Transcript Daylight Both photosynthesis and cellular respiration are

Plant Metabolism &
Productivity Tutorial
Photosynthesis
Where does the energy come from that sustains all life at
the earth’s surface?
The Sun!!
Summarizing reaction of photosynthesis!
C6H12O6
Thought
Questions:
How do plants acquire
these starting reactants?
What do plants do with
these products?
Record your answers to all of the though questions posed in this tutorial in the
homework for Lab #4 in you lab manual. Review the entire tutorial before you
attempt to answer any questions!
Who photosynthesizes?
Plants!
Rhodophyta (red algae)
Who
photosynthesizes?
Zooplankton (an animal)
Volvox
Chlorophyta (green algae)
Diatom
Coccolithophore
Marine and Freshwater
phytoplankton – single celled
and colonial algae
Phaeophyta (brown algae)
Non-planktonic multicellular algae
Who photosynthesizes?
Cyanobacteria
Found in the hot springs
of Yellowstone N.P.
Anatomy of Photosynthesis in Plants
Photosynthesis occurs in the chloroplasts which are located in the cells of
plant leaves. It is here that important light harvesting molecules called
photosynthetic pigments are located.
The anatomy of a plant cell
Note that plant cells have both mitochondria for cell
respiration and chloroplasts for photosynthesis!
Euglena – single cell
freshwater phytoplankton
mitochondrion
chloroplast
nucleus
Phytoplankton also undergo both cell
respiration and photosynthesis!
5 µm
The concept map on the following slide summarizes the
important connections between cellular respiration and
photosynthesis within and between plant cells.
As you toggle through this map see if you can determine
where the sun’s energy is being used to facilitate the
production of new plant tissues needed for plant growth.
Also see if you can determine what energy is not available
to sustain the growth of new tissues.
H2O from soil
CO2 from atmosphere
Energy from sunlight
O2
starch
Plant Leaf Mesophyll Cell
Cellulose
Note that these leafAlso
cells, like many
Glucosecontain
converted
to
cells in plants,
BOTH
(C6H12for
O6) photosynthesis and
chloroplasts
mitochondria
forcell
cellular respiration!
sucrose
Fuels
nucleotides
Amino acids
respiration
Mitochondrion
Fatty acids
ATP
CO2
Exported to other plant
cells to build
Chloroplast
Exported to fuel
respiration in other
plant cells lacking
chloroplasts
i.e. root cell
ATP
CO2
Provides the
material
resources to build
plant cells and
tissues to support
plant growth and
reproduction
Productivity is a measure of the amount of the sun’s energy
captured by plants which is used to sustain the energy demands of
life and provide energy for growth and reproduction.
We can estimate productivity by measuring something that is taken
up by a plant which is proportional to energy uptake.
What do you think this is?
Carbon dioxide! - Used in the Calvin Cycle in
photosynthesis to make carbohydrates. The
rate of uptake of CO2 is directly proportional to
the uptake of light energy from the sun.
Carbon dioxide is also a by-product of cellular
respiration, so the rate of release of CO2 is
directly proportional to how much energy is
ultimately used by plants to run cellular
processes.
The difference
between these
two provides a
measure which is
proportional to
the amount of
energy that is left
over to fuel
growth and
reproduction!
Gross Primary Productivity (GPP) is…
…the total amount of the sun’s energy that a plant converts into
chemical energy (stored in the bonds of organic molecules).
Think of it like your total earnings from a job!
Net Primary Productivity (NPP)
The total amount of the sun’s energy a plant converts into
chemical energy subtracting out the amount of chemical energy a
NPP or Energy
plant uses to fuel cellular respiration.
available for
growth and
or Gross (Total) Productivity – Cellular Respiration
= reproduction
Total Pay
Like…
-
rent
& living expenses!
=
Money left over
to grow your
bank account
Let’s say that we put some plant leaves in a sealed bottle and exposed it to 10
minutes of light and then 10 minutes of dark. During this time we used a CO2 sensor
to measure changes in the concentration of CO2 in the bottle. The following results
were obtained.
CO2 concentration (*ppm)
*ppm = part per million
Light
0
10
Time (minutes)
20
The next 3 slides summarize the changes in CO2 in the bottle with respect to the
metabolic processes occurring in the plant during the light and dark phases of the
experiment.
Remember…
As we calculate productivity the sign of the slope (rate of change of
[CO2]) for each measurement is important because they tell us
whether CO2 is being taken up or released by the plant in your
chamber!
• A negative slope (i.e. -55 ppm/min/g) means the plant is TAKING
UP CO2 from the chamber.
• A positive slope (i.e. 34 ppm/min/g) means the plant is
RELEASING CO2 into the chamber.
Remember that the plant is doing
both photosynthesis & cell
respiration in the light!
Light
 CO2 uptake CO2
release 
The plant is actually taking up
more CO2 than this through
photosynthesis, but we cannot
“see” this in the light because
CO2 is also being released
through cell respiration at the
same time, and we don’t know
how much!
Some amount of CO2 released
from cell respiration
?
?
CO2 uptake  sugars
Photosynthesis
-60
-50 -40
-30 -20
-10
10
20
30
40
Rate of Change in CO2
concentration (ppm/min)
-35.0 ppm/min = the rate of change of [CO2] due
to BOTH respiration and photosynthesis which is
Net Photosynthetic Productivity (NPP)
50
60
Light
 CO2 uptake CO2
release 
During the dark, the plant is
only doing cell respiration so….
…these should be
equal!
So…to calculate gross (or total)
primary productivity (the whole
green box)…
…, we need to add the dark [CO2]
change to the light, but in the
negative direction.
?
-60 -50 -40
-30 -20
-10
10
20
30
40
50
60
Rate of Change in CO2
concentration (ppm/min)
-35.0 ppm/min
(rate of change of
[CO2] in the light)
We do this by subtracting the dark
from the light!
-35.0 – 20.0 = -35.0 + (-20.0) = -55.0 ppm/min
CO2 concentration (ppm)
Here is another possibility!
Light
0
5
Time (minutes)
10
Light
We know that this plant is
photosynthesizing because the
rate of release of CO2 is greater
in the dark than in the light!
In the light some amount of CO2
is used in photosynthesis…
-60 -50 -40 -30 -20
To get gross primary
productivity (GPP)…
…again subtract the dark slope from
the light slope
10.0 – 30.0 = -20.0
 CO2 uptake CO2
release 
+30dark slope
?
-10
…but more CO2 is given off
through respiration
10
20 30
40
50
60
Rate of Change in CO2
concentration (ppm/min)
10.0 ppm/min = the rate of change of
[CO2] in the light due to BOTH respiration
and photosynthesis
This plant is using up more
of the energy it harvested
from the sun to fuel
cellular respiration than it
is gaining through
photosynthesis. This is
indicated by the positive
slope in the light!
Like this plant which is
using more energy just
to stay alive than it is
bringing in through
photosynthesis! To
stay alive, in the short
term, this plant will
have to use energy
stored in organic
molecules like starch.
Using our earnings analogy from earlier…this is like the
person who’s rent and living expenses are GREATER
than their total pay!
This person is spending more than he is earning, and
therefore must be depleting his savings in the bank!
Team think and share…
A plant may be using more energy to fuel life processes (cell
respiration) than it is taking in through photosynthesis either
because its cell respiratory rate is elevated or because
photosynthetic rate is diminished.
What is one potential reason why a plant may be forced to
elevate its cell respiratory rate?
What is one potential reason for why a plant may experience
diminished photosynthetic rates?
Record your answer in your homework for Lab #4!
Thought Question!
CO2 concentration (ppm)
Calculate the gross and net photosynthetic productivity for the plant in this
experiment. What do you think is happening in this plant with regard to the
relationship between cellular respiration and photosynthesis, and why might a living
plant be exhibiting these metabolic characteristics?
Light
0
5
Time (minutes)
Record your answer in your homework for Lab #4!
10