PHOTOSYNTHESIS BIOLOGICAL PRODUCTIVITY What is PHOTOSYNTHESIS Photosynthesis process

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 Ø Water is absorbed by the roots and carried to the leaves by the xylem, Ø and carbon dioxide is obtained from air that enters the leaves through the stomata and diffuses to the cells containing chlorophyll, Ø 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 CO 2 + 12 H 2 O + photons → C 6 H 12 O 6 + 6 O 2 + 6 H 2 O

chlorophyll light-independent reactions/Dark Reactions

The Photosynthetic Process Ø The initial process in photosynthesis is the decomposition of water (H 2 O) into oxygen, which is released, and hydrogen; direct light is required for this process. Ø The hydrogen and the carbon and oxygen of carbon dioxide (CO 2 ) are then converted into a series of increasingly complex compounds that result finally in a stable organic compound, glucose (C 6 H 12 O 6 ), and water. Ø 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 CO 2 +12 H 2 O+ energy = C 6 H 12 O 6 +6 O 2 +6 H 2 O

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 (CO 2) • 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 (H 2 O) • 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. Ø 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. Ø 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/(m 2)(day)] or dry organic matter [kg/(m 2)(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 ØLight energy (sunlight) is the primary source of energy in nearly all ecosystems. ØIt 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. ØFactors 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 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 p. H, 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