Factors affecting photosynthesis

Photosynthesis:

Photosynthesis is the conversion of sunlight, carbon dioxide (CO2) and water into food (sugars) and oxygen by plants, algae and microorganisms. Here’s a look at the fundamentals of photosynthesis and associated studies to aid in developing clean fuels and renewable energy sources.

Oxygenic photosynthesis and anoxygenic photosynthesis are the two types of photosynthetic processes.

Oxygenic Photosynthesis:

• Unicellular or multicellular oxygenic photosynthetic microorganisms exist. These bacteria carry out photosynthesis in the same way plants carry it out.
• They include pigments that absorb carbon dioxide and release oxygen such as phycobilins and phycoerythrin.
• By absorbing CO2 generated by all breathing creatures and returning oxygen to the atmosphere, oxygenic photosynthesis serves as a counterweight to respiration.

Anoxygenic Photosynthesis

• Anoxygenic photosynthesis is a kind of anaerobic bacterial photosynthesis that employs a non–cyclic photosynthetic electron transport chain and reduces inorganic electron donors such hydrogen sulphide, hydrogen or ferrous ions as electron donors

• According to LibreTexts, “Anoxygenic Photosynthetic Bacteria” anoxygenic photosynthesis employs electron donors other than water and does not create oxygen. Green sulphur bacteria and phototrophic purple bacteria are examples of bacteria that go through this process.

Factors Affecting Photosynthesis:

There are fifteen factors affecting photosynthesis. The factors are: 

1. Temperature
2. Carbon Dioxide Concentrations
3. Light
4. Intensity
5. Quality
6. Duration 
7. Oxygen
8. Water
9. Mineral Elements
10. Air Pollutants 
11. Chemical Compounds
12. Chlorophyll Contents
13. Protoplasmic Factor 
14. Accumulation of Carbohydrates 
15. Blackman’s Principle of Limiting Factors. 

Light

The photosynthetically active portion of the light spectrum is between 400 and 700 nm. Photosynthesis relies heavily on a green light (550 nm). The process requires energy, which is provided by sunlight. The intensity, quality and duration of light are all different.

Intensity

When the intensity of light falling on a photosynthesising organ exceeds a particular threshold, the organ’s cells become exposed to chlorophyll-catalysed photo-oxidation. As a result, these organs consume O2 rather than CO2, and CO2 is expelled. When O2 is available, carotenoids are missing or CO2 concentration is low, photo-oxidation is peak.

Quality

The photosynthetic action spectrum in leaves has two significant peaks, one in red and the other in blue. Chlorophylls absorb the most light in these areas. The most effective wavelengths vary depending on the plant.

It’s worth noting that plants can photosynthesise well in blue and red light, but red algae can photosynthesise well in the green light and brown algae can photosynthesise well in blue light. The activity spectrum of blue-green algae peaks in yellow or orange light.

Duration

In general, when a plant is exposed to lengthy durations of light, it will produce more photosynthesis. It has also been shown that plants may sustain uninterrupted and continuous photosynthesis for relatively long periods without any apparent harm. It’s also worth remembering that when the source of light is removed, the rate of CO2 fixation instantly drops to zero.

Water

In the process of carbon absorption, water is a necessary raw ingredient. Photosynthesis consumes less than 1% of the water taken by a plant. Photosynthesis is reduced as the water content of the soil decreases from field capacity to the permanent wilting limit.

CO2 Concentration

• Carbon dioxide makes up almost 0.032 per cent of the atmosphere’s volume, and at this low concentration, it functions as a limiting factor. When light and temperature aren’t limiting variables in the lab, increasing CO2 content in the environment from 0.03 per cent to 0.3-1 percent increases the photosynthetic rate.

• As CO2 concentrations rise, the rate of carbon absorption rises somewhat before becoming independent of CO2 concentration.

• Following that, it stays constant throughout a wide range of CO2 concentrations. Plants’ capacity to exploit high CO2 concentrations varies. High CO2 levels, over the physiological range, have a negative impact on tomatoes, inducing leaf senescence. CO2 concentrations in the atmosphere were as high as 20% during the early days of the world.

Temperature

• Depending on the plant species, the temperature range in which optimal photosynthesis may occur varies. Some lichens, for example, may photosynthesise at temperatures as low as 20°C, whereas conifers can assimilate at temperatures as high as 35°C. Certain blue, green algae and bacteria, on the other hand, live in hot springs and may photosynthesise at temperatures as high as 70°C. On the other hand, Cacti can photosynthesise at temperatures as low as 55°C.

• Because light, CO2 or both are limited in nature, the maximal rate of photosynthesis owing to temperature is not attained. Net photosynthesis has a different response curve to temperature than light and CO2.

• It displays the lowest, highest and lowest temperatures. While C3 plants have ideal rates between 20 and 26 degrees Celsius, C4 plants may have optimal rates between 35 and 40 degrees Celsius. Similarly, temperature affects both light (optimal, 30-35°C) and dark (optimal, 40-45°C) respiration.

Oxygen

Oxygen has been demonstrated to limit photosynthesis in C3 plants but has no impact on C4 plants. C4 plants are thought to exhibit photorespiration, which is stimulated by high oxygen levels. When the oxygen content in the air is dropped from 20% to 0.50%, the rate of photosynthesis rises by 30-50% and CO2, light, and temperature are not limiting variables.

Oxygen inhibits photosynthesis because it would favour a faster respiratory rate using common intermediates, lowering photosynthesis. Second, oxygen may compete with CO2, resulting in reducing hydrogen in place of CO2. Third, O2 hinders photosynthesis by destroying chlorophyll’s excited (triplet) state.

Mineral Elements

Several minerals are required for plant development, as previously stated. Mg, Fe, Cu, CI, Mn and P are all strongly connected with photosynthetic processes.

Air Pollutants

Gaseous and metallic contaminants reduce photosynthetic activity. Ozone, SO2, oxidants, hydrogen fluorides and other substances fall under this category.

Chemical Compounds

When compounds like HCN, H2S, and others are present in modest amounts, they slow down photosynthesis by blocking enzymes. Chloroform, ether and other chemicals inhibit photosynthesis, although the impact is reversible at low doses. Cells, on the other hand, perish in excessive quantities.

Chlorophyll Contents

The rate of photosynthesis was investigated in two types of barley, one with typical green leaves and the other with yellow leaves. The limiting parameters were not CO2, light or temperature. Even though the green-leaved variety had ten times more chlorophyll than the yellow one, the absorption rate per unit area of leaf surface was the same in both species. The chlorophyll in the green leaves is clearly in excess. Because they lack the enzymes or coenzymes to employ the results of light reactions to decrease available CO2, leaves with a high chlorophyll concentration do not photosynthesise quickly.

Protoplasmic Factor

Aside from chlorophyll, some protoplasmic variables impact the photosynthesis rate. They affect the dark responses. These elements are lacking in the seedling’s early stages and develop as the seedling becomes older.

The fact that many plants’ photosynthetic capacity is lost at temperatures over 30°C or at high light intensities, although the cells remain green and alive, suggests that these protoplasmic components are enzymatic.

Accumulation of Carbohydrates

Photosynthate accumulation in plant cells delays and eventually stops the process if it is not translocated. The pace of respiration is sped up due to the accumulated products. Sugar is also turned to starch, and the buildup of starch in chloroplasts limits their effective surface area, slowing the process.

Blackman’s Principle of Limiting Factors:

When several different elements condition a process’s rapidity, the process’s rate is restricted by the slowest factor’s speed.

Conclusion

For photosynthesis to occur, carbon dioxide is required. The half of the leaf within the glass container did not get carbon dioxide, but both halves of the leaf got the same quantity of water, chloroplasts and sunshine.