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Plants
Junior Science
1
1a
All plants belong to the
same kingdom (Plantae).
Plants are called autotrophs,
which means they make
their own food through the
process of photosynthesis
which also produces
sufficient oxygen to the
atmosphere to allow all
living organisms to respire.
Plants have laid down the
fossil fuels that provide
humans with energy.
Every other animal relies on
plants either directly or
indirectly for nutrition.
The Plant Kingdom
Plants grow mainly on land but also can be found in
the oceans and fresh water. They have been on Earth
for millions of years. Plants species currently number
about 260,000.
1a
The Plant Kingdom – the main Phylum (Groups)
Ferns
Flowering
Plants
Ginkos
Plant
Kingdom
Mosses
Cycads
Conifers
Liverworts
Horsetails
1b
Plants are special because
they have leaves and are able
to produce their own food by
the process of photosynthesis
from sunlight using raw
materials that they get from
the air and soil.
Plants can be thought of as
‘food factories’ which provides
most living organisms on Earth
with a source of energy and
nutrients.
They produce the energy that
is at the start of any food chain
and therefore the group of
plants are known as
Producers.
Plants as Producers
1c
The structure and functions of parts of the plant
The Shoot System
Above ground (usually)
Lifts the plant above the soil
Main functions include:
Leaves - photosynthesis
Flowers - reproduction
Fruit – seed dispersal
Stem - food and water transport
The Root System
Underground (usually)
Anchor the plant in the soil
Main functions include:
Absorb water and nutrients
Transport water and nutrients
Food Storage
2c
Plants take up water through root hairs
Extra for
experts
Water moves into the plant through root hairs. Water being drawn up the plants xylem
due to transpiration decreases the pressure inside the root hair cells and this negative
pressure pulls water in.
2c
Osmosis is the diffusion of water molecules through a partially permeable
membrane (extension)
Extra for
Diffusion means
that the net
movement of
particles
(molecules) is
from an area of
high concentration
to low
concentration.
Oxygen, Carbon
Dioxide and water
move across the
cell membrane by
diffusion.
experts
2c
Osmosis is the diffusion of water molecules through a partially permeable
membrane (extension)
Extra for
experts
Osmosis is the diffusion of water only through a partially permeable
membrane from where water is in higher concentration to where it is in lower
concentration. (or where the solute is in higher concentration)
2d
The process of transpiration
Extra for
experts
Transpiration is the process where plants lose water from their leaves.
Water enters a plant through root hairs. When stomata, on the underside of leaves, are
open to allow CO2 to diffuse in and O2 to diffuse out, water vapour evaporates and
diffuses out.
2d
The process of transpiration
Extra for
experts
1. Water enters plant through root hairs by osmosis – high to low concentration
of water. 2. Attraction between water particles pulls water up the plant through
the xylem. 3. Water evaporates from the leaves through transpiration.
GZ Science Resources 2014
2d
The process of transpiration
Extra for
experts
2d
The xylem transports water and the phloem transports the products of
photosynthesis
Extra for
experts
Transport water around
the plant
Special features
>Cells join into long and
tube-like hollow vessels.
>Cells have no end walls,
so form a 'pipeline'
carrying water from leaves
to root.
>Spirals and rings of lignin
surrounding the cells
strengthen the walls, to
withstand pressure of
water.
2d
The xylem transports water and the phloem transports the products of
Extra for
photosynthesis
experts
The xylem is probably the longest part of the pathway that water takes on its way to the
leaves of a plant. It is also the path of least resistance, with about a billion times less
resistance than cell to cell transport of water.
Xylem cells are called tracheids
(cells with narrower diameters)
or vessels (cells with wider
diameters). Their cell walls
contain cellulose and lignin
making them extremely
rigid. Xylem cells contain no
membranes and are considered
dead. These cells overlap to
create a series of pathways that
water can take as it heads to the
leaves. There is no single column
of xylem cells carrying water.
2d
The role that stomata have in the process of transpiration
Stomata are normally found only
on the under or shaded sides of
leaves.
Their function is to capture CO2
from the atmosphere by
exchanging water for carbon
dioxide. The exchange is
accomplished by having water
directly open to air to facilitate the
capture.
Extra for
experts
2d
The role that stomata have in the process of transpiration
extension
Leaves are the main site of
photosynthesis. They make food from
carbon dioxide and water in the
presence of light. As stomata open in
the presence of light, carbon dioxide
will diffuse into the leaf and at the same
time, water vapour will exit the leaf
through the stomata to the surrounding
atmosphere through the process of
transpiration.
Plants will lose water vapour while
taking up carbon dioxide through their
stomata. If this water loss is
uncontrolled, plants can deplete their
water reserve.
Stomata prevent water loss from the
stoma by closing once the leaf has
sufficient carbon dioxide.
2d
Extra for
experts
Plant features that control transpiration
The structure of a plant influences the rate of transpiration. These features can
reduce the rate of water loss from the plant.
cuticle
boundary
A layer of nonmoving air around
the leaf surface that
decreases water
loss. Hair can
increase boundary
size.
A waxy
waterproof layer
on plant
epidermis to
prevent water
loss.
stomata
Pores in the plant that can be
closed to stop plant transpiration
2e
Aquatic environment adaptations
boundary
stomata
>many do not have
stomata as they use
energy to open and
close
>Unimportant to
increase boundary
as mostly
surrounded by
water and reducing
transpiration not
an issue
> Many have large
leaves to maximise
light collection
because they do
not have to reduce
their surface area
exposed for
transpiration
>if they have stomata
they are on the upper
part of the leaf in
contact with the air
(especially in floating
plants)
cuticle
> Thin cuticle or none at all because water retention not
necessary.
> Some have thin cuticle to prevent algae growth and
allow water to roll off
extension
2e
Extra for
experts
Temperate environment adaptations
boundary
stomata
>stomata have active
guard cells that are
triggered to close by
high CO2 in the plant
and low water levels
in the plant or soil.
> Larger leaves are
often found on plants
in the undergrowth
(also because of low
light levels to collect
more light) and
smaller leaves on
plants exposed to wind
– the less surface area
the less boundary to
protect.
> Some plants will lose
there leaves (and
reduce boundary)
during winter when
water is limited.
>closing and opening
of the stomata uses
active transport (ATP)
so comes at a cost.
cuticle
> A cuticle of wax around the plant is present to
prevent water loss through the epidermis layer
of the leaves and stem. The wax is water
repellent but transparent so still allows light to
reach the chloroplasts.
2e
Desert environment adaptations
boundary
stomata
> Many plants have fine hairs
on their epidermis to reduce
air movement and increase
the size of their boundaries –
moist air is also trapped in
the hairs
> Often their stomata are
sunken in pits (crypts) or
in channels
> Leaves can roll up tightly
and reduce surface area
available for transpiration
> Have very small leaves,
reduced them to spines or
lost them completely
cuticle
> Some plants can open
their stomata at night (C4
plants) to get CO2 for
photosynthesis – a
special dark process that
doesn’t directly need
light. Transpiration is
much reduced in this
cooler dark environment.
> Often very thick, leathery and tough – covering the
entire leaf and plant.
> the thick cuticle is shiny and reflects light lowering
the temperature
extension
3a
The significance of photosynthesis in making food
Most living organisms
depend on plants to
survive. Plants convert
energy from sunlight into
food stored as
carbohydrates through
photosynthesis. Because
animals cannot make
their own food they must
eat plants to gain
nutrition. Plants produce
oxygen, which is released
during photosynthesis,
which all organisms need
for respiration.
3a
The adaptations of leaves for photosynthesis
The flat surface of the leaf called
the blade helps capture maximum
sunlight for photosynthesis.
The leaf is attached by a stem-like
petiole to the plant which branch
out into veins. Inside these are
xylem tubes to transport water to
the leaf cells, which they require for
photosynthesis and to keep the leaf
cells turgid or rigid. The veins also
contain phloem tubes which are
able to transport the sugars (and
starch which they are converted
into), produced during
photosynthesis, away to other parts
of the plant for use and storage.
3a
The adaptations of leaves for photosynthesis
A waxy cuticle on the
outside of the leaf
provides a waterproof
covering while remaining
transparent to allow light
into the leaf cells for
photosynthesis.
Openings (usually on the
underside of the leaf)
called stomata allow
carbon dioxide to enter
and diffuse into cells as
well as allowing oxygen to
move in and out.
Two guard cells on
either side of the stomata
open and close the
openings.
extension
Photosynthesis transfers energy from sunlight into energy in chemicals such
as glucose and starch.
3b
Light enters the leaf and is trapped
by chlorophyll contained within
the chloroplasts in the cells.
Water is transported via xylem to
the cell and the carbon dioxide
enters through the stomata and
diffuses to the cell.
These substances react chemically
within the chloroplasts, powered
by the light and glucose (a sugar) is
produced along with oxygen which
diffuses out. The sugar leaves the
leaf via the phloem.
Carbon dioxide + Water +light → Glucose + Oxygen
3d
The structure of a leaf enables photosynthesis to occur effectively
The cells at the top of the leaf are filled with chlorophyll, which gives leaves the green
colour. The chlorophyll allows the leaf to absorb light energy which is required for
photosynthesis. The spaces between cells in the spongy mesophyll allow carbon
dioxide to diffuse around through the cells.
3d
The leaf structure and types of cell inside a leaf
Cuticle: Waxy layer water proofing upper leaves. Upper
epidermis: Upper layer of cells. No chloroplasts.
Protection.
Vascular Bundle: Bundle of many vessels (xylem and
phloem) for transport. Xylem: Living vascular system
carrying water & minerals throughout plant.
Phloem: Living vascular system carrying dissolved sugars
and organic compounds throughout plant.
Palisade Mesophyll: Tightly packed upper layer of
chloroplast containing cells.
Spongy Mesophyll: Lower layer of cells.
Air space: Area for gases to disperse
Lower Epidermis: Lower external layer of cells in leaf.
Stomata: Opening between guard cells for gas & water
exchange.
Guard Cells: 2 cells surrounding stomata that control
rate of gas & water exchange.
3e
Starch test
When a plant
undergoes
photosynthesis it
produces glucose
which is converted
into starch for storage.
If we want to
investigate what
factors are required
for photosynthesis we
use the starch test to
enable us to reach a
conclusion.
4a
The parts of the flower and the role of the flower in pollination, seed
production and dispersal
Plants that
produce
flowers are
known as
angiosperms.
The flowers
are the
reproductive
structures
where
fertilisation
occurs and
seeds are
produced.
4a
The reproductive parts of an insect-pollinated flower
Insect-pollinated flowers
have visible, often colourful
petals that surround the
flower's sexual reproduction
parts. The petals can
"advertise" for specific
pollinators through their
shape, size, colour and
sometimes smell. The
flowers are surrounded by
sepals, which are small and
usually green structures that
protect the flower as its
developing.
The reproductive parts of an insect-pollinated flower and their functioning
4a
The female part of
the flower is called
the pistil. The
pollen from a male
part of a flower is
brought to the
stigma by a
pollinator. This
process is called
pollination.
The pollen travels
down the style into
the ovary to join
with an egg cell
inside the ovules in
a process called
fertilisation.
The male part of a
flower is called the
stamen. The pollen
is produced in the
anther which is
held up by the
filament. The
pollen is collected
by a pollinator. The
pollen contains
male gametes
which will later fuse
with the female
gametes in the
ovule during
fertilisation.
The reproductive parts of an insect-pollinated flower and their functioning
4b
GZ Science Resources 2014
Insect-pollinated Flowers
often contain nectar, a
sweet sugar produced by
the plant, to attract an
insect. As the insect
reaches into the flower
for the nectar it may be
brushed with pollen from
the anther. If the insect
moves to another flower
it may brush the pollen
against the stigma and
therefore pollinate the
flower.
Flowers ripen their male
and female parts of the
flower at different times
to prevent self
pollination.
4b
Summary of pollination in plants
1. The male parts of the flower are the anther and filament
2. The female parts of the flower are the stigma, style and ovary
3. Male gametes are found in Pollen Produced in the Anther
4. Pollen needs to be moved to the female part called the Stigma of the
species of plant to reproduce
same
5. This process is called Pollination
6. Pollination can be helped by Wind Or Animal
7. An example of wind pollination is grass plants
8. A wind pollinated flower is most likely to look like - small, green, unscented
9. An example of animal pollination is a rose plant pollinated by insects
10.An animal pollinated flower is most likely to look like – colourful, with large
petals, perhaps with a scent
The differences in structure between insect-and wind-pollinated flowers
4c
Insect pollinated flowers are easily
seen and often contain scent and
nectar to attract the insects. The male
parts are adapted so they make
contact with the insect as it feeds from
the flower.
Wind pollinated flowers are often small
and green with no scent. Male anthers
protrude out from the flower to allow
the wind to pick up the pollen and
disperse it away from the plant. Male
and female parts develop at different
times.
4c
Examples of insect-pollinated flowers
GZ Science Resources 2014
4c
Examples of wind-pollinated flowers
GZ Science Resources 2014
4d
Fertilisation in flowering plants
Extra for
experts
1. Pollen from either the same
plant (self-pollination) or
another plant (crosspollination) needs to arrive
on the flowers stigma
2. The pollen sends a tube
down the style to reach the
ovule, and the male gametes
(there are two in every
pollen grain) enter the ovule
to fertilise the egg (female
gamete)
3. One male gamete joins with
one female gamete to form a
zygote and the plant is
fertilised. (The fertilised
ovule develops into a seed)
4d
The differences between pollination and fertilisation in flowering
plants
Pollination just refers to
pollen landing on the
female stigma of the
plant. This can either be
with a pollinator or
wind.
Fertilisation refers to
the sperm cell (that was
in the pollen grain)
joining with the egg cell
to form a single cell
(zygote).
Pollination does not
always lead to
fertilisation
Extra for
experts
5a
The formation of seed and fruit from ovule and ovary
Once the flower has been
fertilised by pollen the
ovary grows to form the
fruit.
The ovules become the
seeds.
The outer part of the ovule
grows into the seed coat.
The zygote grows into the
young plant – or embryo
A fruit may have one or
more seeds.
The petals, sepals and other
parts of the flower start to
die and fall off.
5a
Seed dispersal
Pollen is dispersed (or spread) from plant to plant so the flowers can be pollinated and
fertilised seeds produced. Once the Seeds are mature they then also need to be
dispersed so they are not competing with the parent plant for space, light, water and
nutrients. There are various ways that plants have evolved to disperse their seeds;
forming inside fruit that animals will eat and spread, forming structures on the seed so
the wind will carry them away, can float away, be forced away or tangle in the coat of an
animal to be carried away.
5a
Seed dispersal
How are seeds dispersed?
By animals
By the wind
Self dispersal
5b
The conditions needed for germination of seeds
Seeds will remain dormant until they receive
water
warmth
light
oxygen
Then they will germinate.
Other types of seeds may also require
>fire to burn seed coat
>soaking in water
>scratched seed coat
>being digested by animals
Before they germinate
5b
The conditions needed for germination of seeds
Extra for
experts
Testa
The seed contains the
embryo plant and
cotyledons (starch stores)
Water enters the seed
through the micropyle and
activates enzymes.
The water also softens the
testa to allow it to split.
Plumule
(embryo shoot)
Radicle
(embryo root)
Micropyle
Cotyledon
5b
The conditions needed for germination of seeds
Extra for
experts
Plumule
starch
embryo plant
amylase
secreted
maltose
Radicle
This is the first part
to grow out of the
seed as it needs to
absorb more water
The enzymes break
starch down into
maltose and then
glucose. The glucose
is used in respiration
to provide energy for
growth
5b
The conditions needed for germination of seeds
Whilst germinating
the plant uses food
stores in the
cotyledon to provide
energy for growth
germination
The seedling can now
photosynthesise and
make its own food
Plant growth and development
5b
The conditions needed for germination of seeds
Seed loses weight as it uses
up starch stores in the
cotyledons as the seedling
cannot photosynthesise yet
Dry mass/g
Weight increases as
the seedling can
photosynthesise and
plant grows
Dry mass is the
mass of solid
matter with all
water removed
Days
5b
The conditions needed for germination of seeds
Summarise the findings of the experiment shown below:
Pyrogallol (absorbs oxygen)
Oxygen
present
Oxygen
present
No light
Oxygen
present
Oxygen
present
No
oxygen
moist
4oC
A
dry
moist
moist
moist
Warm
B
Warm
C
Warm
D
Warm
E
5c
The structure of a seed
The seed consists of the
seed coat or the testa
which surrounds the
cotyledons or the food
storage area. The
embryo consists of the
radicle which is the
embryonic root and the
hypocotyl which forms
the first shoots and
leaves of the plant. A
small pore in the seed
may be seen called the
micropyle. This is where
the pollen originally
entered the ovule.