyledon
old corms
roots
Further questions
1
The seeds require a period of cold exposure to promote germination; the seeds
may be tulips or seeds from a typically cold zone.
2
In a dry container, not humid, and vacuum sealed (no oxygen) to prevent
germination and to maintain health.
3
Increased germination.
4
The seed cannot obtain enough oxygen to start respiration for germination to
occur.
5
Use a plastic tray or box and place a lamp underneath it to heat the bottom.
6
Provides nutrients for Rhizobia bacteria and neutralises the soil so bacteria
aren’t killed.
7
Heat to crack the nuts, as they have very hard protective shells.
8
a
leaching
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b
scarification
c
abrasion
Plant A—temperate. Plant B—cold. If plant B was grown in Central Australia
cold storage prior to germination would be needed.
2.3 Factors affecting seedling growth
Questions
1
Warmth, sunlight, oxygen, carbon dioxide, soil nutrients and water.
2
Competition for resources will limit:
3

space to grow in, resulting in smaller plants and reduced yields

water availability, resulting in smaller plants and reduced yields

available nutrients, resulting in smaller plants and reduced yields.
As seed size increases, seed sowing spacing needs to increase because of
competition for resources.
4
Leaf size, shape, plant height, root length.
5
No, the roots establish first, then the stem and leaves.
Further questions
1
A fern requires high moisture, humidity and temperate conditions. A eucalypt
requires temperate to hot conditions and moderate rainfall. A geranium
requires temperate conditions and moderate rainfall. A lily has very high water
requirements; conditions can range from cold to hot.
2
The green colour of leaves is actually a mixture of pigments. Chlorophyll
usually hides the other pigments; as leaves die, chlorophyll is reabsorbed and
the yellow and orange colours become visible.
3
Generally red (650 nm) and blue (400–450 nm).
4
Photosynthetic rate would increase but not indefinitely. Eventually the
maximum level of photosynthesis will occur.
5
Sunlight, water, oxygen, carbon dioxide because they are all required for
photosynthesis to occur.
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2.4 Water requirements of plants
Questions
1
A plant that lives under arid conditions with adaptations to overcome heat and
irregular or low water. It would be found in arid regions of Australia, e.g.
Central Australia.
2
They are aerial roots on mangroves that poke out of mud; they absorb oxygen
from air and excrete salt.
3
Spray, drip and flood.
4
Excessive watering problem
Description
Pooling
Collection of water in stagnant ponds can lead
to contamination, insect problems and disease
Wastage
Run-off of water and wastage of our precious
resource
Erosion
Run-off taking topsoil with it and destroying the
soil profile
Leaching
Removal of nutrients from soil profile
Waterlogging
Raising of the water table and filling of soil
pores with water which leads to lack of oxygen
for plants
5
Saving time and labour in large agricultural organisations.
Further questions
1
Absorption of water by pneumatophores at high tide; absorption of water by
pneumatophores from mud at low tide; excretion of salt from salt glands on
leaves so that osmosis can stop plant from losing water from cells.
2
Plants that require cold conditions for germination or flowering to occur.
3
The species will decrease in number and perhaps die out.
4
a
In waterlogged environments oxygen is limited. The aerial roots allow
oxygen to be obtained from the air.
5
b
Maintains osmotic balance, stops water from leaving the plant cells.
a
The roots quickly absorb water after rainfall before the water passes
through the soil profile.
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b
structural
2.5 Asexual reproduction in plants
Questions
1
Cloning is the production of new offspring with identical genetics as the
parents.
2
Benefits include offspring having the same desirable genetic information as
the parent; only one parent is required for reproduction; offspring can be
cloned from the meristematic cells of a parent plant. Disadvantages include a
limited gene pool: large numbers of identical offspring cause a small gene
pool and a reduction in genetic information. If the environment changes, the
species may not be able to adapt and may die out hence causing a decrease in
biodiversity. Cloning can be labour intensive and time costly.
3
Tissue culture produces new individuals by means of a labour-intensive,
human process. Runners can produce new individuals naturally without human
intervention.
4
Native plant
Lignotuber
Epicormic bud
Eucalyptus
yes
yes
Grevillea
no
yes
Hakea
yes
yes
Banksia
yes
yes
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Further questions
1
2
Continuous lighting also provides heat. Plants are not naturally accustomed to
receiving continuous light, the increase in heat can therefore cause overheating
of plants.
3
An example would be to set up different trays with varying amounts of light
exposure, e.g. 12, 15, 20 and 24 hours. Use a datalogger to monitor light in
lux, and temperature of the plants and surroundings.
4
Plants grown by seed establish the fastest, then runners, then tissue culture.
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2.6 Biodiversity
Questions
1
Biodiversity refers to the number of different species living in a particular
environment.
2
Medicinal purposes; they are suited to our conditions; aesthetic value; for food
for native animal species.
3
A gamete is a sex cell; it has genetic information from one parent. A zygote is
formed from the union of two gametes; it contains genetic information from
both parents.
4
For continuation of endangered species, to increase numbers.
5
It has competed with native species for area and resources; it has crowded out
native species and is reducing native species numbers.
Further questions
1
Answer depends on organisation student chooses.
2
a
When a particular species is threatened or endangered, large numbers
of offspring can be produced quickly from small numbers of parent
plants. This can aid biodiversity by maintaining species variation.
b
When organisms are cloned, the genetic information passed on is
identical to that of the parents. This results in a reduced gene pool. In
an environment where conditions may change (perhaps due to human
interference) the organisms may not be adapted to the changed
conditions and thus die out, reducing biodiversity.
3
Fencing, planting of native plant species, removal of introduced species,
working with Landcare to manage land, removal of grazing animals.
4
To maintain the health of our planet.
5
Introduced species compete with or prey on native species. Land management
has destroyed the environment that native plants grow in. People’s ignorance
of the importance of native species.
6
The Australian attitude is much more positive now, readily adopting
conservation principles. Governments are providing funding and support for
conservation projects through environmental policies, Landcare, CSIRO and
grants, as often seen advertised on television.
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Exam-style questions
1
B
2
C
3
D
4
C
5
A
6
C
7
Growth will be very stunted, yellowing of leaves.
8
In general, attach temperature probe, enter the frequency of recordings
required, enter number of recordings required, place probe in appropriate
position, start recordings. Note, procedure will vary for each brand of
datalogger.
9
Cactus
Fern
Low or irregular rainfall
High rainfall
Low to high temperatures
Moderate temperatures
Low humidity
High humidity
10
Stilt roots lift the mangrove out of the water to prevent waterlogging and
collect oxygen. Salt glands release excess salt from plant to maintain osmotic
balance. Pneumatophores collect oxygen from the air during periods of high
tide when generally the roots would be submersed by water.
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Little publicity and/or not notifying the public of the location so that they
cannot interfere. Tissue culture of plant and cuttings and seed collection of
plant.
12
Eucalypts possess lignotubers and epicormic buds which provide new growth
after fire. Hakeas demonstrate epicormic growth after fires. Banksia seeds are
protected in a hard nut which bursts open after fire and releases the seeds
ready for germination.
13
Behavioural—how an organism responds to the environment, e.g. resting in
the heat of the day. Structural—characteristics of an organism’s body that suit
it to the environment, e.g. sunken stomates. Physiological—the way an
organism’s body functions, e.g. dropping branches to conserve water loss.
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Obtain four xerophytic plants, e.g. cacti, and four non-xerophytic plants, e.g.
ferns. Pot each plant in a pot containing the same soil or potting mix. Place
each pot under the same environmental conditions, e.g. in a greenhouse. Only
water with a predetermined amount (depending on plant size and pot size)
once a week. Record observations of each plant at the start and once a week
before watering. Cacti should continue growing and show no detrimental
effects. The ferns should wilt, leaves should go pale in colour and, if left long
enough, die. This would show that xerophytic plants are adapted to low water
availability.
15
The plant utilised the water from the soil and carbon dioxide from the air to
photosynthesise and produce food for the plant to grow.
16
a
To determine the ideal temperature for acacia seeds to germinate.
b
100C provided the best germination percentage for acacia seeds.
c
temperature
d
Yes; 100C gave the best germination.
e
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Species
Smoke
Abrasion
Scarification
Leaching
√
Acacia
Dianella
√
Xanthorrhoea
√
√
√
Banksia
Grevillea
√
Clianthus
√
Deep yellow wood
18
Heat
√
Vacuum packaging removes all air and prevents entry of moisture to the seeds
which prevents the seeds from germinating or spoiling from fungal growth.
19
In the technique of tissue culture a small piece of meristematic tissue is taken
and grown in a nutrient solution to produce clones of an adult plant.
20
Having an understanding of how plants function allows us to manipulate plant
growth to meet our needs, to improve the quality of plants and to increase
plant numbers.
21
Increasing the light and temperature will increase plant growth until the
temperature reaches too high a level.
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Plants have different water requirements depending on their means of
reproduction, e.g. ferns need moisture to reproduce, and if they require water
for support, e.g. herbaceous plants such as geraniums use water for turgidity.
Plants such as xerophytes are adapted to low water availability.
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