Environmental
factors
affecting
photosynthesis
and
respiration
rates
By Tamta, Natalya and
Amelia
How the differences in light affect
the rate of photosynthesis
Increasing the light intensity on the plant will increase the
rate of photosynthesis.
Bright light is a basic element of photosynthesis, but
variations in the colour of light have an effect on plants. The
entire spectrum of light hits the plant's leaves at the same
time, but there are some colours that are known to cause
higher amounts of photosynthesis than others. Chlorophyll is
the cause of each plant's individual colouring and there are
four kinds of pigments that create the chlorophyll.
The colour that has the highest influence on photosynthesis is
blue, which is why many plant growers use blue lights to
grow indoor plants. Red light is next best for photosynthesis
and yellow light creates the lowest amount of light
absorption.
If a plant does not receive adequate light it will attempt to
reach the light by growing taller.
How the differences in light
affect the rate of respiration
Respiration is the opposite of photosynthesis. When the lights
are out, the photosynthesis process ceases but the respiration
continues. The plant will use oxygen to break down food
substances, which is released as energy in the form of heat.
Carbon dioxide is produced and expelled as a result of this
process. When the lights are on the plants absorb carbon
dioxide and expel oxygen. So the levels of light does not
affect the rate of respiration.
How the levels of oxygen
and carbon dioxide affect
the rate
Photosynthesis
The amount of oxygen:
Plants release oxygen (O2) once they have photosynthesized;
they do not need oxygen levels to be high in order to have
photosynthesis occurring. Plants have no use for oxygen so
no matter the oxygen levels, it does not affect the plant, as
long as there is carbon dioxide available.
Chemical equation:
6CO2+6H2O
C6H1206+6O2
The amount of carbon dioxide:
Plants need carbon dioxide (CO2) in order to photosynthesize.
By increasing the amount of carbon dioxide, the rate of
photosynthesis will generally increase. Carbon dioxide levels
determine the maximum rate of photosynthesis. It does not seem
to matter how much carbon dioxide there is in the air for plants
to live. However, we need plants as they take in the carbon
dioxide and release oxygen.
Word equation for photosynthesis:
Carbon dioxide+water+sunlight
glucose+oxygen
Respiration
The amount of oxygen:
In order for plants to respire, they need high levels of oxygen.
Oxygen is needed to burn the glucose made from
photosynthesis. They use the oxygen and the glucose to move;
they burn it off as their energy, like a car burns off petrol to
move. The higher the levels of oxygen, the higher the rate of
respiration and the more the plant can move. They burn the
glucose in the plant cells so that it is slow and gradual. If a
plant was to burn glucose in the air, the reaction would be
rapid and uncontrolled.
The amount of carbon dioxide:
Plants only need oxygen and glucose in order to respire.
These materials are the products of photosynthesis. They do
not need carbon dioxide as they release CO2 in respiration.
The more carbon dioxide there is, the plant would absorb it
through photosynthesis and release it through respiration.
Which part of the day does…
Photosynthesis occur in:
Photosynthesis occurs during the day when sun is out so as
to absorb as much sunlight as possible. It does not occur at
night as there is no sunlight available to supply energy.
Photosynthesis
is occurring
Photosynthesis is
not occurring
Respiration occur in:
A plant is always respiring. Plants are continuously taking
in oxygen and giving off carbon dioxide and water. A plant
relies on oxygen levels in order to respire so it does not affect
the plant whether it is day or night to respire.
Respiration
occurs day
and night
How the water availability affects
the stomata opening during
photosynthesis
Transpiration rates go up as the temperature goes up,
especially during the growing season, when air is warm
due to stronger sunlight and warm air. Water levels
can affect the opening and closing of a plants stomata.
A plant needs water in order to photosynthesize. If the
plant does not have enough water available, the plant's
stomata will shut so as to hold water and not dry out.
However, this is a tricky process as the plant will be
unable to take in carbon dioxide so the photosynthesis
will cease. If the water levels are high, a plants stomata
will open to absorb water and to expel used and
unneeded water.
How the water availability
affects the stomata opening
during respiration
Water also affects the stomata during respiration. A plants
does not need water in order to respire, so if there are high
levels of water, a plant will not take in any water so the
stomata will close. However, a plants stomata will open
during respiration so as to take in oxygen and expel carbon
dioxide.
A plants stomata will open and close during respiration and
photosynthesis depending on the water levels.
What does a plant need to
achieve maximum
photosynthesis rate
The rate of photosynthesis depends on the availability of
carbon dioxide, the amount of light available and the
temperature. Increasing any of these factors increases the
rate of photosynthesis. Carbon dioxide levels determine the
maximum rate of photosynthesis. Plants in their natural
surrounding seldom reach their maximum rate of
photosynthesis. On a bright sunny day, carbon dioxide is he
limiting factor since air only contains 0.04% of the gas. In
the early morning and late afternoon, temperature and light
are most likely to be limiting factors. At night there is no
photosynthesis. In order for a plant to achieve the maximum
photosynthesis rate, carbon dioxide, water and sunlight need
to be available in high levels.