Transcript biological productivity

PHOTOSYNTHESIS
&
BIOLOGICAL PRODUCTIVITY
What is
PHOTOSYNTHESIS
Photosynthesis - process in which green plants and
algae utilize the energy of sunlight to manufacture
carbohydrates from carbon dioxide and water in the
presence of chlorophyll
 Water is absorbed by the roots and carried to the leaves by
the xylem,
 and carbon dioxide is obtained from air that enters the
leaves through the stomata and diffuses to the cells
containing chlorophyll,
 the green pigment (chlorophyll) is capable of converting
the active energy of light into a latent form that can be stored
(in food) and used when needed.
A commonly used equation for photosynthesis is:
carbon dioxide + water + light energy → glucose + oxygen + water
6 CO2 + 12 H2O + photons → C6H12O6 + 6 O2 + 6 H2O
chlorophyll
light-independent
reactions/Dark Reactions
The Photosynthetic Process
 The initial process in photosynthesis is the decomposition of water
(H2O) into oxygen, which is released, and hydrogen; direct light is
required for this process.
 The hydrogen and the carbon and oxygen of carbon dioxide (CO2 )
are then converted into a series of increasingly complex
compounds that result finally in a stable organic compound,
glucose (C6 H12O6 ), and water.
 This phase of photosynthesis utilizes stored energy and therefore
can proceed in the dark. The simplified equation used to represent
this overall process is;
6 CO2 +12 H2O+ energy = C6H12O6 +6 O2 +6 H2O
Summary of stages of photosynthesis
Structure of a chloroplast
Rate of Photosynthesis
The rate of photosynthesis is defined in terms of the rate of oxygen
production either per unit mass (or area) of green plant tissues or per
unit weight of total chlorophyll.
The amount of light, the carbon dioxide supply, the temperature, the
water supply, and the availability of minerals are the most important
environmental factors (abiotic) that directly affect the rate of
photosynthesis in land plants.
The rate of photosynthesis also is determined by biotic factors such as
the plant species and its physiological state - e.g., its health, its
maturity, and whether or not it is in flower/fruiting etc.
Factors that influence the rate of
photosynthesis
1. Light intensity and temperature
• At the moderate temperatures and at low to medium light
intensities, the rate of photosynthesis increases as the intensity
increases and is independent of temperature.
• As the light intensity increases the rate becomes increasingly
dependent on temperature and less dependent on intensity; light
“saturation” is achieved at a specific light intensity, and the rate
then is dependent only on temperature if all other factors are
constant.
• In the light-dependent range before saturation, therefore, the rate
of photosynthesis is determined by the rates of photochemical
steps. At high light intensities, some of the chemical reactions of
the dark stage become rate-limiting. At light saturation, rate
increases with temperature until a point is reached beyond which
no further rate increase can occur.
Factors that influence the rate of photosynthesis
2. Carbon dioxide (CO2)
• The rates of these reactions can be increased somewhat by
increasing the carbon dioxide concentration.
• During the past century, the level of carbon dioxide in the
atmosphere has been rising due to the extensive combustion
of fossil fuels. This increase in carbon dioxide directly
increases plant photosynthesis, but the size of the increase
depends on the species and physiological condition of the
plant.
• Furthermore, if increasing levels of atmospheric carbon
dioxide result in climatic changes, including increased global
temperatures as some meteorologists predict, these changes
will affect photosynthesis rates.
Factors that influence the rate of photosynthesis
3. Water (H2O)
• For land plants, water availability can function as a limiting
factor in photosynthesis and plant growth.
• Besides the requirement for water in the photosynthetic
reaction itself, water is transpired from the leaves; that is, water
evaporates from the leaves to the atmosphere via the stomates.
they permit the entry of carbon dioxide but also allow the exit
of water vapour.
…..Water
• In hot and arid climates the stomates may close to
conserve water, but this closure limits the entry of
carbon dioxide and hence the rate of photosynthesis.
• If the level of carbon dioxide in the atmosphere
increases, more carbon dioxide could enter through a
smaller opening of the stomates, so that more
photosynthesis could occur with a given supply of
water.
Factors that influence the rate of photosynthesis
4. Minerals
• Several minerals are required for healthy plant growth and
for maximum rates of photosynthesis.
• Nitrate or ammonia, sulfate, phosphate, iron, magnesium,
and potassium are required in substantial amounts for the
synthesis of amino acids, proteins, coenzymes,
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA),
chlorophyll and other pigments, and other essential plant
constituents.
• Smaller amounts of such elements as manganese, copper,
and chlorine are required in photosynthesis.
Importance of Photosynthesis
> Animals and plants both synthesize fats and proteins
from carbohydrates; thus glucose is a basic energy
source for all living organisms.
 The oxygen released (with water vapor, in
transpiration) as a photosynthetic byproduct,
principally of phytoplankton, provides most of the
atmospheric oxygen vital to respiration in plants and
animals, and animals in turn produce carbon dioxide
necessary to plants.
 Photosynthesis can therefore be considered the
ultimate source of life for nearly all plants and
animals by providing the source of energy that
drives all their metabolic processes.
BIOLOGICAL PRODUCTIVITY
What is
BIOLOGICAL PRODUCTIVITY
Biological Productivity can be defined as the amount and rate of
production which occur in a given ecosystem over a given time
period. It may apply to a single organism, a population, or entire
communities and ecosystems.
Biological productivity = Primary productivity is the rate at which
biomass is produced per unit area by plants, expressed in either units of
energy [joules/(m2)(day)] or dry organic matter [kg/(m2)(year)].
Gross primary production (GPP) is the total energy fixed by
photosynthesis per unit time.
Net primary production (NPP) is the gross production minus losses due to
plant respiration per unit time, and it represents the actual new biomass.
Secondary production is the rate of production of biomass by
heterotrophs.
Biomass
The organic materials produced by plants, such as leaves, roots, seeds, and
stalks.
The term “biomass” is intended to refer to materials that do not directly go into
foods or consumer products but may have alternative industrial uses.
Common sources of biomass are (1) agricultural wastes, such as corn stalks,
straw, seed hulls, sugarcane leavings, bagasse, nutshells, and manure from
cattle, poultry s; (2) wood materials, such as wood or bark, sawdust, timber
slash, and mill scrap; (3) municipal waste, such as waste paper and yard
clippings; and (4) energy crops, such oil palm,
Ecosystems Concept
An ecosystem is a complete community of living organisms (biotic) and the
nonliving materials (abiotic) of their surroundings. Thus, its components include
plants, animals, and microorganism; soil, rocks, and minerals; as well as
surrounding water sources and the local atmosphere.
The size of ecosystems varies tremendously. An ecosystem could be an entire
rain forest, paddy field, rubber plantation, dairy farm, poultry house, fish pond
or a backyard garden. Even the body of an animal could be considered an
ecosystem, since it is home to numerous microorganisms.
FACTORS AFFECTING PERFORMANCE OF
BIOLOGICAL PRODUCTIVITY
Common major factors that control the
biological productivity are;
1. Abiotic factors
2. Biotic factors, and
3. Management
ABIOTIC FACTORS
Abiotic, meaning not alive, are nonliving factors
that affect living organisms.
The way in which plants and animals grow and
carry out their different activities is a result of
several abiotic factors.
These factors are light, temperature, water,
atmospheric gases, wind as well as soil (edaphic)
and physiographic (nature of land surface) factors.
Others can be physical such as pond, lake, ocean,
desert, mountain, etc.
…...... Abiotic Factors Affecting Productivity
Light
Light energy (sunlight) is the primary source of energy in
nearly all ecosystems.
It is the energy that is used by green plants (which contain
chlorophyll) during the process of photosynthesis; a process
during which plants manufacture organic substances by
combining inorganic substances.
Factors such as quality of light, intensity of light and the
length of the light period (day length) play an important part
in an biological productivity.
…...... Abiotic Factors Affecting Productivity
Temperature
The distribution of plants and animals is greatly influenced by
extremes in temperature for instance the warm season. The
following are examples of temperature effects on the
productivity of ecosystems:
•some fruit trees such as the peach require a cold period each
year so that it can blossom in the spring;
…...... Abiotic Factors
Water
Plant and animal habitats vary from entirely
aquatic environments to very dry deserts.
Water is essential for life and all organisms
depend on it to survive in especially desert
areas.
Some tropical fruit trees’ e.g. durian,
rambutan and mango require some degree
of water stress to flower and yield fruits.
…...... Abiotic Factors
Atmospheric gases
The most important gases used by plants and animals are oxygen,
carbon dioxide and nitrogen.
Oxygen is used by all living organisms during respiration.
Carbon dioxide is used by green plants during photosynthesis.
Nitrogen is made available to plants by certain bacteria and through
the action of lightning.
…...... Abiotic Factors
Soil (edaphic factors)
These factors include soil texture, soil air, soil temperature, soil water,
soil solution and pH, together with soil organisms and decaying matter.
The main Soil Factors
BIOTIC FACTORS
Biotic, meaning of or related to life, are living factors. Plants,
animals, fungi, and bacteria are all biotic or living factors.
Yield potential of organisms (plant, animal, algae) is the
main determining factor of productivity. It is control by the
genetic set-up which can be manipulated.
Abiotic factors have direct influent on genetic expression,
performance and subsequently productivity
Management and human intervention
Proper management of the ecosystems can influent
productivity
This include modification of abiotic factors to
improve organisms (plant, animal, algae )
productivity