A clear paleontological window on cyanobacterial evolution opened about 2000 Ma, indicating an already-diverse biota of blue-greens. Cyanobacteria remained the main producers throughout the Proterozoic Eon (2500-543 Ma), because the redox structure of the oceans favored photoautotrophs capable of nitrogen fixation.

Green algae joined blue-greens as major primary producers on continental shelves near the end of the Proterozoic, but only with the Mesozoic (251-65 Ma) dinoflagellates, coccolithophorids, and diatoms did primary production in marine shelf waters take modern form.

Cyanobacteria play an essential role in marine ecosystems as primary producers in oceanic gyres, as agents of biological nitrogen fixation, and, in modified form, as the plastids of marine algae.

This new type of chlorophyll named ‘chlorophyll f’ is found in stromatolites–rock-like structures built by cyanobacteria in Western Australia‘s Shark Bay. The new pigment can utilize lower light energy than other known types of chlorophyll. It is the fifth known type of chlorophyll.

The discovery was announced by Dr. Min Chen, a scientist working at the University of Sydney. “Discovering this new chlorophyll has completely overturned the traditional notion that photosynthesis needs high energy light,” Chen said.

Chlorophyll is the green colored pigment that in found in the leaves of plants. It is also found in many bacteria. It enables plants to trap the energy of sunlight and convert it into carbohydrate by absorbing carbon dioxide from the atmosphere. Photosynthesis is a crucial process for the sustenance of life on our planet.

Via: English.News.cn

Air pollution can affect photosynthesis adversely. For example, smog can block out light that is needed for photosynthesis, affecting photosynthesis through which plants convert CO₂ to sugars and oxygen.

Air pollution can also cause “acid rain.” Acid rain is a popular term for the atmospheric deposition of acidified rain, snow, sleet, hail, acidifying gases and particles, as well as acidified fog. Acid rain harms the leaves of a plant, which reduces how well it can conduct photosynthesis.

Carotenoids present in green leaves can absorb the upper frequency band of the visible light spectrum i.e. violets, blue, dark green frequencies. Since leaves also contain carotenoids, plants will be able to perform photosynthesis but only to a small extent.

Stored energy wouldn’t be used for photosynthesis, or at least the light reactions – note the light reactions are the ones that use light energy to generate ATP and NADPH. The dark reactions use these molecules to generate oxygen and sugars. Stored energy would most likely undergo respiration to generate energy from pre-existing sugars.

These are:

- Light irradiance and wavelength
- Carbon dioxide concentration
- Temperature

At constant temperature, the rate of carbon assimilation varies with irradiance, initially increasing as the irradiance increases. However at higher irradiance this relationship no longer holds and the rate of carbon assimilation reaches a plateau.

At constant irradiance, the rate of carbon assimilation increases as the temperature is increased over a limited range. This effect is only seen at high irradiance levels. At low irradiance, increasing the temperature has little influence on the rate of carbon assimilation.

As carbon dioxide concentrations rise, the rate at which sugars are made by the light-independent reactions increases until limited by other factors.

- Production of oxygen: Photosynthesis is the reverse of respiration. This is why the supply of atmospheric oxygen is not exhausted by respiration and combustion. The forests of the world contribute more than 60% of the world’s oxygen demands. They also absorb the massive doses of carbon dioxide exhaled into the atmosphere by modern industrial societies.

- Food production: Plants manufacture all their body-building and energy-producing substances from simple raw materials using the energy of the sunlight. Animals obtain their food from plants.

- Energy: Fossil fuels such as coal are formed from plants and as such the energy stored in them comes from photosynthesis.

Carbon Dioxide + Water = Glucose + Oxygen

[in the presence of chlorophyll and sunlight]

6CO₂ + 6H₂O ——–> C₆H₁₂O₆ + 6O₂

[or]

6CO₂ + 12H₂O ——–> C₆H₁₂O₆ + 6O₂ + 6H₂O

- Carbon dioxide
- Water
- Chlorophyll
- Sunlight

Chlorophyll is the green pigment that is present in the plants. It is needed for photosynthesis as it traps sunlight.

Equation of photosynthesis:

Carbon dioxide + water + light + chlorophyll = glucose and oxygen

• Absorption spectrum: A curve showing the wavelength of light absorbed by photosynthetic pigment.
• Action spectrum: The curve depicting the quantum yield at different wavelengths of light.
• Cytochromes: Iron containing colored porphyrin or heme compounds which are exclusively electron transporters.
• Cardinal values: Minimum, optimum and maximum values of a factor controlling a physiological process.
• Cyclic photophosphorylation: Photophosphorylation coupled to cyclic electron transport chain. It is associated with PS-I and found in some bacteria.
• Emerson effect: The increase in photosynthetic activity on the successive application of beams of different wavelengths.
• First channels: Intergranal lamellae.
• Photo-system: They are pigment systems for trapping light energy.
• Photophosphorylation: Synthesis of ATP at the expense of radiant energy during photosynthesis.
• Photosynthetic unit: The number of photosynthetic pigment molecules required to release one molecule of oxygen.
• Quantasome: It is a distinct morphological structural unit in the thylakoid which embodies a photosynthetic unit.
• RuBP: Ribulose biphosphate. Carbon dioxide acceptor in C₃ cycle.

Other Topics:

• Mineral and nitrogen nutrition in plants
• Sources of essential elements for plants
• Role of nitrogen in plant nutrition